Month: November 2022

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.

As a concentration gradient is then formed between the water layers at the nanobubble surface and the bulk fluid, more hydroxide ions begin diffusing from the bubble through this diffusion layer to the surface of the bubble. The thickness of this layer can be found by Prandtl’s equation, where the fluid velocity is the velocity of the Brownian motion of the bubble as predicted by the Langevin equation, using the Ornstein-Uhlenbeck process. The same layer also acts a diffusion region for protons, which diffuse in from the bulk layer once they are depleted or their concentration changes, and must also be affected by the distance they must diffuse through to reach the nanobubble surface. These phenomena are further examined in the following sections. At the same time, protons from the diffusion layer also reach the hydroxide ion-rich surface, but much more slowly, at a rate about five times slower than the hydroxide ions. Upon reaching the surface, they start eliminating the hydroxide ions into water molecules, which further increases the dilution of both ions, and encourages diffusion from the bulk layer to the interface, which is probably a monolayer. When the three processes, of hydroxide diffusion, proton diffusion, and hydroxide elimination by protons, are in steady state or in dynamic equilibrium, we have a fixed amount of area which is not covered by hydroxide ions, however temporarily and will allow the diffusion of gas into the water. Taking an average, we can define a percentage of surface area of the nanobubble,chicken fodder system which will remain available for diffusion, which will be in proportion to the radius of the bubble.

This can be done by taking the size of one hydroxide ion, then finding the capacity of a nanobubble’s surface to adsorb hydroxide ions, correlating it with the number of ions being eliminated, and taking a ratio with the capacity which is a function of area, which is a function of radius. The rate at which the adsorption of the hydroxide ion takes place would then depend on two separate phenomena: firstly, the repulsion by the hydroxide ions already physisorbed onto the surface, which would force the ion to move along the surface until it finds a location that is unoccupied, and secondly, the velocity of the hydroxide ion as it travels through the hydrodynamic layer of the nanobubble. The velocity can be found by calculating the surface charge on the nanobubble, and using it and the initial distance between a particular ion to find the potential that drives it to move. The potential for the hydroxide ion to move to the nanobubble surface decreases as the surface charge increases, and thus the rate will eventually dwindle down to zero as the bubble achieves stability, and the potential will reach a constant value. The rate for the elimination of the physisorbed hydroxide ions, on the other hand, will only increase the surface charge density increases, since the elimination is accomplished by positively charged protons attracted to a negatively charged surface. The same equations for ionic mobility can be used to calculate the velocity of travel for the protons, but there is no equation needed for the rate of adsorption, as they simply react with the adsorbed hydroxide ion to give two molecules of water. The balance between these two rates thus depends on the time at which the reactions are taking place, which will ultimately determine the area needed for the diffusion of the gas into the water. To find the ion mobility, we first consider an ideal case where a newly-formed and shrinking bubble has no hydroxide ions physisorbed onto its surface, and is formed in pure water with a pH of 7. This gives us, assuming a perfectly uniform distribution of ions in the water, a concentration of 10-7 moles of hydroxide and protons each in the surrounding hydrodynamic layer.

Thus, the amount of both available to be physisorbed can be found by simply taking a section of the hydrodynamic layer up to the distance from the surface where we wish to find the concentration and time needed to reach the surface for the ions present at that distance from the surface. We take the volume of this section and multiply by molarity and Avogadro’s number to get the actual number of ions present, as shown below. In the derivation of the force balance presented in section 3.2, the formula takes into account the contribution of the repulsion between hydroxide ions adsorbed to the surface of the nanobubble. This section estimates the number of the ions adsorbed to the surface of the nanobubble, and uses the terms associated wit their arrangement to calculate this contribution and to examine the possibility that they can, indeed help to balance the inward and outward pressures exerted on the nanobubble surface and thus provide an explanation for their stability. Both possibilities of stationary and nanobubbles in motion are assumed and calculated to provide estimates for the repulsive force, and are substituted along with representative values in the derived equation for the force balance, and the result is presented. However, the stationary nanobubble is an ideal case, and in actual situations the bulk nanobubble is usually in motion due to Brownian motion, which also prevents it from rising to the surface. Thus, it can be established that the bulk solvent for a bulk nanobubble in motion, only consists of the boundary layer that moves with the nanobubble as it moves through the solvent. It also must supply the ions needed to stabilise it, and must contain the ions that are adsorbed. We may use the Blasius solution of the Prandtl equation, since, by comparing the size of the nanobubble to the size of the water laminae we may approximate the relative curvature to be negligible, as well as the flow being laminar due to the fluid itself being static, and hence the flat plate approximation may apply.

Thus, the approximate thickness of the boundary layer d is obtained with equation as before in section 4.4. From Figures 2 and 3 for the same assumed conditions, we obtain a boundary layer thickness of about 60 microns. The exact volume of water available to interact with the nanobubble is, therefore about 9 × 10-19 litres. This, at pH 7,fodder systems for cattle contains even less than one hydroxide ion, assuming uniform distribution of ions before the nanobubble is formed. Thus, drawing on the number of ions derived previously, even adding one ion to this volume significantly decreases the Debye length of the hydroxyl ions within the boundary layer. This in turn opens the possibility of pH being as high as 15 within the boundary layer, and the possibility of the number of ions being adsorbed being far larger. At pH 15, using the same equations as before, we obtain the Debye length to be 0.01 nm, with a corresponding surface charge of 2426 C, and the corresponding number of ions adsorbed to the surface being about 1.51 × 1022. This, however, exceeds the number of hydroxyl ions that there is room for on the surface, which is only about 1 × 10଺ . This allows us to consider that the nanobubble surface might, in fact, be fully saturated, which, gives the Debye length a value of 0.2 nm, a corresponding surface charge of 1.21 × 10-18C, and a pOH of 0.26, corresponding to a pH of 13.74. The inter-ionic distance, x, can also be found using equation , by substituting the same values used earlier for radius and the number of ions. This gives a value for x to be about 85 nm. Comparing with the Debye length of the hydroxyl ions at pH 7, which is given by equation , it is shown to be well within the range of electrostatic effects of the hydroxyl ions in solution.

This also implies that any movement of the ion which would disturb it from its equilibrium position, such as the diffusion of gas out of the bubble, will have a high activation energy, thus reducing the rate of diffusion and providing an explanation for the long lifetimes of bulk nanobubbles. The inter-ionic distance for the completely saturated nanobubble is assumed to be zero, with ions being in direct contact with each other. While this is an extreme case, it remains possible. In this case, then, the ions would completely block the diffusion of the gas within the bubble to the bulk fluid by simple steric repulsion, giving the nanobubble a very long lifetime. However, since we do have a limit to the lifetime, it is clear that this extreme case does not exist, but it is likely that the reality approaches it, and that the pH of the boundary layer surrounding the nanobubble is significantly higher than the bulk solvent outside it.In a second possible case, the force acting to shrink the nanobubble may be considered to be equal and opposite to the force of repulsion between hydroxyl ions that are adsorbed to the surface.Thus, it is concluded that hydroxyl ions adsorbed to the surface do not assist significantly in balancing the internal and external pressures of the nanobubble. As stated in section 4.1, the other contributing factor to the change in the rate of diffusion is the effect of the hydroxide ions adsorbed to the surface. The mechanism of their actual inhibition would, conceivably be due to the steric hindrance imposed by them for an oxygen molecule attempting to leave the nanobubble. However, the spacing between the ions calculated in section 3.3.2 is far too high for any significant barrier to the diffusion. However, oxygen in gaseous state, that is to say, the oxygen molecule, is highly electronegative, and may offer significant repulsion to the hydroxide ions, as may other electronegative gases such as nitrogen. This would mean that the repulsive forces would, in theory require the ions adsorbed to the surface to change the spacing between them in order to permit the gas molecule to diffuse through an area free of the repulsion that force it to stay inside the nanobubble. This also implies that any movement of the ion which would disturb it from its equilibrium position, such as the diffusion of gas out of the bubble, will have a high activation energy, thus reducing the rate of diffusion and providing an explanation for the long lifetimes of bulk nanobubbles. This possibility is analysed in this chapter, and can apply to oxygen, nitrogen and air, as it is a mixture of the two. Takahashi et al. report the zeta potential of microbubbles to be constant and independent of size, which, since the surface charge density is directly proportional to the zeta potential, implies that surface charge density is also constant. This indicates that the microbubble, as it shrinks, releases adsorbed ions from its surface in order to maintain the same surface charge density. We can assume that the shrinkage is thus opposed by the tendency of hydroxide ions to be de-adsorbed, since hydroxide ions appear to be in a lower energetic state when adsorbed to the surface of the nanobubble, than in solvation, which appears to be at a higher energy state. They would, therefore be forced to go into solution if the nanobubble cannot accommodate them on its surface due to shrinkage. However, for the nanobubble to shrink, the gas molecules contained within must escape, and to do so they must have sufficient momentum to provide the energy needed for the hydroxide ions adsorbed on the surface to be de-absorbed. Thus, the gas molecules require sufficient kinetic energy, which, when transmitted to the ions, must permit them to be de-adsorbed. We can also characterise this with a change in the force of repulsion between ions adsorbed on the surface and a change in the inter-ionic distance. The hydroxide ions, then, clearly have a role in inhibiting diffusion of the gas molecules contained within the nanobubble into the bulk fluid. The mechanism for this inhibition is assumed to be by means of ion-lone pair repulsion, between the hydroxide ions adsorbed to the surface and the lone pairs of the oxygen atoms within the nanobubble.

Comparison of the variations in the percentage of 14C partitioned into starch with changes in starch accumulation could indicate if there are additional regulatory mechanisms leading to turnover, i.e.simultaneous synthesis and degradation.Cold, mild osmotic and salinity stress triggered enhanced starch accumulation at ED in the source.Twelve hours later , only cold and mild salinity kept starch accumulation high relative to the non-stressed control.In comparison, the 14C that partitioned into starch decreased from ED to EN , thus, the increased starch content observed might be due to inhibited starch degradation early in the day.A similar pattern was found in the roots — higher starch accumulation even though there was no change in the percentage of 14C partitioned to starch over the same period.Because the starch-sugar inter conversion in source leaf was acutely regulated in response to environmental cues, we further examined if changes in starch metabolism and sugar export was accompanied by the regulation of the known T6P/SnRK1 stress signaling pathway genes.Te transcript level of five selected genes in source leaf exposed to 300mM mannitol and 200mM NaCl stress, which triggered the most dynamic changes in starch metabolism, were evaluated.These genes are involved in starch synthesis, sucrose transport, and are components of the T6P/SnRK1 stress signaling pathway.AtTPS1 encodes trehalose-6-phosphatesynthase, AtSnRK1.1 and AtSnRK1.1 encode two major isoforms of SnRK1,dutch bucket for tomatoes the central players of the T6P/SnRK1 pathway.AtAPL3 encodes the large sub-unit of ADP-glucose pyrophosphorylase that catalyzes the first committed step in starch biosynthesis.AtSWEET11 encodes a transporter that exports sucrose from leaf mesophyll cells into the phloem for transport to sinks.Our measurements showed that AtSnRK1.2 was up-regulated by osmotic and salinity stress after 6hours of treatment.

However, the transcription of AtTPS1 and AtSnRK1.1 did not change.AtSWEET11 was down regulated by severe osmotic stress at the end of day.AtAPL3 was up-regulated at MD and at EN by 300mM mannitol stress, and was up-regulated from ED to EN by 200mM NaCl.Our overall aim was to develop a comprehensive map of time-dependent changes in carbon allocation and partitioning, to see how these processes were affected under different stresses.In our study, the 14C partitioning in source and different types of sinks over the diurnal cycle was examined.Under control conditions, 14C distribution into different metabolic pools in source and sink This issue, followed expectation based on previous knowledge.Source leaf, sink leaves and roots This issues showed different carbon partitioning, with most dynamism in the source.Most carbon in source leaf flowed into storage compounds , and less flowed into structural compounds during the day.This result is similar to a previous study.Te roots also generally incorporated more carbon into RICs while sink leaves partitioned more into starch.This indicates a clear differentiation in carbon use between sink leaves and roots.Carbon allocation to the sinks was modulated by all abiotic stress conditions used in our study.Stress conditions should reduce photosynthetic capacity and carbon available for export.Knolling et al.showed that carbon export from the source to sink leaves was reduced in Arabidopsis experiencing dark-induced carbon-starvation.Our study included roots, which is a stronger sink than leaves.We found that the C-fluxes into the roots were more vulnerable to stresses than those into sink leaves.Furthermore, plants might regulate carbon allocation differently in response to long-term and short-term stresses requiring caution when making comparisons between studies.Durand et al.observed a higher percentage of 14C allocated into roots in the long-term water defcit stressed Arabidopsis.However, data from plants exposed to short-term stress in our study and plants exposed to a 16h night showed the opposite results: reduced percentage of 14C exported into roots.This underscores that timing, intensity, and type of stress regulate carbon allocation differently, even if some stresses show similar responses.

Osmotic, salinity, and cold stress all triggered complex changes in carbon partitioning and shared some commonalities.All stresses increased the carbon partitioned into sugars in both source and sink This issues.They also decreased the 14C partitioning into starch in the source leaf while increasing organic acids and amino acids.Each stress had a more dramatic impact on source leaf than the sink This issues, with most changes occurring within the first 12h of stress application.Te abiotic stresses used here all triggered decreased 14C flux into RICs in the roots.Among the major metabolites pools affected, changes of carbohydrates were most consistent.Kolling et al.observed an increase of 14C into sugars and a reduction of 14C flux into the RICs pool in both source and sink leaves.However, in our study, the increased 14C flux into sugars in the source leaf was due to the re-partitioning of 14C from storage compound , while the increase in the sink could be explained by the reduced 14C partitioning into structural compounds.Different abiotic stresses may uniquely regulate carbon use.Only cold stress caused a decrease in 14C in RICs in source leaf.Osmotic and cold stress, but not salinity stress, increased 14C flux into organic acids and amino acids in root This issues, and enhanced 14C into amino acids in sink leaves.Only cold and salinity stress, provoked changes in 14C in protein in source and sink leaves.Higher 14C in protein at the early stage of the stress progression may be due to the accumulation of stress-responsive proteins and enzymes.When stress continued, storage compound like the storage, cytosolic, and vacuolar proteins are degraded and recycled to provide energy and substrates for respiration.The regulation of starch accumulation by abiotic stress in Arabidopsis were mainly studied during the day and only focused on leaves.Mild-to-moderate mannitol stress triggered starch accumulation, whereas higher mannitol concentrations or severe drought led to decreased leaf starch.Moderate-to-severe salinity decreased starch in Arabidopsis leaves.Cold stress induced starch accumulation in leaves in some studies, while decreased starch accumulation in others.Our study differentiated between source and sink This issues, and starch content was regulated by abiotic stress in both.There was a lack of congruency in the starch accumulation and 14C-starch partitioning under cold, mild osmotic, and salt stress in source and roots.Higher starch content in sink under stress might be due to decreased starch utilization.In the roots, more 14C accumulated as sugars because of the decreased 14C partitioning into structural compounds.In this case, it might not be necessary to degrade starch into sugars.

Starch, as a sugar reservoir, regulates plant carbon balance to avoid potential famine.Maintaining sugar levels by cycles of synthesis and degradation of starch could permit metabolic fexibility with respect to starch-sugar interconversion.Te sugars so produced may act as Reactive Oxygen Species scavengers, osmoprotectants and be an immediate source of carbon and energy to mitigate against stress.Sugar conversion to starch in leaves may prevent feedback inhibition of photosynthesis, and higher starch in the roots could help gravitational response under stress, and enhance biomass for better foraging.Transcripts levels of T6P/ SnRK1 pathway genes were regulated by abiotic stress in this study.AtSWEET11, one of the sucrose transporters, is important in whole-plant carbon allocation.It is expressed when sucrose export is high and repressed during osmotic stress in Arabidopsis leaves, when presumably export is lower.In our study, AtSWEET11 was down regulated by osmotic stress at the end of day, which suggests that the export of sugar to the sinks was inhibited.Te repression was likely due to feedback inhibition by excess sugars, this is supported by our data, which showed more 14C in sugars in the source leaf at ED, and decreased 14C imported into roots.AtAPL3 was shown to be up-regulated by 150mM NaCl stress in Arabidopsis.Our study also observed the up-regulation of AtAPL3 by 200 mM NaCl,blueberry grow pot and 300 mM mannitol stress.Interestingly, the percentage of 14C partitioned into starch was reduced, and the end point starch content remained unchanged.Changes in the post-transcriptional regulation of AGPase rather than at the transcriptional level under stress may underscore starch contents assayed.SnRK1 has a pivotal role in regulating carbohydrate metabolism and resource partitioning under stress.In this study, AtSnRK1.2 was up-regulated by osmotic and salinity stress after 6 hours of stress treatment.However, the transcript of AtTPS1 and AtSnRK1.1 did not change, indicating a possible delayed response to stress compared with AtSnRK1.2.Te inconsistency in transcript changes of AtSnRK1.1 and AtSnRK1.2 might also be due to the specifcity of these isoforms in terms of spatial expression and function.In maize, salinity stress triggered more starch and sugar accumulation in both source and sink This issues and the transcripts of the ZmTPSI.1.1 and ZmTPSII.2.1 genes in the source leaf were down-regulated, while SnRK1 target genes AKINβ was affected mainly in the sink but not in the source.Large-scale metal contamination can result in severe environmental damage, and remediation efforts represent a substantial financial burden for industry, government and taxpayers.Anthropogenic metal inputs include spoil from metal mining operations, fallout from refinery emissions, waste disposal, electroplating, combustion of fossil fuels, and agricultural application of pesticides and bio-solids.Traditional remediation efforts are not feasible for large-scale impacts and therefore alternative remediation strategies are necessary when vast areas of land have been contaminated.Hyper accumulator plants concentrate trace metals in their harvestable biomass , thereby offering a sustainable treatment option for metal-contaminated sites and an opportunity to mine metal-rich soils.Cultivating nickel hyper accumulator plants on metal-enriched soils and ashing the harvestable biomass to produce Ni oreis an economically viable alternative for metal recovery.Soils suitable for Ni phytomining include serpentine soils and industrially contaminated soils.Serpentine soils develop from ultramafic parent material and thus contain appreciable quantities of Ni, cobalt , chromium , manganese , iron and zinc.The Ni : Co ratios in serpentine soils typically range from 5 to 10.Anthropogenic metal inputs generally involve discharge of a mixed-element waste stream.For instance, emissions from Ni smelters are typically enriched with other trace metals from the ore , Co, leadand Zn.Heavy metals are incorporated into enzymes and are thereby toxic to living organisms in excessive amounts.Cobalt contamination is an environmental concern, and the radionuclide 60Co is classified as a priority pollutant.Hyper accumulator plants used to extract Ni from metal-enriched soils must be tolerant of co-contaminants.Therefore, the effects of metal co-contaminants on the physiology and biochemistry of hyper accumulators, and ultimately on the efficiency of metal phytoextraction, is of concern for metal recovery efforts.Several first-row transition metals have important roles in biological systems as activators of enzymes or as key components of enzyme systems.Cobalt is essential for Rhizobium , free-living nitrogen-fixing bacteria and cyanobacteria.However, there is no evidence that Co has a direct role in the metabolism of higher plants.Nickel is the element most recently classified as an ‘essential’ plant nutrient and is a key component of the Ni-containing enzyme, urease.Transmembrane transport systems with specificity for Ni or Co have not been identified in higher plants.

The nickel hyperaccumulator, Alyssum murale, a herbaceous perennialnative to Mediterranean serpentine soils, has been developed as a commercial crop for phytoremediation/phytomining.Hyperaccumulator species of Alyssumaccumulate Co from Co-enriched soils ; Cobalt accumulation is most efficient in mildly acidic soils, whereas Ni is most effectively accumulated from neutral soils.Alyssum sequesters Ni via epidermal compartmentalization, a metal sequestration strategy exploiting leaf epidermal This issue as the sink for metal storage.Epidermal cell vacuoles are responsible for Ni sequestration in Alyssum , and vacuolar sequestration has been recognized as a key component of cellular-level metal tolerance tolerance for several hyper accumulator species.However, Co sequestration in Alyssum epidermal cell vacuoles has not been reported previously.Information regarding metal localization and elemental associations in accumulator plants is crucial to understanding the mechanisms of hyper accumulation and tolerance.Synchrotron-based techniques such as X-ray microfluorescence and computed microtomography can be used to image elements in hyper accumulator plants.SXRF imaging of an intact, transpiring thallium accumulator showed that Tl is distributed throughout the vascular network, and X-ray absorption spectroscopy identified aqueous Tlas the primary species in plant Thissue.X-ray CMT imaging techniques such as differential absorption and fluorescence microtomography resolve the three-dimensional distribution of elements within a sample, and hydrated biological specimens can often be analyzed with minimal or no sample preparation and alteration.DA-CMT and F-CMT were used to visualize Fe localization in seeds of mutant and wild-type Arabidopsis, revealing that Fe storage in seeds was mediated by the vacuolar Fe transporter.F-CMT and DA-CMT showed Ni enrichment in leaf epidermal This issue of A.murale grown in Ni-contaminated soils.Soils naturally enriched or industrially contaminated with Ni typically have co-contaminants present; however, the influence of common metal co-contaminants on Ni hyper accumulation remains poorly understood.In the present work, the effect of Co and Zn on Ni accumulation and localization in A.murale was examined.

The foliar fertilizer product “CleanStart,” “Kick-Off,” and “GroZyme” were obtained from Ag Spectrum Company.0.1% Silwet L-77was added in each solution.The solutions were applied to the leaves of sunflower 8 h before darkness , and all plant Thissues except the sprayed leaf were covered to prevent inadvertent spray application.The petioles of all sprayed leaves were carefully protected by coating the leaf base petiole junction with lanolinand Teflon membranes.Four plants were treated as one replication, with three replications for each treatment.The foliar application of the fertilizers was replicated one time after 7 days, and then plants were harvested 7 days later.GroZyme is a microbial fermentation product derived from a proprietary mix of organic cereal grains inoculated with specific bacterial cultures and fermented.The fermentation process occurs under controlled environmental conditions until a specific metabolic profile is achieved at which time the live bacterium are liaised and the material is filtered to remove large particles.This concentrate is then extended and stabilized to make the final product.Soil applications of GroZyme have been reported to alter soil microbial activity and nitrogen transformations.The metabolic basis for the biological activity of foliar applied GroZyme is not known.However, field observations suggest that GroZyme functions to enhance plant growth by enhancing K metabolism and sugar transport.CleanStart is derived from ammonia, urea, orthophosphoric acid and potassium hydroxide,ebb flow tray and Kick-Off is a micro-nutrient mix of Fe, Mn, Cu, Zn predominantly derived from nitrate sources with additional surfactants and stabilizers.The elemental composition of all spray applications is provided in Table 1.Mid-sections of leaf petioles were cut from the leaves treated with different foliar treatments.Leaf cross-sections were cut with a cryotomeat a temperature of −20◦C.

Single sections of each treatment were selected under light microscopy for their ultra structural integrity and then freeze-dried under −20◦C for 3 days prior to μ-XRF analysis.Since μ-XRF analysis is time consuming and expensive only single samples from each treatment could be analyzed.Given that true replicate analyses could not be performed additional steps were taken to avoid the potential for experimental artifacts and to avoid any sample selection or analysis bias.All treatments were carefully controlled such that treatment conditions and experimental duration were identical; petioles were then taken from the four replicate plants and multiple sections from each petiole were prepared as described above.All sections were then assessed by light microscopy for ultra structural integrity and a single section was then selected and transported to the Stanford Synchrotron Radiation Laboratory for μ-XRF analysis.Samples selected in this fashion, therefore represent unbiased examples of treatment effects.To investigate the effects of different fertilizers on retranslocation of nutrients in the leaves of sunflower, μ-XRF mapping was performed.Cross sections of petioles were cut from the sun- flower plants at approximately 1.0 cm below the leaves and imaged under a light microscope prior to utilization for μ-XRF imaging.The cross section of petiole was composed of epidermis, parenchyma, vascular bundle containing xylem, phloem, and surrounding collenchyma.The microscope image in Figure 1 shows that the phloem within the vascular bundle exists as a discrete layer of cells on the abaxialside of the vascular bundle with xylem on the adaxial or upper side of the petiole.The entire vascular bundle is enclosed in Thissue that is likely collenchyma.Integrated intensity for Zn and other elements were calculated from the spectrum and normalized by the intensity of the Compton scattering peak.Elemental mapping for the measurement area was obtained from the normalized intensity for each element.The elemental distribution maps of Zn , Ca , and Kin the petioles collected from sunflowers plants with different treatments are presented in Figures 2A–F, together with corresponding photographs taken using an optical microscope.

The quantification of the fluorescence yields was normalized by I0 and the dwell time.The normalized X-ray fluorescence intensities were scaled to different color brightness for individual elements, with the brightest spots corresponding to the highest elemental fluorescence.Each map indicates the relative distribution of the three elements, and the scale of fluorescence counts for individual elements is the same for each map.Very slight signals of Znwas noted in the petioles collected from the control and CleanStart treated plants of sunflower.At the resolution used in these experiments it is not possible to determine if the deposition of Zn in regions other than the phloem was resent in xylem or in collenchyma immediately adjacent to the xylem.A modest increase in the K signal in petioles was also observed in the Clean Start treatment.Foliar application of “Kick-Off,” a product containing Co, S, Fe, Cu, Mn, Mo, and Zn chelated with EDTAto sunflower leaves resulted in a marked increase in the concentration of Zn detected in the petioles with a notable deposition in a narrow band corresponding to the phloem Thissues of the petiole and a more diffuse band in the xylem/collenchyma region , while no such preferential localization to phloem Thissues was noted for control, CleanStart or ZnSO4 treatments and no phloem specific accumulation of other elements was observed.Application of ZnSO4 at the same Zn levels as used for all Zn treatments to the sunflower leaves also increased phloem Zn in the petiolesas compared with the controls , but the effect is much less pronounced than that of “Kick-Off.” The combined foliar application of “Kick-Off”with “CleanStart” resulted in a similar enhancement in Zn uptake and preferential distribution of Zn to phloem Thissues and xylem/collenchyma.The addition of the bio-stimulant product GroZyme resulted in a much more concentrated enrichment of Zn in the phloem and xylem/collenchyma region of the petiole vascular bundle.Low spatial resolution μ-XRF imaging provides only semiquantitative data.To further investigate the effects of “CleanStart” and “GroZyme” on phloem mobility of foliar applied Zn, microXRF scanning at higher resolution was performed, focusing on the vascular Thissues of the treated leaf veins.The Zn concentration in the petiole was also determined along a single scan line that transected the petiole and passed through the vascular system.Both “CleanStart” and “GroZyme,” which do not contain Zn, clearly increased the FIGURE 5 | Concentrations of Znin the petioles collected from sunflower plants treated with different foliar fertilizers.Full expanded leaves of sunflower were treated with control, CleanStart, Kick-Off, CleanStart + Kick-Off, CleanStart + Kick-Off + GroZyme, and ZnSO4, and the Zn concentration of leaf veins were analyzed by ICP-MS.

Compositions of the nutrients in different treatments were shown in Table 1.Data points and error bars represent means and SEs of three replicates.concentration of Zn following Kick-Off application.The patterns of Zn deposition in the “Kick-Off” + “CleanStart” and “KickOff” + “CleanStart” + “GroZyme” were far less diffuse and more intensely located in the phloem region and xylem/collenchyma than the pattern of Zn in petioles from leaves provided with “Kick-Off” or ZnSO4 alone.Intensity analysis across a single scan line through the vascular system of the petiole demonstrated that the peak of Zn densities in the phloem Thissues and xylem/collenchyma was markedly increased with addition of the biostimulant “GroZyme” to “Kick-Off”+“CleanStart” treatments.Total concentrations of Zn and other elements including Fe, K, Cu, Ca, and Mn etc.were determined by ICP-MS for the petioles collected from the sunflowers treated with different foliar fertilizers.The results showed that Zn concentrations in the leaf veins of sunflower ranged from 29.2 to 36.7 mg kg−1 DW.While the overall pattern of Zn concentration differences analyzed by ICPMS corresponded with the μ-XRF analysis results the total Zn concentration was not significantly different between treatments.Similarly, no difference in Fe, K, Cu, Ca, and Mn was observed among any treatments.The apparently greater sensitivity of μ-XRF is primarily a consequence of the ability of μ-XRF to analyze specifically within phloem and closely associated vascular organs while ICPMS provides analysis of the total petiole.Since vascular Thissue represents only a very small proportion of the petiole as a whole, and as the petile was fully mature at the time of treatment, changes in vascular Thissue element concentration may not be seen against the background of the bulk of petiole Thissue in which Zn was not increased.Efficacy of foliar applied nutrients depends not only on the absorption of the nutrients but also on the transport of these nutrients to other plant parts.It has been suggested that even a relatively small transport of foliar nutrients out of treated leaves and Thissues may have a short-term,flood and drain tray critical benefit to the plant.Knowledge of the ability of an element to be transported from the site of application is critical to provide insight into the longevity and potential nutritional impact of foliar application on non-sprayed Thissues.Analysis by μ-XRF in the present study shows clearly enhanced transport and localization of Zn in the vascular system of the sunflower petiole 7 days after application of “Kick-Off,” which contains Zn-EDTA , while Zn was not detectable in the petiole of the control plants and was very low in the petiole of ZnSO4 sprayed leaves.This demonstrates clearly that Zn is phloem mobile in sunflower and that the use of Zn-EDTA results in greater phloem Zn transport than ZnSO4 alone.While it has been demonstrated that Zn-EDTA is superior to ZnSO4 under some circumstances, it has not been demonstrated that the EDTA molecule can penetrate the leaf cuticle.It cannot be determined from this current research if the superiority of the EDTA containing Kick-Off material is a consequence of enhanced cuticular penetration or enhanced transport of the Zn once it enters the leaf.The ‘Kick-Off’ material also contains the micro-elements including Fe, Cu, Mn, and Mo and this may also enhance Zn uptake as has been observed previously.The addition of “CleanStart” derived from ammonia, urea, orthophosphoric acid and potassium hydroxide, significantly increased the phloem transport and xylem/collenchyma deposition of Zn when co-applied with ‘Kick-Off’.Addition of Urea to foliar Zn sprays, for example, is known to enhance Zn uptake and efficacy and the N status of cereals is known promote Zn retranslocation.While it is clear that addition of the multi-elements present in the Clean Start enhanced Zn retranslocation into sunflower petioles, the mechanism of this effect remains uncertain.

The chemical form in which a foliar nutrient is applied will influence plant nutrient uptake by altering the point of deliquescence of the applied foliar fertilizer thereby altering its solubility on the leaf surface, or by altering the charge on the ion of interest to facilitate its movement through the cuticle and cell wall.There is no direct evidence, however, to suggest that the formulation of a fertilizer spray can directly influence the transport of the absorbed nutrient from the site of application.The addition of the bio-stimulant “GroZyme” clearly enhanced Zn translocation when co-applied with “Kick-Off” and “CleanStart”.Grozyme is a non-living microbial fermentation product derived from a proprietary mix of organic cereal grains inoculated with specific bacterial cultures and fermented.The specific functional metabolite in GroZyme has not been identified.However, extensive field trials and research published in this issuehave demonstrated positive growth effects and enhanced translocation of K and other nutrient elements.Previous research utilizing soil applications of GroZyme has also shown that this product was able to alter microbial populations in a soil environment and improve N mobilization and uptake of soil nutrients especially organic nitrogen.The benefit of bacterial source metabolites on efficacy of foliar fertilizers has been demonstrated previously and it is plausible that the microbial extracts present in GroZyme have the capability to form metal complexes that enhance Zn uptake or mobility.Many putative bio-stimulants also contain plant growth hormones or plant signaling molecules that may alter plant metabolic processes and stimulate growth and indirectly influence the movement of substrates, including minerals, within the plant.In these experiment, the high spatial resolution and direct imaging capability of μ-XRF was useful in distinguishing differences in Zn transport through the vascular system of sunflower that could not be detected by ICP-MS.XRF provides a powerful strategy to trace foliar applied microelements within the plants with high sensitivity, a result that is consistent with our previous studies.This technique will be useful to facilitate the development of foliar fertilizers and application techniques that optimize transport of nutrients from site of application, which is one of the most important challenges to the foliar fertilizer industry.Heavy metal contamination, such as cadmiumand lead , in various environmental mediaposes a severe threat to ecological and human health as long as they are bio-available.Although there are natural sources of these elements, anthropogenic releases from activities such as metal mining and smelting, coal combustion, trace levels in fertilizers and even some wastewater sludge and biosolids, can increase concentrations to high levels in soils and sediment beds of lakes and rivers.