Tag: hydroponic

In comparison with pesticides, only sporadic research has shown detoxification of PPCPs by POD and GST in plants. In the present study, activities of POD and GST increased in a dose-dependent manner in both roots and leaves after exposure to PPCPs . This observation was consistent with Bartha et al. and Huber et al. , who observed oxidation of diclofenac by plant peroxidases, and also glutathione conjugation in Typha latifolia. These mechanistic studies, together with our results, clearly show that the POD and GST enzyme families may play an important role in transformation and conjugation of PPCPs in plants. Glutathione is one of the major soluble low molecular weight antioxidants, and also the major non-protein thiol in plant cells , contributing to maintain the cellular redox homeostasis and signaling. Moreover, conjugation with xenobiotics by GSH may be a common pathway for plant metabolism of various man-made chemicals . Glutathione conjugation with diclofenac , 8:2 fluorotelomer alcohol and chlortetracycline have been previously observed in plants. It is well known that these processes require extensive utilization of reduced GSH as an electron donor and subsequently produce oxidized glutathione . The changes in the cellular glutathione pool, specially the associated ratio of reduced to oxidized glutathione, play a central role in plant defense responses . Glutathione homeostasis after exposure to trace levels of PPCPs, however,growing hydroponically has not been well documented so far. In this study, the glutathione content increased at low PPCP doses, while decreased to normal levels at the highest PPCP treatment level . The GSSG content was unchanged when the PPCP concentrations were low , but showed a significant increase when the PPCP concentration was increased to 50 mg L! 1 . The depletion observed in cellular GSH could contribute to the PPCP-induced oxidative stress and detoxification of xenobiotics.

Meanwhile, the different responses of GSH in root and leaves indicated that roots may be the main site to express PPCP toxicity and induce PPCP detoxification. Given the dominance of GSH conjugates as observed for pesticides, it is possible that trace contaminants such as PPCPs may be removed similarly by GSH conjugation. It is therefore imperative to conduct further research to explore the mechanisms and pathways of PPCP phytotransformation by GSTs after uptake by plants.On the whole, the present study provided evidence that some PPCPs may be translocated systemically, and ultimately posed toxicity effects in higher plants. Oxidative stress response may reflect the intensity of PPCP treatment and sensitivity of plant species to PPCPs, and may be used as indicators for early plant response to trace organics introduced into agroecosystems. Furthermore, plants may detoxify PPCPs through different mechanisms, including enhanced antioxidant defense systems to prevent oxidative damage and increased activities of xenobioticmetabolizing enzymes. These mechanisms help maintain plant physiological, biochemical and molecular functional integrity, offering the possibility to use some of these endpoints as biomarkers for predicting phytotoxicity induced by PPCPs and likely other man-made chemicals. Further research is needed to evaluate the physiological and biological responses of plants in realistic field practices, such as irrigation with treated wastewater or fertilization with biosolids and animal wastes in agriculture.The Paharpur Business Centre and Software Technology Incubator Park is a 7 story, 50,400 ft2 office building located near Nehru Place in New Delhi India. The occupancy of the building at full normal operations is about 500 people. The building management philosophy embodies innovation in energy efficiency while providing full service and a comfortable, safe, healthy environment to the occupants. Provision of excellent Indoor Air Quality is an expressed goal of the facility, and the management has gone to great lengths to achieve it. This is particularly challenging in New Delhi, where ambient urban pollution levels rank among the worst on the planet.

The approach to provide good IAQ in the building includes a range of technical elements: air washing and filtration of ventilation intake air from rooftop air handler, the use of an enclosed rooftop greenhouse with a high density of potted plants as a bio-filtration system, dedicated secondary HVAC/air handling units on each floor with re-circulating high efficiency filtration and UVC treatment of the heat exchanger coils, additional potted plants for bio-filtration on each floor, and a final exhaust via the restrooms located at each floor. The conditioned building exhaust air is passed through an energy recovery wheel and chemisorbent cartridge, transferring some heat to the incoming air to increase the HVAC energy efficiency. Flooring is a combination of stone, tile and “zero VOC” carpeting. Wood trim and finish appears to be primarily of solid sawn materials, with very little evidence of composite wood products. Furniture is likewise in large proportion constructed from solid wood materials. The overall impression is that of a very clean and well-kept facility. Surfaces are polished to a high sheen, probably with wax products. There was an odor of urinal cake in the restrooms. Smoking is not allowed in the building. The plants used in the rooftop greenhouse and on the floors were made up of a number of species selected for the following functions: daytime metabolic carbon dioxide absorption, nighttime metabolic CO2 absorption, and volatile organic compound and inorganic gas absorption/removal for air cleaning. The building contains a reported 910 indoor plants. Daytime metabolic species reported by the PBC include Areca Palm, Oxycardium, Rubber Plant, and Ficus alii totaling 188 plants . The single nighttime metabolic species is the Sansevieria with a total of 28 plants . The “air cleaning” plant species reported by the PBC include the Money Plant, Aglaonema, Dracaena Warneckii, Bamboo Palm, and Raphis Palm with a total of 694 plants .

The plants in the greenhouse numbering 161 of those in the building are grown hydroponically, with the room air blown by fan across the plant root zones. The plants on the building floors are grown in pots and are located on floors 1-6. We conducted a one-day monitoring session in the PBC on January 1, 2010. The date of the study was based on availability of the measurement equipment that the researchers had shipped from Lawrence Berkeley National Lab in the U.S.A. The study date was not optimal because a large proportion of the regular building occupants were not present being New Year’s Day. An estimated 40 people were present in the building all day during January 1. This being said, the building systems were in normal operations, including the air handlers and other HVAC components. The study was focused primarily on measurements in the Greenhouse and 3rd and 5th floor environments as well as rooftop outdoors. Measurements included a set of volatile organic compounds and aldehydes, with a more limited set of observations of indoor and outdoor particulate and carbon dioxide concentrations. Continuous measurements of Temperature and relative humidity were made selected indoor and outdoor locations. Air sampling stations were set up in the Greenhouse, Room 510, Room 311, the 5th and 3rd floor air handler intakes,growing strawberries hydroponically the building rooftop HVAC exhaust, and an ambient location on the roof near the HVAC intake. VOC and aldehyde samples were collected at least once at all of these locations. Both supply and return registers were sampled in rooms 510 and 311. As were a greenhouse inlet register from the air washer and outlet register ducted to the building’s floor level. Air samples for VOCs were collected and analyzed following the U.S. Environmental Protection Agency Method TO-17 . Integrated air samples with a total volume of approximately 2 L were collected at the sites, at a flow rate of <70 cc/min onto preconditioned multibed sorbent tubes containing Tenax-TA backed with a section of Carbosieve. The VOCs were desorbed and analyzed by thermodesorption into a cooled injection system and resolved by gas chromatography. The target chemicals, listed in Table 1, were qualitatively identified on the basis of the mass spectral library search, followed by comparison to reference standards. Target chemicals were quantified using multi-point calibrations developed with pure standards and referenced to an internal standard. Sampling was conducted using Masterflex L/S HV-07553-80 peristaltic pumps assembled with quad Masterflex L/S Standard HV-07017-20 pump heads. Concentrations of formaldehyde, acetaldehyde, and acetone were determined following U.S. Environmental Protection Agency Method TO-11a . Integrated samples were collected by drawing air through silica gel cartridges coated with 2,4-dinitrophenylhydrazine at a flow rate of 1 Lpm. Samples utilized an ozone scrubber cartridge installed upstream from the sample cartridge. Sample cartridges were eluted with 2 mL of high purity acetonitrile and analyzed by high-performance liquid chromatography with UV detection and quantified with a multi-point calibration for each derivitized target aldehyde. Sampling was conducted using Masterflex L/S HV-07553-71 peristaltic pumps assembled with dual Masterflex L/S Standard HV-07016-20 pump heads. Continuous measurements of PM2.5 using TSI Dustrak model 8520 monitors were made in Room 510 and at the rooftop-sampling site from about 13:30 to 16:30 of the sampling day. The indoor particle monitor was located on a desk in room 510 and the outdoor monitor was located on a surface elevated above the roof deck. Carbon dioxide spot measurements of about 10-minute duration were made throughout the building during the afternoon using a portable data logging real-time infrared monitor . Temperature and RH were monitored in the Greenhouse, room 510 and room 311 using Onset model HOBO U12-011 data loggers at one-minute recording rates. Outdoor T and RH were not monitored. The measured VOC concentrations as well as their limits of quantitation by the measurement methods are shown in Table 2. Figures 1-6 show bar graphs of these VOCs. Unless otherwise shown, all measured compounds were above the minimum detection level, but not all measurements were above the LOQ.

Those measurements with concentrations below the LOQ should be considered approximations. These air contaminants are organized by possible source categories including: carbonyl compounds that can be odorous or irritating; compounds that are often emitted by building cleaning products; those associated with bathroom products; those often found emitted from office products, supplies, materials, occupants, and in ambient air; those found from plant and wood materials as well as some cleaning products; and finally plasticizers commonly emitted from vinyl and other flexible or resilient plastic products. The groupings in this table are for convenience; many of the listed compounds have multiple sources so the attribution provided may be erroneous. The carbonyl compounds include formaldehyde that can be emitted from composite wood materials, adhesives, and indoor chemical reactions; acetaldehyde from building materials and indoor chemistry; acetone from cleaners and other solvents. Benzaldehyde sources can include plastics, dyes, fruits, and perfumes. Hexanal, nonanal, and octanal can be emitted from engineered wood products. For many of these compounds, outdoor air can also be a major source. Formaldehyde and acetone were the most abundant carbonyl compounds observed in the PBC. For context, the California 8-h and chronic non-cancer reference exposure level for formaldehyde is 9 µg m-3 and the acute REL is 55 µg m-3 . The 60 minute average formaldehyde concentrations observed in the PBC exceeded the REL by up to a factor of three. Acetone has low toxicity and the observed levels were orders of magnitude lower than concentrations of health concern. Hexanal, nonanal, and octanal are odorous compounds at low concentrations; odor thresholds established for them are 0.33 ppb, 0.53 ppb, and 0.17 ppb, respectively . Average concentrations observed within the PBC building were 3.8±0.8 ppb, 3.5±0.6 ppb, and 1.4±0.2 ppb, for these compounds, respectively, roughly ten times higher than the odor thresholds. Concentrations of these compounds in the supply air from the greenhouse were substantially lower, although stillin excess of the odor thresholds. The concentration of hexanal and nonanal roughly doubled the ambient concentrations as the outside air passed through the greenhouse. Octanal concentrations were roughly similar in the ambient air and in the air exiting the greenhouse. Concentrations of benzene, d-limonene, n-hexane, naphthalene and toluene all increased in the greenhouse air in either the AM or PM measurements. The measured levels of these compounds were far below any health relevant standards, although naphthalene concentrations reached close to 50% of the California REL of 9 µg m-3 . The concentrations of these compounds were generally somewhat higher indoors relative to the greenhouse concentrations.

Maximum concentrations of N2O were observed in the soil at 10–15 cm, shallow depths where lateral diffusion away from the dripper could only account for a small loss of N2O compared with losses to the atmosphere. It was also observed that water tended to flow laterally, past the surface wetting front, through a sandy horizon above a clayey horizon which begins at around 50 cm depth, also diminishing net lateral gas diffusion. The model is highly sensitive to variability in N2O concentration data, and at the plot level the calculations showed fluctuations between production and consumption by depth which were not plausible or consistent.Where possible, curves were fit to the concentration data of the form N2O conc = ae, which provided the dc/dz terms. Furthermore, concentrations of N2O measured at 5 cm were generally much lower than at 10 cm and led to frequent estimates of net consumption near surface. It was deemed likely that these samples had been contaminated by atmospheric air. Production of N2O at 10 cm was therefore calculated with reference to ambient N2O concentrations at 0 cm instead of the 5 cm concentration data. Measurements spaced several hours apart determined that an average 4.4% of total production was accounted for by change in concentration over time during the measured days. Ultimately no treatment statistics could be reported with the profile production data, but the model revealed general patterns and treatment effects on the depths of N2O production. The highest emissions, which were seen in summer and fall,hydroponics growing system were associated with the most consistent patterns of N2O distribution in the soil profile. Results from Days 2, 3 and 4 after fertigation, not shown, had similar distributions to those measured on Day 1, although with a slightly higher fraction of N2O concentrated in the deeper soil, 40–60 cm.

The relative stability in depths of production was seemingly contradictory to the changes in N distribution seen in soil solution ; but it was notable that distribution of extractable N , showed less change at the same points . N2O concentration patterns under most days and treatments were bimodal, with a shallow peak at 10–15 cm and a deeper peak around 45–60 cm, in the zone of higher clay content. The deeper peaks were sometimes strong 3–4 days after fertigation, especially in the Standard UAN treatment, illustrating the deeper distribution of N under higher rates of UAN application. Calculations in UAN treatments after winter typically showed points of highest production at 10–15 cm depth, usually underlain directly by the points of greatest consumption, at 15–20 cm . The calculations for 20 and 30 cm might underestimate production, because of more significant lateral diffusion of N2O around 30 cm, where WFPS generally declined . Production was seen at the lower peaks around 45 cm, but calculations suggested that N2O produced in these lower peaks was generally consumed before reaching surface , consistent with the findings of Neftel et al. . This helps to explain why emitted N2O was less per unit applied in Standard UAN than in HF UAN. Calculations in HF NO3 profiles generally showed much lower net N2O production/consumption than the UAN treatments. This is credited to the more even distribution throughout the soil of applied NO3, vertically and laterally, which led to low concentrations. Production profiles further suggest that a high proportion of the N2O produced in this treatment was consumed before it could be emitted from the surface. Overall, surface emissions of N2O decreased more quickly over the days following fertigations than did soil gas concentrations and calculated in-soil production rates, suggesting greater importance of production near surface during the first and second days. Under the driest conditions, seen on Day 3 after fertigation in late summer, increased N2O concentrations at 60 and 80 cm were concurrent with the lowest post-fertigation surface emissions. Calculations of N2O production for that date showed consumption at 45 cm in both HF treatments , supporting the conclusion that N2O produced deeper was being consumed at points immediately above, as well as possibly diffusing downwards.

Although the averaging of soil gas profiles by treatment limited the options for statistical analysis, the factors driving N2O production in the soil could still be assessed. Multiple linear regressions of surface emissions and of production at 15, 30 and 60 cm were carried out using calculated N2O production per treatment per day at those depths, and the corresponding averaged NH4 + in solution, NH4 + in soil extracts, NO3 in solution, NO3 in soil extracts, WFPS and temperature. Treatments were pooled because the dataset was limited within each treatment and the differences seen when HF NO3 was separated were minor. Regressions had little predictive capability at 30 and 60 cm depth. Nevertheless, it was notable that WFPS had negative coefficients at both depths, indicative of more complete denitrification with greater soil moisture. At 15 cm, the Adjusted R2 was only 0.14 but several alternative analyses gave better predictions. When excluding negative production values, an Adj. R2 of 0.58 was seen, which rose to 0.68 when reduced to extractable NH4 + , WFPS and temperature. If production at 10 cm was averaged with that at 15 cm, most negative values were eliminated, and using all data and variables the Adj. R2 was 0.21, or 0.26 with extractable NH4 + , NO3 in solution, WFPS and temperature. These results caused some questioning of the calculations of N2O production and consumption, which were volatile even in averaged forms, so regressions were carried out with soil gas concentrations as well. At 15 cm, all variables regressed to Adj. R2 of 0.26; reduced to NH4 + , WFPS and Temperature, the Adj. R2 was 0.32. Concentration averaged between 10 and 15 cm had an Adj. R2 of 0.41, while reduced to NH4 + , WFPS and Temperature, the Adj. R2 was 0.49. Regression of surface emissions followed the same pattern, being compared to NH4 + and NO3 in soil extracts at 2.5 cm depth, WFPS and temperature, where NO3 was found insignificant. The adjusted R2 of this regression is not reported because it is less complete than the analyses above. The superior predictive capability of extractable NH4 + at 15 cm and near surface was unexpected, since it is usually assumed that only the NH4 + in solution is available for microbial consumption .

However, little relevant investigation has been done in soils and the question can be raised whether microbial foraging on clays can desorb ammonium .The persistence of input effects on the functioning of the soil microbial community is an important agro-ecological concern. Here several assays of nitrification and denitrification capacity tested for persistent treatment effects which could influence N2O emissions. Soils were collected in late August after a month of irrigations without fertilizer. Treatment differences were of interest, not the comparison of assay results to field rates. The most ready metric of a soil’s denitrification response to NO3 amendments is its denitrification enzyme activity ,hydroponic equipment designed to assess soil process rates before they are affected by the synthesis of additional enzymes. Since fertigation applications make a large amount of NO3 available in a short time, the preevent DEA of a soil may play a significant role in denitrification derived N2O emissions. Results showed very similar N2O production by the two HF treatments in a DEA assay, which were significantly higher than Standard UAN . Over 24 h, characterized as Denitrification Potential , this initial difference was persistent, although it lost statistical significance. Given that drip fertigation saturated zones are not entirely dissimilar from the conditions of these assays, it was expected that DEA and DP modified with acetylene might also suggest differences in the product ratio of denitrification in the field treatments. Results were inconclusive, with widely dispersed values. Rates of ammonium oxidation to nitrite, as an index of nitrification potential, supported the importance of frequency and rate of NH4 + application, HF UAN > Standard UAN > HF NO3, but differences were only significant between the HF UAN and HF NO3 treatments . Strict chemoautotrophs typically dominate nitrification in cropped soils , and their numbers are more likely to be affected by availability of NH4 + than are the heterotrophs largely responsible for N2O emission through denitrification. Higher amounts of available nitrite are known to stimulate nitrifier denitrification and associated N2O losses , so a persistent effect of NH4 + application on ammonium oxidation to nitrite could increase N2O emissions under HF fertigation. Ammonium oxidation and DEA assays are predicated upon standard conditions, the former being oxic, open, shaken slurry, and the latter completely anoxic.

Actual oxygen availability in drip zones may cover a wide range between those points, but is expected to be limited. Little data is available, but Gil et al. found 4.97% O2 in the sampled soil air of a clay loam in an avocado orchard under drip. It can be assumed that many surfaces within larger aggregates would have lower O2 , being well suited for nitrifier denitrification, which takes place at <5% O2, while denitrification requires <0.05% O2 . It was therefore deemed useful to test the persistent effects of HF fertigation on potential soil production of N2O at 3% O2 . The only treatment differences were in microcosms with NO3 amendments , where N2O was presumably derived mainly from denitrification inside aggregates, supporting DEA results . The lack of HF treatment effects with NH4 + may be due to high rates of adsorption on soil surfaces expected with this N source , leading to gradual liberation. Nevertheless, emissions of N2O with NH4 + amendments were higher than those with NO3, confirming the large potential contribution of nitrifier denitrification from drip zones. The alternative explanation, being a general, rapid turnover from nitrifier-produced NO2 and NO3 to denitrifier produced N2O, has not consistently been supported by isotopic studies in laboratory . Assessments of N2O/ product ratio using acetylene in DEA, DP, and 3% O2 incubation assays did not give robust support to the hypothesis that greater microbial capacity for nitrification and/ or denitrification should correlate to a higher portion of complete reduction of N to N2 . It must be noted that N2O is more likely to be reduced to N2 when NO3 is limited , which it was not in the DEA test and DP tests. Further, the reduction of N2O to N2 dominates under anoxic conditions , which were not prevalent in the 3% O2 test. The factors affecting the “completeness” of nitrifier denitrification to N2 have been little studied and may be distinct from those affecting denitrifier denitrification. Lastly, tests of residual NO3
suggested that acetylene may have slightly inhibited NO3
reduction. The comparison of N2O from HF UAN with a HFNO3
-based treatment including Ca2 raises the question of whether differences may be ascribable to the opposite pH effects of the fertilizers. HF Ca2 + KNO3 did produce a significantly higher pH than HF UAN within 6 months of the treatment’s inception . This could partly explain lower N2O emissions from the HF NO3 treatment , but the effectis likely not a strong one because all were in neutral range . Our observation of 2.0 greater N2O emissions from HF UAN than from HF NO3 agrees well with Abalos et al. , who saw 2.4 greater N2O emissions from urea than from calcium nitrate in a drip-fertigated melon field in Spain. The greater predictive capacity of extractable NH4 + over NO3
provided evidence of a high contribution of nitrifier denitrification to N2O emitted in the field. This was supported by laboratory tests of our field soils at 3% O2, and concurred with findings by Vallejo et al. , as well as by Sanchez-Martin et al. , who calculated that with dripfertigated ammonium sulfate, 45% of N2O came from nitrification. Considering both field and laboratory data, frequency effects in the application of UAN were only seen in nitrate denitrification rates and in N present at 60 cm depth. Nitrifier capacities do not seem to have been affected, due perhaps to the adsorption of fertilizer NH4 + and its gradual release over time. Still, rates of nitrifier denitrification in the field may have seen concentration effects, as a corollary of frequency differences.

Based on the results, we propose the presence of quantitative trait locus or loci for root traits in the distal 15% of the physical length of 1RS arm. In cereals, most of the gene rich regions for agronomic traits are concentrated in the distal ends of the chromosomes . Kim et al. conducted Weld studies for the agronomic performance of 1R from different sources of origin. They found 1RS increases the grain yield significantly, and interestingly, all the lines with 1RS did not show significant differences for shoot biomass. They did not look at the root traits, which could have also been useful. In a similar study, Waines et al. compared 1RS from different sources to study root biomass in hexaploid as well as tetraploid wheats. The translocated hexaploid wheats with 1RSAmigo and 1RSKavkaz showed 9 and 31% increase in root biomass than Pavon 76, respectively. Similar results were reported for the durum wheat ‘Aconchi’ versus Aconchi with the 1RS arm. These studies point toward the definite presence of gene for greater rooting ability on 1RS, and also the differential expression of alleles from different sources of 1RS in root traits. In a recent study on rice root anatomy, Uga et al. identified a QTL for metaxylem anatomy on the distal end of the long arm of chromosome 10. In another comparative study of rye DNA sequences with rice genome, the distal end of the long arm of chromosome 10 of rice was syntenic to 1RS . Both these studies provide evidence to support the general applicability of our mapping method to locate the probable region on 1RS,hydroponic grow system carrying gene/QTL for root traits. Our present finding on root studies prepares a platform to find gene/QTL for root traits on 1RS.

Future work will focus on use of a larger number of recombinant lines to narrow down the QTL region of 1RS responsible for increased root traits and find the molecular markers linked to these QTL. Ultimately, this would lead to our goal of physical mapping and then positional cloning of the root QTL.The increasing use of NPs in commercial products has led to NP-accumulation in the environment and within the food chain.Chronic exposure to NPs can lead to health issues as some inorganic NPs have biological activity at the cellular and sub-cellular level with an unknown cytotoxicity and genotoxicity.In particular, metal oxide NPs are the most abundant form of NP in the environment with the most potential toxic risks.Locating, quantifying, and imaging NPs in vivo can provide information on bio-distribution and fate of NPs in living systems.However, many challenges to quantitatively assess their bio-distributions under realistic environmental exposure concentrations remain.To date, the visualization of most NPs within plants has relied on the use of micro-X-ray fluorescence spectrometry , confocal microscopy, TEM, SEM, scanning transmission electron microscopy , or scanning transmission ion microscopy .The most prominent quantification techniques have been inductively coupled plasma spectroscopy utilizing either optically emission spectroscopy or mass spectrometry .These techniques required mineralization of the plant material generally with hydrogen peroxide and nitric acid, and may not be sufficiently sensitive enough to quantify small changes in the amount of a metal ion.Notably, high background concentrations of essential nutrients make detecting and quantifying the small variation in NP-related metal ion content an analytical challenge as the measurement is often of the same magnitude as noise or at the detection limit.

Optically tagged NPs have also been investigated, but the challenge of overcoming the plants’ own bioluminescence can make quantification difficult.Although used in medical imaging, radio labeled NPs for noninvasive tracking and quantification in plants have not been significantly explored.Prior radio labeling of NPs for medical imaging has utilized three main approaches: post radio labeling via attachment of chelator to NPs first, then reaction with the a metal radio nuclide; preradiolabeling, where a radioactive prosthetic group, a small molecule that the radioisotope is attached, followed by attachment to the NP; and direct radio labeling.Of these three main radio labeling approaches, the third approach has been the only method used to study NP distribution in plants where Zhang et al.reported the use of [141Ce]CeO2-NPs produced via neutron bombardment of CeO2-NPs to study distribution in cucumbers. The produced radionuclide 141Ce has a 32.51 day half-life, and the specific activity of the synthesized [141Ce]CeO2-NPs was 2.7 μCi/mg of NP.Despite numerous approaches to analyze NPs, a combination of technologies is required due to the low detection limits and high resolution needed to address the intact nature of NP-transport into plants. Thus, multiple tools must be utilized to quantify and determine the intact nature of NPs at a given location within biological environments .Previous studies have provided conflicting evidence about the intact nature of NP uptake and transport into plants: some studies indicated intact NP uptake and vascular transport,some observed NPs in plants due to dissolution events and reformation within the plant tissue,and still others have indicated that NPs cannot be transported into plants.These varied observations could be linked to inadequate techniques available to track NP movement in vivo. The main challenge in determining intact NP transport into plants is ruling out NP dissolution, as reductive precipitation and formation of NPs within plant tissue has been documented.Even natural formation of NPs within plants and fungi is known.

Further complicating the picture is the fact that many studies assessing NP uptake exposed plants over long periods of time from 2 to 130 days, with very large amounts of NPs per plant, which could make dissolution events more prevalent.Avoiding excessive exposure to the NPs and carefully analyzing the stability of the administered NPs are key to avoid erroneous conclusions due to NP-dissolution and subsequent reformation. In this study we evaluated an analytical method using a radioactive label to non-invasively track and quantify transport and accumulation of NPs in lettuce seedlings in vivo. This method studied NP-size dependent transport immediately upon exposure , an early time frame that has rarely been explored in plants.The visualization of NP transport and accumulation in lettuce seedlings was done by autoradiography and PET/CT imaging and further confirmed by gamma-counting, SEM, and TEM. Our study was designed to use highly uniform NPs of two size sets , which were theoretically too large for passive transport across plant tissues.To ensure a narrow size distribution with a uniform geometric shape and the ability to thoroughly investigate stability , a preradiolabeling method with the PET-radioisotope copper-64, the “clickable” chelator ADIBO-NOTA, and commercially available spherical Fe3O4- NPs containing azides was explored. This radio labeling approach yielded a high specific activity and allowed for size characterization of the NPs after the plant accumulation and imaging period, and avoided complication from fabricating radioactive NPs and production of less stable NP material with a larger size distribution. Rigorous stability studies were carried out at a variety of pHs to investigate possible dissolution of the 64Cu-radiolabeled NPs and substantiate the intact nature of NP-transport into lettuce seedlings.To date the uptake, bio-accumulation, bio-transformation, and risks of NPs in food crops is not well understood.Most studies on NP uptake in plants have focused on the effects of NPs on plants, and have not focused on the transport or entry of intact NPs. Several studies concluded that NPs do not gain entry into plants,vertical grow rack while those that do show NP uptake in plants have found the NP amounts to vary widely between 0.05 μg/g and 38983 μg/g of plant.In vivo tracking of NP transport in plants has traditionally relied on destructive analytical techniques to quantify NP-uptake and accumulation, requiring mineralization for metal quantification mostly by ICP.These analytical techniques face the challenge of being sensitive enough to reliably measure the small changes in metal concentrations caused by NP-uptake and accumulation within the plant. The extensive range of NP accumulation reported in plants suggests that NP-uptake is dependent on several parameters: quantity of NP administered per plant, plant species, NP-size, NP-composition, and duration of exposure.Further complicating the understanding of NP transport and accumulation in plants are the studies that have observed NP-uptake due to dissolution.Collectively the variations of parameters in every study on NP transport in plants have made direct comparison and accurate conclusions challenging. Thus, it was our goal to develop a noninvasive visualization approach to track and quantify the distribution of intact radiolabeled [ 64Cu]-NPs in lettuce seedlings. Using 64Curadioactively tagged NPs, we employed a range of complementary noninvasive analytical tools including autoradiography and PET/CT imaging to spatially and temporally visualize and quantify intact-NP uptake and accumulation in plants. The stability study described demonstrates dissolution of the [ 64Cu]-NPs did not occur. Ligand effects on NP mobility within the lettuce was minimized by modification of ≤5% of the NP surface with [64Cu]-ADIBO-NOTA as to negligibly change the NP surface properties.

No ligand detachment or leaching of 64Cu-ion from the NPs within the imaging time frame and at various pHs was observed, by both HPLC and gamma counting analysis, indicating that the radioactive signal in the lettuce seedlings was due to intact [64Cu]-NPs. Additionally, indirect evidence further supported that the observed uptake was from intact [64Cu]-NPs as control lettuce seedlings given only [64Cu]CuCl2 had much higher radioactivity with 4-fold higher concentrations in the cotyledons and 10-fold higher concentrations in the root . These control plants also had visibly higher amounts of radioactivity in each part of the plant by autoradiography images suggesting that if the observed radioactivity was due to [64Cu]CuCl2, then the uptake should be much higher. Furthermore, the use of covalently bound optical-tagged NPs also exhibiting high stability and illustrated the same NP movement from the root to the cotyledon . Thus, helping to substantiate that NP-uptake and transport to the cotyledon was from intact NPs. TEM-sectioning of the plant tissue also helped to corroborate the presence of NPs within the plant tissue . It should be noted that detection of NPs within plant tissue via TEM is challenging,but based on our stability studies of the 64Cu-radiolabeled NPs along with the short exposure time that the observed uptake was attributed to intact [64Cu]-NP transport through the roots and into the cotyledons. This study has shown that NPs were transported intact into plants and can be tracked non-invasively using a radioactive tag for in vivo imaging by autoradiography and PET/CT and quantification using a gamma counter. This method allows for a highly sensitive method capable of quantifying NP amounts in an individual seedling, a level that would be challenging by the traditional ICP quantification.However, different accumulation patterns for the cotyledons were observed for the two different sized [64Cu]- NPs , while the root and whole plant were similar . Most of the accumulation for the larger [ 64Cu]-NPs was within the first hour, where cotyledon NP amounts were ∼0.35 ± 0.15 μg/g with the only significant increase after 1 h between the 12 and 24 h time point in which accumulation plateaued at around ∼0.7 μg/g . The larger [64Cu]-NPs also had higher accumulation than the [64Cu]-NPs at the early time points up to the 4 h time period. The smaller [64Cu]-NPs had ∼8.8 fold increase in cotyledon accumulation from the 4 h time point to the 24 h time point with an increase of ∼1.6 fold between 12 and 24 h time period appearing to have a linear increase in absorption over time. The differences in cotyledon accumulation between the two sized [ 64Cu]-NPs maybe linked to NP size effects on the lettuce hydraulic conductivity. Our work suggests that [64Cu]-NPs around 20 nm in size appear to clog root cortical cell walls, or pit membrane preventing further uptake, explaining why 11 reaches a plateau, while the smaller [64Cu]- NPs continued to increase in amount over time. Initial studies with duckweed also illustrated [64Cu]-NP accumulation in regions of growth and at the node and apex of the cotyledons , suggesting that [64Cu]-NP transport to the cotyledons could occur via the phloem. The TEM images further shows the appearance of intact NPs in the lettuce tissue within the expected size range for the [64Cu]-NPs , but [64Cu]-NPs had a size that appeared smaller than those administered; suggesting that the plant may filter larger NPs and has a size-threshold for uptake , which may also explain the clogging phenomenon.In summary, the combined analysis of the imaging by autoradiography and PET/CT and TEM suggested that both sized [64Cu]-NPs are transported intact from the root to the cotyledons.

Antisense suppression of NtAQP1 in tobacco lowered the level of expression of several PIP1 homologues and resulted in a significant decrease in protoplast membrane water permeability, reduced root hydraulic conductivity and decreased transpiration. The results of heterologous expression in Xenopus oocytes suggest that, in addition to functioning as a water channel, NtAQP1 is also a membrane CO2 pore that facilitates the transport of CO2 across membranes. The movement of CO2 between the substomatal cavities and the sites of carboxylation within chloroplasts, through plasma and chloroplast membranes, is generally termed leaf mesophyll conductance. The ability of NtAQP1 and its Arabidopsis homolog AtPIP1,2 to function as CO2 membrane transport facilitators has been demonstrated in in vivo experiments. Increased expression of NtAQP1 in tobacco plants enhanced CO2 incorporation and stomatal conductance; whereas antisense suppression of NtAQP1 had the opposite effect. In other studies, over expression of AtPIP1,2 or NtAQP1 in tobacco plants significantly enhanced the rates of growth, transpiration and photosynthesis; whereas antisense suppression of NtAQP1 in tobacco plants and T-DNA insertion Arabidopsis mutants in AtPIP1,2 reduced gm and led to lower rates of photosynthesis. Unlike NtAQP1, over expression of Arabidopsis hexokinase in Arabidopsis and tomato plants decreased photosynthesis, transpiration and growth. AtHXK1 is a sugar sensing enzyme that monitors glucose levels, hydroponics growing system most likely in mesophyll cells of photosynthetic tissues.

When glucose levels are sufficiently high, this enzyme inhibits the expression of photosynthetic genes, decreases chlorophyll levels and reduces the rate of photosynthesis. In addition, AtHXK1 also stimulates stomatal closure and decreases transpiration in response to increasing sugar levels. In light of the opposite effects of AtHXK1 and NtAQP1 on photosynthesis and growth, we examined the relationship between AtHXK1 and NtAQP1 using double transgenic plants that express AtHXK1 and NtAQP1 simultaneously. We found that NtAQP1 significantly compensated for the growth inhibition imposed by AtHXK1, primarily by enhancing mesophyll CO2 conductance and the rate of photosynthesis, while the hydraulic conductivity in those plants remained unchanged.The hydraulic conductance of the tomato root system was assessed using plants grown hydroponically and was determined by measuring the flow induced in response to 1 bar of applied pressure. De-topped root systems were fitted with a plastic tube filled with deionized water and connected to a beaker located on a balance . The root system was sealed in a chamber containing the hydroponic solution in which the plants had been grown. The pressure in the chamber was regulated using a needle valve, which was adjusted to allow a small leak into the chamber, so that the air used to pressurize the chamber also served to aerate the medium. Water flow through the root system was automatically recorded by a computer at 30 s intervals. At the end of each experiment, the roots were dried in an oven for 72 h at 90uC and the dry weight of the root system was then measured.Whole-plant transpiration rates and relative daily transpiration were determined using lysimeters, as described in detail by Sade et al.. WT, AQP1, HK4, AQP1xHK4 and grafted plants were planted in 3.9-L pots and grown under controlled conditions. Each pot was placed on a temperature-compensated load cell with digital output and was sealed to prevent evaporation from the surface of the growth medium. A wet, vertical wick made of 0.14 m2 cotton fibers partially submerged in a 1-L water tank was placed on a similar load cell and used as a reference for the temporal variations in the potential transpiration rate. The output of the load cells was monitored every 10 s and the average readings over 3-min intervals were logged in a data logger for further analysis.

The whole-plant transpiration rate was calculated as a numerical derivative of the load cell output following a data smoothing process.Over expression of NtAQP1 in tobacco plants enhanced leaf mesophyll CO2 conductance , hydraulic conductivity, stomatal conductance , transpiration and photosynthesis. Expression of NtAQP1 in tomato plants also enhanced photosynthesis, stomatal conductance and transpiration. However, in our study, NtAQP1 did not enhance photosynthesis, stomatal conductance or hydraulic conductivity relative to WT plants and enhanced transpiration only slightly . These differences may be due to the different tomato genotype used in our study or to different expression levels of NtAQP1. Nevertheless, photosynthesis, stomatal conductance and transpiration were elevated by NtAQP1 in the double-transgenic plants , as compared to the HK4 parental line. Yet, the hydraulic conductivity of AQP1xHK4 remained low as in the HK4 plants, implying that the increased transpiration that was observed is not directly related to hydraulic characteristics. Rather, the increased transpiration is most likely due to high gm values in the mesophyll, which opens stomata and increases the influx of CO2 to help maintain constant levels of Ci in the sub-stomatal cavity. High levels of AN, gs and gm, accompanied by constant Ci , were also reported in previous studies of tobacco plants over expressing NtAQP1. AtHXK1 is a sugar-sensing enzyme that inhibits the expression of photosynthetic genes, decreases chlorophyll levels and reduces the rate of photosynthesis in response to increasing sugar levels. As a result, tomato and Arabidopsis plants with high levels of AtHXK1 expression display severe growth inhibition directly correlated to AtHXK1 expression and activity levels. It is likely that part of the growth inhibition imposed by AtHXK1 is the result of insufficient photosynthesis, since the increased photosynthesis rate observed in AQP1xHK4 plants partially eliminated this growth inhibition. The increased rate of photosynthesis observed in AQP1xHK4 plants, despite the low level of expression of the photosynthetic gene CAB1 in those plants, can probably be attributed to NtAQP1, which accelerates CO2 mesophyll conductance.

The CO2 mesophyll conductance of HK4 plants is significantly lower than that of WT plants and is enhanced by simultaneous expression of NtAQP1, indicating that CO2 mesophyll conductance significantly affects growth. It appears that, in addition to its known sugar-sensing effect , AtHXK1 also reduces gm, perhaps by reducing the expression of TRAMP , the tomato homolog of NtAQP1. Indeed, lower gm levels have been observed in tobacco NtAQP1 antisense lines and Arabidopsis pip1;2 mutants . In those studies, the decrease in gm was accompanied by lower Cc. In agreement with the findings of those studies, the HK4 plants in our study exhibited lower Cc than the WT plants and the expression of NtAQP1in the double-transgenic plants led to full complementation of Cc . Interestingly, the HK4 plants had lower electron transport rates than the WT plants, while a clear recovery was observed in the AQP1xHK4 plants despite the low level of expression of the photosynthetic gene CAB1 in the AQP1xHK4 plants . It has previously been shown that expression level of NtAQP1 which affects gm levels also affects electron transport rates. Flexas et al. hypothesized that modified intercellular CO2 concentrations may trigger differences in the leaf photosynthetic capacity, so that the photosynthetic machinery can adjust to the change in mesophyll conductance. This would also explain why gm usually scales with photosynthetic capacity, as has been observed in broad comparisons of different species. The effect of AtHXK1 on gm suggests that HXK might coordinate photosynthesis with sugar levels by several mechanisms in different cell types. It inhibits expression of photosynthetic genes and reduces gm most likely in mesophyll photosynthetic cells. In guard cells HXK mediates stomatal closure in response to sugars and reduces stomatal conductance. These findings support the existence of a multilevel feedback-inhibition mechanism that is mediated by HXK in response to sugars. When sugar levels are high,hydroponic grow systems likely when the rate of photosynthesis exceeds the rate at which the sugar is loaded and carried by the phloem, the surplus of sugar is sensed by HXK in mesophyll and guard cells, which respond in concert to reduce both unnecessary investments in photosynthetic capacity and water loss. This response includes reducing the expression of photosynthetic genes, slowing chlorophyll production, diminishing mesophyll CO2 conductance and closing the stomata. In addition to these effects in shoots, HXK reduces the hydraulic conductivity of stem and roots via an as yet unknown mechanism. This reduction in hydraulic conductivity occurs independently of stomatal conductance, as it also happens in the double-transgenic plants that have WT levels of stomatal conductance . Nevertheless, grafting experiments indicate that neither over expression of AtHXK1 in roots nor expression of AtHXK1 in the stem has any visible physiological effects. Rather, over expression of AtHXK1 in shoots is necessary and sufficient to obtain a photosynthesis effect and growth inhibition. The dominant effect of AtHXK1, lowering hydraulic conductance in AQP1xHK4, might be the reason for the intermediate transpiration rate of AQP1xHK4 plants, which is lower than that of WT plants , despite the increase in stomatal conductance to levels similar to that of WT plants . It has been suggested that NtAQP1 might play independent roles in leaves and roots, a hydraulic role in roots and a membrane CO2 permeability role in shoots. The improved gm observed in the double-transgenic plants supports the notion that, in leaves, NtAQP1 functions as a CO2 transmembrane facilitator and that the complementation effect of NtAQP1 may be primarily attributed to its affect on CO2 conductance in leaf mesophyll. The roles of HXK and PIP1 in the regulation of photosynthesis, stomatal conductance and transpiration are well established. This study suggests that HXK and PIP1 together may influence these central properties of plant physiology and, eventually, plant growth.

Monoclonal antibodies represent the fastest growing class of therapeutics and have been especially beneficial in the treatment of cancer. Since the approval of the first anti-cancer monoclonal antibody in 1986, several innovations have improved the potency of monoclonal antibodies used in immunotherapies that offer increased drug efficiency and/or lower drug dosage for a specific treatment. Among them, glycan engineering of the oligosaccharides attached to Asn297 of the Fc region of the heavy chain has been shown to affect antibody-dependent cell-mediated cytotoxicity , complement dependent cytotoxicity , and binding to the neonatal Fc receptor, FcRn. specific oligosaccharides influence the affinity of the antibody Fc domain to Fc receptor present on effector cells resulting in altered biological functions. For example, the removal of terminal galactose residues on mammalian cell-derived antibodies lowered C1q binding, while ADCC activity is almost completely dependent on the presence or absence of fucose residues bound to the glycosylation core. Several approaches have been employed to manufacture a monoclonal antibody with a decreased or absent core fucosylation. One strategy is to use cell lines or organisms with modified glycosylation pathways. The alteration of the expression of key enzymes in the host glycosylation pathway such as the mammalian α1,6-fucosyltransferase, the plant α1,3-fucosyltransferase, the GDP -mannose 4,6-dehydratase, or the β1,4-N-Acetylglucosaminyltransferase III led to afucosylated antibodies with improved anti-tumor activity. This led to the approval of mogamulizumab and obinutuzumab in 2012 and 2013, respectively, both produced in glycoengineered mammalian cell lines. Another approach to alter the antibody glycosylation profile is to modify the culture conditions of the host cells by adjusting the growth environment or supplementing the media with inhibitors of enzymes in the glycosylation pathway such as N-butyldeoxynojirimycin , mannostatin A, swainsonine, or kifunensine. Kifunensine from the actinomycete Kitasatosporia kifunense 9482 inhibits class I α-mannosidases and blocks N-glycan synthesis at the Man8GlcNAc2 or Man9GlcNAc2 stage before the core fucose is added. In mammalian cell culture, kifunensine was successfully employed to produce protein with >90% high-mannose content. This effect was similar across many different proteins including antibodies, suggesting that this simple treatment could be applied broadly. Compared to other α-mannosidase I inhibitors, kifunensine is highly effective on mammalian cell culture without significantly affecting cell growth or protein yield, even at concentrations as low as 100 ng/mL culture. Similar to mammalian cell studies, kifunensine was used in conjunction with the Nicotiana benthamiana transient protein expression systems to produce proteins with >98% afucosylated high-mannose glycans. In plants, the non-human α1,3-fucose and β1,2-xylose residues are commonly added in the Golgi apparatus after mannose trimming by mannosidases in the endoplasmic reticulum. Upon kifunensine treatment, addition of α1,3-fucose and β1,2-xylose residues were not observed on the Man3 to Man9 structures. However, the amount of kifunensine used in these studies was at or above 1.16 µg/mL, which significantly increases production costs at the manufacturing scale. Kifunensine is currently being used to manufacture a recombinant glucocerebrosidase in HT1080 fibrosarcoma cells to treat type 1 Gaucher disease.

The productivity of rainfed farming is also affected by the selection of planting date, which often depends on the timing of the first effective rainfall events. For this joint soil-terrain-climate analysis, all regions with a growing season of two months or shorter were assigned a suitability value of zero and thus classified as unsuitable for agriculture. We then evaluated the capacity of land for rainfed farming by using a precipitation cut-of of 250 mm year−1 , which is often regarded as the minimum threshold for the rainfed farming . As shown in Table 1, the inclusion of the length of growing period and precipitation threshold into the analysis only slightly reduced the total area of high-quality lands from 5.8 to 5.4 million ha. This implies that most lands with suitable soil and terrain conditions also receive sufficient amount of moisture to sustain rainfed agriculture. On the contrary, the area of unsuitable lands increased from 39.7 to 112.9 million ha when precipitation and duration of growing season thresholds were superimposed on the soil and topographic constraints. This increase in unsuitable acreage was mainly driven by the demotion of lands from the very poor class to the unsuitable class . The addition of moisture constraints also reduced the area of medium suitability lands by 4.8 million ha. In summary, for the rainfed farming suitability analysis, 125 million ha of Iran’s land might be classified as poor or lower ranks whilst only 18 million ha meet the required conditions for the medium or higher suitability classes . The geographical distribution of these land classes is mapped in Fig. 4. Almost the entire central Iran ,growing strawberries vertical system and the vast majority of land area in the eastern , southeastern and southern provinces were found to be unsuitable for rainfed farming. Almost half the area of Khuzestan and three-quarters of Fars provinces were also characterized unsuitable. Over the entire east, only in the northern part of Khorasan Razavi province, is there a belt of marginally suitable lands satisfying the requirements of a potentially prosperous rainfed agriculture .

In the next step of the analysis, the suitability of land was scaled with the annual precipitation over the range of 100 to 500 mm year−1 . The lower limit is deemed to exclude the desert areas for agricultural use whilst the upper limit represents a benign moisture environment for the growth of many crops. This last analysis, here after referred to as precipitation scaling method, makes no assumption as to whether the cropping practices rely on rainfall or irrigation to satisfy crop water requirement and may thus represent a more comprehensive approach for agricultural suitability assessment. The same minimum length of growing period and soil/topographic constraints as with the two previous methods were used in this analysis. Compared to the rainfed agriculture analysis, the precipitation scaling method mainly changed the distribution of lands within the lower suitability classes . For example, a great proportion of lands within the unsuitable class was shifted up to the very poor and poor classes. This implies that, to a limited extent, irrigation can compensate for the below threshold precipitation . Nevertheless, water availability cannot necessarily justify agriculture in areas with low soil and topographic suitability. This has an important implication for water management in Iran that has a proven record of strong desire for making water available to drier areas through groundwater pumping, water transfer, and dam construction. The majority of high-quality lands , which also retains sufficient levels of moisture are located in the western and northern provinces of Iran . Kermanshah province accommodates the largest area of such lands followed by Kurdistan . High-quality lands were estimated to cover 33% and 21% of these two provinces, respectively. Other provinces with high percentages of high quality lands were Gilan , Mazandaran , West Azerbaijan , and Lorestan . For 17 provinces, however, high-quality lands covered less than 1% of their total area .To estimate the total area of croplands within each suitability class, we visually inspected 1.2 million ha of Iran’s land by randomly sampling images from Google Earth . The proportion of land used for cropping increased almost linearly with the suitability values obtained from the precipitation scaling method . Total cropping area in Iran was estimated to be about 24.6 million ha, which is greater than the reported value by the Iran’s Ministry of Agriculture. This authority reports the harvested area; hence, the fallow or abandoned lands are not included in their calculation of active agricultural area.

Our visual method, however, captures all lands that are currently under cultivation or had been used for cropping in the near past that are now in fallow or set-aside . The relative distribution of croplands amongst the suitability classes shows that about 52% of the croplands in Iran are located in areas with poor suitability or lower ranks as identified by the precipitation scaling method. Particularly concerning are the 4.2 million ha of lands that fall within the unsuitable class. Approximately 3.4 million ha of cropping areas occur in good and very good lands . However, no agricultural expansion can be practiced in these areas as all available lands in these suitability classes have already been fully exploited. Medium quality lands comprise 12.8 million ha of Iran’s land surface area , of which about 8.6 million ha have been already allocated to agriculture . Nevertheless, due to their sparse spatial distribution and lack of proper access, only a small portion of the unused lands with medium suitability can be practically deployed for agriculture. Using FAO’s spatial data on rainfed wheat yield in Iran, we estimated the mean yield for wheat cropping areas located within each of the six suitability classes. As shown in Fig. 7, the yield of the rainfed wheat increased proportionally with improving suitability index, showing that our suitability index adequately translates to crop yield. Using the observed yield-suitability relationship , we estimated that 0.8 million ton of wheat grain might be produced per year by allocating 1 million ha of the unused lands from the medium suitability class to rainfed wheat cropping.Whilst the insufciency of water resources has long been realized as a major impediment to developing a productive agriculture in Iran, our study highlights the additional limitations caused by the paucity of suitable land resources.Tat is, Iran as a member of Convention on Biological Diversity is obliged to fulfil Aichi Biodiversity Targets whose Target 11 requires Iran to expand its protected area to 17% by 2020, which is almost double the size of the current protected areas in Iran .

Agriculture also needs to compete with other types of land uses with urbanization being an important driver of agricultural land loss. By converting arable lands to a barren desert, desertification is a growing global concern, particularly in the MENA region and Iran. The redistribution of croplands from the low-quality lands to more suitable ones has potentials to improve crop yields and the sustainability of agriculture in Iran. A recent global-scale study concluded that by reallocating croplands to suitable environmental conditions, the global biomass production could increase by 30% even without any land expansion. However, reallocation planning requires accurate mapping of croplands, which is not currently available for Iran. Inefficient agricultural practices in unsuitable lands need to be avoided as they produce little yields at the cost of exacerbating land degradation and water scarcity problem. Our estimations shows that rainfed wheat production from a small acreage of 1.0 million ha in the medium suitability class can equal that from 5.5 million ha of lands in unsuitable or very poor areas . Although this conclusion may not hold for other crops grown in Iran,growing vegetables in vertical pvc pipe the wheat crop could be a good candidate to make such a generalization as wheat is the most widely cultivated crop in the country and is considered as a very low demanding plant, which has adapted to a broad range of contrasting environments. Redistribution of croplands, however, will not be a trivial task for both the Iranian decision makers and stakeholders due to various sociol-economic and logistic barriers. Lands found suitable for agriculture may not be easily accessible if scattered sparsely or occur in remote areas. Given the land and water limitations, increasing the crop production in Iran needs to be achieved through sustainable intensification, which has been found a promising approach for ensuring food security in several global-scale studies. As such, it is of vital importance for Iran to properly use its limited agricultural lands, improve water use efficiency, optimize crop pattern distribution, and adopt modern cultivation techniques. Practicing certain industrial agriculture methods in the unsuitable lands might be a viable strategy to sustainably maintain these lands in the agricultural sector while avoiding the potential socio-economic and political costs associated with redistribution of agricultural lands and farming populations. For example, protected agriculture can be established at some of these locations to cope with both land suitability and water availability constraints. While water insufficiency is a major limiting factor for both field and protected farming, the latter will be affected to a lesser extent. Our suitability assessment is based on a general set of requirements known to affect the productivity of a large number of crops, but there would exist crops with exceptional adaptive traits that can grow under less favourable conditions.

Although we used the most updated geospatial data at the finest available resolution, the result of our suitability analysis should be interpreted in commensuration with the reliability and quality of the original data. For example, whereas the GlobCover database reliably maps the distribution of forests and rangelands in Iran, our visual inspection of satellite images showed that sometimes their utilized method lacks the required precision to distinguish cultivated from uncultivated croplands. Although soil erosion was not directly incorporated into our analysis, the use of slope at the very high resolution implicitly accounts for this effect. The interaction between variables and the quality of subsoil are among other factors that can be considered in the future studies. This study used precipitation as the only water availability factor. Including surface water and groundwater availability can further improve the adequacy of the land evaluation analysis. Given the good correlation between water availability and land suitability for agriculture, the general findings of this study are not expected to change significantly by the inclusion of water availability conditions. Nevertheless, due to the current water shortage constraints across the country, the potential agricultural capacity of the country is likely to decrease when water availability is added to the analysis. Although global projections suggest that the suitable lands may expand with climate changes, how these changes, particularly in precipitation pattern, would affect the suitability of Iran’s land for crop production in the future is subject to high degree of uncertainty and needs further work.Atmospheric carbon dioxide has increased about 35% since 1800 , and computer models predict that it will reach between 530 and 970 ppm by the end of the century . This rise in carbon dioxide could potentially be mitigated by crop plants, in which photosynthesis converts atmospheric carbon dioxide into carbohydrates and other organic compounds. The extent of this mitigation remains uncertain, however, due to the complex relationship between carbon and nitrogen metabolism in plants . Carbon metabolism provides the energy and carbon molecules to synthesize organic nitrogen compounds in plants, whereas nitrogen metabolism provides the amino groups for all proteins . Proteins include all enzymes that catalyze biochemical reactions in plants, including carbon metabolism. Any environmental perturbation that interferes with nitrogen metabolism sooner or later inhibits carbon metabolism.The focal point of crop responses to rising carbon dioxide levels is the enzyme rubisco . Rubisco is the most prevalent protein on Earth and contains as much as half of the nitrogen in plant leaves. It catalyzes two different chemical reactions: one reaction combines a 5-carbon sugar RuBP with carbon dioxide, and the other reaction combines this same sugar with oxygen. The reaction of RuBP with carbon dioxide produces a 6-carbon compound that immediately divides into two molecules of a 3-carbon compound , hence the name C3 carbon fi xation .

During the cultivation, four independent samples were taken at a given time point for fresh and dry weight analysis, sugar analysis, and quantification of rrBChE and total soluble protein . The bioreactor run was terminated at day 5 following induction and the rice cell aggregates were allowed time to sediment . The culture medium was withdrawn from the bioreactor through a sampling port using a peristaltic pump and stored at 4 ◦C The bioreactor head plate was then opened. Rice cell biomass was collected and vacuum-filtered on Whatman Grade 1 . Fresh biomass was weighed and stored at −20 ◦C. Performing a media exchange using 1.25-times-concentrated sugar-free medium together with 1.25-times-reduced culture volume and addition of kifunensine prior to and after the media exchange resulted in increased total production levels of active rrBChE, volumetric productivity, and specific productivity by 1.5 times, 3.4 times, and 1.5 times, respectively, compared with a bioreactor run with same operating conditions but no kifunensine treatment. Moreover, kifunensine enhanced the excretion of recombinant rrBChE glycoprotein through the secretory pathway, leading to 44% of total rrBChE in the culture medium at day 5 following induction and increasing extracellular rrBChE purity to 1.6% rrBChE/TSP compared with 0.8% cell-associated rrBChE/TSP. Coomassie-stained SDS-PAGE and Western blot analyses showed different migration bands of rrBChE with and without kifunensine treatment due to different N-glycan structures. N-Glycosylation site-specific analysis revealed increased oligomannose glycans at site N57, N246, N341, and N455 in both purified cell-associated and culture medium-derived rrBChE in the presence of kifunensine, while the mass transfer limitation of kifunensine was thought to be the main reason for the weak inhibition of α-mannosidase I in this bioreactor study.

At the laboratory scale, we produced ~16 mg of rrBChE in a 2 L working volume during a 12-day batch run,vertical farming supplies corresponding to a volumetric productivity of 0.680 mg L−1 day−1 . A technoeconomic model developed for semicontinuous large-scale production of rrBChE at a higher volumetric productivity showed that the process could be cost-effective with a cost-of-goods sold of ~$660/gram, less than 3% of the estimated cost of plasma-derived hBChE at ~$25,000/gram. The addition of compounds to the culture medium to alter the function of glycan-modifying enzymes is the simplest method to modify N-glycan structure of a target glycoprotein compared to other methods. As a bio-processing approach, it does not require alteration of the primary amino acid sequence of the target protein , or time-consuming glycoengineering of the host that could impact cell growth or viability, yet still allows secretion of the product into the culture medium. For example, adding kifunensine for N-glycan modification is a simple and effective way of obtaining oligomannose glycoproteins with reduced plant-specific xylose and fucose moieties. However, this method may not be cost-effective in large-scale production depending on the production level and market price of the glycoprotein product, the amount and frequency of kifunensine addition , and the price of kifunensine in bulk quantities. Currently, at our laboratory-scale pricing for kifunensine , the addition of 5 µM kifunensine in NB-S increases induction medium costs by ~14-fold and contributes ~$225 in reagent costs for the 5 L bioreactor run. Although the cost of the growth and induction medium is still significantly lower than mammalian cell culture medium, and the price of kifunensine is likely to decrease more than 10-fold with larger demand and bulk pricing, it may be advantageous to reduce bioreactor working volume during the induction phase to minimize kifunensine cost, enhance mass transfer, and concentrate extracellular rrBChE. Employing current genomic editing techniques such as CRISPR/Cas9 to knock out XylT and FucT genes to remove plant-specific α-1,3 fucose and β-1,2 xylose in host rice lines, similar to what was done in N. tabacum BY-2 cell lines without negative impacts in terms of cell growth rate, would be worth investigating as an alternative to modify N-glycans of secreted glycoproteins, such as rrBChE, for large-scale operations.

Graminaceous plants, like other so-called metal-tolerant plants, mostly sequester metals in roots to protect reproductive and photosynthetic tissues . The ability to store metals in underground tissues is used in phytoremediation to reinstall a vegetation cover on heavily contaminated areas and limit the propagation of metals into the food chain . Panfili et al. showed that the grass species Festuca rubra and Agrostis tenuis accelerate the weathering of zinc sulfide when grown on contaminated dredged sediment, thus increasing Zn bio-availability in the rhizosphere. After two years of plant growth, micrometersized Mn-Zn black precipitates were observed at the surface of Festuca rubra roots, but not characterized . Zinc precipitation may be a bio-active tolerance mechanism in response to metal toxicity, or a passive mineralization at the soil-root interface . Clarifying this issue and determining the mineralogy and structure of this natural precipitate is important to enhance the effectiveness of using graminaceous plants in phytoremediation. These questions are addressed here with electron microscopy and synchrotron-based microanalytical tools, including X-ray fluorescence , extended Xray absorption fine structure spectroscopy and X-ray diffraction . Micro-XRD was employed to determine the nanocrystalline structure of the Mn-Zn precipitates and the nature of defects through modeling of their scattering properties . We show that the root precipitates are present in the root epidermis and consist of a poorly crystallized phyllomanganate with a constant Zn:Mn ratio higher than reported so far for any natural and synthetic manganate.The composition in major elements of the dredged sediment was 68.3 % SiO2, 6.9 % CaO, 4.8 % Al2O3, 2.4 % Fe2O3, 0.7 % P2O5, and 7.2% organic carbon, and the composition in a trace metals was 4700 mg.kg-1 Zn, 700 mg.kg-1 Pb, and ~270 mg.kg-1 Mn. Seeds of F. rubra were sown in plastic pots filled with 40 kg of either the untreated sediment, the sediment amended with 3 wt. % hydroxylapatite, or the sediment amended with 5 wt. % Thomas basic slag.

The pots were placed in a greenhouse without artificial lighting and daily irrigated with tap water in an amount similar to the mean rainfall in northern France. After two years of culture, the pots were dismantled to collect samples. The texture and color of the sediment in areas colonized by the roots were similar to a brown silty soil, whereas the initial sediment was black and compact. Roots of F. rubra from the treated and untreated pots were washed meticulously with distilled water to remove soil particles from the surface and then freeze-dried. The speciation of zinc in the initial sediment and in the rhizosphere of F. rubra after the two years of vegetation was described previously . Briefly, in the untreated and unvegetated sediment, Zn was distributed as ~50% sphalerite, ~40% Zn-ferrihydrite, and ~10 to 20% -hydrotalcite plus Zn-phyllosilicate. In the presence of plants, ZnS was almost completely dissolved, and the released Zn bound to phosphate and to Zn phyllosilicate plus -hydrotalcite . The coaddition of mineral amendment did not affect the Zn speciation in the vegetated sediment. The Zn:Mn and Ca:Mn ratios were measured with an Eagle III µ-XRF spectrometer equipped with a Rh anode and a 40 µm poly-capillary. The spectrometer was operated under vacuum at 20 kV and 400 µA,vertical lettuce tower and fluorescence was measured for 300 s per point. Micro XRF, XRD and EXAFS data were collected on beamline 10.3.2 at the Advanced Light Source . Short root fragments were attached to the tips of glass capillaries and cooled down to 110-150 K to minimize radiation damage . X-ray fluorescence maps were taken at 10 keV incident energy, with a beam size ranging from 5×5 µm to 16×7 µm . Fluorescence counts were collected for K, Ca, Mn, Fe and Zn with a seven-element Ge solid-state detector and a counting time of 100 ms per pixel. For µ-EXAFS measurements, the vertical beam size ranged from 5 to 7 µm. A maximum of two spectra per precipitate were taken at either the Mn or the Zn K-edge to prevent the reduction of tetravalent to divalent Mn and the increase of structural disorder under the beam . Diffraction data were collected with a CCD camera at 17 keV and exposure times of 120-240 seconds. At this energy, the incident flux and absorption cross-sections are low enough to make radiation damage during an exposure negligible even at room temperature. A background pattern was recorded next to each precipitate to subtract the scattering contribution from the root so as to obtain the precipitate pattern. Diffraction patterns collected on different precipitates were all statistically identical, and thus summed up to optimize data quality. Calibration of the energy and camera distance were obtained using an Al2O3 standard and Fit2D software . This software was also used to calculate the one-dimensional XRD traces from the radial integration of the two-dimensional patterns. Under the optical microscope, the Mn-Zn precipitates appear as black stains about ten to several tens of micrometers in size on the root surface . They are also observed in back scattered electron microscopy due to the presence of high-Z elements , but always are hardly noticeable in secondary electronimaging mode . This suggests that the precipitates are engulfed in the root epidermis and do not coat the root surface as iron and manganese plaques do . No differences were observed among precipitates from plants grown in the untreated and mineral amended sediments. This result, together with the compartmentation of the precipitates inside the roots, suggests a biological origin. This interpretation is supported also by the absence of Zn-rich phyllomanganates in the surrounding soil matrix . Elemental mapping of F. rubra roots shows that Zn is associated with Mn in localized spots, and uniformly distributed without manganese in the vascular cylinder as expected for this nutritive element .

All roots have Zn in their central stele, but not all are speckled with Mn-Zn precipitates. Some root fragments are partly covered by Zn-free Fe-rich plaques . These plaques are made of ferric oxyhydroxides, as indicated by their optical rusty color . In Zn-Mn-Ca tricolor representation all Mn-Zn precipitates generally have the same color , even among different roots , meaning that the relative proportions of Zn, Mn and Ca are about the same. The correlation coefficient between Zn and Mn counts for the precipitates is 0.8, with P-value < 0.0001 for the Anova F-test . The Zn:Mn atomic ratio was calculated from the relative absorption jumps measured at the Mn and Zn K-edges on four particles. For each particle, a pre-absorption edge background was removed first, and then a linear fit to the post-edge region was extrapolated back to the edge to measure edge jumps. The ratio of the Zn to Mn edge jumps is 0.310, which translates into a Zn:Mn ratio of 0.46 when taking into account the atomic absorptions of the two elements. A consistent 0.44 value was obtained independently with the Eagle III spectrometer. This analysis also confirmed that root precipitates have a constant Ca:Mn ratio. An atomic ratio of 0.41 was calculated after correction of the Ca-fluorescence from the root. Micro-EXAFS spectra were recorded in the vascular cylinder of four distinct roots, at spots containing little Mn. All spectra were indistinguishable, indicating that Zn speciation is uniform, and thus averaged. The resulting Root spectrum has the same frequency as the MnZn precipitate spectrum, which suggests that Zn is also mostly tetrahedral in the roots . However, in contrast to Mn-Zn precipitate, the second and third oscillations of the Root spectrum are not split, indicative of “light” back scatters from second-shell contributions. Consistently, the best spectral match to our organic and inorganic database of the Root spectrum was provided with Zn in a biofilm . This reference has 80 ± 10% Zn complexed to phosphoryl groups and 20 ±10% to carboxyl groups . Consistent with this other study, consideration of carboxyl and phosphate ligands alone, did not yield an optimal fit to the data. Zinc preferential binding to phosphate groups has been reported also in the roots of Arabidopsis halleri and A. lyrata grown hydroponically, on bacterial and fungi cells, and in biofilms . These studies have shown that Zn has a higher affinity for phosphate than for carboxyl groups, which is consistent with the predominance of the phosphate species in F. rubra roots. As the optimal fit to data was obtained using a trial-and-error approach, the sensitivity of the XRD simulations to key structural parameters needs to be assessed. A key parameter for birnessite’s ability to sorb trace metals is the origin of the layer charge.

Transport was significantly hindered at acidic conditions and high ionic strengths , and the deposited nanoceria may not have been re-entrained by increasing the pH or lowering the ionic strength of water. At neutral and alkaline conditions , and lower ionic strengths , partial breakthrough of nanoceria was observed and particles could be partially detached and re-entrained from porous media by changing the solution chemistry.In a more complex system, heteroaggregation, i.e. between a nanoparticle and another particle in the environment, is more likely to occur due to the greater concentration of environmental particles.It has been shown that in various solutions, the agglomeration and sedimentation rate of nanoceria were dependent on NOM content and ionic strength.In freshwater, with a high TOC, and low ionic strength, nanoceria dispersion were stable with a low rate of sedimentation.In algae medium, Quick et al.showed that the sedimentation decreased with increasing NOM content. The fraction of nanoceria that remained suspended in algae medium increased with increasing NOM content. The main mechanism explaining the increased stability is the adsorption of NOM to the particle surface. Recently, Li and Chen61 measured and modeled the aggregation kinetic of nanoceria in the presence of humic acid , in monovalent and divalent solutions. HA has been shown to stabilize nanoceria in all KCl concentration. However at high CaCl2 concentration HA enhanced the aggregation of nanoceria probably owing to the bridging attraction between nanoceria,vertical aquaponics system which is induced by the HA aggregates formed through intermolecular bridging via Ca2+ complexation.

The stability and mobility of nanoceria in dilute NaCl solution was also greatly enhanced in the presence of humic acid, fulvic acid, citric acid, alginate and CMC due to electrostatic effect.Even in the presence of NOM in the media, homoaggregation was measured in several studies. Keller et al.measured >500 nm aggregates formed in sea water whereas ~300 nm aggregates were stable in suspension for a high TOC. Van Hoecke et al.measured nanoceria aggregation in algal test media, between 200 and 1000 nm but the extend of the agglomeration was dependent on pH, NOM, IS. Increasing pH and ionic strength enhanced aggregation, while NOM decreased mean aggregate sizes. Organic molecules that can adsorb onto the particle surfaces provide a barrier to aggregation but were not able to overcome the van der Waals forces holding small nanoparticles aggregates together.In a simulated freshwater ecosystem in laboratory, sediments were measured as the major sink of nanoceria with a recovery of 75.7% of total nanoceria after 15 days. In several types of soil, Cornelis et al. showed, by investigated the retention of nanoceria, that nanoceria retention in soil is low. The retention of nanoceria in soils was proposed to be associated with naturally occurring colloids, such as Al, Si, and Fe oxides.Contrary to some other manufactured nanoparticles , nanoceria have an inherently low solubility. Negligible solubility was reported; e.g. in freshwater system over 72 h,in moderately hard reconstituted water for h2 or in algal medium for 3 days.Similarly, Röhder et al. measured a low dissolved Ce concentration in different algae exposure media ranging from 0.01 to 0.11% total Ce, and 0.47 to 1.13% in the presence of EDTA. However, they show that the dissolved Ce may be responsible for the observed toxicity in Chlamydomonas reinhardtii.

The dissolution of nanoceria has been shown to be very low in 16 different types of soil spiked with nanoceria.Dissolution of nanoceria studied in an artificial soil solution was only significant at pH 4 and was less than 3.1% of total Ce. Ce redox state is affected by environmental transformation. A reduction of CeIJIV) to Ce in nanoceria has been observed during the contact between nanoceria and E. coli, in C. elegans, 2 in cucumber plants, and to a lesser extent in corn66 and soybean.The Ce reduction may explain the toxicity induced by these nanoparticles by suggesting oxidative damage of macromolecules or generation of ROS.The reduction of Ce was not observed in all studies: Ce was found as Ce in the roots seedlings of cucumber, alfalfa, tomato, corn and soybean seedling exposed to 4000 mg l−1 of nanoceria.However, nanoceria interaction with HA and with biological media induced a decrease of Ce proportion measured by EELS.This may indicate that nanoceria had been oxidized in the presence of humic substances and biological media. The presence of phosphate in media can modify nanoceria properties. Zhang et al.identified the formation of cerium phosphate from a nanoceria suspension, KH2PO4 and a reducing substance . Singh et al.suggested that the interaction of nanoceria with phosphate may have caused the formation of cerium phosphate at the particle surface, in which cerium is mainly present as Ce. They showed that binding of phosphate anions to nanoceria leads to the complete disappearance of superoxide dismutase activity and concomitant increase in catalase mimetic activity.To summarize, the few available studies showed that the properties of environmental media modifies the stability and the chemical state of nanoceria. But we lack sufficient knowledge to understand and predict the extent of transformations in the environment and the risks associated with the release of nanoceria on biological systems.Wastewater treatment plants are an important intermediate pathway for NP to soil and water.NPs may undergo transformations before being discharged with treated effluent or biosolids. Transformations of two varieties of nanoceria, pristine and citrate-functionalized, were followed in an aerobic bioreactor simulating wastewater treatment by conventional activated sludge.

This study indicates that the majority of nanoceria was associated with the solid phase where a reduction of the CeIJIV) NPs to Ce occurred. After 5 weeks in the reactor, 44 ± 4% reduction was observed for the pristine nanoceria and 31 ± 3% for the citrate-functionalized nanoceria, illustrating surface functionality dependence. The authors suggest that the likely Ce phase generated would be Ce2S3. At maximum, 10% of the CeO2 will remain in the effluent and be discharged as CeO2, a Ce phase.Nanoceria can also be toxic and/or provoke changes in the microbial communities involved in wastewater treatment therefore affecting the performance of the wastewater treatment process. Garcia et al.evaluated the effect of nanoceria on the activity of the most important microbial communities of a WWTP: ordinary heterotrophic organisms, ammonia oxidizing bacteria, and thermophilic and mesophilic anaerobic bacteria. A great inhibition in biogas production and a strong inhibitory action of other biomasses were caused by nanoceria coated with hexamethylenetetramine . On the contrary, the study of Limbach et al., 2008,showed that an ordinary heterotrophic organisms biomass from a municipal WWTP in Switzerland was not affected by 1000 mg l−1 of non-coated nanoceria. This discrepancy could be related to differences in the characteristics of the bacterial community and the nanoparticles properties used in both studies.The literature assessing the fate and effects of nanoceria on terrestrial plants is not extensive, and far less work has been done with other terrestrial organisms such as soil invertebrates. The existing work will be reviewed in terms of three separate parameters or endpoints; toxicity, translocation, and transformation. Papers reporting findings under hydroponic exposure in plants will be covered first, followed by plant studies done under soil conditions.Ma et al.were among the first to investigate potential nanoceria phytotoxicity. The authors reported that the seed germination of 7 different species was completely unaffected by 2000 mg l−1 of nanoceria suspension. Similarly, subsequent root elongation tests with these plant species was largely unaffected by nanoceria; only lettuce root growth was suppressed by 34% at this concentration. Lopez-Moreno et al. also showed that nanoceria at 2000–4000 mg l−1 had no overt toxicity on soybean, although particles were detected within root tissue by synchrotron X-ray absorption spectroscopy . The authors did report genotoxicity as measured by random amplified polymorphic DNA assay; however, the precise nature of the molecular effects is not known. In a follow up study, the same group reported the effects of 0–4000 mg l−1 nanoceria exposure on alfalfa, corn,farming vertical cucumber and lettuce growth.The germination and root elongation of several of the species were enhanced at lower concentrations but were significantly inhibited at 2000 and 4000 mg l−1 .Interestingly, shoot elongation was enhanced in nearly all cases. ICP-OES was used to confirm ceria presence within the seedlings, although root and shoot tissues appear to not have been separated prior to analysis. After dilute acid rinsing, XAS confirmed that the oxidation state was unaltered in the root tissues of these four plant species.

Zhang et al. reported a concentration-dependent sorption of nanoceria to cucumber roots in a 14 day hydroponic exposure. Most of the adsorbed nanoceria were only loosely bound to the root surface and more than 85% of the nanoparticles could be washed off with deionized water. Translocation of the particles to shoot tissue was minimal but measurable, and interestingly, 7 nm size particles were found at significantly higher amounts than 25 nm nanoceria. In a follow up 21 day hydroponic study, exposure to 2000 mg l−1 bulk CeO2 and nanoceria resulted in no toxicity to cucumber.Although minimal root to shoot translocation was noted, soft X-ray scanning transmission microscopy and XANES were used to show measurable bio-transformation to CePO4 in roots and cerium carboxylates in shoot tissue. Notably, the authors hypothesize that root exudate mediated dissolution of nanoparticles precedes ion uptake, subsequently followed by in planta reduction to nanoceria and/or bio-transformed products. Similarly, Schwabe et al.observed plant exudate induced changes in solution pH, nanoceria agglomeration and particle size. However, they reported no phytotoxicity to pumpkin and wheat after 8 day exposure at 100 mg l−1 nanoceria; no cerium was detected in wheat shoots but minimal translocation in pumpkin yielded tissue levels of 15 mg kg−1 . Interestingly, the association of cerium with the roots of both plant species was reduced in the presence of NOM. Rice exposed to nanoceria at 63–500 mg l−1 experienced no visible signs of phytotoxicity, although altered lipid peroxidation, electrolyte leakage, and other enzyme activity suggested possible oxidative stress.Wang et al.noted that tomato seeds harvested from plants previously exposed to nanoceria yielded a “second generation” of individuals that produced less biomass, transpired less water, possessed differential root morphology, and exhibited overall higher levels of reactive oxygen species that did seeds from unexposed plants.Birbaum et al.were the first to report on nanoceria exposure to terrestrial plants under soil conditions. The authors reported that after 14 day exposure with the nanoceria in the irrigation water , no ceria was found in the leaves or sap of corn plants. However, no mention was made of toxicity or of root ceria content. Interestingly, the authors included an aerial exposure on leaves and although nanoceria could not be washed from the tissue, the particles were not internalized or transferred to new growth. Similarly, Wang et al.grew tomato in the presence of nanoceria-amended irrigation water and reported either no impact or slight enhancements in plant growth and yield. The authors did observe ceria in the shoots, including edible tissues, which suggests translocation, but the mechanism and form of element transfer is unknown. Zhao et al.observed that after one month of growth in soil, corn roots accumulated significantly greater quantities of alginate coated nanoceria than uncoated particles but no mention was made of toxicity. These authors also noticed that soils with high organic matter generally enhanced the association of nanoceria with roots but reduced the translocation to shoots, regardless of the surface properties of nanoceria. However, the effect of soil organic matter was more significant on uncoated nanoceria than alginate coated nanoceria. Although translocation in general was low, μXRF did confirm the presence of nanoparticles within vascular tissues, as well as in epidermal and cortex cell walls, suggesting an apoplastic uptake pathway. A separate study with cucumber showed that up to 800 mg nanoceria/kg soil did not demonstrate any adverse effect on a suite of plant physiological indictors such as the net photosynthesis rate, leaf stomatal conductance, but nanoceria at this concentration did lower the yield of cucumber by 31.6%. The authors also observed nanoceria in the vasculature of leaf veins, providing further evidence that nanoceria may be transported from roots to shoots with water through vascular tissues.Priester et al. noted that soybean exposed to 100–1000 mg kg−1 nanoceria had root ceria content of up to 200 mg kg−1 but that translocation was minimal.

After the initiation of asymmetric division, the primordia emerge, form active meristems, and break through the epidermal cells to become new lateral roots. Auxin is essential for various steps in the course of root development—from cell fate acquisition to meristem initiation, emergence, and elongation . In Arabidopsis, auxin is mainly synthesized in young apical tissues of the shoots and roots . Indole-3-acetic acid is considered the major form of auxin, with tryptophan being its precursor . Among the four pathways of IAA biosynthesis from Trp, the indole-3-pyruvic acid pathway is the major pathway in Arabidopsis . In the IPyA pathway, tryptophan aminotransferases convert Trp into IPyA, and YUCCAs synthesize IAA from IPyA, a rate-limiting step for the pathway . In rice, FISH BONE encodes a Trp aminotransferase; loss of function results in pleiotropic abnormal phenotypes, which include small leaves with large lamina joint angles, unusual vascular development, and defects in root development, which are all consistent with a decrease in internal IAA levels . Mutations in CONSTUTIVELY WILTED1result in narrow and rolled leaves, in addition to the decreased growth of lateral and crown roots . Conversely, the over expression of OsYUC1 causes an increase in IAA accumulation, and auxin-overproducing phenotypes are observed . Such phenotypes are subject to the presence of the transcription factor WUSCHEL-RELATED HOMEOBOX 11 , a key regulator of root development . In rice,vertical farming aeroponics auxin induces WOX11 transcription, which establishes the YUCCA–auxin–WOX11 module for root development . Ethylene also controls root development. Treatment with low concentrations of an ethylene precursor, 1-aminocyclopropane- 1-carboxylic acid , promotes the initiation of lateral root primordia.

In contrast, exposure to higher ACC concentrations inhibits such initiation considerably, while also promoting the growth of already existing lateral root primordia . The regulation is linked tightly with auxin . For example, ethylene application results in the accumulation of auxin at the tip of Arabidopsis primary roots through the promotion of auxin synthesis mediated by WEAK ETHYLENE INSENSIVE2/ANTHRANILATE SYNTHASE α1 and WEI7/INSENSIVE2/ ANTHRANILATE SYNTHASE β1 . WEI2 and WEI7 encode the α and β subunits, respectively, of anthranilate synthase , a rate-limiting enzyme in the biosynthesis of the auxin precursor Trp . In rice, ethylene also increases endogenous IAA concentrations in the roots; however, the effect is minimized in mutants defective in YUC8/REIN7, which participates in auxin biosynthesis . The homeobox genes are critical for growth and development because they regulate cell fate and plant specificity . A family of zinc-finger homeodomain proteins has an N-terminal conserved domain containing several cysteine and histidine residues for potential zinc binding, in addition to a C-terminal domain containing a homeodomain . Most ZF-HD proteins do not have an intrinsic activation domain, which suggests that interactions with other factors are necessary for transcriptional activation . In addition, all 14 members of the ZF-HD gene family in Arabidopsis are predominantly expressed in floral tissues and play key roles in their development . One member, AtHB33, which is negatively regulated by ARF2, is required for seed germination and primary root growth . Among the 11 ZF-HD genes in rice, the over expression of OsZHD1 and OsZHD2 induces leaf curling by controlling the number and arrangement of bulliform cells . Here, we report that the overexpression of OsZHD2 in rice improves root growth by enhancing meristem activity. We demonstrated that the homeobox protein elevated ethylene concentrations by increasing the transcript levels of ethylene biosynthesis genes. We further obtained ChIP assay data that revealed an interaction between OsZHD2 and the chromatin of ACS5. Analyses of transgenic rice plants carrying DR5::GUS and DR5::VENUS revealed that the expression of the DR5 reporter gene was induced following treatment with ACC, an ethylene precursor.

The results suggest that OsZHD2 increases the biosynthesis of ethylene and subsequently auxin, which stimulates root growth.Untreated irrigation water runoff and untreated recycled irrigation water have been shown to introduce and spread microbial pathogens, such as Pythium and Phytophthora, in commercial nurseries .These pathogens belong to the Oomycota and are often referred to as water molds that are most active during wet and humid periods and produce flagellated spores, called zoospores that can spread through the water. Phytophthora sp. cause diseases in agriculture, arboriculture and natural ecosystems, and the estimated losses associated with these pathogens are in the billions of dollars . Of particular concern in California is the spread of P. ramorum, causal agent of Sudden Oak Death . Costs associated with SOD incorporate costs to property owners, ornamental nursery industry, and the state and federal government. There are hundreds of thousands of susceptible oak trees located on near developed communities. Infected trees in these areas will need to be removed, disposed of, and replaced at the cost of the landowner or local government. Kovacs et al. estimated that this would amount to a discounted cost of$7.5 million and an associated $135 million in losses to property values for single family homes in California. Sudden Oak Death was first noticed in the 1990s when California hikers along the central coast reported oaks suddenly dying . This die off was frequently found along the interfaces between urban and natural areas. In 2000 the pathogen causing SOD, P. ramorum, was isolated and researchers soon noticed that it belonged to the same species as a newly described pathogen from diseased rhododendrons and viburnums in European nurseries in 1993 . P. ramorum causes foliar and shoot blight on many plants, including important ornamental species, and bleeding cankers on the tree trunks leading to the death of the plant on relatively few hosts, like coast live oak and tan oak . This disease is responsible for the death of tens of thousands of trees in California and Oregon and most strongly affects tanoak, coast live oak, California black oak, and Shreve’s oak . P. ramorum also causes severe damage on plantations of the non-native Japanese larch in the United Kingdom and Ireland; the disease on this new host was named ‘Sudden larch death’ . Abundant inoculum can be produced on foliar hosts and spread from there to both foliar and non-foliar hosts.

Due to this mode of transportation, there are instances of the Phytopthora species moving from ornamental nurseries to the natural environment due to uncontrolled contamination . Nevertheless, few nurseries currently treat their irrigation water . Instead, nurseries use fungicides to control the spread of fungal pathogens and oomycetes, which increases costs and promotes the growth of resistant plant pathogens. In addition, these plant pathogens may be suppressed when under the presence of fungicides and proliferate when the fungicide is discontinued . For these reasons, various techniques, including the use of chlorine, ozone and UV light, have been used to mitigate the spread of the pathogen, but each technique has its drawbacks. Most methods for the treatment of irrigation water can be costly for small operations. The most common treatment method used is liquid chlorine injection. This technique requires consistent addition, monitoring of chlorine concentrations, assessment of the system water quality and on-site storage . The chlorine dose needed is dependent on water quality because the high nitrogen and organic content in the dissolved and suspended matter incorporated in irrigation run-off increases the chlorine demand on the system. Ozone has similar limitations to using a liquid chlorine injection, but it can be generated on demand. Nevertheless, generally ozone has higher capital costs compared to the use of liquid chlorine and ultra-violet light treatment . Ultraviolet light works as a disinfectant by exciting the nucleic acids in DNA and RNA. This excitation results in the dimerization of adjacent nucleic acids and prevents the further transcription of the DNA or RNA and inhibits replication. Since UV disinfection is a physical treatment process, it avoids generating toxic by-products caused by the use of oxidizing chemical disinfectants, such as chlorine. Similarly, there is no additional smell or taste added to the water, no danger of overdosing the disinfectant,vertical indoor hydroponic system and no need to store hazardous materials on site. Another benefit of UV disinfection over chlorine and ozone is that it alone is effective against both bacterial and viral pathogens. The ability of a UV system to disinfect agricultural water run-off is dependent on its ability to deliver a UV dose sufficient to inactivate the pathogens of concern. The UV dose depends on the intensity of the UV light emitted by the lamps, on the flow rate of the water through the system, and on the UV transmittance of the water. Factors that determine the UVT include the level of suspended solids, the turbidity, color, and the concentration of soluble organic matter. The run-off from agricultural activities is often high in dissolved and suspended matter and the resulting turbidity can thus be sufficiently high as to lower the water’s transmittance of UV radiation thereby increasing, sometimes by more than 4-fold, the UV dose that is required to inactivate Pythium and Phytophthora . Thus it is important that the water quality parameters of the untreated influent be quantified to ensure that the UVT does not fall below a level that would reduce UV light penetration and thus inhibit its germicidal ability. It is also important that the UV system itself, through aspects of its design, remains capable of delivering sufficient UV dose even when the UVT is low. One way to increase the UV dose is to reduce the flow rate of the water through the system thereby increasing the time in which the pathogens are exposed to the UV light.

In many commercial applications, this is not an acceptable remedy due to the large quantities of runoff water generated in daily operations. Moreover, by decreasing the flow rate, the resulting flow can become laminar leading to significant reduction in mixing. When mixing is reduced, the disinfection efficiency in conditions of low UVT is also reduced since the pathogens that are not brought sufficiently close to the source of the UV light can leave the system without having received sufficient dose for inactivation. Recently, a novel system for water disinfection with UV light was developed and tested with success in the treatment of effluent from a number of municipal waste water treatment plants . This system, by virtue of a number of features unique to its design, has the potential of being particularly suitable for use in agricultural and horticultural operations where the water run-off is often low in UV transmittance. The new system also benefits from being free of the problem of ‘lamp fouling’ that is present in most commercially-available UV systems. In such systems, the UV-emitting lamps are immersed within the water being treated and hence, with time, become covered with bio-film and mineral deposits that reduce the intensity of the emitted light and necessitate frequent system shut downs for cleaning. The objective of this study was to introduce this system to the plant-pathology community by testing it, in situ, at a facility for the study of diseases of ornamental plants to assess its performance in inactivating P. ramorum in actual irrigation run-off water representative of that obtained in commercial nurseries.The UV system presented here is shown in Fig. 1. Untreated water enters the system into a pressure vessel located at the bottom of the column and exits this vessel through a series of nozzles arranged along the circumference of a circle. Affixed to the top of this vessel is aquartz cylinder; quartz being one of the few materials that allow UV-C radiation to pass through. The manner in which the water enters this cylinder causes it to rotate as it rises to the top. The rotating motion, coupled with the presence of a drain port at the cylinder base, lead to the formation of a central air vortex in the shape of a cone with its broad base located at top of the cylinder. The UV lamps are arranged around the outside of the quartz cylinder and thus do not come in contact with the water being treated. In this way, the problem of lamp ‘fouling’ does not arise. The combined rotational and axial motions of the water rising induce high levels of shear stress on the inside walls of the quartz cylinder. These high levels of shear stress provide a self-cleansing mechanism in that they prevent material from adhering to the inside of the cylinder which thus remains free of ‘fouling’.

This includes the development of irrigation systems, application of fertilizers, and use of bio-engineered crops and other bio-technologies , as well as the implementation of new farming systems .Although the use of fertilizers and irrigation can reduce the gap between actual yields and the maximum potential yields of existing crops, new advances in biotechnology can increase the maximum potential yields by engineering crop varieties with improved “harvest index” , water use efficiency, photosynthetic efficiency, or drought tolerance. Between the 1960s and 2005 the green revolution has allowed for a 135% increase in crop yields worldwide by intensifying production through irrigation, fertilizers, and improvements in the harvest index. In the next few decades crop yields will have to keep increasing in order to meet the increasing demand for agricultural products . This is a major challenge because, recently, crop yields have been stagnating after decades of growth . The analysis of factors limiting the increase of crop yields shows that so far technological improvements aiming at the enhancement of photosynthetic efficiency have played only a marginal role in the increase of crop yields, and for most crop plants, the photosynthetic efficiency is far below the biological limits . The next stage of the green revolution could use modern technologies from genetic engineering and synthetic biology to improve the mechanisms of light capture, sunlight energy conversion,ebb and flow and carbon uptake and conversion . For instance, in full sunlight conditions, most plants absorb more light than they can use. To avoid damaging photo oxidation from excess light, plants typically dissipate excess light as heat .

To improve efficiency, plants could capture less light or improve the way they respond to changes in light availability resulting from variations in cloudiness . Additional gains can be obtained by developing crop varieties with improved water use efficiency, pest resistance, or temperature stress tolerance . Genetic engineering technology is commonly used to develop genetically modified organisms, including new crop varieties. Unlike traditional breeding techniques and artificial selection for desired traits, transgenic methods allow for more precise genetic modifications by inserting specific genes from other species to improve crop performance . The use of transgenic crops in agriculture has been and still is at the center of a heated debate because of possible risks and unintended consequences, including possible gene mutation, accidental activation of “sleeper” genes, interactions with native plant and animal populations, and gene transfer . Other controversial points deal with intellectual property rights and the control of the biotechnology corporations on the agricultural sector. A detailed analysis of this debate is beyond the scope of this review.Transgenic methods, which have been extensively used to improve crop varieties , can be adopted to induce genetic modifications in livestock species by inserting specific genes in organisms that do not have a copy of those genes .Other studies have investigated mammary gland-specific transgenic livestock to change the fat content in goat’s milk, reduce saturated fats in dairy products, and improve disease resistance in lactating cows .As noted in section 2, the ongoing increase in meat consumption worldwide is challenging the agricultural system. Livestock production uses roughly 30% of global ice-free terrestrial land and contributes to 18% of global GHG emissions associated with deforestation, methane emission, and manure management . It has been argued that the increasing demand for meat could be met by culturing animal tissues in vitro in the lab, without having to raise livestock.

These methods could strongly reduce the carbon, land, and water footprints, as well as exposure to food borne pathogens , and cardiovascular diseases by making healthier meat products. Moreover, in vitro meat production would address ethical concerns on animal welfare. In his book “Thoughts and Adventures,” Winston Churchill predicted that “… Fifty years hence, we shall escape the absurdity of growing a whole chicken in order to eat the breast or wing, by growing these parts separately under a suitable medium…” . Churchill’s prophecy is now about to become true. In the last few decades scientists have developed methods to produce muscle tissue ex vivo . Meat culture technology was initially developed for medical applications to produce insulin and implants. Three different approaches have been used, namely, stem cell isolation and identification , ex vivo culture of cells taken from a live animal and put in vitro, or tissue engineering . Applications to the meat industry are facing some major challenges because, to be marketable, cultured meat needs to look and taste like real meat. Thus, research on in vitro meat production is working on appearance, texture, and taste to improve the resemblance to real meat. Today, only small amounts of meat have been produced in vitro and served in a handful of restaurants in the United States. It has been estimated that, compared to meat from livestock production, cultured meat allows for substantial savings in land and water resources, emits less GHGs, and uses less energy than ruminants .It is commonly believed that crop plants need soil, in addition to water, nutrients, and light, for their growth. However, it is possible to grow plants without soil but in water with adequate mineral additions. Known as hydroponics, this technique can be used indoors and outdoors, in recirculating, as well as in flow-through, systems. The main advantages of hydroponics with respect to soil cultivation is that plants do not need to invest much in root growth to find nutrients; they grow faster and take less space.

Moreover, hydroponics allows for more efficient nutrient/fertilizer regulation. This technique, however, can be expensive when considering the cost of the system, its maintenance, and energy requirements. A more effective use of resources can be attained with a multi-trophic system, known as aquaponics, that combines hydroponics with aquaculture. In other words, nutrient-rich water from fish tanks is used for plant growth . This system is inspired by old agricultural practices, such as the introduction of fish in rice paddies or the use of nutrient-rich fish-tank water for irrigation . In aquaponic systems, fish produce nitrogen-rich waste that is mineralized by bacteria and taken up by plants . Thus, bacterial biomass and vegetation filter the water in the fish tank, thereby allowing for a recycling of water and minerals and P; this system turns waste products from aquaculture into nutrients for hydroponic production. In this sense, aquaponic is a good example of circular economy, as described in section 11.4.1. The main limitation of this system is that it requires relatively large capital investment and skilled maintenance, and is therefore more suitable for commercial farming than for subsistence agriculture in the developing world.The use of modern technology and the intensification of agricultural production are often invoked as the desired approach to meeting the increasing demand for crops without causing additional land use change . As noted repeatedly in the previous sections, the downside of this approach is that it typically requires investments that rural communities in the developing world cannot afford . Therefore, in many cases agricultural intensification might entail a transition from small-holder semi-subsistence farming to large-scale commercial agriculture.An alternative approach to achieve food, water, and energy security is offered by agroecology. Small-scale farming can capitalize on local knowledge to attain relatively high yields without having to resort to agribusinesses and their technology . In recent years, there has been a renewed interest in peasant agriculture and its use of poly cultures , agroforestry, green manure,greenhouse benches compost turfing, and high-residue farming , without adopting soil tillage or agrochemicals. These traditional practices conserve soils, water, biodiversity, and ecological integrity, while favoring resilience. It would be impossible to review here this rich body of literature but we will instead focus on the significance of these methods in the context of meeting the growing food demand. It has been argued that a shift to agroecology can substantially increase crop production in a sustainable way and that small-scale peasant agriculture is not condemned to achieve low yields as often assumed in the literature. Rather, there is evidence that small family farms can be much more productive and resilient than larger ones . The use of poly cultures in agroecology allows for the attainment of higher and more stable yields, enhances economic returns, and favors diet diversity, while making more efficient use of land, water, and light resources . Thus, small-scale farming with agroecological methods could contribute to meeting the growing demand for agricultural products. Recent estimates indicate that about 525 million small-scale farms exist around the world and provide a livelihood for about 40% of the global population . However, the ongoing changes in the agrarian landscape worldwide entail the replacement of small-holder agriculture with large-scale commercial farms. This transition can be related to a number of factors, such as the globalization of agriculture through trade, LSLAs, better access to credit by commercial farmers, differences in land tenure, use of agricultural subsidies in economically more developed countries, and lack of protection of domestic production against subsidized foreign agricultural products .

This transition has the effect of reducing the opportunities to use small-scale agroecological methods as an approach to increase food availability.A continuation of current trends in production, consumption, and resource use is wholly unsustainable. There is an urgent need to enhance food security without increasing the human pressure on the environment . A current push in the literature is to identify solutions that minimize trade-offs across multiple agricultural, environmental, and economic dimensions . Some of this work has shown the potential to maintain or reduce current levels of resource use while increasing crop production, thereby eliminating large inefficiencies in production systems. One such study found that if nitrogen fertilizer was spatially distributed more efficiently, it would be possible to increase cereal production by ~30% while maintaining current levels of nitrogen application . Likewise, it is possible to use different irrigation and soil management strategies to close the crop yield gap by one half without increasing cropland area or irrigation use . Other work showed that, by redistributing crops on the basis of their suitability, it is possible for the United States to realize a modest water savings and improve calorie and protein production without adversely impacting feed production, crop diversity, or economic value . Similarly, recent research investigating global scenarios of crop redistribution to minimize irrigation water consumption has shown that it is possible to increase food production and feed an additional 825 million people while reducing irrigation water consumption by 12% without losing crop diversity or expanding the cultivated area .Collectively, these results show the benefits of a more efficient use of natural resources for food or energy production. There could be, however, some unwanted effects. Highly optimized systems are not necessarily more resilient . They often lack important redundancies that play an important role in providing resilience to the FEW system . When resources are used more efficiently their consumption can increase rather than decrease. Known as Jevon’s paradox , this rebound effect has been observed for irrigation systems and has been termed the irrigation paradox . Indeed investments in water-saving irrigation technology may result in a decrease in groundwater levels and environmental flows . Unless policies limit the extent of the irrigated land, what typically happens is that more land is irrigated and water-resource availability decreases, which may exacerbate water scarcity and soil salinity problems . Of course, these changes also have some positive effects, such as increased crop production. Approaches aiming at an increase in agricultural efficiency need to first clarify which resource needs to be used more efficiently . If irrigation water is applied to close the yield gap , the land is used very efficiently but not necessarily the water. But, if water is scarce and large expanses of land are available, it makes more sense to use the land less efficiently and the water more efficiently by irrigating a larger area but with smaller water applications. This practice is known as deficit irrigation in that it leaves crops in a water deficit state . These caveats stress the need to account for food demand, livelihoods, and the environment when developing more effective strategies for achieving a sustainable food system.The population factor has been somewhat more marginal in the recent food security debate, but is starting to resurface in the analysis of sustainable food systems. 

The complexity of sociohydrological dynamics, the variability of institutional settings, and the inter dependencies of water with other key dimensions, such as food and energy, could benefit from innovative adaptive governance approaches .The idea that the development of water infrastructure is important to economic development has often been considered as a corollary to classical models of economic development postulating the need for “growth” in the agricultural sector, followed by the development of industry and services . The rationale for this growth model is that investments in water infrastructure are required to develop irrigation systems that would lead to higher crop yields . It has been argued that in some developing countries, economic development has been impeded by strong intra-annual and inter annual variability in hydrologic conditions that expose crops to often unpredictable water stress; therefore, investments in water infrastructures are urgently needed across the developing world . Even though these claims have not been conclusively supported by data, they are often invoked to advocate for new investments in dams and other “gray” infrastructures, such as canals, pipelines, or other hydraulic structures . This model of economic development, however, remains controversial because such infrastructures could cause irreversible environmental damage and often serve the needs of large-scale commercial agribusinesses rather than subsistence farmers, whereas green approaches, based on water harvesting, small farm-scale ponds,potted blueberries and new crop water management techniques with low evaporative losses of water are likely more effective and less costly .

Recent research on this topic has highlighted the benefit of building small decentralized water harvestings and storage facilities as a sounder and economically more viable alternative to large dams . Indeed, farm-scale reservoirs and small retention ponds better suited for decentralized approaches to water management are more likely to serve small-scale farmers and reduce the cost of conveyance and distribution systems .Human activities require energy to power systems of production, transportation, heating, and cooling . In preindustrial societies energy options were relatively limited and mainly consisted of wood burning and draft animals , which in turn required land and water for the production of fuel wood or fodder. Thus, land and water availability constrained energy production in the preindustrial world . The industrial revolution provided unprecedented access to power with engines fueled by fossil materials that required almost no land or water . After 1950, there was a massive energy transition in the “Great Acceleration” period, with particularly large increases in fossil fuel-based energy systems . This transition toward a high-energy society after 1950 coincided with dramatic socioeconomic changes, including increased agricultural production , as well as an increased rate of manufacturing, economic growth, urbanization, and demographic growth . Such trends occurred along with a reduction in the amount of labor effort needed by the societal metabolism, that is, the way materials and energy are exchanged within societies, among societies, and between societies and nature . The benefits of the increasing reliance on fossil fuels, however, came at the cost of burning, in just a few decades, much of the readily available oil and gas, thereby depriving future generations of these energy options. At the same time, fossil fuel consumption increased atmospheric CO2 concentrations with important impacts on the global climate . Today the energy system suffers from major problems that are a legacy from the twentieth century: energy consumption mostly relies on nonrenewable sources and increases as a result of population and economic growth, while about 3 billion people have no access to safe and reliable energy sources.

In year 2017, 2.8 billion people relied on biomass, coal, or kerosene for cooking . Household air pollution from these sources is linked to millions of premature deaths, along with health and environmental impacts on local communities . Moreover, across the developing world several billion hours are spent every year collecting fire wood for cooking, mostly by women. This time could be put to more productive uses such as education . The ongoing continued reliance on fossil fuels is a major contributor to GHG emissions, air pollution, and associated health and environmental problems . In recent years, there has been a big push for the development of more efficient systems of energy production from renewable sources, such as solar and wind power . Societies will likely increasingly rely on renewable energy and gradually reduce dependence on fossil fuels . In the meantime, however, humanity needs to deal with the challenge of curbing CO2 emissions, while removing inequalities in the access to energy. To date, one in five people still lack access to modern electricity in their homes; three billion people use wood, coal, charcoal, or animal waste for heating and cooking . Access to affordable, clean, and reliable energy, which is listed as one of the UN’s SDGs , is a major challenge of our time. Achieving this goal and, more generally, enhancing energy security—defined as “the uninterrupted availability of energy sources at an affordable price” —requires improvements to the systems of energy production and distribution that may ultimately exacerbate competition for water with agriculture, as explained in sections 7 and 8.Seafood production includes a wide range of species groups , production environments , and production methods . Since seafood species are, by definition, aquatic organisms, seafood production is intimately related to water resources. However, water-resource requirements for seafood production are as varied as the species produced and the production methods used . Aquaculture is currently the fastest growing production component in the global food system , and as much as one half of seafood consumption is now derived from farmed fish . Water use for aquaculture is similar to that for terrestrial food production, such as water use for feeds, but water use for aquaculture differs owing to its large water storage requirements.

Aquaculture feed dependence varies by species, with some species requiring essentially no aqua feeds and others relying almost completely on feeds . The water footprint of aqua feeds varies depending on feed composition, which varies by species and time on the basis of the prices of different ingredients . Recently, efforts have been made to replace fish meal and fish oil in aqua feeds with crop-based ingredients in order to improve the sustainability of aquaculture by supplanting the use of capture fisheries for the production of aqua feed based on fish meal and fish oil . While a shift toward crop-based aqua feeds may reduce pressures on wild fisheries, it also increasingly links seafood consumption to terrestrial agriculture. This shift in feed source may have a trade-off with water use though because production of crop-based feeds typically uses more water than the production of fish meal and fish oil . Large water storage requirements for aquaculture differentiates the water use types and processes that are most relevant for aquaculture from those relevant for agriculture or livestock farming . Water storage creates a competitive use for water resources, alters the rates and timing of evaporation and seepage, and can involve large quantities of in situ water use . In situ water use is essential for providing habitat for inland capture fisheries, and minimum environmental flows are needed to maintain appropriate salinity levels in brackish water ecosystems. Although crucial for these capture fisheries and some forms of aquaculture,square plastic pot in situ water use can be difficult to quantify and cannot be directly compared to consumptive water use in agriculture systems. Despite these methodological challenges, as the seafood sector grows , it is increasingly important to consider water use for seafood production.Water and energy are interconnected, largely in terms of the water use involved in power generation but also indirectly as a result of hydrological alterations associated with hydro power development . Fuel production and power generation rely on water availability, and the supply of water requires energy . Both water and energy are finite resources that, in a rapidly changing world, are set to be placed under increasing stress. New energy technologies implemented to “decarbonize” the economy of industrial societies are increasing our reliance on water-intensive fuels , further exacerbating the interconnection between energy production and water resources. For example, bio-fuel production, concentrating solar power , and carbon capture and storage require large amounts of water. Thus, water availability may challenge existing energy operations and is increasingly recognized as a factor determining the physical, economic, and environmental viability of energy production projects.The rising importance of the water-energy nexus has been recognized by the IEA’s World Energy Outlook . Moreover, the energy sector is increasingly concerned about the effects of climate change on the water cycle. More than three quarters of the world’s top energy companies indicate that uncertainty in water availability is a major source of risk for their business operations . Water shortages have already caused the shutdown of coal-fired power plants in India and are affecting the choice of location and technology used for energy projects in China . In south Texas, shale oil and gas extraction using hydraulic fracturing has competed for water with agriculture through a water market, thereby increasing water prices in the region .

Years of drought in the State of California have reduced the hydro power share of total energy production from 30% to 5% . Dam construction is another rapidly evolving nexus issue for the food-water nexus and the energy-water nexus . On the one hand, dam construction can have significant economic benefits in addition to supplying renewable energy . However, these benefits can come at substantial social and environmental costs in some river basins . Dam construction alters natural flow regimes and the connectivity of river systems, which can disrupt the movement of organisms and sediment, whereas water storage associated with dam operations regulates river flow, which can alter geomorphic processes and disrupt ecological functions both upstream and downstream . Hydropower generation is influenced by the year-to-year variations in rainfall that increase the risk of climate-related electricity supply disruption in dry years . While thousands of hydropower dams are planned or currently under construction globally , three large river basins have particularly large numbers of hydropower dam projects and collectively hold about one third of freshwater fish species . The Mekong contains the world’s largest inland fisheries, which are an important source of food for local populations. These fisheries are particularly sensitive to dam construction because of disruptions of migratory fish stocks .Water use for crude oil production greatly varies, depending on technology used, local geology of the reservoir, and operational factors . Relatively large amounts of “fossil” water, corresponding to roughly 7 times the volume of oil produced, are extracted with the oil . The produced water is injected into disposal wells, reinjected into the reservoir to improve oil recovery efficiencies, or treated with energy-intensive technologies and added to the water cycle.Primary oil recovery, that is, the natural flow of oil into production wells, has a small water footprint of extraction. However, primary recovery usually extracts less than one third of the hydrocarbons stored in the geologic formation from which they are extracted. To maximize reservoir production, more expensive and advanced technologies, such as secondary and tertiary oil recovery, are implemented. Secondary recovery via water injection uses large amounts of water to improve oil production. Water allocations can come from different sources; for example, in Russia, water is withdrawn from freshwater resources, and in Saudi Arabia, the water used is typically either brackish water or seawater . Tertiary oil recovery or enhanced oil recovery via thermal recovery is even more costly and energy demanding. In this case, high-pressure steam is injected into the hydrocarbon reservoir to reduce heavy oil viscosity and increase the production flux. Another water-intensive enhanced oil recovery technique is tertiary recovery via CO2 injection. CO2 is captured from the “flue” gas emitted using water-based technologies, such as absorption through amine scrubbing . Carbon dioxide is subsequently stripped from the solvent by heating and transported and injected into the hydrocarbon reservoir to enhance oil production . In recent years unconventional fossil fuels have received increased attention as important energy sources . Shale oil and oil sands are expected to contribute to a growing share of our future energy needs.