Increase In WUE Research Articles

Assessing spatiotemporal dynamics of water use efficiency in ecologically vulnerable karst landscapes

Study regionSouthwest China Study focusWater use efficiency (WUE) is a key variable for understanding the carbon and water cycling processes in ecosystems. There exists the world's largest continuous karst topography in Southwest China, rendering it a quintessential ecologically vulnerable region. Therefore, determining the trends in WUE changes between karst and non-karst ecosystems is of great significance for understanding the carbon and water cycling processes in ecologically vulnerable areas. In this study, various analysis methods were utilized to explore the spatiotemporal variations, persistence characteristics, and the impact of complex climatic variability of WUE in Southwest China. New hydrological insights for the region(i) The rate of increase and multi-year average of WUE in karst ecosystem is higher than that in non-karst ecosystem. (ii) In the future, the proportion of area with decreasing in WUE will be higher in karst ecosystem than in non-karst ecosystem. (iii) There are significant differences in the correlation between WUE and climatic factors in different ecosystems. (iv) The dominant climatic factor for WUE in karst ecosystem is vapor pressure, while in non-karst ecosystem, it is precipitation. The research results can provide a theoretical basis for studying the carbon and water cycling processes in karst ecosystem.

Modeling Nitrogen Fate and Water and Nitrogen Use Efficiencies under Different Greenhouse Vegetable Production Systems Using the WHCNS-Veg Model.

Quantitative evaluation of the effects of diverse greenhouse vegetable production systems (GVPS) on vegetable yield, soil water consumption, and nitrogen (N) fates could provide a scientific basis for identifying optimum water and fertilizer management practices for GVPS. This research was conducted from 2013 to 2015 in a greenhouse vegetable field in Quzhou County, North China. Three production systems were designed: conventional (CON), integrated (INT), and organic (ORG) systems. The WHCNS-Veg model was employed for simulating vegetable growth, water dynamics, and fates of N, as well as water and N use efficiencies (WUE and NUE) for four continuous growing seasons. The simulation results revealed that nitrate leaching and gaseous N emissions constituted the predominant N loss within GVPS, which separately accounted for 11.5-59.4% and 6.0-21.1% of the N outputs. The order of vegetable yield, N uptake, WUE, and NUE under different production systems was ORG > INT > CON, while the order of nitrate leaching and gaseous N loss was CON > INT > ORG. Compared to CON, ORG exhibited a significant increase in yield, N uptake, WUE, and NUE by 24.6%, 24.2%, 26.1%, and 89.7%, respectively, alongside notable reductions in nitrate leaching and gaseous N loss by 67.7% and 63.2%, respectively. The ORG system should be recommended to local farmers.

Cultivation model and deficit irrigation strategy for reducing leakage of bundle sheath cells to CO2, improve 13C carbon isotope, photosynthesis and soybean yield in semi-arid areas

A better understanding of the photosynthesis and soil water storage regulation of soybean production will be helpful to develop a water conservation strategy under a rain-fed farming system. Reducing the leakage of CO2 bundle sheath cells and improving the photosynthesis capacity and gas exchange characteristics of soybean leaves will contribute to increase yield under the dryland agricultural system and provide a scientific basis. Therefore, during 2019 and 2020, soybean exposed to different cultivation modes to analyze the response curves of photosynthesis and CO2 under different deficit irrigation strategies. In this study, we used two cultivation models: RB: ridge covered with biodegradable film and furrow area not covered; CF: conventional flat land planting under four deficit irrigation modes (R: rainwater irrigation; IB: branch stage irrigation (220 mm); IP: Irrigation during podding (220 mm); IBP: branch stage irrigation (110 mm), podding stage irrigation (110 mm). Compared with CF-IBP treatment, RB-IBP had significant effects on rainwater collection, SWS, and soybean yield. Photo-response curve analysis showed that RB-IBP treatment a significant increase in Pn, Gs, Ci, Tr, leaf WUE, and chlorophyll ab content. Under different irrigation strategies, maximum net photosynthetic rate (Pnmax), light saturation point (LSP), and apparent quantum efficiency under RB-IBP treatment (α), Pn under respiration rate and CO2 response curve were significantly higher than that under CF cultivation mode. Compared with RB culture mode under different irrigation strategies, CF cultivation mode significantly increases Δ13C and CO2 sheath cell leakage (Փ); it also led to a significant decline in the ratio of Ci/Ca concentration. This study shows that RB-IBP treatment is the best water-saving strategy because it means reducing the leakage of CO2 from the bundle sheath, thus significantly increasing soil water storage, photosynthetic capacity, and soybean yield.

Enhancement of productivity, water- and nutrient use efficiency and economics through drip fertigation and tray seedlings in FCV tobacco (Nicotiana tabacum) under irrigated Alfisols of Andhra Pradesh

A field experiment was conducted for two consecutive seasons (2014–16) and a bulk trial for one year (2016– 17) at ICAR-Central Tobacco Research Institute Research station, Jeelugumilli, West Godavari district, Andhra Pradesh under semi arid tropical climate to study the effect of different combinations of drip irrigation, furrow irrigation, tray seedlings, normal seedlings, drip ferti-gation and soil application of fertilizers at 3rd, 25–30, 40–45 days after planting or 10, 25–30, 40–45 days after planting, on green leaf yield (GLY), cured lead yield (CLY), grade index (GI), leaf nicotine and reducing sugars, water- and fertilizer use efficiency as well as economics in FCV tobacco (Nicotiana tabacum). The experiment was laid out in a RBD with five replications, nine treatment combinations and was conducted with specified treatments for the first two years and bulk plots during the following year. Two separate plots, viz. N0 P26.2K99.6 (T10) and N120P26.2K0 (T11) were grown for comparison and calculation of N and K use efficiencies during the first two years. T4 (drip irrigation, tray seedlings, drip fertigation at 3rd, 20–25 and 40–45 DAP) and T2 (drip irrigation, tray seedlings, drip ferti-gation at 10, 25–30 and 40–45 DAP) recorded increased GLY by 23.87, 16.95, CLY by 16.67, 13.83 and GI by 23.43, 21.46% during first and second years, respectively and also higher leaf nicotine when compared to furrow irrigation, normal seedlings, soil application of fertilizers (T9 ) i.e. farmers practice. N, P, K uptake and nitrogen and potassium use efficiencies under different treatments were evaluated. Bulk plots grown with tray seedlings, drip irrigation and drip fertigation accrued additional profit of `25,285, benefit: cost ratio of 1.82, WUE of 11.74 kg of cured leaf/ ha-mm of water as compared to 5.77 kg of cured leaf/ha-mm in normal seedlings, furrow irrigation and soil application of fertilizers. Only 57.2% of total quantity of furrow irrigation is required for drip irrigation and there is 203.5% increase in WUE with drip irrigation as compared to furrow irrigation.

Analysis on water use efficiency of Populus euphratica forest ecosystem in arid area

Water use efficiency (WUE, the ratio of gross primary productivity (GPP) to evapotranspiration (ET)) reflects the coupled relationship between water loss and carbon gain in the process of plant photosynthetic carbon assimilation. As a dominant tree species in arid area, Populus euphratica plays an important ecological role in slowing desertification. Here, continuous observations of carbon, water, and energy fluxes were carried out in Populus euphratica forest with eddy covariance (EC) technique in 2018. We systematically explained the variation characteristics of energy fluxes and WUE at different time scales, and explored the main controlling factors of WUE in drought-stressed environment based on the synchronous meteorological data. Results showed that the carbon exchange of the Populus euphratica forest ecosystem occurred mainly during the growing seasons (April–October). During this period, the entire ecosystem appeared as a carbon sink with the potential to sequester atmospheric carbon dioxide. The average daily WUE was 2.2 g C/kg H2O, which was lower than other temperate forests (2.57–6.07 g C/kg H2O) but higher than grassland, wetland, and cropland. We also concluded that an increase in carbon dioxide concentration (CCO2) and air relative humidity (RH) could promote the increase of WUE. Nevertheless, WUE was negatively correlated with air temperature (Ta), photosynthetically active radiation (PAR), and normalized difference vegetation index (NDVI). Additionally, WUE increased under moderate soil water content (SWC), but decreased due to the continuously rising SWC. WUE was more strongly affected by factors affecting water consumption than carbon uptake. Under the conditions of high temperature, strong radiation and low humidity in the summer, the growth rate of ET was much larger than that of GPP. This study not only contributes to our understanding of the carbon, water, and energy dynamics of the Populus euphratica forest ecosystem but also provides an important reference for ecological conservation and ecological restoration in arid regions.

Dramatic increase in water use efficiency with cumulative forest disturbance at the large forested watershed scale

BackgroundForest disturbance induced changes in the coupling of forest carbon and water have important implications for ecosystem functioning and sustainable forest management. However, this is rarely investigated at the large watershed scale with cumulative forest disturbance. We used a combination of techniques including modeling, statistical analysis, and machine learning to investigate the effects of cumulative forest disturbance on water use efficiency (WUE, a proxy for carbon and water coupling) in the 19,200 km2 Chilcotin watershed situated in the central interior of British Columbia, Canada. Harvesting, wildfire, and a severe Mountain Pine Beetle (MPB) infestation have gradually cumulated over the 45-year study period, and the watershed reached a cumulative equivalent clear-cut area of 10% in 1999 and then 40% in 2016.ResultsSurprisingly, with the dramatic forest disturbance increase from 2000 to 2016 which was mainly due to MPB, watershed-level carbon stocks and sequestration showed an insignificant reduction. This resilience was mainly due to landscape-level carbon dynamics that saw a balance between a variety of disturbance rates and types, an accumulation of older stand types, and fast growing young regenerated forests. Watershed-level carbon sequestration capacity was sustained, measured by Net Primary Production (NPP). A concurrent significant decrease in annual evapotranspiration (ET), led to a 19% increase in WUE (defined as the ratio of NPP to ET), which is contrary to common findings after disturbance at the forest stand-level. During this period of high disturbance, ET was the dominant driver of the WUE increase.ConclusionsWe conclude that disturbance-driven forest dynamics and the appropriate scale must be considered when investigating carbon and water relationship. In contrast to the stand-level trade-off relationship between carbon and water, forested watersheds may be managed to maintain timber, carbon and water resources across large landscapes.

Salinity Effects on Germination and Plant Growth of Haloxylon Ammodendron at Qaidam Basin

Haloxylon ammodendron is one of the dominant characterizations of groups in Qaidam Basin. The salinity effects on H. ammodendron was determined by evaluating photosynthetic characteristic and seed germination feature responses in saline conditions in this paper. The reduction of Pn was corresponded to the decreasing Gs in the afternoon, when there was a slight increase in WUE corresponded to Pn and Tr during 15:00 to 17: 00p.m in the field trails. There was a delay in Pn and Tr to reach the postmeridian peak under 2% and 3% NaCl, while the daily mean values of WUE under 2% and 3% NaCl were higher than the 0% NaCl control. H. ammodendron seeds were found retaining 72% of germination rate under salinity degree high up to 3.51% saline solution. The values of GP, GE, GI and VI decreased evidently under 0.72% saline solution, whereas the reduction was indistinctive from 0.72% up to 2.14% saline solution without salt injury below 2.14% saline solution. Although the plant showed a slight sensibility to light salinity, H. ammodendron retained a certain potential of seed germination and seedling growth under salinity stress.

Utilization of grafting technique for sustaining cantaloupe productivity and quality under deficit irrigation water

BackgroundWater use efficiency (WUE) is becoming a decisive factor for agricultural expansion to face water shortage. To meet the needs of high population density in Egypt, we have to use modern irrigation systems and new cultivation technologies. The current study is aiming to apply grafting technique for ameliorating the impact of deficit water on cantaloupe productivity and fruit quality. Two commercial cultivars (Ideal and Veleta) were grafted on two rootstocks (Cobalt and Strong-Tosa) and self-grafting. The seedlings were treated with three different irrigation levels: 100, 75, and 50% of Class A pan Evapotranspiration (ETc).ResultsThe results showed that moderate irrigation level (75% ETc) increased the early yield, fruits number, by 15.3 and 17.4%, respectively, compared to control irrigation treatment (100% ETc). No significant variation was found concerning total yield between 100 and 75% ETc, so this led to an increase in WUE of moderate irrigation level (75% ETc) by 34.3%, compared to control irrigation treatment (100% ETc). Increasing deficit levels up to 50% ETc reduced the total yield by 47.4%, but it increased the WUE by 8.8%, compared to the non-deficit irrigation level (100% ETc). Meanwhile, grafting both cultivars on Cobalt rootstock improved the fruit number, total yield, and WUE by 39.2%, 26.9%, and 24.1%, respectively when irrigated with the moderate irrigation level (75% ETc), as compared to the non-grafted plants which recorded the highest decrease when irrigated with deficit irrigation level (50% ETc).ConclusionFinally, the combination treatments of Ideal/Strong-Tosa, Veleta/Cobalt, or Ideal/Cobalt irrigated with moderate irrigation level (75% ETc) increased the WUE by 97.3, 83.4, and 65%, respectively, compared to the control treatment (non-grafted plants of the same cv. at 100% ETc) and recorded higher flesh thickness, TSS and firmness.

Observed and modelled historical trends in the water-use efficiency of plants and ecosystems.

Plant water-use efficiency (WUE, the carbon gained through photosynthesis per unit of water lost through transpiration) is a tracer of the plant physiological controls on the exchange of water and carbon dioxide between terrestrial ecosystems and the atmosphere. At the leaf level, rising CO2 concentrations tend to increase carbon uptake (in the absence of other limitations) and to reduce stomatal conductance, both effects leading to an increase in leaf WUE. At the ecosystem level, indirect effects (e.g. increased leaf area index, soil water savings) may amplify or dampen the direct effect of CO2 . Thus, the extent to which changes in leaf WUE translate to changes at the ecosystem scale remains unclear. The differences in the magnitude of increase in leaf versus ecosystem WUE as reported by several studies are much larger than would be expected with current understanding of tree physiology and scaling, indicating unresolved issues. Moreover, current vegetation models produce inconsistent and often unrealistic magnitudes and patterns of variability in leaf and ecosystem WUE, calling for a better assessment of the underlying approaches. Here, we review the causes of variations in observed and modelled historical trends in WUE over the continuum of scales from leaf to ecosystem, including methodological issues, with the aim of elucidating the reasons for discrepancies observed within and across spatial scales. We emphasize that even though physiological responses to changing environmental drivers should be interpreted differently depending on the observational scale, there are large uncertainties in each data set which are often underestimated. Assumptions made by the vegetation models about the main processes influencing WUE strongly impact the modelled historical trends. We provide recommendations for improving long-term observation-based estimates of WUE that will better inform the representation of WUE in vegetation models.

Root Growth, Water and Nitrogen Use Efficiencies in Winter Wheat Under Different Irrigation and Nitrogen Regimes in North China Plain.

Excessive nitrogen (N) application combined with water shortage has a negative effect on crop production, particularly wheat (Triticum aestivum L.) production in the North China Plain. This study examined root growth and water and nitrogen use efficiencies in wheat grown on loam soil in the North China Plain, from 2012 to 2014 using a fixed-position experiment initiated in 2010. The experiment followed a completely randomized split-plot design with four replications, taking irrigation [no irrigation (W0) versus irrigation at jointing plus flowering (W2)] as the main plot and N treatment (0, 180, 240, and 300 kg N ha-1) as the subplot. Compared with W0, W2 increased grain yield and root weight density (RWD) by up to 91.3 and 57.7% in 2012–2013, and 15.5 and 43.0% in 2013–2014, respectively, across all N application rates. Irrigation had no effect on grain water use efficiency (WUEY), but caused a decrease in biomass WUE at vegetative growth stage (WUEF) and at grain-filling stage (WUEM). Significant improvements in grain yield and biomass WUE during vegetative growth stage, and reductions in nitrogen-use efficiency (NUE) and RWD, were observed with increasing N application. Compared with non-N treatment, N treatment increased yield by up to 98.9 and 93.7% in 2012–2013 and 2013–2014, respectively, decreasing RWD by 12.0 and 16.9%. Correlation analysis further revealed that RWD was positively correlated with grain yield, evapotranspiration (ET) and NUE. NUE was also positively correlated with nitrogen uptake efficiency (UPE). Overall, the findings suggest that optimal N application improves NUE by increasing above–ground nitrogen uptake as a result of optimized RWD and a synchronous increase in WUE, thus increasing yield. Under the experimental conditions, an N application rate of 240 kg N ha-1 plus irrigation at jointing and flowering is recommended.

Effects of Fertilizer Application Rate and Planting Density on Photosynthetic Characteristics, Yield and Yield Components in Waxy Wheat

Waxy wheat (Triticum aestivum L.) is grown throughout the world for its specific quality. Fertilization and planting density are two crucial factors that affect waxy wheat yield and photosynthetic capacity. The objectives of the research were to determine the effects of fertilization and planting density on photosynthetic characteristics, yield, and yield components of waxy wheat, including Yield, SSR, TGW, GNPP, GWPP, PH, HI, Pn, Gs, Ci, E and WUE using the method of field experiment, in which there were three levels (150, 300, and 450 kg ha–1) of fertilizer application rate and three levels (1.35, 1.8, and 2.25 × 106 plants ha–1) of planting density. The results suggested that photosynthetic characteristics, yield, and yield components had close relationship with fertilization levels and planting density. Under the same plant density, with the increase of fertilization, Yield, SSR, TGW, GNPP, GWPP, HI, Pn, Gs, E and WUE increased and then decreased, PH increased, but Ci decreased. Under the same fertilization, with the increase of plant density, Yield, SSR, TGW, GNPP, GWPP, HI increased and then decreased, PH, Pn, Gs and E increased, PH and WUE declined. The results also showed that F2 (300 kg ha–1) and D2 (1.8 × 106 plants ha–1) was a better match in this experiment, which could obtain a higher grain yield 4961.61 kg ha–1. Consequently, this combination of fertilizer application rate and plant densities are useful to get high yield of waxy wheat.

Water relations and photosynthetic water use efficiency as indicators of slow climate change effects on trees in a tropical mountain forest in South Ecuador

The effects of an increasing moisture on trees of the tropical species-rich mountain rain forest in the South Ecuadorian Andes was investigated, using the daily total water consumption (TWC) and the instantaneous water use efficiency (WUE, ratio of photosynthetic CO2 uptake per water loss by transpiration) as ecophysiological indicators. Two canopy and one sub-canopy tree species, (Vismia tomentosa, Clusiaceae, an as of yet unknown Lauracee, and Spirotheca rosea, Bombacaceae) were the experimental objects. Seasonal changes as well as a long-term (18 months) trend of increasing precipitation caused an inverse reaction of the TWC of the trees. Because of a rather unlimited water supply to the trees from a permanently high water content of the soil, transpiration followed mainly the atmospheric demand of water vapor, and increasing moisture hence reduced water loss by transpiration. It was hypothesized that in spite of the reduction in transpiratory water loss photosynthetic carbon acquisition would be not or less affected due to an increase in water use efficiency. Concomitant measurements of photosynthetic net CO2 uptake showed the expected increase of WUE in V. tomentosa and S. rosea, but no clear reaction of the Lauracee. Accompanying measurements of stem extension growth confirmed an undiminished growth of V. tomentosa and S. rosea but showed also suspended growth of the Lauracee during the wettest months. While TWC can be continuously monitored with the heat dissipation technique, WUE is determined by leaf porometry in campaigns for which access to the canopy is required. Simultaneous recordings of the gas exchange of leaves at 4 different positions in the crown of one of the experimental trees (V. tomentosa) showed the usability of the trait WUE in combination with the total daily water consumption as indicator set for assessing the response of trees to a subtly changing climate. However, not all tree species appear as likewise useful indicator trees.

Seasonal responses of terrestrial ecosystem water-use efficiency to climate change.

Ecosystem water-use efficiency (EWUE) is an indicator of carbon-water interactions and is defined as the ratio of carbon assimilation (GPP) to evapotranspiration (ET). Previous research suggests an increasing long-term trend in annual EWUE over many regions and is largely attributed to the physiological effects of rising CO2 . The seasonal trends in EWUE, however, have not yet been analyzed. In this study, we investigate seasonal EWUE trends and responses to various drivers during 1982-2008. The seasonal cycle for two variants of EWUE, water-use efficiency (WUE, GPP/ET), and transpiration-based WUE (WUEt , the ratio of GPP and transpiration), is analyzed from 0.5° gridded fields from four process-based models and satellite-based products, as well as a network of 63 local flux tower observations. WUE derived from flux tower observations shows moderate seasonal variation for most latitude bands, which is in agreement with satellite-based products. In contrast, the seasonal EWUE trends are not well captured by the same satellite-based products. Trend analysis, based on process-model factorial simulations separating effects of climate, CO2 , and nitrogen deposition (NDEP), further suggests that the seasonal EWUE trends are mainly associated with seasonal trends of climate, whereas CO2 and NDEP do not show obvious seasonal difference in EWUE trends. About 66% grid cells show positive annual WUE trends, mainly over mid- and high northern latitudes. In these regions, spring climate change has amplified the effect of CO2 in increasing WUE by more than 0.005gCm(-2) mm(-1) yr(-1) for 41% pixels. Multiple regression analysis further shows that the increase in springtime WUE in the northern hemisphere is the result of GPP increasing faster than ET because of the higher temperature sensitivity of GPP relative to ET. The partitioning of annual EWUE to seasonal components provides new insight into the relative sensitivities of GPP and ET to climate, CO2, and NDEP.

Physiological, Anatomical and Metabolic Implications of Salt Tolerance in the Halophyte Salvadora persica under Hydroponic Culture Condition.

Salt tolerance mechanism of an extreme halophyte Salvadora persica was assessed by analyzing growth, nutrient uptake, anatomical modifications and alterations in levels of some organic metabolites in seedlings imposed to various levels of salinity (0, 250, 500, and 750 mM NaCl) under hydroponic culture condition. After 21 days of salt treatment, plant height, leaf area, and shoot biomass decreased with increase in salinity whereas the leaf succulence increased significantly with increasing salinity in S. persica. The RWC% of leaf increased progressively in salt-treated seedlings as compared to control. Na+ contents of leaf, stem and root increased in dose-dependent manner whereas there was no significant changes in K+ content. There was significant alterations in leaf, stem, and root anatomy by salinity. The thickness of epidermis and spongy parenchyma of leaf increased in salt treated seedlings as compared to control, whereas palisade parenchyma decreased dramatically in extreme salinity (750 mM NaCl). There was a significant reduction in stomatal density and stomatal pore area of leaf with increasing salinity. Anatomical observations of stem showed that the epidermal cells diameter and thickness of cortex decreased by salinity whereas thickness of hypodermal layer, diameter of hypodermal cell, pith area and pith cell diameter increased by high salinity. The root anatomy showed an increase in epidermal thickness by salinity whereas diameters of epidermal cells and xylem vessels decreased. Total soluble sugar content remained unchanged at all levels of salinity whereas reducing sugar content increased by twofold at high salinity (750 mM NaCl). The starch content of leaf decreased progressively in NaCl treated seedlings as compared to control. Total free amino acid content did not change at low salinity (250 mM), whereas it increased significantly at higher salinity (500 and 750 mM NaCl). The proline content increased in NaCl treated seedlings as compared to control. There was no significant changes in polyphenols level of leaf at all levels of salinity. The results from the present study reveal that seedlings imposed with various levels of salinity experience physiological, biochemical and anatomical modifications in order to circumvent under extreme saline environment. The vital mechanisms of salt tolerance in S. persica are higher accumulation of organic metabolites, increase in leaf succulency, efficient Na+ sequestration in the vacuole, K+ retention in the photosynthetic tissue and increase in WUE by reducing stomatal density. Therefore, S. persica is a potential halophytic species to be cultivated in saline lands to eliminate excess salt and make it favorable for agriculture.

Wind increases leaf water use efficiency.

A widespread perception is that, with increasing wind speed, transpiration from plant leaves increases. However, evidence suggests that increasing wind speed enhances carbon dioxide (CO2 ) uptake while reducing transpiration because of more efficient convective cooling (under high solar radiation loads). We provide theoretical and experimental evidence that leaf water use efficiency (WUE, carbon uptake per water transpired) commonly increases with increasing wind speed, thus improving plants' ability to conserve water during photosynthesis. Our leaf-scale analysis suggests that the observed global decrease in near-surface wind speeds could have reduced WUE at a magnitude similar to the increase in WUE attributed to global rise in atmospheric CO2 concentrations. However, there is indication that the effect of long-term trends in wind speed on leaf gas exchange may be compensated for by the concurrent reduction in mean leaf sizes. These unintuitive feedbacks between wind, leaf size and water use efficiency call for re-evaluation of the role of wind in plant water relations and potential re-interpretation of temporal and geographic trends in leaf sizes.

Changes in water use efficiency and water footprint in grain production over the past 35 years: a case study in the North China Plain

Water use efficiency (WUE, defined as the ratio of grain yield divided by the crop water use) considers the water used directly in the field. Water footprint (WF, calculated as the sum of green, blue and grey WF) also includes the water use of farm inputs and the possible environmental effects of crop water use. This study used the two metrics to assess the WUE and WF of winter wheat and summer maize, an annual double cropping system in the North China Plain (NCP), using field data collected at a fixed site from 1980 to 2014 as a case study. The results show that there was seasonal variation in the WUE and WF of winter wheat and summer maize in response to fluctuations in grain production and farm inputs. Annual average WUE was increased from 1.21 kg m−3 in 1980s to 1.80 kg m−3 recently, and the annual average WF was decreased from 0.90 m−3 kg to 0.78 m−3 kg. The contribution of the WFgreen, WFblue and WFgrey to total WF was 23.4%, 62.0% and 14.5% for winter wheat, and 59.4%, 26.7% and 14.0% on average for summer maize, respectively. The WFblue took up about half of the WF, indicating the dependence of grain production on irrigation in this region. The results from this study also showed that the increase in WUE was much greater than the decrease in WF due to the fast increase in WFgrey. The continuous increase in farm inputs from 1980s to present offset some improvement in crop water productivity. The WF metric can not only quantify the consumptive water use, but also evaluate the environmental impacts related to entire agricultural production systems. Thus, WF measure may be a more comprehensive approach than that of WUE in assessing the effectiveness of crop water use and its environmental influence.

Water deficit regimes trigger changes in valuable physiological and phytochemical parameters in Helichrysum petiolare Hilliard & B.L. Burtt

The genus Helichrysum Miller is a source of many bioactive metabolites commonly used in traditional medicine. In particular, Helichrysum petiolare Hilliard & B.L. Burtt shows activities as antiseptic, anti-inflammatory and in the control of anxiety disorder. Biosynthesis and accumulation of secondary metabolites is a defense mechanism of plants and it is strictly influenced by the surrounding environmental conditions. In this study, drought was imposed on H. petiolare (HEL008 clone CREA-Sanremo collection) to understand the effect of water stress on the dynamics of plant biomass and secondary metabolites production, and the morphological and physiological mechanisms involved in plant responses. H. petiolare was cultivated for 34 days under three water regimes: 100% of container capacity (CC, control), 50% CC (moderate water stress), and 0% CC (severe water stress). Plant growth traits, leaf water potential, gas exchange parameters, phenol, flavonoid, and anthocyanin content, and antioxidant activity changes were determined twice a week, while the volatile organic compounds (VOCs) and essential oils (Eos) at the end of the trial. Severe water stress dramatically reduced aerial and root dry weight, chlorophyll and carotenoid content, leaf water potential, water use efficiency (WUE, A/E), transpiration rate (E), stomatal conductance (gs), net photosynthetic rate (A) and antioxidant activity. Moderate water stress induced only slight changes and led to an increase of WUE at the end of the experiment. The total amount of VOCs and Eos was not affected by water stress while their quality changed. Moderate water stress increased the main constituents of both VOCs, i.e. the monoterpene hydrocarbons, and Eos, i.e., the oxygenated sesquiterpenes. In conclusion, this H. petiolare cultivation under the applied moderate drought condition could lead to a double benefit i.e., water-saving irrigation practice and high quality metabolite production.

Alternate wetting and moderate drying increases rice yield and reduces methane emission in paddy field with wheat straw residue incorporation

AbstractWheat residue incorporation into the rice paddy field is becoming a popular practice in rice production in China's main rice‐growing area but risks an increased emission of greenhouse gases. This study investigated if an alternate wetting and moderate drying (AWMD) irrigation regime in rice production reduces CH4 emission and increases grain yield when wheat straw residues are incorporated into rice paddy field. One super rice variety was field‐grown in 2012 and 2013 and subjected to four irrigation and straw incorporation treatments: continuously flooded (CF) without straw incorporation (−S), AWMD without straw incorporation (AWMD−S), then CF with straw incorporation (CF + S) and AWMD + S. When compared with the CF, the AWMD regime increased grain yield and water use efficiency (WUE, grain yield over the amount of water used) by 2.7% and 27.6%, respectively, under −S, and by 18.0 and 50.0%, respectively under +S. The AWMD + S treatment also significantly increased nitrogen use efficiency (NUE) compared with the CF + S treatment. The increase in grain yield, WUE and NUE in the AWMD regime, especially under +S, were attributed mainly to a greater root oxidation activity, deeper root distribution and increases in productive tillers, crop growth rate and nonstructural carbohydrate remobilization during grain filling. There was a total of 0.49 kg N2O‐N ha−1 more loss in the AWMD than in the CF regime. However, the AWMD regime substantially decreased seasonal CH4 emissions, global warming potential (GWP, including both CH4 and N2O) and greenhouse gas intensity (grain yield over GWP) by 49.8%, 45.2% and 46.7%, respectively, under −S, and by 57.5, 55.9% and 62.6%, respectively, under +S, when compared with the CF regime. The results demonstrate that the AWMD is an effective practice to increase grain yield and resource‐use efficiency and reduce environmental risks especially, when wheat straw is incorporated into paddy field.

Comparative assessment of the sensitivity of oilseed rape and wheat to limited water supply

AbstractThe drought‐sensitivity of oilseed rape (OSR, Brassica napus cv. SW Landmark) was investigated, using the more widely studied crop species wheat (Triticum aestivum cv. Tybalt) as a benchmark. The water relations of OSR and wheat were compared in lysimeter and controlled environment experiments to test the hypothesis that the growth of OSR is restricted to a greater extent by soil drying than wheat and to determine whether the greater sensitivity results from differences in root or shoot traits. Plants were grown, with or without irrigation, in 1.2 m tall lysimeters packed with a sandy clay loam soil. The experiment was conducted in an open‐sided glasshouse to encourage air flow and to resemble a field environment as far as possible; plant population densities were equivalent to commercial crops. Irrigated OSR (evapo)transpired more water than wheat (498 vs. 355 mm), but had a comparable water use efficiency (WUE; 4.1 vs. 4.4 g DW mm−1 H2O). Oilseed rape showed a greater reduction in above‐ground growth (52% vs. 21%) and a smaller increase in WUE (27% vs. 45%) when water was withheld. Oilseed rape also responded to soil drying at a lower soil moisture deficit than wheat; transpiration rates fell below the potential of irrigated plants when plant available water remaining in the soil profile declined from 54 to 23% compared to 38 to 9% for wheat. The root hydraulic conductivity of young OSR plants, measured on root surface area basis, was about twice that of wheat, and was comparable on a root length basis. The results show that OSR was more sensitive to a restricted water supply than the benchmark species wheat and that the greater sensitivity resulted from differences in shoot, rather than root, characteristics. The root system of OSR was at least as efficient as wheat at extracting water from soil.

Influence of Exogenous Glycinebetaine on Hot Pepper under Water Stress

A study was conducted to evaluate the effect of exogenous application of glycinebetaine (GB) on physiological response in hot-pepper (Capsicum annuum L. vs. Arka Lohit and Pusa Jwala) under water stress. Glycinebetaine was applied to seeds as well as plants through foliar applications. Water stress affected considerably the morphophysiological parameters in both the cultivars. However, in glycinebetaine (GB) treated plants, plant height, leaf area (LA), flower and fruit number and total dry matter (TDM) were greater compared to the untreated stress plants (T4) under water stress. Glycinebetaine application enhanced the photosynthesis (PN) in water deficit experiencing plants, mostly due to a greater stomatal conductance (gs) and carboxylation efficiency of CO2 assimilation. In both the cultivars after 12 day of stress, the PN decreased from 10.1 to 1.0-1.3 μ mol m-2 s-1 in untreated stressed plants (T4), while in the treated stressed plants PNhad reduced to 2.0 - 3.0 μ mol m-2 s-1 (T1 - T3). The application of GB increased the WUE in both the cultivars. The better WUE in treated plants of hot-pepper under stress was attributed to the improved PN. The higher per plant yield in the GB applied plants under stress in both the cultivars associated with higher PNrate, gs and WUE in treated plants. Though there was an increase in PN rate, WUE and plant yield in the treated plants (T1 - T3), the better results were found in the plants (T2) where seeds were treated and foliar application was given at the time of imposing stress.