July 2023 – Page 2 – Nature Ecrogrow

The inflows and outflows of river leakage appear to remain fairly consistent over time

By plotting the residuals on a map of the parent model domain, we were able to assess the distribution of wet and dry wells in our model. Blue colors indicated an excess of water in certain wells, red and orange colors indicated wells that were more “dry,” and green colors represent a satisfactory residual value. A satisfactory residual value means that the difference between the observed and simulated equivalent heads were small, indicating good model performance. The black square on the residual map is a reference point for the area of the child model domain’s boundary.The outputs of the parent model are data of groundwater fluxes, which includes the magnitude of volumetric flow through each model cell and the direction. The groundwater flux was calculated at each cell in every layer of the model for each stress period . The hydraulic head, or groundwater elevation above sea level in meters, was plotted as orange contours with the magnitude and direction of groundwater flux for Layers 1, 6 and 9 with black arrows . These three layers were chosen out of all nine layers because they were deemed representative of the top, middle, and bottom of the model’s layers. The length of each arrow represents the magnitude of groundwater flux, with the arrow pointing in the direction of flow. The map also includes a black square that serves as a reference point of the child model area, and the flow that occurs at and around the child model’s boundary at each layer. The maps show that the general flow of groundwater in the parent model is towards the cone of depression and the pumping wells in that area, with water flowing away from the Sacramento River near the recharge sites in the child model area.The results of Scenario 1, which was run using the child model, represents the baseline model run performance and outputs,blueberry pots using the original and unaltered deep percolation data from Davids Engineering. For this baseline scenario, we assessed the model performance using a similar analysis to the parent model performance.

The one-to-one plot for the child model is a plot of the observed and simulated equivalent heads with a gray line indicating the line of equal value . The colors of the dots represent the binned residual head data.The binned residual heads were also plotted on a map of the child model domain, indicating the location of the four groundwater monitoring wells used to collect continuous and periodic groundwater elevation data during the recharge studies at each ag-MAR field site . The location and shape of the field sites are outlined in black, and the four colored dots show the location of the groundwater monitoring wells and their average residual simulated head value. Yellow colors indicate “dry” wells , green colors represent good model performance , and blue colors indicate “wet” wells .The child model outputs of Scenario 1 include the magnitude and flow direction of volumetric groundwater fluxes in each model cell, calculated using MODFLOW’s groundwater flow equation at each stress period in the model run; the child model is transient and has 451 stress periods, or days, that it simulated in its model run. Head contours are plotted as orange lines and flow magnitude and direction plotted as black arrows illustrate the direction and magnitude of groundwater flow . Groundwater generally flows southwest, with water flowing away from the Sacramento River in the area near the recharge sites. Only the first layer was plotted, since this is the only layer of interest due to it being the layer of the child model in which the RCH package defines recharge to occur.A more in-depth analysis of the model performance was conducted to understand how the observed and simulated equivalent heads change over time at each of the four groundwater monitoring wells in the child model domain. Hydrographs of the observed and simulated equivalents were plotted for each groundwater monitoring well; the head, or groundwater elevation ASL was plotted on the primary y-axis, while recharge rates was plotted on the secondary y-axis as a bar plot .

Hydrographs and recharge rates were plotted together for each well to illustrate the relationship between groundwater elevation and recharge rate over time. In half of the groundwater monitoring wells we observed simulated equivalent values greater than the observed values, and in the other half of the wells we observed simulated equivalent heads less than the observed values. The difference between the observed and simulated equivalent head values were the greatest for the Field_15 well, with a 12-14 m difference, while the difference between the observed and simulated values for the other three wells were significantly less, with a 2-6 m difference. This discrepancy may arise from the spatial variation in where the groundwater monitoring wells are located . The Field_2_2019, Well_2b, and Well_34 monitoring wells are all located near each other, near the Sacramento River. In contrast, the Field_15 well is located the farthest away from the Sacramento River and the other three wells. Recharge rates varied over time among the four groundwater monitoring wells. For Field_2_2019 and Field_15, recharge gradually increased in mid- to late September of 2019 and remained constant throughout the remainder of the flooding period in October of 2019. For Well_2b and Well_34, recharge rates increased rapidly in September of 2020, remained fairly constant through October of 2020, and slowly decreased during November of 2020 .Additional child model outputs from Scenario 1 include the water budget components that flow into and out of the model’s cells, calculated during each stress period of the model run. The water budget components plotted include storage , river leakage , recharge , storage and river leakage . A stacked bar chart was made to represent the magnitude of the rates of each water budget component over time . Water that flows into the model cells from storage, river leakage, and recharge are plotted in light green, light orange, and blue, respectively. These inflows are specified as positive rates on the y-axis.

Water that flows out of the model cells and are transferred to storage and river leakage are plotted in dark green and dark orange, respectively. These outflows are specified as negative rates on the y-axis. The rates of each component were plotted to see the variations over time, such as seasonal differences in recharge or storage. The child model results of Scenario 2 represent increased rates of deep percolation during the same recharge periods as Scenario 1, where deep percolation values were increased by one order of magnitude. Similar to Scenario 1, we analyzed the hydrographs of observed and simulated equivalent heads over time at each of the four groundwater monitoring wells . Groundwater elevation levels were plotted on the primary y-axis, and recharge rates were plotted as a bar chart on the secondary y-axis to compare the observed and simulated equivalent heads with recharge rates over the course of each recharge period. Both simulated equivalent head values were plotted from Scenario 1 and Scenario 2 to display the hydrologic difference between the two scenarios. Overall, the hydrographs of the simulated equivalent heads for Scenario 2 are consistently higher than those of Scenario 1. Recharge rates varied over time among the four groundwater monitoring wells for Scenario 2. For Field_2_2019 and Field_15, recharge gradually increased in mid- to late September of 2019 and remained constant throughout the remainder of the flooding period in October of 2019. For Well_2b and Well_34, recharge rates increased rapidly in September of 2020, remained fairly constant through October of 2020,best indoor plant pots and slowly decreased during November of 2020 .The water budget components extracted from the child model results of Scenario 2 were represented with a stacked bar chart . Each of the components plotted are the same as the components plotted for Scenario 1. The water budget components plotted are storage , river leakage , recharge , storage and river leakage . The main difference is that the scale of the rates of the components is several times larger than that of Scenario 1. Recharge rates are largest during the flooding periods at the ag-MAR field sites. Inflows to the model cells from storage are also greatest during the periods of high recharge rates, and outflows from the model cells to storage start to increase after a few weeks of recharge.The results of Scenario 3 represent a repetition of the 2019 recharge program for ten consecutive years.

Because of the large difference in time discretization between Scenarios 1 and 2 and Scenario 3, the analysis of the model performance of Scenario 3 was conducted individually without an initial comparison with the first two scenarios. Hydrographs of the observed and simulated equivalent head values were plotted for each groundwater monitoring well on the primary y-axis, while recharge rates were plotted on the secondary y-axis . The groundwater elevation and recharge rates were plotted together to demonstrate their relationship over the course of the ten years. The simulated head values were plotted alone for this ten-year model run because there are no projected groundwater elevation data from the year 2020 to 2029. The pattern of the hydrograph is repetitive, as each consecutive year is a replication of the previous one. The same can be said for the bar chart of the recharge rates. As recharge rates peak, the simulated heads also reach their peak.The water budget components that were an output of the child model for Scenario 3 are plotted as a stacked bar chart . The components of interest that were plotted as rates either into or out of the child model’s groundwater system included storage , river leakage , recharge , storage and river leakage . The rates of these inflows and outflows to the groundwater system span the ten years that the model was run for Scenario 3. The graph follows a consistent pattern, for each component, as the whole ten years is a replication of the first year . There is no visible increase in any of the water budget components’ rates over time, as the pattern is very consistent.From analyzing the model performance of the parent model through the one-to-one plot of observed and simulated equivalent heads , it is evident that most of the data are a good fit to the one-to-one line, with the exception of the cluster of red dots in the lower left area of the plot. This group of heads had a residual greater than -100 m, meaning the difference between the observed and residual heads at these groundwater monitoring wells were greater than -100 m. Other than this cluster of red residuals, the binned residual head data indicated that the majority of the values of the observed and simulated equivalent heads were fairly close, with a difference of less than -100 m to 30 m. The overall shape of the distribution of dots on the one-to-one plot suggest that we were mostly underestimating the heads in certain areas, resulting in a more conservative estimation of heads in the parent model domain. The residual map of the parent model shows the distribution of groundwater monitoring wells and how dry or wet they are according to the color of the well points . The northern half of the parent model domain showed good to fairly good model performance, with the green and yellow colored residual points indicating a small difference between the observed and simulated equivalent values of head. Within the black square, the area of the child model domain, most of the groundwater monitoring wells indicate an underestimation of heads . The areas where the residuals were smallest were areas near surface water features along the eastern boundary of the parent model domain, such as Butte Creek, Butte Slough and the West Borrow Ditch, as well as some parts of the Sacramento River in the domain area. The cluster of red dots that were shown in the one-to-one plot are seen in the middle to southern half of the parent model domain . The red dots indicate an area of low groundwater elevation, forming a cone of depression. The cone of depression shown by the parent model results is not a surprising discovery.

Trends in the popularity of tree types over time can be reflected in nursery offerings

We developed an interview protocol that was approved by the UCLA Institutional Review Board, and sent formal letters to a subset of each category. We followed up with e-mails and telephone calls to set up interviews to ascertain what factors have been driving tree choice in Los Angeles. We were able to obtain no interviews with retail nurseries after attempting to reach a dozen. None responded either to our e-mail inquiries, and those we reached by telephone to ask for an interview declined. We interviewed two sales people in person from wholesale nurseries, and two municipal arborists, one in Santa Monica and one in Beverly Hills. The interviews were based on an interview protocol that asked about drivers of supply and concerns driving demand for municipal arborists.Using the negative binomial regression count model with 95% confidence intervals, the increase in the number of species offered in the most recent time period 1990–2011 was significant compared to time periods 1900–1929, 1930–1959, and 1960–1989. The 95% confidence interval of time period 1990–2011 did not overlap with the 95% confidence intervals of the other time periods . There was no significant difference in the number of species offered between time periods 1900–1929, 1930–1959, and 1960–1989. A polynomial contrast indicated a significant linear and quadratic trend with time. The number of genera offered in time period 1990–2011 was also significantly higher when compared to the number offered in time periods 1900–1929, 1930–1959, and 1960–1989. However,plant pots plastic as with species of trees, no significant difference in the number of genera was observed between time periods 1900–1929, 1930–1959, and 1960–1989. The 95% confidence interval of the 1990–2011 time period did not overlap with the 95% confidence intervals of the other time periods .

A significant linear and quadratic trend was observed with time.There was no observable change in the number of California native species offered over time . While California boasts several dozen native trees, as mentioned above, there are only 14 native to Southern California, including such species as weedy willows that do not do well in an urban environment and cannot be used as street trees. Many of California’s native trees do not thrive in Southern California’s Mediterranean climate, like bristle cone pine, white fir, and pacific yew, among others. In the case of non-native species, the number of species offered in time period 1990–2011 was significantly greater than the number of species offered in time periods 1900–1929, 1930–1959, and 1960–1989. Similar to the pattern with deciduous species, the numbers of species offered between time periods 1900–1929, 1930–1959, and 1960–1989 were not significantly different. Both linear and quadratic trends were observed with time for non-native species .Gymnosperm species showed a unique trend.While the number of species offered in time period 1990–2011 was not significantly different from time periods 1900–1929 and 1960–1989, it was significantly different from time period 1930–1959. The results of the polynomial contrast indicated a quadratic trend with time . Angiosperm species followed the same pattern as deciduous species and non-native species; the number of species offered in time period 1990–2011 was significantly greater than the number of species offered in time periods 1900–1929, 1930–1959, and 1960–1989. There was no significant difference in the number of angiosperm species offered in time periods 1900–1929, 1930–1959, and 1960–1989. A significant linear and quadratic trend was observed with time . Palm trees are highly visible and arguably iconic in the Los Angeles landscape. Interestingly, the number of palm species offered in time period 1900–1929 was significantly greater than the number of species offered in time period 1930–1959. However,there was no statistically significant difference in the number of species offered in time periods 1930–1959, 1960–1989, and 1990–2011.

An overall quadratic trend was observed with time .Our research numbers rely on tree nursery catalogs, and indicate an increase in the tree species choices offered by nurseries in the region over time, even though the actual numbers of nurseries in the region have declined in number . According to our interviews, increases in knowledge about disease susceptibility and the importance of having a diverse selection of street tree species, for example, were cited as among reasons for the increase in the number of species offered by nurseries. Another reason cited is that as individuals, land developers, and city planners hear about new species from breeders, conferences, or personal contacts, they request these new species from the nurseries in the region .At regional to global scales there is strong evidence of declines in species diversity in non-urban ecosystems accompanied by increases in exotic species . Research on urban biodiversity however, shows that there are increases in biodiversity in cities due to invasive species as well as human interventions in planting horticultural species . Unlike in non-urban habitats where Sax and Brown and Peet found that native and exotic diversity are often positively correlated, suggesting that where species richness has increased , urban floristic diversity often comes at the expense of the native landscape. To create optimal conditions for construction, native vegetation is scrapped, fill is often brought in as well as top soil, contours and topography altered, irrigation may be added, soils are compacted, and high rates of fertilizers and chemicals are applied . This does not mean, however, that the urban plant palate is depauperate. As Kowarik points out, urban areas may be more species rich compared to their surrounding environments. Urban floristic diversity is driven by anthropogenic biophysical changes in the landscape and human choice in revegetation as well as urban morphology and climate. These are significantly different drivers of species diversity than in non-urban environments. Since Los Angeles is in asemi-arid environment, remnant or feral vegetation in non-cultivated spaces of the urban environment tends to be weedy and scrubby and trees rarely regenerate, except where there is water.

In irrigated but poorly maintained areas, such as in freeway interchanges, one might find a mix of eucalyptus, Schinus terebinthifolius, Ailanthus altissima, and other opportunistic species. In non-irrigated areas, there are low-growing grasses and Mediterranean-region invasive plants. There are fewer non-built lots than in other cities in the U.S., for example Baltimore or Detroit. Los Angeles County is most densely populated and the most populous in the U.S ; and there is little open land outside of parks. There has been a significant increase in tree diversity in Los Angeles from the 14 native species present in Los Angeles County before European contact. Our results show that there are now over 500 commercially available species of trees . Muller and Bornstein describe between 95 and 408 tree species currently being planted in California cities, with an average of 185 per community. This confirms our findings of high available diversity. That study also reported that the number of approved species for future public planting is only 29% of the species in the existing inventory. If the goal of tree planting in the city is biodiversity, this is troubling. However, it is likely that approved species must satisfy concerns about water use, tree size,blackberry pot maintenance and other issues pertaining to feasibility and management costs. These attributes are also important issues relevant to urban biodiversity as tree mortality in urban areas is high, and there are constrained municipal budgets for tree maintenance . The increase in nursery catalog offerings has accelerated in the past two decades. It is difficult to quantify trends in diversity of tree planting and we acknowledge there is not necessarily a causal link between diversity of offerings shown in tree nursery catalogs and what is found in the urban landscape. Still it is worth considering the extraordinary diversity of offerings and to further investigate how that may affect urban tree planting in different cities in the Los Angeles region, and between different land uses: parks, street trees and trees in private yards. Perhaps, as Muller and Bornstein caution, there may in fact be a decline in the public tree planting sphere, but an increase in private tree diversity. Other questions that emerge from this work include whether there is a similar trend in other cities, the link between biodiversity and urban forest function, and important measures of biodiversity other than taxonomic. For example, tree diversity in Nordic cities showed that 70% of all newly planted trees in street environments belonged to one clone of Tilia . Genetic diversity of urban forests may be a critical factor in urban forest health and sustainability. Overall, little is still known about urban trees in different parts of the globe, including their biodiversity, health, maintenance regimes, and the reasons why people plant some species and not others.Over the study period there were significant shifts in tree types, with an increase in deciduous tree species. Deciduous species shed their leaves in the cooler months and provide shade in the hotter summer months and thus are functionally different than evergreen species. Such changes in the availability of functional types may affect the structure of the urban forest of Los Angeles, as old and diseased trees will likely be replaced by the tree species now available. Such a change may also affect the ecosystem services provided. For example, while research is increasingly showing that trees do little to sequester carbon in cities relative to the amount of carbon generated in fossil fuel combustion, and there is little evidence to date that trees improve air quality,trees do mitigate outdoor heat fluxes through outdoor shading and evapotranspiration . More city-level studies of trees and water use, their impacts on outdoor heat related to their size and canopy and the trade-offs with water use and maintenance, would help municipal arborists better choose trees if ecosystem benefits were a desired outcome.

Employing a chronological analysis to analyze the species currently and historically available to plant in a region offers a novel way to understand urban tree composition.In Los Angeles County, seventy new species have been offered within the last decade .While it is likely that not all species of trees offered by the nursery industry are successfully planted, there are additional interesting questions to be asked about the increase in species availability. These include the role of horticultural research, the dissemination paths for new species and/or new hybrids, the drivers of choice and adoption, and the impacts of such trees on the region itself. Will the new trees change water demand? Will they affect allergies? Will they change maintenance costs for cities, or the public? Will they provide habitat for birds and insects? Pairing this information with other costs such as tree maintenance, as well as people’s preferences and purchases of specific species, can help inform policy and decision makers of environmental benefits and costs of urban forests in a given region. According to the Sales Manager of a nursery we interviewed, while having low-maintenance trees is an important criterion, functionality and beauty are still more significant variables in selling trees .We found over a dozen trees that have been consistently offered over the century. These include coast redwoods and giant Sequoia . These species are native to California but not to the Los Angeles region , and Sequoia trees found in Los Angeles tend to show signs of stress and are not widely grown . Tree catalogs may not match nursery stock and availability, nor are they necessarily good predictors of tree survival rates. The species that were found to be sold throughout the 112 years include flowering trees, deciduous and evergreen trees, a palm, but no trees native to Southern California. Thus further research must be conducted to determine the reasons for new tree species introductions, their popularity, and whether tree nursery catalogs are truly good predictors of the biodiversity of trees in the urban forest. This would link the functional traits that are desired with the catalog information.Trade-offs between reproduction and longevity are among the most comprehensively researched areas of life history theory . Testosterone and other steroid hormones play critical roles in the development and maintenance of many sexually dimorphic traits in males resulting from sexual selection, but at a cost; ceteris paribus, energetic investments in reproductive effort trade-off against investments in somatic maintenance . Since fitness gains of investment in reproduction earlier in life often outweigh the gains from somatic repair, reproduction is usually prioritized over longevity.

Quercetin galactoside did not significantly differ among the treatments

The effective concentration of GA can vary markedly according to sensitivity of the variety to the hormone. For example, ‘Thompson Seedless’ requires multiple applications and large cumulative amounts of GA exceeding 100 ppm, while a single application of 10 ppm of GA can triple the size of ‘Black Finger’ berries. GA is also known to potentially delay maturity, increase pedicel thickness, and increase berry abscission depending on the application time. If applied on the whole vine on sensitive varieties, GA can also harm reproductive meristems and reduce subsequent yield. The molecular aspects of the synthesis, signal perception, and transduction of GA in grapes have been reported. The study of the effects of cytokinins on grape development focused largely on forchlorfenuron -N′-phenylurea, a synthetic cytokinin known as CPPU, that has been tested and applied to regulate fruitset, size, and shape in several fruit crops. In grapes, CPPU was also reported to delay maturation and reduce berry skin color, increase berry pedicel thickness and rigidity, increase cuticle content, and reduce weight loss of the rachis. CPPU is commercially applied at levels of 5 ppm or lower due to its potential adverse effects on maturation and post harvest quality. The time frame for application of CPPU is usually similar to that of GA and often in combination with GA at reduced concentrations. Other cytokinins such as benzyl adenine had similar effects but a concentration of 500–1000 ppm was required to increase berry size. Phenylpropanoids are a large class of plant secondary metabolites derived from aromatic amino acids, phenylalanine in most plants or tyrosine in some monocots.

The main branches of the phenylpropanoid pathway include lignans and lignins, stilbenes, coumarins, isoflavonoids, flavonoids, and PAs. The biosynthesis of PAs, anthocyanins,hydroponic pots and flavonols share common steps in the flavonoid pathway. In grape berries, the first committed steps in PA biosynthesis are catalyzed by leucoanthocyanidin reductase and anthocyanidin reductase by converting anthocyanidins to flavan-3-ols such as -catechin and -epicatechin , respectively. The resulting -epicatechin and -catechin derivatives can be oxidized to quinones, which are polymerized. However, it is not clear whether this polymerization of the soluble precursors proceeds enzymatically by laccases or non-enzymatically. The subunits of PA are derived from 2,3-cis-flflavan-3-ols -epicatechin and -epigallocatechin , as well as from 2,3-trans-flflavan-3-ols -catechin and -gallocatechin and are most commonly linked via 4 β → 8C−C bonds. The PAs are oligomeric and polymeric flflavan-3-ols that can range in size from 2 to 30 or more subunits. The regulation of the phenylpropanoid pathway was studied extensively in grapes with respect to anthocyanins, PAs, and other branches of the pathway with emphasis on the role of R2R3-MYB, bHLH, and WD40 transcription factors and their target genes. Our previous study demonstrated that CPPU causes a marked increase in tannin content of Thompson Seedless. Thompson Seedless is a major variety but it does not produce anthocyanins and is very low in volatile content. In the current study we presented the following questions: how do CPPU and GA affect tannin accumulation in a variety that is rich in anthocyanins and volatile compounds; and how are biological processes at ripening affected by the treatments. These questions were addressed at the phenological level, by the analysis of relevant metabolites from the phenylpropanoid pathway, by volatile composition, and by transcriptome analysis.Experiments were carried out on Vitis vinifera cv. Sugrasixteen that will be referred as ‘Sable’. Vines of ‘Sable’ were grafted on Richter root stock that was 7 year old and grown in Israel in the Lachish area . All viticulture practices were performed as describepreviously.

The experimental plot comprised of four replications of three vines each, arranged in a randomized block design. Clusters were manually sprayed to full wetness with the growth regulators gibberellic acid and forchlorfenuron in a concentration of 20 and 5 ppm, respectively, with 0.025% Triton-X100 as a wetting agent. A combination of GA and CPPU was also sprayed on the berry at the same concentrations. ‘Sable’ was treated on 14 May 2018 at the berry diameter of 6.0 ± 0.08 mm. Phenological data for ‘Sable’ was collected at the time of treatment , and 7, 34, 51, and 70 days post treatment . Sampling for metabolites, volatiles, and gene expression was carried out at 51 and 70 d after treatment, the time points which represent the beginning and end of commercial harvest. Sampling at all time-points was of 90 berries pooled from 20 to 30 clusters randomly collected from the four vineyard replications. For metabolite and RNA-seq analysis, a disk of 14–16 mm was removed along the longitudinal axis of each berry and was frozen in liquid nitrogen. The berry disks were homogenized in three replicates of 30 disks each using an IKA homogenizer with liquid nitrogen and were stored at −80 °C for further analysis. The remaining part of the berries was used for measurement of total soluble solids and titratable acidity .Measurements of TSS and TA in ‘Sable’ berries of GA, CPPU, and GA + CPPU treatments were carried out as previously described. The juice was obtained by using a fruit juicer from 30 berries. TSS was determined by a digital refractometer and denoted as °Brix. TA was measured by means of titration with 0.1 N NaOH to pH 8.2 with a Metrohm automatic titrator and expressed as tartaric acid equivalents. All the above analyses were performed on fresh samples at the harvest date. Informal tasting was done by three expert tasters that scored the samples in hedonic scale of 1–9 .Sample preparation and microscopic examination of ‘Sable’ berries at 33 d after GA, CPPU, and GA + CPPU treatment were performed as described by Tyagi et al.. Briefly, transverse hand sections from ‘Sable’ berries of GA, CPPU, and GA + CPPU treatment were immediately immersed in a solution containing formaldehyde, acetic acid, ethanol, and water in ratios of 10: 5: 50: 35, respectively.

After fixation, tissue sections were serially diluted by ethanol and subsequently a stepwise exchange of ethanol with Histoclear was carried out. Samples were embedded in paraffin and cut with a microtome into 12 μm thick sections. Sections were stained with Safranin O that stains nuclei, lignified suberized, or cutinized cell wall in red, and with fast green FCF that stains cellulose in green-blue and sections were examined under a light microscope .Gibberellin and cytokinin applied at fruit-set are known to increase berry size, but due to the complexity of agricultural systems, the intensity of the response can vary among seasons. The PGR treatments were performed at a fruitlet size of 6.0 ± 0.08 mm on ‘Sable Seedless’. Fruitlet diameter and weight increased significantly by application of both GA and CPPU measured 7 d after treatment . Interestingly, at 34 d post treatment, berry diameter and weight of CPPU-treated berries was smaller than the control but this trend was reversed at later time points. At 51 and 70 d after the treatments, CPPU increased berry weight and diameter significantly with respect to the control and the GA treatment. The GA treatment increased berry size by 17.5% and 13.4% at 51 and 70 d, respectively, but at a later time point, the difference was not statistically significant from the control. The diameter and weight of berries treated with the combined treatment of GA + CPPU was higher than that of CPPU alone at both 51 and 70 d. Brix of the control grapes was higher at all time-points followed by GA and CPPU . At 34 d,grow pot berries treated with GA + CPPU had higher Brix as compared to CPPU-treated berries, but at later time points there were no differences among the two treatments. CPPU had a major effect on TA that was much higher than the other treatments at 34 d after treatment . At both 34 and 51 d, GA seemed to mitigate the effect of CPPU on TA. With respect to appearance of the berries 34 d after the treatment, there was a clear delay in color development by CPPU and the treatment of GA + CPPU . Transverse sections of the berries showed that the epidermal layer was thicker either in both GA- and CPPU-treated berries or the combined treatment as compared to the untreated control . Informal tasting done by experts indicated excellent taste rated as 8 with multiple aromatic notes for the control and GA treatments, while in berries from the CPPU treatment there was some astringency that reduced the score to 7.5 or 7.0 for the combined treatment.The cytokinin CPPU was shown to increase total tannins in Thompson Seedless that bears green berries. It was therefore of interest to determine what effect CPPU has on black berries and if GA has similar effects. HPLC analysis was carried out for glucosides, acylated and coumaroylated forms of delphinidin, cyanidin, petunidin, peonidin, and malvidin . CPPU and GA + CPPU treatments reduced the levels of the majority of these compounds at both 51 and 70 d as compared to the control. Quantitatively, CPPU reduced the levels of the anthocyanin glucosides by ca. 50% at both time points. The GA + CPPU treatment reduced the levels of the anthocyanin glucosides to ca. 75% and 53% at 51 and 70 d, respectively, as compared to the control.

At 51 d post treatment, GA reduced the inhibitory effect of CPPU but this effect was not maintained at 70 d . Anthocyanin glucosides are the major form present in ‘Sable’ comprising 63–71% of the total anthocyanins and the remaining are acetylated and coumaroylated forms . Interestingly, CPPU reduced the proportion of the glucoside forms at both 51 and 70 d and this decrease was accompanied by an increase in coumaroyl glucosides at both time points and acetylated glucosides at 70 d. GA had an intermediate effect on the proportion of the anthocyanin forms. Flavonols are an important branch of the flavonoid pathway and therefore it was of interest to determine the effect of the treatments on major grape flavonols . Myrcetin glycoside was the major flavonol detected with an average of 81–89% among the compounds tested. While variation among replications was significant, two trends are worth noting. At 51 d, CPPU alone or in combination with GA reduced the levels of flavonols to ca. 60% of the control. At 70 d there was an increase in levels of the flavonols and decrease in the effect of CPPU.Flavan-3-ols are the building blocks of the PA chains that are synthesized in the early stages of berry development. Figure 2c displays the three major flavan-3-ols: -catechin, -epicatechin , and -epigallocatechin . Clearly, CPPU-treated berries contained more flavan-3-ols and their level increased during ripening. At the late sampling, GA + CPPU reduced the level of the flflavan-3-ols as compared to the CPPU treatment alone. The hydroxycinnamic acid derivatives, caffeic acid, caftaric acid, coutaric acid, and ferulic acid changed in different ways: caftaric acid was highest in the early stage in CPPU-treated berries; caffeic acid levels were reduced by CPPU at the early stage and it was absent in the late harvest; coutaric acid levels were induced by CPPU and reduced by the combined treatment relative to the control; the levels of ferulic acid were low but increased with ripening without a distinct pattern .To further investigate the effect of GA, CPPU, and GA + CPPU on PA composition, phloroglucinolysis was performed and differences were monitored using HPLC . Phloroglucinolysis hydrolyzes the polymeric PAs generating terminal units and extension units with phloroglucinol adduct . CPPU increased the levels of C, EC, EC-P, and EGC-P. GA did not affect the levels of the PA monomers while the treatment with GA + CPPU reduced the levels of C, ECG, EC-P, and EGC-P only at 70 d after the treatments . Monomeric PAs did not change with ripening with the exception of ECG that was lower at 70 d compared to the control treatment. The total PA level clearly shows the effect of CPPU and also shows that the combined treatment reduced the level of PAs at 70 d in agreement with the data on the free monomers . The treatments with GA or CPPU had minor effects on the % galloyl units but the combined treatment reduced their level. The mean degree of polymerization was significantly lower in CPPU and GA + CPPU treatments as compared to the control .

Spurs that bore fruit in a given year rarely flowered or bore fruit in a subsequent year

In spite of these efforts, relative fruit set is still variable and little improved since the early data reported in 1959 by Kester and Griggs. But, is fruit set the main limiting process for almond productivity? Another approach could be to increase the number of flowers per acre — but that approach demands more information on the eco-physiological basis that regulates flowering of almond spurs . Individual spurs tend to alternate bear with only a small percentage of spurs flowering the year after bearing . The authors have observed tagged spurs in outer canopy– exposed positions to live at least 15 years. To investigate this, an almond spur dynamics research project was initiated by Lampinen and colleagues in 2001. This study was designed to quantify the dynamics of spur renewal, fruitfulness and longevity and to determine how these dynamics are impacted by orchard management practices. Results from the study indicated that the number of flowers borne by individual spurs is a function of spur leaf area in the previous year and whether or not the spur bore a fruit in the previous year.Furthermore, spur mortality was much higher in spurs that had low previous year spur leaf area because fruit bearing competes with leaf growth and decreases the amount of source organ available on bearing spurs . Although there was a strong tendency for individual spurs to not bear fruit in successive years,pot raspberries whole trees or orchards are not strongly alternate bearing because fewer than 20% of the spurs on a tree bear fruit in a given year . In addition, the spur dynamics study documented that the key to ensure the largest flowering over an orchard’s life is to have the largest number of spurs possible with the optimal leaf area for flowering.

Proper irrigation during the previous year vegetative season and even after harvest can help to minimize spur death and has been reported to have a critical impact on subsequent bloom and fruit set . The almond spur dynamics study also provided information regarding the importance of PYSLA in determining subsequent spur flowering, fruit bearing and survival as well as the fact that spur fruit bearing in turn, reduces spur leaf in the same year . Thus, spur flowering and fruiting in two sequential years is relatively rare . However, the total number of flowering spurs on a tree may be of limited significance if greater relative fruit set of the flowers can compensate for decreased flower numbers in the orchard. Thus, understanding the relative impact of flower number and relative fruit set on almond tree yield in commercial orchards is essential for guiding efforts to improve orchard productivity and help growers determine the most profitable practices for almond crop management. To address this question we analyzed flowering and fruit set data recorded during the almond spur dynamics project. The study was conducted in a 145-acre orchard, planted in 1996, at 24 feet between and 21 feet within rows. The orchard planting consisted of rows of ‘Nonpareil’ alternating with pollinizer rows of ‘Monterey’ , and ‘Wood Colony’ . The orchard was located in Kern County on a sandy-loamy soil. Irrigation was carried out by micro-sprinklers and irrigation schedule was based on weekly measurement of midday stem water potential that was maintained between −0.7 and −1.2 MPa. Nitrogen was applied at 110 to 220 pounds per acre and leaf N content was between 1.95% and 2.45% over the period of the experiment. Bee hives were placed at a density of two to three hives per acre prior to bloom.

During the experiment, weather conditions during the pollination period were not limiting for bee activity. The orchard was divided into six equal-sized replicate blocks and 50 spurs were tagged in eight ‘Nonpareil’ trees within each of the six blocks. A total of 2,400 spurs were marked with aluminum tags in late March and early April 2001. Twelve spurs were selected on each of the northeast and northwest quadrants of individual trees and 13 spurs were selected on each of the southeast and southwest quadrants of the same trees. Tagged spurs were located at positions ranging from shaded to exposed portions of the canopy at a height of 3 to 12 feet. During the first 4 years of the study, lost tags or dead spurs were replaced with spurs in close proximity with similar light exposure to the original tagged spurs. The dynamics of annual growth, flowering, fruitfulness and spur mortality were quantified annually. For more detail see Lampinen et al. . The number of flowers produced on each tagged spur was counted in the spring of each year from 2002 through 2007. Multiple year records of PYSLA , previous year bearing, number of flowers in the current year and number of fruit in the current year were used to assess spur behavior in relation to PYSLA in spurs that bore no fruits in the previous year. These analyses involved data from 6,980 spurs spread over the 6 years. Kernel yield of the individual trees with tagged spurs and the kernel yield of the orchard containing those trees were also recorded for 6 years . Statistical analyses were carried out using ANOVA to test the significance at P < 0.01 of relationships between PYSLA and current year spur flower density , current year spur fruit density and current year spur relative fruit set. The same test was also used to test the significance of the relationship between tree yield and tree spur population relative fruit set and spur flower density . The number of flowers differentiated during the previous year is the first component of yield in fruit trees .

In almond spurs, flower formation was closely related to spur leaf area in the previous year . Thus, if the leaf area of each spur on a tree were known, the number of flowers that a tree would bear in the following year could be estimated, and, if spur relative fruit set were constant, spur fruit bearing and yield of that tree could be predicted. However, although the relationship between spur fruit density and PYSLA was significant, it was weaker than the relationship between spur flowering and PYSLA . This was because fruit set was highly variable in almond across years. Relative fruit set varied from 19% to 36% . These data apparently support the large effect of season, and particularly weather conditions, on the fruit set process. In almond, rainfall during the bloom period has been reported to affect pollinator activity and to wash pollen off stigmas . Anther dehiscence also can be affected by rain and high relative humidity . Temperature affects pollen germination, pollen tube growth , ovule degeneration and pollinator activity in the field . Wind can also affect pollinator activity. On the basis of this information, some have hypothesized that yield fluctuations can be explained mainly by variations in climatic factors . Actually, large relative fruit set variability also occurred among individual trees . This fluctuation could be a result of “on-trees” and “off-trees” occurring in the same orchard and season . On the other hand, fluctuations of relative fruit set of spur populations in different trees exposed to the same climatic conditions suggest that climatic conditions are not the major factor influencing tree spur population fruit set. In this experiment, at the spur level, there was no correlation between the PYSLA and relative fruit set in the current year . Thus, whereas previous year conditions are fundamental for flower formation on spurs , previous year leaf area did not appear to influence current year spur relative fruit set. Furthermore, spur fruiting was associated with reduced spur leaf area in the current season, suggesting that current year spur leaf area does not exert any influence on spur relative fruit set . In this experiment, the number of nuts borne by individual trees was significantly correlated with the number of nuts borne by the tagged spur populations in those trees . This suggests that our spur sample was relatively representative of the spur population of the trees. On a whole tree basis,plastic garden pots tree yield was not correlated with mean relative fruit set measured on tree spur populations. Instead, tree yields appeared to be more closely correlated with flower density on the tagged spur population. Thus, while relative fruit set is obviously important, it was not the primary yield limiting factor in this orchard situation, and increased relative fruit set when floral densities were low did not compensate for lower numbers of flowers . There were significant correlations between spur flower density and tree yield over years ; for individual years, the relationship was significant in 4 of the 6 years of our experiment . On the other hand, the relationship between tree relative fruit set and tree yield was not significant in any of the 6 years of the experiment.

However, it should be noted that the coefficients of determination were low due to the large number of points and the limited size of the spur sample compared with the total number of spurs borne by each tree; only 5.3% of the variability in tree yield can be explained by spur flower density. These results support the validity of flower density as an important parameter in the evaluation of almond cultivars . These data support the importance of total flower production for obtaining large crops. As a result of these spur dynamics studies, it is clear that the key to optimizing yields in commercial almond orchards is to focus on maximizing healthy populations of productive spurs. Some spur mortality is unavoidable and linked to insufficient spur leaf area associated with spur bearing and spur shading . Thus, continued productivity is dependent on spur renewal that is achieved by ensuring that there is annual growth of as many existing spurs as possible and new shoots that provide sites for new spurs . Health of spurs is also a function of total canopy light interception and good light distribution with the tree canopy . It is clearly important to select cultivars with the ability to produce large numbers of flowers and have crop management practices aimed at limiting abiotic stresses during the vegetative season . In an experiment not potentially biased by experimental manipulation , these results support the assertion of Kester and Griggs that reductions in total number of flowers due to adverse orchard conditions are not likely to be compensated for by increased relative fruit set when adequate pollinizers and pollinators are present and can result in some measure of crop reduction. Such was the case in this study since it was conducted in an orchard in which the ‘Nonpareil’ trees were flanked by two pollinizer cultivars selected for bloom overlap with ‘Nonpareil’ and relatively high populations of bee pollinators were placed in the orchard each year to facilitate pollination. Had such factors not been present in the orchard during bloom, it is likely that relative fruit set would have varied even more among years and measured tree yields would have been more dependent on variations in relative fruit set.Refrigeration can lead to post harvest loss and waste , although it is the most effective strategy to maintain the quality and prolong the shelf-life of horticultural products. The rates of metabolic reactions increase 2–3-fold for every 10°C rise in temperature, and low-storage temperature delays deterioration by slowing down respiration and ethylene production, and by reducing pathogen growth and water loss. Commodities such as apples, blackberries, blueberries, cherries, and grapes benefit from refrigeration, however, in produce originating from tropical and subtropical regions, such as tomato, banana, pineapple, potato, and basil, refrigeration may lead to injury. Postharvest chilling injury is initiated when the tissues of cold-sensitive species are stored between 0 and 15°C, but becomes apparent after transfer to warmer conditions. Because the affected species are taxonomically diverse and the organs affected vary, for example, fruit, tuber, root, leaf, and stem, PCI symptoms can be variable . However, some common phenotypes include tissue browning or blackening, pitted surfaces, shriveling, negative changes in texture, carbohydrates and aroma volatiles, and fungal infection. PCI severity is determined by many factors with temperature and storage time being the most important. If low temperatures are mild and exposure istransient, many metabolic functions will resume after rewarming, and visible symptoms may not develop.

The only genes that shared both conserved blocks were the pair formed by At2g27250 and At2G27240

Together, this evidence suggests the presence of a larger cis-regulatory module that may include up to five other transcription factors besides WUS. Slightly further downstream, another conspicuous feature of the 3’ enhancer is the presence of two large and perfectly conserved sequence blocks, spanning 42 and 32 bp, respectively . Both the size and the degree of sequence conservation in these two regions were exceptional in that they exceeded those found in the coding region of AtCLV3. The two regions also overlapped with the DNA family transposable element At2TE50665, suggesting that these may represent coding sequences of the transposon, rather than AtCLV3 regulators. When examined with the 5bp sliding window, the two conserved blocks were found to be surrounded on both sides by a strikingly periodic arrangement of three cis-motifs, spaced 11bp apart, strongly reminiscent of the pattern associated with the WUS-binding region. Superficially, the region around the two conserved blocks resembled an inverted repeat , though the underlying sequence in each half showed little or no sequence similarity. The repeated occurrence of this pattern suggests that the cis-motifs are organized around a higher-ordered protein structure, each of which may bridge up to 5-7 unique transcription factors. Such clustersof cis-motifs can be described as cis-regulatory modules, which in recognition of their similar structure, are provisionally identified here as CRM 1, 2, and 3 . Of the three modules, evidence from the WUS binding sites and a promoter deletion analysis, suggests that only CRM1 has a direct role in AtCLV3 activation. Although CRM2 and CRM3 might belong to a transposable element,drainage gutter the overall sequence of At2TE50665 is poorly conserved. It is also an old transposon, which likely shared a common ancestor with all five orthologs more than 20mya.

Suspecting functional diversification, the two large sequence blocks were subjected to additional BLAST searches in order to similar motifs in the A. thaliana genome. The genes located next to the motifs were identified, and there expression patterns of a select subset of identified genes were compared using microarray data using the eFP browser. In all, 32 genes were identified, most of which contained only one of the two conserved blocks.Unexpectedly, this analysis revealed that many genes had similar expression patterns in the lateral root cap, the columella, and root procambium tissue . This root expression pattern was also found to be shared between At2G27240 and AtCLV3, though the root expression of CLV3 was much reduced compared to its levels in the SAM. Further alignment of the oligomers returned by the blast searches identified three potential cismotifs, each of which was found to correlate with these expression patterns. Motifs were clearly related to root expression patterns, whereas the third motif was less tissue specific, but associated with several disparate structures in the shoot. However, the predicted transcription factor binding sites found within CRM2 and CRM3 did not strongly support any of these putative functions. The AAATCTAT motif overlapped with a predicted cytokinin response element , and an AGAMOUS binding site. Cytokinin responses occur in both root and shoot tissues, though AGAMOUS expression is clearly confined to the flowers, indicating a shoot-related function. The root-related function of the TGGCGATTTCG motif was at least partially supported by a predicted “right part of the root hair cis-element” motif, but the associated transcription factor is unknown. Finally, the ATTATCCTTAAT motif overlapped with two predicted targets, one for AtHB-2/HAT4, which has root and shoot expression patterns, and the other was a computer identified “sucrose response element” originally identified from lateral buds.

To test the function of the identified regulatory regions, a series of deletions were performed in the pCLV3m:H2B-YFP reporter construct . This construct containes three previously described mutated WUS binding sites, which enhanced expression of the reporter by 120% . Five large deletions, each about 500bp long were initially performed in the regulatory regions, three of which occurred in the upstream 1.5kb region and two in the downstream 1.2kb . Based on initial findings, two of the initial deletions were subdivided into smaller segments, identified here as 3.1, 5.1, and 5.2 . Most deletions produced a binary on-off response in the SAM, though a faint signal remained in the flower meristems of deletions 4 and 5, which occurred in 25% of all independent alleles. Only deletion 5.1 produced an intermediate fluorescent signal, though the pattern indicates reflection off the surface of the SAM, rather than actual fluorescence. Overall the deletions revealed that the AtCLV3 promoter is located in a small region between -154 and +25 bp TSS, while the 3’ enhancer required sequences between +584 and +1389 bp TSS . These regions closely correspond to the previously identified conserved footprints, and contained 8 out of 10 footprints in the 5’ promoter, all four footprints in the 3’UTR, and 14 out of 18 in the 3’enhancer region.Previous deletions of AtCLV3 found the 5’ promoter region was less than 812 bp long, and detected a large 3’ enhancer approximately 950bp long. These findings are broadly consistent with the results of the present study, where deletions 1, 2, 3, and 3.1 further narrowed down the 5’ promoter to just 154bp, and deletions 4, 5, 5.1 and 5.2 support the existence of a regulatory region just 805bp long in the 3’ enhancer. However, the two studies disagree in the functional annotation of these regulatory regions, as the present analysis found only positive regulatory regions , while both positive and negative regulatory functions were found in a previous deletion analysis. Disregarding the 5’ end of deletion V1 which had no significant footprint in the present analysis, a comparison of the two studies revealed that the previously identified negative regulatory region, corresponds to a 334 bp sequence containing CRM2 and CRM3.

Meanwhile, the positive regulatory region corresponded to a 290 bp sequence containing CRM1. The source of the discrepancy is obscure, but might potentially be related to the different techniques used to observe CLV3 expression. The previous deletion analysis relied on a GUS reporter system that used whole plant extracts, which might have missed ectopic expression patterns, while the present study did not attempt to observe any other tissue outside of the SAM. Thus it would be of interest to examine similar deletion constructs in a future study, to see if ectopic expression patterns actually occur following the loss of negative regulatory region. The slight increase in the reporter expression in the mutant control compared to a wild-type pCLV3:H2B-YFP reporter is consistent with the repressive function of WUS transcription factors, but suggests that WUS alone is insufficient to repress CLV3 expression. The failure to detect strong reporter activity in deletions 5 and 5.1 might also indicate an interaction between their regulatory modules, as the presence of CRM1 alone could not activate the reporter in the absence of CRM2 and CRM3. The reverse is also true, as CRM2/3 were not able to activate the reporter in the absence of CRM1 . It is not clear how the modules might interact with each other, as CRM1 is separated from CRM2/3 by 280-335bp, indicating that they are located on non-adjacent nucleosomes. There are however, four conserved regions located between CRM1 and CRM2 , which if recognized by additional DNA binding proteins, might help bridge the nucleosome gap. The AtCLV3 expression pattern occurs in an inverted cone-shaped domain in the apex of the SAM,large square pots and displays layer-specific patterns. The L1 is often strongest, while the signal intensity fades with tissue depth. In tangential sections, L2 cells often have noticeably weaker expression levels . However, the L2 “gap” often disappears in perfect longitudinal sections, suggesting that AtCLV3 is actually expressed in two closely spaced domains: a broad L1 sheet in the CZ, and a smaller, but roughly spherical domain directly underneath. Ideally, it would be possible to predict these two patterns using the conserved cis-motifs identified in this study, but unfortunately the function of individual regulatory regions often cannot be completely determined with the available data. Deletion 3.1 for example , suggests that Motif #2 and the redundantly predicted MYB site have no apparent function in the 5’ promoter, yet this contrasts with their unique and strongly conserved footprints. There is also predicted cytokinin-response element located at -102bp, but it is poorly conserved among the four orthologous sequences. A predicted AGL15 binding site might produce the L1 pattern by partially suppressing L2-L4 expression, as AGL15 is known to interact with transcriptional repressors such as TOPLESS and SAP18. However, an examination microarray data with the eFP browser suggests that AGL15 is only transcribed in a small subset of root tissues, where it is unlikely to affect the SAM.

However, considering that the AGAMOUS-LIKE gene family contains more than 100 members , it is possible that one or more of them might function redundantly to suppress AtCLV3 in a subset of SAM cells. If these four cis-elements are removed from consideration, the remaining portion of the AtCLV3 5’ promoter is surprisingly small, and is potentially less than 66bp long. Within this small region are three predicted cis-motifs, in addition to the previously noted initiator for a TATA-less promoter, and several conserved regions around the transcriptional start site. Two of the cismotifs, GT-1 and AGAMOUS, partially overlap with each other and are clear transcriptional activators. The presence of the AG site might also explain the weak expression pattern found in the flower meristems of deletions 4 and 5. The role of GT-1 is harder to explain though, as it is homogenously expressed in most plant tissues, and presumably would lead to widespread ectopic expression of AtCLV3. However, the absence of such ectopic expression patterns might be explained in terms of a nearby auxin response element, which is recognized by the AUXIN RESPONSE FACTOR1. Based on the pDR5rev:3xVENUS-N7 reporter, no auxin responses occured in the SAM itself, but they can be readily detected in the apices of lateral anlagen. Although it is not immediately clear how this might relate to AtCLV3 expression patterns in the CZ, a review of the ARF gene family finds that it includes 5 activators and 17 repressors. The cone-shaped expression domain of AtCLV3 is thus most consistent with repressive auxin responses in the peripheral zone, and might even suggest that the “cone” shape is actually pyramidal based on the auxin response foci observed with the pDR5rev:3xVENUS-N7 reporter. This model is also consistent with the peripheral expression of ARF3 and ARF9, both of which have been demonstrated to be transcriptional repressors. However, this interpretation is at odds with the transcriptional activator ARF5/MONOPTEROS, which is also largely expressed in the peripheral zone, and trace amounts extend into the CZ. As AtCLV3 itself is known to be up regulated by auxin responses at least within the narrow confines of the CZ, the potential functional significance of the GT-1 site might be questioned by an alternative regulatory hypothesis. It is equally probable for example, that AtCLV3 is activated in the CZ primarily by ARF5 or other ARF paralogs, and repressed though an unrelated molecule produced in the peripheral zone. So long as this occurs at levels below the detection threshold of the pDR5rev:3xVENUS-N7 reporter, this model would be indistinguishable from the GT-1 activation/peripheral auxin repression model. Currently, the only evidence that might be able to discriminate between these two hypothesis is rather indirect, and relies on the enhancement of cytokinin responses through the alcohol inducible RNAi system to silence ARR7/15 expression . Interestingly, the CLV3 expression level was reduced in this system, which is consistent with auxin-based activation. In contrast with the promoter, the 3’ enhancer region of AtCLV3 is quite large, with conserved regions spanning a minimum of 460 bp. This region quite likely contains three cis-regulatory modules, each of which may contain 5-7 unique cis-motifs, and together they might support upwards of 20 different transcription factors from multiple gene families. Clearly, regulation of AtCLV3 from the 3’ enhancer is likely to be complicated. One hint about how this might occur lies in the regular spacing of cis-motifs 11-15 bp apart, which is suggestive of helical phasing. The motifs themselves show little or no sequence similarity between modules, implying that transcription factors themselves are interchangeable, while their spacing pattern is governed by a higher-order protein complex that bridges all 5-7 cis-motifs simultaneously.

We see a similar effect for the number of hierarchical levels within a community

We believe that the positive association between population density and war found in previous studies is a result of omitted variable bias. That is, failure to include all relevant control variables will lead to biased coefficient estimates. Obviously, any study relying on bivariate methods fails to include the relevant controls. We show in the appendix how omitted variable bias could, in our particular case, lead to a wide range of values for the association between population density and war. Leaving out important variables that are both highly correlated with population density and positively associated with war—variables such as the use of metal or the existence of writing and record-keeping—causes our measure for population density to capture variation that belongs to these other variables, and gives the false result that population density is positively associated with war. The exact source of the negative relationship between population density and war is unclear. But we speculate that it may be due to the reluctance of others to attack high population density communities or to the reluctance of high population density communities to attack others. The former is plausible since high population density communities would have improved land and structures worth defending, and would have the potential to field large, well-equipped forces for effective defense. The latter because relatively complex high population density communities may find war a costly disruption, both to their economy and to the ambitions of their elites, who are likely to have non-war strategies for obtaining and keeping status. We had speculated that communities with little political autonomy would be less likely to go to war,plastic garden pots since any antagonism toward an external community would require the approval of the larger polity before actual war could develop. The estimated coefficients reveal a more complex pattern, as shown in Figure 4: both totally dependent and fully autonomous communities have a higher propensity to go to war than do communities that are semi-autonomous.

It seems likely that the semi-autonomous are constrained by the larger polity from freely engaging in war, but are also too loosely controlled for the larger polity to draw them into irrelevant wars. On the other hand, totally dependent communities can be forced into wars by the larger polity, while the fully autonomous can enter any war that they choose. Most warlike of all are communities which have equal status to other communities in a pluralistic society. Such equal status may be the consequence of an often-exercised willingness to fight other communities. The theoretical minimum for the number of levels is two ; v236 considers up to a maximum of four levels. As Figure 5 shows, communities with this maximum number of levels are much less likely to engage in external war than are other communities. Decisions to engage in external war may be more difficult when larger numbers of political actors must agree, as would be the case in larger, more complex, communities. As an example, one might consider the Mae Enga, of the New Guinea highlands, who deliberate the war decision in large meetings, where all fighters have the chance to speak . From the above, one can see that features of communities with a low propensity to engage in war include: high population densities ; relatively complex community-level political structures ; and ties to other communities that constrain the free exercise of war . These features reflect a more complex social and material order. Chronic war is the enemy of order, since its object is to destroy the crops, structures, institutions, and lives of a people. One would expect a community with a long history of peace to have evolved a complex social and material life, able to sustain high population densities. Thus, the features identified by our model may be a cause of low levels of war, as we hypothesize, but can also be a consequence. Our results provide some insight into causality, in the form of the endogeneity tests. Since these show that no independent variables are endogenous, our estimated model in Table 5 can therefore be interpreted as representing solely the causes of external war, not consequences.

Three of the 12 major habitat dummies survived to the final model . Relative to all other habitat types, societies found within temperate coniferous forests or boreal forests/taigas have lower incidences of external warfare. Conversely, societies who make their homes in temperate broad leaf and mixed forests experience higher incidences of warfare. These results confirm Nolan’s suggestion that there are features of biophysical environments that affect the frequency of war. Though the exact paths of that effect are not clear, they are independent of the confounding effects of subsistence and cultural transmission, which are controlled for in our model. The general thesis of the ecological-evolutionary theorists is that ecology, subsistence type, and population density are the dominant determinants of the frequency with which a society goes to war. Table 7 shows that ecology, subsistence type, and population density together account for only about 17 percent of the variation in the frequency of external war. If one broadens the set of variables to include technology facilitating war , the broader set accounts for about 27 percent of the variation in the dependent variable. Thus, only when quite broadly defined does the general thesis of the ecological-evolutionary theorists find strong support in our results. Otterbein has argued that sociopolitical variables have much more influence than economic or ecological variables in determining the frequency and nature of war. Variables reflecting political organization account for about 11 percent of the variation in the frequency of external war; variables reflecting the strategies by which elites gain status account for another 10 percent. Add to this the five percent accounted for by the degree to which the supernatural supports morality, and the resulting 26 percent of variation in frequency of external war accounted for by sociopolitical factors is about the same as the 27 percent accounted for by the broadly defined ecological evolutionary variables. Some believe that the frequency of war may simply be a function of who a society happens to have as neighbors: Keely suggests that hostile neighbors may be the most important determinant of whether a society is warlike, and Younger finds that more isolated societies are more peaceful.

We include two variables that provide some measure of the effect of neighbors, and together they account for about 12 percent of the variation in the frequency of external war. The first of these confirms Younger’s view that more isolated societies are more peaceful. The second— our network lag term—shows the effect of cultural transmission. The network lag term’s optimal composite weight matrix indicates that societies will tend to engage in war at much the same frequencies as their geographical neighbors and their co-religionists. Table 5 contains two pieces of evidence suggesting that a society will not be much influenced by the frequency with which their ancestors went to war: the near-zero value of the composite weight for linguistic phylogeny, and the high p-value for the LM test for spatial lag based on linguistic phylogeny. In other words, there is evidence here that vertical transmission does not account for the frequency of external war. We re-examine Patrick Nolan’s empirical work on the causes of war. We criticize his methods, which consist of bivariate or tri-variate tabular analyses, for sacrificing variation, for ignoring confounding variables, for failing to show the relative importance of the analyzed effects, for ignoring Galton’s problem, and for ignoring the problem of missing data. Our approach is to build a multivariate model,square pots which uses multiple imputation to handle the problem of missing data, and uses a network lag term to handle Galton’s problem. Our results reinforce Nolan’s conclusions on a few points, notably the positive association between metal technology and war. And while this relationship is important, it is hardly decisive—accounting for about 6.5 percent of the variation in the frequency of external war. When we evaluate the total importance of all factors related to ecology, subsistence, population density, and technology, we find that together they explain about 27 percent of the variation in the frequency of external war. This is comparable to the 26 percent explained by a broad set of sociopolitical factors. Thus our results suggest that those who argue for ecological-evolutionary theory, such as Nolan, are about as correct as those who argue that sociopolitical factors are the main determinants of war, such as Otterbein . This serves as an example of the superiority of multivariate methods: by including all of the most likely determinants of war, one can gain a sense of their relative importance. For the first of the two specific hypotheses advanced by Nolan—more productive subsistence leads to more frequent war—we find only qualified support. Taking the proportion of subsistence derived from agriculture as a measure of productivity, we find the relationship to be quadratic. As Nolan would predict, increases in agriculture’s importance leads to increases in the frequency of external war, but for non-agricultural societies only. For societies primarily relying on agriculture, we find a result opposite to that predicted by Nolan: increases in agriculture’s importance lower the frequency of external war.

Our results explicitly contradict Nolan’s second hypothesis: that higher population densities lead to higher frequency of war. We find a strictly negative relationship, in which high population densities discourage war. In the appendix we show that omitted variable bias is the probable reason that other studies failed to find a negative relationship. This highlights again the necessity of multivariate models in cross-cultural research—only by considering all important confounding factors can a model be free of omitted variable bias. Finally, we feel encouraged that our results support an optimistic view of peace among human societies. The propensity to engage in war is not vertically transmitted, is not a behavior that a society is locked into by the practices of its ancestors, but rather appears to be a product of current conditions. And many of the features of contemporary societies appear to be those which favor peace: high population densities; moderately restricted political autonomy; more complex political structures; widespread belief in moralizing gods; and the prevalence of capitalism as a means for elites to gain status. If peace is our goal, perhaps we are heading in the right direction.In alternate bearing theory, there are three competing hypothesis that attempt to explain how the fruit negatively influence vegetative growth. The competition hypothesis suggests that the demand between two sink tissues determines the flow of nutrients to each organ, the inhibitor hypothesis suggests that either the leaves or the fruits suppress flower development even when nutrient supplies are adequate, while the dominance hypothesis suggests that the fruits reverse the apical dominance mechanism, suppressing the apical meristem and subsequent vegetative growth. Although the competition hypothesis is favored by the growth trade-off observed in many alternate bearing species, there been few attempts to determine which of the mechanisms predominates in actual growing tissues. One way of doing this would be to observe the expression profile of actively growing meristems subjected to a heavy fruit load, as each of the hypothesis could be expected to produce a unique signature of up and down regulated genes. For example, a recent genetic study of alternate bearing apple trees was able to demonstrate several genes related to auxin and gibberellin hormone pathways were located in alternate bearing quantitative trait loci. The presence of auxin genes could be used to support the fruit dominance hypothesis, while gibberellin and floral induction genes might indicate the presence of an inhibitor pathway. An impressive set of microarray data from alternate bearing mandarin scions found that several glucan and trehalose sugar-related genes were activated during the ON year. The authors further argued that the FT paralogs CiFT1 and CiFT3 were involved in suppressing vegetative growth, but recommended more work to validate this idea. One aspect not captured by either study is the degree of fruit load, which varies continuously over the annual production cycle and may even produce a concentration gradient in the case of the inhibitor theory. However, even if reported in terms of the alternate bearing index or fruit biomass, the use of averaging and biological replicates would obscure the signal before dosage sensitive responses could be extracted from the data.

Seven replications of 10-tree plots received the pruning and nutritional treatment combinations

A number of transcriptome studies have been conducted and reported to characterize the gene expression dynamics in citrus-HLB interactions. These studies indicated that many citrus genes/pathways were modulated by HLB. The present study was conducted to gain comprehensive insight about the underlying molecular mechanisms in citrus-HLB interactions. Twenty-two publicly available citrus gene expression datasets, including 18 from HLB-susceptible and four from HLB-resistant citrus selections, were retrieved; and previously identified, differentially expressed genes were analyzed using the LIMMA and the RankProd methods. Out of a combined list of 7,412 DEGs, we identified the most significant 65 common genes and 30 R-dataset-specific DEGs. Gene Ontology analysis of these DEGs suggested that carbohydrate metabolism and transport, and stress response were the core pathways in citrus modulated by HLB. The 30 Rdataset-specific DEGs were mainly coded for LRR proteins, chitinases, CDR, miraculins, or lectins. Weighted gene co-expression network analysis of 2,499 DEGs revealed 21 modules with major hub genes. The miRNA nested network analysis suggested that csi-miR167 and csimiR396 could affect citrus transporters and defense response pathways, respectively. Collectively, these meta-analyses suggested candidate genes for further gene expression analysis,macetas de 5 litros over-expression analysis, or other genetic modification towards increased HLB resistance in citrus. Citrus Greening was first detected in Puerto Rico in 2009 affecting orange and lemon .

The causal agent was confirmed as Candidatus Liberibacter asiaticus. CG is transmitted by the Asian Citrus Psyllid Diaphorina citri Kuwayana and by human mediated grafting transmission. A survey conducted in 2010–2012 showed that the disease is widely spread in Puerto Rico. Consequently, efforts on an education program were established by the Extension Service to train agricultural agents on identification of CG and citrus orchard management practices. In order to maintain pathogen-free bud wood material, the Agricultural Experiment Station of the University of Puerto Rico, Mayagüez Campus has moved all the germplasm to insect-proof screen houses. Initially, all the germplasm was located on AES at Isabela, Puerto Rico. Currently, new collections have been moved to AES at Rio Piedras and Adjuntas, Puerto Rico. AES is the only one that has protected citrus bud wood that is certified CG free in Puerto Rico. In 2014, AES started a new institutional initiative to integrate various researchers to work with the critical citrus situation. The new initiative formed the project Production of Healthy Citrus Plants in Puerto Rico. This project combines the certification of disease free citrus plants and the development of new methodology on the production of pathogen-free citrus plants in screen-protected houses. The certification will detect citrus greening, citrus variegated chlorosis, citrus leprosis, citrus exocortis, and citrus canker. On the other hand, the new methodology will explore different media components, fertilization, container design and size, different rootstock and varieties in order to accelerate root growth and whole plant development. Current status of the screen-protected houses, current germplasm collection, and practices will be presented.In the state of Colima, Mexico, there are 20,000 hectares of Mexican lime . The Asian citrus psyllid has been present there since 2004, while the ‘Huanglongbing’ disease was detected in 2010. Seven months after the first detection, HLB positive trees were found in all producing areas of the state.

In June 2013, a systematic sampling was done in 299 orchards checking 7500 trees, resulting that 100% of the orchards and 100% of the sampled trees had HLB symptoms, which had a canopy portion affected by the disease ranging from 25 to 75%. During 2010, 2011, and 2012, the number of fruits per square meter of canopy in different orchards was quantified. In these 3 years, the results were similar; it was observed that trees with HLB symptoms in over 75% of the canopy tend to reduce their production of fruit between 40 and 60%. Also, it was evident that asymptomatic sectors in HLB-affected trees present good production and good fruit size. And contrary to that, symptomatic sectors have chlorotic foliage, a reduced yield, and a fruit size slightly smaller in comparison with fruits from healthy trees. Until nowadays, in Mexican lime, it has not been detected misshapen fruit, inverted ripening, or an increased number of aborted seeds related to HLB. During 2013, an average yield of 14.4 t/ha was recorded, representing a reduction of 23.4 and 39.7% compared to that recorded in 2010 and 2012, respectively. This partly reflects the effect of HLB on Mexican lime production in Colima. It has been observed that an integrated crop management, with special emphasis on nutrition, although with a lower yield, allows HLB-affected trees to continue producing fruit. This represents an option for producers while HLB tolerant varieties are generated.Severe pruning has been suggested as a strategy to rejuvenate citrus trees which have been adversely affected by HLB. Pruning rebalances a tree’s root to canopy ratio and thus allows an infected tree to increase its capacity to set fruit. An experiment was initiated at the UF/IFAS Southwest REC in February 2010 to measure the effects from severely pruning HLB-infected trees. Four years of data including shoot growth, canopy development, and fruit yield were collected from 2010 through 2013. Fifteen-year-old Valencia orange on Swingle citrumelo root stock grown on two-row beds typical of citrus in the Florida flat woods were selected, pruning one row and leaving the other row unpruned.

Three foliar nutritional treatments plus a standard grower fertilizer program were applied to both pruned and unpruned trees.The harvestable yield from pruned trees was minimal in 2010, the year of pruning, and constituted the largest financial penalty when attempting to rejuvenate HLB-infected trees through severe pruning. Production from pruned trees recovered during the second season and was statistically equal to production from unpruned trees. In 2012 and 2013, production from pruned trees surpassed the production from unpruned trees. Juice quality data generally showed no significant differences between pruned and unpruned trees. Cost effectiveness of pruning, however, depended on the enhanced foliar nutritional program. Pruned trees on two of the three nutritional programs produced nearly a box more fruit than unpruned trees receiving the same nutritional program. The increase in net returns was estimated to nearly $4 per tree. The cost of severe pruning plus the value of yield loss in the first year after pruning was estimated to be less than $2.30 per tree. Foliar nutritional programs have been adopted by nearly all Florida citrus growers as a strategy to maintain production from HLB-infected trees. Important questions arise, however, as to the relative importance and necessary quantity of micro- and macro-nutrients. Five years of production and cost data were collected from a trial on a commercial block of Valencia on Swingle on which various combinations of nutritional supplements were applied three times a year corresponding to the spring, summer, and fall flushes. Nine foliar treatments were designed and replicated five times over a 30-acre block. All treatments received a uniform ground fertilizer application and a uniform psyllid control spray program. The foliar treatments represented various combinations of micro- and macro-nutrients. Annual fruit yield and juice quality were recorded for each treatment and analyzed both by individual year and cumulatively across the 5-year period. Fruit revenue was estimated using average fruit prices reported in the Annual Citrus Summary . The costs of the individual nutritional treatments were itemized using 2013 retail fertilizer prices. Significant yield differences between all foliar nutritional programs and a standard were noted starting in the second year of the trial.

Those treatments that combined both micro- and macro-nutrients yielded the greatest yield benefits. While the treatment with the greatest complement of microand macro-nutrients resulted in the largest numerical yield gain, the yield differences among most of the foliar nutritional programs were not significantly different. The costs of nutritional products, however, ranged significantly from $100 to $550 per acre.Huanglongbing or citrus greening, caused by the phloem-limited bacterium Liberibacter asiaticus , is threatening the viability of the citrus industry in the United States. The search for an effective treatment of HLB is imperative. Using the closest culturable relative to Las, Liberibacter crescens ,macetas cultivo as a model organism, we have quickly and inexpensively screened a variety of likely phloem mobile compounds for effectiveness prior to field experiments. An existing model describes the optimal chemical characteristics of phloem mobile xenobiotics as: an octanol/water partition coefficient between -1.5 and 2.5, a molar volume ≤300 cm3mol- 1 , and ionizability between 2 and 15 . Following these assumptions, we selected and screened 145 compounds for Lc sensitivity using a high-throughput 96-well assay method. The percent inhibition was evaluated for multiple concentrations of each compound and the MIC90 and MIC50 was noted. Of the 145 screened compounds, 50 showed ≥90% inhibition at one or more concentrations. Of those, 12 were penicillins, 16 were cephalsporins, 2 were carbapenems, 7 were tetracyclines, 6 were aromatic hydrocarbons, 3 were nitro compounds, and 4 were organic chemicals . The 27 quinolines and 20 sulfones tested showed little impact on Lc growth. Our next step is to test the phytotoxicity of those antimicrobials that are phloem mobile and inhibit Lc. Oxytetracycline fits these criteria and showed no phytotoxicity after repeated foliar sprays at 200 ppm. Using this selection and assay method, we can efficiently sift through multiple treatment options and only select the most suitable for more laborious field-testing, and ideally provide a short-term treatment option for commercial citrus growers. Eventually, these results could help guide the production of effective novel compounds that will provide additional treatment options.Current strategies for managing Huanglongbing include area–wide psyllid vector control, inoculum removal, use of clean planting stock, and foliar nutritional supplements to sustain productivity of groves with infected trees. Foliar nutritional supplementation has had mixed results, in part, because the basis for such supplementation to suppress HLB has either not been established or is useful in correcting specific nutrient deficiencies observed in trees. The possibility that other mechanisms such as toxicity and other nutrient interactions could be interfering with tree metabolism has not been addressed. In this multi-year field/lab study , the impact of HLB infection on leaf mineral contents of adequately-fertilized grapefruit and sweet orange trees was investigated in Texas. Symptomatic and non-symptomatic leaves from known HLB-infected trees and leaves from non-infected trees, selected based on visual observations and qPCR tests, were analyzed for mineral composition .

Leaves from HLB-infected trees had significantly higher TNC levels than leaves from healthy trees. HLB-infected trees also exhibited significant decreases in leaf nitrogen , phosphorus , magnesium , calcium and zinc , and significant increases in sodium , copper , and boron concentrations of symptomatic leaves compared to healthy trees, whereas asymptomatic leaves from HLB-infected trees had intermediate values. Significant correlations were obtained between leaf nutrient concentration and CT values. The present observations shed further light on the physiological and biochemical changes associated with HLB disease development. Since these groves were well fertilized, the observed differences seem to arise, at least in part, from an imbalance in uptake of soil minerals, suggesting that the decline in leaf/tree physiological function may be due to toxicity associated with elevated tissue concentrations of Na and other trace elements.In 2011, we have demonstrated that feeding dsRNA targeting specific genes within the insect are toxic through RNA silencing mechanisms. This approach opened the door to use psyllid specific dsRNAs that high amounts are by citrus tristeza virus in the phloem, the site of the viral replication and D. citri site of feeding. Some of the dsRNA molecules can move in the citrus once expressed in the phloem into the xylem a minor site of psyllids feeding. Two important targets were selected: a) important gut digestive enzyme and b) enzymes that control synthesis and metabolism of juvenile hormone, an important hormone that controls metamorphism, egg development, and behavior. D. citri infected with Liberibacter asiaticus were allowed to feed on citrus trees that were transfected with CTV synthesizing dsRNA targeting digestive and juvenile hormone synthesis and metabolic enzymes. Adult D. citri were assayed initially by PCR for L. asiaticus and allowed to lay eggs on the leaves and the newly emerged adults were assayed for number of surviving adults and for L. asiaticus titers using PCR. A marked decrease in the number of the surviving adults was noted when compared with controls citrus trees that did not express dsRNA. The surviving adults when assayed by PCR were negative for L. asiaticus indicating that expressing specific dsRNA molecules in citrus can be highly effective against the spread of L. asiaticus by D. citri. A road map to control psyllid infestations and L. asiaticus spread will be discussed. Only two therapies have been shown to be effective for treating trees infected with “Candidatus Liberibacter asiaticus” : thermal therapy and bactericide therapy. There have been reports of several bactericides reducing CLas titer and alleviating HLB symptoms.

Consumers and stores could return infected eggs for a full refund

Infected eggs from these two major egg producers were distributed in fourteen U.S. states, including California. Eggs were recalled using specific plant numbers and codes that allowed tracing back to the box level, leaving no infected eggs in stores.The three egg recalls received extensive national and local media coverage on the television, radio, newspapers, and the Internet. To measure media coverage of the event, we conducted a Lexis-Nexis search, which gave us the daily count of newspaper articles that appeared on the 2010 Salmonella egg outbreak, starting 15 days before the event up to 60 days after the event. Figure 1 shows the number of articles in major newspapers that include the words “Salmonella” and “Eggs” on a given day. Media interest persisted over a six-week period following the event, in particular covering farm inspections that found numerous violations and showed that the egg farms were infested with flies, maggots, rodents and overflowing manure pits, as well as both farm owners testifying before Congress. The fact that there were three consecutive egg recalls within one week could have led consumers to think that this was a major outbreak, and not a regular food recall. Furthermore, given the information provided by the media coverage, some consumers may have obtained information or updated their beliefs on the egg industry as a whole. If consumers were perfectly informed, did not update their beliefs, and expected no further recalls, we could anticipate no effect of the event on consumer purchases. However, if consumers did not have perfect information on the outbreak or the recall codes,macetas de 10 litros updated their beliefs about the egg industry, or “overreacted” to the recalls, we could expect a drop in egg purchases following the event, at least temporarily.

We find that the latter was true.Using a unique product-level scanner data set of a national grocery chain that has stores in both high and low income zip codes, we examine how consumers reacted to the three consecutive egg recalls. First, we test whether consumers changed their egg purchases in California following the recalls. We examine media coverage on the highly publicized outbreak and hypothesize that media coverage is the channel through which consumers became informed about the event. Second, we study whether consumers substitute away from conventional eggs towards other types of specialty “greener” eggs that may be perceived as having a lower probability of Salmonella, such as organic or cage-free eggs. Eggs are currently produced under a variety of methods, but 95% of the national egg production in 2010 came from conventional battery cages. In our California and Washington sample, around 90% of eggs sold came from battery cages. Table 1 summarizes some of the differences between conventional eggs and non-conventional eggs. It is unclear if consumers were aware of the debate in the United States about the link between the type of egg and the probabilities of Salmonella infection. We hypothesize two possible results for purchases of unaffected eggs. On one hand, consumers might substitute away from conventional types of eggs to non-conventional specialty eggs . On the other hand, some consumers might choose to reduce all egg purchases, leading to a decline in purchases of all types of eggs. Third, we investigate whether different socio-economic groups reacted differently to the egg recalls. In particular, we look at whether income and household size affect the response to the recalls. To do this, we use demographic data for the zip code where the store is located. Income may affect the response if wealthier consumers are able to substitute to greener alternatives, which can cost up to twice as much as traditional shell eggs.

Finally, we examine whether separate areas within California reacted differently to the egg recalls. Due to its distribution system, our national grocery chain had infected eggs only in Northern California. We use variation within California to test whether consumers in Southern California reduced egg purchases as well. We use a technique known as differences-in-differences to estimate the effect of the three recalls on egg sales and use a control state that did not receive infected eggs, Washington. We are also able to control for seasonality by using data from previous years around the event date. The differences-in-differences approach consists in comparing changes in egg purchases in affected areas in California to changes of egg purchases in comparable but recall unaffected areas in Washington. If we were to focus only on the changes in California, we could not conclude that those changes were caused by the recalls. We could only show that they are correlated with the recalls. Indeed, other confounding factors, such as macroeconomic conditions, could be responsible for changes in California egg purchases. We net out such factors by using changes for comparable stores in Washington as counter factuals. We use the fact that infected eggs could be traced to the box level to establish a clear definition of the treatment and follow a panel of over 600 stores during a four-year period. Further, given the geographical distribution of infected eggs, we are able to measure potential spillovers to unaffected areas of California.We begin by plotting the evolution of daily sales around the “event week” in California. Figure 2 plots changes in egg purchases for all shell eggs for stores in California only. The category all shell eggs includes 2 classes and 7 sub-classes . The figure plots data starting 30 days before the “event day” up to 35 days after the event day. Changes in egg purchases take into account price, as well as factors that are constant across stores, aggregation levels and day of the week .

Egg sales show a large drop a few days after the first recall and a small increase between the second egg recall and the third recall. Sales reach their lowest level in the time period around 11 days after the first egg recall. This suggests that, if egg purchases decreased due to the egg recalls, there was a small time lag between the time the recalls were made and the time that the effect was reflected in lower purchases in stores. Using our econometric model, we proceed to formally test the effect of the three egg recalls and find a 9% significant reduction in egg sales in California. Given an overall price elasticity for eggs in U.S. households of around -0.1, this sales reduction is comparable to an almost 100% increase in price. Consistent with a rather inelastic demand, the effect is very similar with and without prices. We find that the decrease in sales was driven by a drop in purchases of traditional large shell eggs and find no evidence of substitution toward other greener type of eggs, such as organic or cage-free eggs. More specifically, we find that purchases of large traditional shell eggs significantly decreased by 10% in California in the month following the event. Large traditional eggs had the largest market share of sales in our sample in 2009 . Sales of the other types of eggs do not change significantly due to the recalls. For jumbo, brown, cage-free and nutrient-enhanced eggs , we find no significant effects of the recalls. Sales for extra-large traditional shell eggs and for organic eggs seem higher but the recalls still have no significant effect.When matching each grocery store with the socio-economic characteristics of the zip code in which it is located, we are able to investigate heterogeneous effects of the recall. We study whether income and household size affect the response to the recalls,macetas de 7 litros where income is the demeaned average income in the zip code in which the store is located and household size is the demeaned average household size in the zip code in which the store is located. Socio-economic data come from the 2000 U.S. Census. While we find no correlation with income, we do find that areas that had a larger than average household size decreased egg purchases significantly more. A caveat to the results is that it is possible that more affluent customers diverted egg purchases to farmers’ markets or high-end grocery stores after the egg recalls and thus the estimates would suffer from selection bias. The data allow only for the identification of effects with purchases undertaken at the national grocery chain. We also find differentiated effects among Northern and Southern Californian stores. Although the national grocery chain had infected eggs only in Northern California, we find that Southern Californian stores had lower egg sales as well. The overall sales reduction in Southern California was half as large as the reduction in Northern California, and is consistent with media and reputation effects being significant determinants of demand, even in the absence of an actual food recall. Studies on the effects of safety warnings on spinach , beef or fish have also found significant consumer responses. However, the persistence of the effect may vary depending on the type of good and availability of substitutes. For example, while the effect of a safety warning on spinach had a long-term effect, our results for eggs suggest that the effect was temporary.

To test the robustness of our findings, we perform several checks. First, we test the sensitivity of the baseline results to various assumptions about the seasonality parameters. We use only data for one year before the recall instead of using, as above, all previous years . This yields very similar drops in purchases as when we include all previous years. Second, we test the sensitivity of the baseline results to using Washington as a control state by excluding data from Washington and using stores in Southern California as controls. The rationale is that we may assume that stores in Southern California have similar trends to stores in Northern California. Once again, using Southern California stores as counterfactuals for Northern California store patterns yields very similar estimates of the egg recalls. Third, we test the sensitivity of the baseline results to using only one month after the event week. We obtain data on a second post-event month and include a total of eight weeks after the event week for all years. While this additional robustness check gives us similar results to the ones from the main specification, we find that the effect lasted more than one month.When matching each grocery store with the socio-economic characteristics of the zip code in which it is located, we are able to investigate heterogeneous effects of the recall. We study whether income and household size affect the response to the recalls, where income is the demeaned average income in the zip code in which the store is located and household size is the demeaned average household size in the zip code in which the store is located. Socio-economic data come from the 2000 U.S. Census. While we find no correlation with income, we do find that areas that had a larger than average household size decreased egg purchases significantly more. A caveat to the results is that it is possible that more affluent customers diverted egg purchases to farmers’ markets or high-end grocery stores after the egg recalls and thus the estimates would suffer from selection bias. The data allow only for the identification of effects with purchases undertaken at the national grocery chain. We also find differentiated effects among Northern and Southern Californian stores. Although the national grocery chain had infected eggs only in Northern California, we find that Southern Californian stores had lower egg sales as well. The overall sales reduction in Southern California was half as large as the reduction in Northern California, and is consistent with media and reputation effects being significant determinants of demand, even in the absence of an actual food recall. Studies on the effects of safety warnings on spinach , beef or fish have also found significant consumer responses. However, the persistence of the effect may vary depending on the type of good and availability of substitutes. For example, while the effect of a safety warning on spinach had a long-term effect, our results for eggs suggest that the effect was temporary.

The Qavail conceptualizes the maximum limit to water supply from the soil-root-stem system

The understanding of processes affecting plant water availability has fundamental and applied implications. Recent studies have recognized the key role of roots in promoting acclimation to different types of stress; mainly through preferential growth and control of hydraulic properties that regulate transpiration . A better understanding of root response is, therefore, key for understanding water fluxes through the soil-plant-atmosphere continuum. Accordingly, here we examine the effect of root growth and plant hydraulic conductance on water availability for canopy transpiration of young walnut trees under different levels of water stress.The study was conducted from April 2015 to July 2015, using nine 8-month-old potted walnut trees cv. Chandler, grafted onto Paradox root stock in an experimental greenhouse at the University of California, Davis. Plants were grown in 0.02 m3 pots filled with a 1:3 mixture of a fine sand and organic compost. As the experiment was conducted over a short period and the plants were young, the size of the pots was considered suitable. Pots were kept covered with aluminum foil to avoid soil evaporation and their transparent walls were covered with plastic sheets that were black inside and white outside, to protect roots from light exposure. All pots were maintained at field capacity for at least a week before the beginning of each 10-days period experiment. Replicates were monitored over time due to the careful tracking of soil-plant properties and limited availability of leaf psychrometers and high precision weighing scales for all individuals. Hence,macetas 30l the experiment was replicated using three different plants per treatment monitored over 10- days in three different time periods , for a total of nine receiving one of the irrigation treatments and three control plants.

While temporal replications integrate the effect of different insolation and temperature conditions in the greenhouse at each 10-day sampling event, we expect to observe consistent shifts between T100, T75, T50 throughout the experiment.Stem water potential was measured on expanded terminal leaflets located close to the trunk, every 15 min and averaged to hourly values, with a psychrometer/hygrometer , model PSY-1 . The leaflet equipped with the psychrometer was fully covered with an insulation capsule limiting temperature fluctuations . As the monitored leaf did not transpire, the measurement was representative of stem rather than leaf water potential. An independent measurement of stem water potential was carried out weekly on fully expanded leaflets with a pressure chamber . Prior to this destructive measurement, leaflets were enclosed in foil-laminate bags for at least 10 min . Plant transpiration rate was quantified by automatic weighing of pots on a high precision weighing scale every ten minutes, averaged to hourly values. Draining water was collected daily in plastic reservoirs attached laterally to the bottom of the pots by flexible rubber tubing. Hence, the weight of leaching water did not affect the weighing scale reading until its collection. Both the added irrigation water and collected leachate were weighed and removed from the water balance in order to evaluate the weight loss due to TR . Bulk soil water potential at soil-root interface was monitored by one tensiometer per pot, placed at approximately the midpoint of the root system at 0.2 m depth, and recording data every ten minutes to generate average hourly values. Its porous ceramic cup was connected through a water-filled PVC tube and a smaller acrylic glass tube equipped with a pressure transducer. A rubber cap on top of the tensiometer ensured its air tightness.

All plant and soil measurements were continuously recorded with a data logger located inside the greenhouse. Hourly average air temperature and relative humidity were obtained in an automatic micrometeorological station placed inside the greenhouse. The reference evapotranspiration was obtained by use of an atmometer Model E , that gives one pulse at each 0.254 mm of evaporated water . Hourly vapor pressure deficit was estimated by the difference between saturated and actual vapor pressure. Saturated vapor pressure was calculated using air temperature based on the Tetens formula . Actual vapor pressure was obtained by saturated vapor pressure multiplied by fractional humidity. We used an empirical water stress indicator based on plant relative transpiration . For each plant, the potential daily transpiration was estimated as a product of the plant standard daily transpiration by the ratio of the actual daily transpiration to TD* of the unstressed plant . The water stress indicator was simply calculated as the ratio of TD to plant potential daily transpiration. An undisturbed leaf was harvested and water extracted using a custom-made cryogenic distillation system suitable for isotopic analysis, adapted from previous studies of this kind . Briefly, the leaves were transferred to individually cut 1.27 cm diameter pyrex tubes where the leaf material was held in place by stainless steel wool. After attachment to a vacuum manifold, leaves were frozen in liquid nitrogen and air evacuated to 100 mTorr. The tube was then flame sealed to preserve the vacuum, and subjected to gravity assisted cryogenic distillation, the top of the tube at 110° C, bottom at −20° C. After distillation, the tube was removed and ice water isolated by flame sealing the tube again to separate water and leaf material. Leaf material was separated and ground to a powder using liquid nitrogen in a mortar and pestle. 3 mg samples were submitted for δ13C determination at the UC Davis Stable Isotope Facility by continuous flow GC-IRMS on a PDZ Europa ANCA-GSL elemental analyzer interfaced to a PDZ Europa 20- 20 isotope ratio mass spectrometer . The water samples were transferred to 2 mL vials and was analyzed for δD by equilibration with water vapor and added hydrogen gas, assisted by a platinum black powder catalyst. Next, CO2 was added to the system and equilibrated with water vapor for δ18O analysis.

Water analysis was performed at the University of Miami by using multi-flow system connected to an Isoprime mass spectrometer . To standardize isotopic data, values are reported in del notation with reference standards as in the equation below. The visible root length was monitored weekly over five weeks from the beginning of each 10-days period experiment by combining root mapping on the transparent walls of the pots and observation of inner root length with minirhizotrons , which provide a nondestructive method for repeated root observations . In addition, weekly root length observations started five weeks before each 10-days period experiment in order to follow the Rl pattern through time. Minirhizotrons consisted of transparent acrylic tubes with an inner diameter of 50 mm, and wall thickness of 3 mm. We used one tube per pot, installed at an angle of 45°, and sealed with silicon. Analyses of Rl were performed weekly with a BTC minirhizotron digital image capture system , located inside the minirhizotron tube. Each observation consisted of systematically taking pictures at one-centimeter intervals from the top to the bottom of the pot in three dimensions, totaling approximately 90 pictures per tube. The Rootfly software was used to analyze root length semi-automatically.Analysis of covariance of linear regressions between hydrogen and oxygen isotope ratios of leaf water showed significant differences in intercept between treatments , but no differences in slope . All experimental pots were covered to suppress soil evaporation, therefore, differences between treatment regression lines relative to the source water line are attributed to changes in leaf transpiration. Differences in intercept tracked expected declines in transpiration rates under drought stress and are consistent with changes in iWUE inferred from carbon isotope ratios . There was no difference between T100 and T75 with respect to iWUE or d-excess, indicating physiological acclimation and maintenance of a steady balance between photosynthesis and transpiration. However, iWUE and dexcess of T50 trees was significantly different from the others, indicating low stomatal conductance .Snapshots of root growth over time are shown in Fig. 6. In general, under well-watered conditions, new roots started to grow before the old roots died and were more frequently observed . Large variability was recorded for relative external and internal patterns of root growth at each sampling event. However, the cumulative total and living root growth detected by the minirhizotron showed significant changes with greater growth observed in the well-watered treatment . Crucially,maceta 25 litros root growth patterns were proportionally and positively related with d-excess . This indicates the existence of a fundamental trade off between root growth and iWUE , by which canopy transpiration and root development can be estimated based on changes in leaf stable isotope ratios. It is important to note, however, that differences between T100 and T75 with respect to either root growth or iWUE were not statistically significant. Therefore, acclimation is possible at that level and high physiological stress seems to be required to study costs and benefits of such a trade off with respect to changes in water supply.Our observations confirmed the decreasing TR as a response of midday depressions of leaf water potential , showing the minimum ψstem in T50 between −1.0 MPa and −2.0 MPa, which was strongly and positively correlated with ψsoil, explaining low TR under deficit irrigation . Indeed, stomata are expected to be completely closed in walnut trees when leaf water potential reaches −1.6 MPa and similar ψstem values and associated stomatal closure have been previously reported in stressed walnut trees , as transpiration rates decrease to prevent leaf dehydration under moderate to high Tair and VPD .

Otherwise, the strong and positive correlation between TR and evaporative demand was noticed for well-watered plants , as observed in previous studies , followed by strong and moderate water limitation . Multiple lines of isotopic evidence integrate the effect of physiological responses to treatments during the entire experiment and corroborate a significant decline in TR under deficit irrigation. Leaf water regressions show significant deviation from source water with reducing water loss by transpiration earlier under water stress has also been recognized in peanut and pearl millet . Here, our results showed an early and rapid decline in transpiration followed by stabilization of water loss in stressed trees, which is consistent with the fraction of “transpirable” soil water general mechanism of declining TR and with the classic descriptions of the plant water stress function . The nonlinear decrease of TR as a function of ψsoil and ψstem can be seen as a water conservative strategy to prevent water loss and leaf dehydration long before being limited by water supply from the soil-root system . Such a strategy lowers the risk of hydraulic failure and increases the iWUE. Considering that the major part of the walnut orchards are located in areas periodically affected by drought and due to its high water requirement over seasons, this observed trend and its further understanding has a key role in the identification and use of relevant physiological traits in plant breeding programs, allowing greater water-use efficiency under deficit conditions. The observed values of Kh fall in the typical range reported for young tree species and annual crops . Our results highlight the decrease of Kh under moderate and strong water limitation . Water deficit is one of the most important factors affecting Kh , and its decline in response to decreasing stem water potential under water deficit has been reported in walnut at ψstem approaching −1.8 MPa due to cavitation . However, we observed reduced Kh long before reaching such negative stem water potentials . As our Kh only includes hydraulic resistances between the stem and the soil-root interface, its reduction might have been fostered by a combination of poor soil-root contact under lower soil water content and altered root permeability that were described in other species.It turns out that in the T75 treatment, a reduction of stomatal opening due to water limitation occurred long before transpiration was limited by Qavail. Functionally, such stomatal regulation might play the role of extra security margin against hydraulic failure and translate into a so-called water saving behavior at longer term . The results also suggest that the supply-demand view in plant transpiration modeling is inappropriate for walnut, so that more complex models are needed . Despite the significant effect of water deficit on various plant properties, root growth responses over time did not correlate with any other recorded variable, and could did thus not explain changes of Kh. However, our observations suggest that healthy roots rapidly shifted to decaying roots with the continuity of water stress, which means a reduction of root activity and less capacity to take up water .

Regulations may also limit the ability of specialty crop operations to store water

Microirrigation allows for precise delivery of water to the container-plant system and provides the potential to implement fertigation if controlled release fertilizers are not used or are depleted before the end of the growing season.Freshwater is a finite resource. Yet, demand for water has increased due to population growth and increasing water use by agricultural systems needed to support larger populations . Although most nursery and greenhouse crops do not feed people directly, these plants can enhance human well-being and expand our connection to the natural environment . Globally, agriculture is estimated to use 69% of freshwater supplies, while industry and energy use is 23% and household consumption is 8% . Concerns regarding water scarcity, particularly in arid or semi-arid regions such as the western USA and Australia, intensify during times of drought, but long-term water use continues to be a major problem. The majority of the specialty crops, grains, fruits, vegetables, and nuts consumed within USA and exported around the world are produced in the western USA . During times of drought, allocation and conservation of a limited water supply among agriculture, industry, and household use receive increased attention. During 2015–2016, much of California was in either extreme or exceptional drought,cultivar arandanos the two highest categories, impacting over 36 million people in the state . Growers were forced to fallow land and remove established agricultural specialty crops because of limited water availability. Changing weather patterns can significantly impact both crop yield in non-irrigated land and the volume of water required to supplement rainfall in irrigated lands .

Agricultural systems, in general, will likely need to produce more plants with less water, use lower-quality water, or both . Crop water use efficiency, defined as the water volume required to produce a given dry mass of yield, and water use reduction can be accomplished in part by breeding for drought tolerance , but growers must also conserve water through irrigation and other management practices . Increased crop water use efficiency can be achieved via precise water quantity delivery to the container based on crop-based demand to limit leaching from over-irrigation. Additionally, irrigation type , timing , and use of new technology have been reported to increase irrigation efficiency. Regardless of method, improved water application and scheduling precision reduces the presence of agrichemicals and other contaminants in production runoff .Transport of contaminants from irrigation runoff into the neighboring ecosystem is a concern for all agricultural production, but particularly in specialty crop production . Contaminants of concern in specialty crop operations can either be removed, recycled on-site, volatilized, or transported off-site, depending upon production practices at the operation and prevailing environmental conditions. Contaminant presence, along with increased economic and regulatory pressure to develop alternative irrigation water sources, results in a challenge for many growers. Recycling runoff water for irrigation is an ideal solution from a water quantity standpoint, in that the water is already available on-site, reducing volume of water needed from other sources. This recycled water also contains contaminants that could be detrimental to the environment; recycling water would help to limit agrichemical escape into the environment . Growers are typically concerned about negative impacts of bioactive concentrations of pesticides or phytopathogens which may diminish crop health if they are present in recycled runoff water.

Perception of risk associated with these contaminants represents a significant barrier to grower adoption and use of this readily available water source . Fertilizers deliver plant essential mineral nutrients to ensure optimal growth, but application of fertilizers in excess of plant requirements can result in nutrient leaching; of particular environmental concern are nitrogen and phosphorus . Fertilizer runoff from agriculture, including specialty crop production, is a major problem in a number of impaired waterways and can lead to environmental problems such as algal blooms . The ability to recycle mineral nutrients is perceived as a benefit for some growers, and these recycled fertilizer salts are sometimes accounted for in their nutrition programs, particularly in greenhouse production . Agrichemical residues in water can be detrimental if not mitigated, as both surface water and groundwater can become contaminated . The fate and transport of agrichemicals depends on a number of factors, including location applied, soil characteristics, slope, and timing of rain/irrigation events . Chemicals vary in their modes of action and half-lives in the environment ; thus, managing agrichemical contaminants in recycled runoff can be challenging. However, prevention of contamination and remediation of contaminants to minimize reapplication injury to the crop and environmental/biotic damage is feasible using best management practices . Phytopathogen contamination can create economic and ecosystem stressors, causing disease within both the operation and the surrounding ecosystem via runoff . Economic analysis of production losses attributed to phytopathogens in container-grown specialty crops is not widely available, making it difficult to calculate the impact on grower profits and the surrounding environment. Specialty crop production losses to pathogen infection have been estimated to range from 5 to 30% for some crop taxa, but losses are likely to be crop specific and fluctuate annually based on environmental and production conditions.

Ecosystems may be negatively impacted by the discharge of pathogens from crop production facilities via plant transport from nurseries and eventual pathogen escape into the environment as illustrated by the pathogen causing sudden oak death, Phytophthora ramorum . While fungicide applications can suppress pathogen growth, in general they are not curative. As a result, many growers prefer to minimize potential for crop infection by either sanitizing water before it is used or not reusing runoff. Management of pump intake depth and location within a reservoir were identified by Ghimire et al. as key mechanisms for limiting introduction of pathogen propagules via irrigation water. Additional insights into propagule movement,survival, persistence, and/or pathogenicity in production runoff and their economic and environmental impacts are potential areas of future study In 1972, the USA passed the Clean Water Act, which created an impaired waters list [also known as the 303 list], which identifies bodies of water that do not meet water quality standards, including chemical contaminants, dissolved oxygen, excess algal growth, or other factors that may reduce the ecological health of a waterway . The goal of this list is to remediate impaired waters and remove them from this list. Many areas of the USA contain impaired waterways. In 2016, the US Environmental Protection Agency listed 42,509 impaired waterways on the 303 list due to aforementioned impairment. Cumulatively since 1995, 69,486 TMDLs have been assigned to water bodies, of which 13,313 are for high pathogen loads, 6235 for excessive nutrient loads, 3950 for excessive sediment loads, and 1351 for pesticides . Although agriculture is not the sole contributor to impairment in these impaired waterways, reducing the environmental impact of agriculture via non-point source contaminant reduction should be a conservation goal.Runoff from specialty crop container operations is from two sources: uncontaminated water and operational water. In this context, uncontaminated water is water from rainfall events that has not come into contact with production areas, crops, agrichemicals, retention basins, or runoff collection reservoirs that collect and retain production runoff, nor should it contain contaminants above background levels . Runoff from a greenhouse roof is an example, as this water should not require treatment prior to leaving an operation or mixing with operational water to supplement the irrigation water supply. Operational water is any water flowing from, in, through, or around production areas. As a result of contact with soils, agrichemicals, and phytopathogens, this water may have elevated concentrations of contaminants, which may require treatment before reuse or release, depending on operational needs and local regulations.Ideally, both operational water and uncontaminated water would be captured, treated, and released from or reused by container operations. This is not always possible for nursery or greenhouse operations for a number of reasons. Often, operations have geographic limitations that constrain their capacity to capture runoff. Rainfall events in some regions of the USA are intense over short durations, resulting in runoff volumes that exceed the capacity of existing containment infrastructure. In some parts of the country, a high water table can limit feasibility to capture or treat runoff water. Saltwater intrusion and storm surges are also major concerns, particularly in coastal areas . Some operations, especially smaller or more urban operations, may be land limited, so there may not be sufficient land area to store water for treatment or reuse. Other areas may not be able to store water due to topography or soils . These limitations must be considered when developing regulations and implementing BMPs for a particular area or operation.As populations increase,macetas plastico particularly in the western USA where water is more limited, state and local regulations may limit the amount of water that can be captured or stored at an operation. For example, Oregon requires all users, including nursery and greenhouse operations, to obtain water rights permits to store rainfall in a containment reservoir since it is considered a state resource .

Similar regulations may become more common across the country as water becomes more limited and may be a short-term advantage to producers not under those restrictions.The following information about layout and site design is meant to represent the ideal production scenario; however, site constraints and owner priorities will dictate what is possible. A new operation should be designed to balance water collection, water storage, and production to ensure ample amounts of quality water. Containment reservoirs should be situated at the lowest part of the nursery,allowing water to flow freely towards the containment reservoir while minimizing contact with production areas . Chen reported remediation benefits associated with a multi-reservoir design, where water flows through multiple reservoirs before it is recycled. Pathogens are relatively short-lived without a host; therefore, if multiple ponds are used to increase water retention time, fewer pathogens survive to reinfest plants . If multiple reservoirs are not available, locating the irrigation pump intake as far from the entrance of operational water as possible in order to increase hydraulic retention time and 1 m above the bottom of the reservoir can help reduce pathogen loads applied to crops . In greenhouse operations, one or more cisterns may be used to store irrigation runoff , particularly for ebb and flood systems. Return water must be treated prior to storage or reuse to reduce or remove pathogens, particulates, and other potentially harmful constituents that can impact the irrigation system and plants. One of the most important steps to ensuring efficient capture of runoff water is proper grading and utilization of well-drained bed base such as coarse gravel. These measures can reduce disease incidence by minimizing standing water under containers and convey water to containment reservoirs for reuse or remediation . Grading may be minor or extensive, depending on the layout of the property and the site design. More detailed information regarding infrastructure and surface water recycling is available in Bilderback et al. ; Merhaut ; Yeager .Remediation can be defined as the process of removing chemicals, pathogens, and other constituents of concern to reduce loads of harmful substances to a water system . Contaminant type, required load reduction, and the economics and efficacy of treatment technologies depend on a number of factors at each operation. Below, we highlight research that evaluates various treatment technologies and assess where technologies may be of most effective use in production systems. A summary of each technology, scalability, relative cost , contaminants managed, and relative efficacy for each technology are presented in Table 1.Filtration is accomplished via several mechanisms including adhesion , flocculation , impaction , interception , and straining . Contaminant removal efficacy is in part determined by particle size, contaminant loading rate, and flow rate; these should be considered when selecting treatment technologies. Important considerations for filtration include both the flow rate and the loading rates of contaminants that must be removed, as well as the cost of installation and upkeep .Rapid sand and glass filters consist of tanks that hold sand or glass of a specific particle size . As water moves through the sand or glass, particulates are removed. These filters are able to process large volumes of water quickly . As sand or glass particle size decreases , filters are able to remove smaller particles, but require more force to move the same volume of water per unit time.