Decreased Water Use Efficiency Research Articles

Spatio-temporal heterogeneity and driving mechanism of ecosystem water use efficiency in the Loess Plateau, China

Study regionThe Loess Plateau, China Study focusThe trade-off between carbon uptake and water loss, characterized by ecosystem water use efficiency (WUE), deeply influences ecosystem sustainability. In this study, WUE was estimated based on GPP from the Moderate Resolution Imaging Spectroradiometer (MODIS) product and ET simulated by the Priestley Taylor Jet Propulsion Laboratory (PT-JPL) model. The emerging hot spot analysis (EHSA) was used to comprehensively examine the spatio-temporal heterogeneity of WUE. Additionally, the Geodetector model was employed to identify the main drivers of WUE and quantify the interactive effects of drivers on WUE, focusing on different vegetation types. New hydrological insights for the regionResults indicated obvious spatial heterogeneity of WUE under different vegetation and hydro-climatic conditions. Significant increases in WUE occurred in sub-humid cropland and grassland areas that have experienced large-scale ecological restoration and agricultural intensification. By contrast, slight decreases in WUE were observed in semi-arid grassland areas, some of which were accompanied by intensifying cold spots. It was noteworthy that WUE in some hot spots with excessive vegetation coverage also showed a slight downward trend. Further, the WUE pattern in cropland/forests/grassland was dominated by the interaction of vegetation coverage (characterized by the Normalized Difference Vegetation Index, NDVI) and precipitation/air temperature/vapor pressure deficit, with NDVI playing a leading role and hydro-climatic drivers playing a supporting role.

Heat shock combined with salinity impairs photosynthesis but stimulates antioxidant defense in rice plants

The interactive mechanisms that occur between heat shock and salt stress and their reflexes on photosynthesis and redox metabolism in plants are little understood yet. We tested the hypothesis that heat shock negatively interacts with salt stress, affecting most intensely K+/Na+ homeostasis, stomatal closure, and CO2 assimilation, in comparison to PSII activity and oxidative stress in rice leaves. 31-day old rice plants were previously exposed to 0 and 100 mM NaCl for eight days at 27 °C and afterwards two groups were transferred to high temperature (42 °C, heat shock) for 10 hours (heat and heat + salt) whereas two other groups remained at 27 °C (control and single salt treatments). Heat-salinity interaction greatly stimulated Na+ accumulation in leaves causing intense decrease in K+/Na+ ratios, inducing significant osmotic and ionic alterations. Stomata were closed intensely causing drastic impairment in CO2 assimilation and decrease in water use efficiency. In contrast, the PSII activity was much lesser affected, corroborated by a low increase in the fraction of closed reaction centers of PSII and slight decrease in electron transport rates. Despite that unbalance in photosynthesis, combined stress partially favored oxidative protection as indicated by a reduction in the levels of H2O2 and lipid peroxidation associated with reduction in the contents of reduced forms of ascorbate and glutathione. These favorable antioxidant responses were accompanied by increases in the activities of ascorbate peroxidases, superoxide dismutases, glutathione peroxidases, and phenol peroxidases whereas catalases and glycolate oxidases decreased. These antioxidant responses were not enough to mitigate overall physiological damages caused by combined stress, as indicated by drastic increase in membrane damage and decrease in relative water content in leaves. Heat shock drastically aggravates the negative effects caused by salt stress on the photosynthetic efficiency, especially CO2 assimilation, despite the heat – salinity interaction has partially favored the antioxidant defense.

Dissecting the Characteristics and Driver Factors on Global Water Use Efficiency Using GLASS Data Sets

AbstractEcosystem water use efficiency (WUE) is a crucial parameter for understanding the interaction between carbon and water cycles. However, the spatio–temporal evolution and drivers of WUE remain unclear. This study utilized global annual scale global land surface satellite gross primary productivity and evapotranspiration data from 1982 to 2018 to estimate WUE and analyze its spatio–temporal characteristics. Additionally, the study investigated the response of WUE changes to five environmental factors (precipitation [PRE], soil moisture, temperature [TEM], palmer drought severity index, and vapor pressure deficit [VPD]) on WUE changes using partial correlation and structural equation modeling. The results suggested that the global annual WUE increased markedly over the study period, at an average rate of 0.0016 gC m−2 mm−1 H2O year−1. In contrast to the existing knowledge on the drivers of WUE change, climate change was found to have a larger contribution to WUE changes at the global and regional scales, especially in terms of TEM and VPD. A positive correlation between TEM and WUE was observed, but extreme TEM could lead to a decrease in WUE. VPD had the most significant direct effect on WUE, and its negative effect offset the positive influence of TEM especially in hyper‐arid, semi‐arid, and arid regions. These findings offer new insights into the impact of VPD and global warming on WUE.

Multicontamination Toxicity Evaluation in the Model Plant Lactuca sativa L.

Many contaminated soils contain several toxic elements (TEs) in elevated contents, and plant-TE interactions can differ from single TE contamination. Therefore, this study investigated the impact of combined contamination (As, Cd, Pb, Zn) on the physiological and metabolic processes of lettuce. After 45 days of exposure, TE excess in soil resulted in the inhibition of root and leaf biomass by 40 and 48%, respectively. Oxidative stress by TE accumulation was indicated by markers-malondialdehyde and 5-methylcytosine-and visible symptoms of toxicity (leaf chlorosis, root browning) and morpho-anatomical changes, which were related to the change in water regime (water potential decrease). An analysis of free amino acids (AAs) indicated that TEs disturbed N and C metabolism, especially in leaves, increasing the total content of free AAs and their families. Stress-induced senescence by TEs suggested changes in gas exchange parameters (increase in transpiration rate, stomatal conductance, and intercellular CO2 concentration), photosynthetic pigments (decrease in chlorophylls and carotenoids), a decrease in water use efficiency, and the maximum quantum yield of photosystem II. These results confirmed that the toxicity of combined contamination significantly affected the processes of lettuce by damaging the antioxidant system and expressing higher leaf sensitivity to TE multicontamination.

Plant water source effects on plant-soil feedback for primary succession of terrestrial ecosystems in a glacier region in China

Despite the extensive research conducted on plant-soil-water interactions, the understanding of the role of plant water sources in different plant successional stages remains limited. In this study, we employed a combination of water isotopes (δ2H and δ18O) and leaf δ13C to investigate water use patterns and leaf water use efficiency (WUE) during the growing season (May to September 2021) in Hailuogou glacier forefronts in China. Our findings revealed that surface soil water and soil nutrient gradually increased during primary succession. Dominant plant species exhibited a preference for upper soil water uptake during the peak leaf out period (June to August), while they relied more on lower soil water sources during the post-leaf out period (May) or senescence (September to October). Furthermore, plants in late successional stages showed higher rates of water uptake from uppermost soil layers. Notably, there was a significant positive correlation between the percentage of water uptake by plants and available soil water content in middle and late stages. Additionally, our results indicated a gradual decrease in WUE with progression through succession, with shallow soil moisture utilization negatively impacting overall WUE across all succession stages. Path analysis further highlighted that surface soil moisture (0– 20 cm) and middle layer nutrient availability (20– 50 cm) played crucial roles in determining WUE. Overall, this research emphasizes the critical influence of water source selection on plant succession dynamics while elucidating underlying mechanisms linking succession with plant water consumption.

Molecular and Physiological Responses to Exogenously Applied Melatonin in Spinach Under Deficit Irrigation Conditions

Melatonin, an important phytochemical, encourages plants to redirect growth in response to environmental stresses. The study aims to investigate the changes in the morphological, physiological, biochemical, and molecular properties of spinach subjected to the exogenous application of melatonin (MEL) at different doses under different water stress. The following four irrigation levels were applied: I100 (complete irrigation), I80 (20% water deficit), I60 (40% water deficit), and I40 (60% water deficit). MEL was applied through a spray on the leaves in three doses—0, 50, and 100 µM. In the present study, the application of MEL50 exhibited no significant decrease in water use efficiency (WUE) at the I80 irrigation level compared to the I100 irrigation level, while a significant decrease in the WUE was observed beyond this point. The application of MEL contributed to influencing the morphological parameters while also positively affecting the photosynthesis activity and, contribution to the antioxidant defense system. It was observed that the genes involved in the carbon metabolism of photosynthesis), the antioxidant mechanism, and the continuity of photosynthesis, all of which affect the expression of melatonin, facilitated water stress reduction in spinach. Therefore, it was inferred that the application of MEL50I80 could serve as an important irrigation strategy in semi-arid regions with limited water resources.

Divergent impacts of VPD and SWC on ecosystem carbon-water coupling under different dryness conditions

Ecosystem water use efficiency (WUE) is an indicator of carbon-water interactions and is defined as the ratio of gross primary productivity (GPP) to evapotranspiration (ET). However, it is currently unclear how WUE responds to atmospheric and soil drought events in terrestrial ecosystems with different dryness conditions. Additionally, the contributions of GPP and ET to the WUE response remain poorly understood. Based on measurements from 26 flux tower sites distributed worldwide, the binning method and random forest model were employed to separate the sensitivities of daily ecosystem WUE, GPP, and ET to vapor pressure deficit (VPD) and soil water content (SWC) under different dryness conditions (dryness index = potential evapotranspiration/precipitation, DI). Results showed that the sensitivity of WUE to VPD was negative at humid sites (DI < 1), while the sensitivity of WUE to SWC was positive at arid sites (DI > 2). Furthermore, the contribution of GPP to VPD-induced WUE variability was 63 % at humid sites, and the contribution of ET to SWC-induced WUE variability was 68 % when SWC was less than the 60th percentile at arid sites. Consequently, one increasing VPD-induced decrease in GPP was generally linked to a decrease in WUE at humid sites, and one drying soil moisture-caused decrease in ET was linked to a WUE increase under low SWC conditions at arid sites. Finally, VPD had a stronger effect on WUE than SWC when VPD was less than the 90th percentile or SWC was greater than the 50th percentile. Our findings underscore the importance of considering ecosystem dryness when investigating the impacts of VPD and SWC on ecosystem carbon-water coupling.

Compensatory response of ecosystem carbon-water cycling following severe drought in Southwestern China

Climate change has increased the frequency and length of droughts, but many uncertainties remain regarding the impacts of this aridification on terrestrial ecosystem function. Vegetation water use efficiency and carbon sequestration capacity are crucial determinants that both respond to and mediate the effects of drought. However, it is important to note that the consequences of drought on these processes can persist for years. A deeper exploration of these “drought legacy effects” will help improve our understanding of how climate change alter ecosystem carbon-water cycling. Here, we investigate the spatial patterns of drought legacy effects on remotely-sensed vegetation greenness (NDVI), net primary productivity (NPP) and water use efficiency (WUE) in southwestern China, a biodiversity hotspot that was impacted by an extreme drought in 2009–2010, with a particular focus on the tradeoff between WUE and NPP. Despite widespread negative drought legacy effects in NDVI (impacting 61.26 % of the study region), there was a general increase in NPP (58.68 %) and a decrease in WUE (67.53 %) in the year following drought (2011). This drought legacy effect was most evident in forests, while drought legacies in grasslands were less common. Drought legacies were also most apparent in relatively warm and humid areas. During the study period (2002 to 2018), we found that drought impacts on WUE also lagged behind changes in NPP by 1–2 years in forests, which highlights how drought legacies may manifest differently across ecosystem processes. Our study demonstrated that severe drought conditions may significantly affect the carbon sequestration capacity and water use efficiency of vegetation in southwestern China, and that forests may compensate for the detrimental effects of water stress by increasing water use and biomass growth after drought episodes.

Plant size directly correlates with water use efficiency in Arabidopsis.

Plant transpiration is a fundamental process that determines plant water use efficiency (WUE), thermoregulation, nutrition, and growth. How transpiration impacts on such essential physiological aspects and how the environment modulates these effects are fundamental questions about which little is known. We investigated the genetic and environmental factors underlying natural variation in plant transpiration and water use efficiency in a population of natural Arabidopsis thaliana accessions grown under homogeneous conditions. As expected, we observed large variation of total transpiration capacity, transpiration per surface unit, and WUE among A. thaliana accessions. Despite the variation of stomatal density and ABA content in the population, WUE did not correlate with any of these parameters. On the contrary, a surprising direct correlation was found between WUE and projected leaf area, with bigger plants displaying a more efficient use of water. Importantly, genome-wide association studies further supported our observations through the identification of several loci involved in WUE variation, mutations in which caused a simultaneous reduction in plant size and a decrease in WUE. Altogether, our results strongly suggest that, although WUE depends on many parameters, plant size is an adaptive trait with respect to water use in A. thaliana.

Physiological and Histological Characterization of the ESB1 TILLING Mutant of Brassica rapa L.: Potential Use in Biofortification and Phytoremediation Programs

Enhanced suberin1 (ESB1) is a protein whose mutation is correlated with an increase in root suberin and altered nutrient concentrations. Here, we show a physiological and histological characterization of esb1 mutant plants of Brassica rapa L. Therefore, the potential use of this mutant in selenium (Se) biofortification and/or cadmium (Cd) phytoremediation programs was also evaluated by applying 20 μM of Na2SeO4 and 0.49 μM of CdCl2 to a nutrient solution. With respect to wild type (WT) plants, an increase in root suberin was observed in esb1 at the level of the exodermis. This increase in root suberin did not affect photosynthesis performance. However, the esb1 mutant showed an increase in transpiration rate and a decrease in water use efficiency. Additionally, root histological changes affected the transport and concentration of some mineral elements. Thus, our results suggest that esb1 mutants of B. rapa would not be useful for Se biofortification because no significant differences were observed between the two genotypes at the leaf level. Nevertheless, the esb1 mutant reduced Cd translocation to the leaves and increased Fe and Cu uptake, so ESB1 mutation could be useful for Cd phytoremediation and Fe and Cu biofortification, although further research is needed. Therefore, this study provides detailed information on the effect of ESB1 mutation in B. rapa and suggests its potential use in biofortification and phytoremediation programs.

Effects of SiO2 nanoparticles on root structures, gas exchange, and antioxidant activities of Cunninghamia lanceolata seedlings under drought stress

Increasing evidence shows that silicon possesses important physiological functions in plants, thus, silicon fertilizers are used widely in agriculture. However, few attentions were paid on the effects of silicon dioxide nanoparticles (SiO2NPs) on plant growth and resistance to abiotic stresses. In this present study, different amount of SiO2NPs were applied in pots with Cunninghamia lanceolata seedlings, and their root development, gas exchange, and drought resistance were investigated. These results showed that SiO2NPs treatment increased total root length, root volume, and the numbers of root tips of these seedlings under drought stress. Specific root area (SRA) and specific root length (SRL) also increased. SiO2NPs treatment altered anatomical structures of the first-order lateral roots of C. lanceolata seedlings under drought stress (i.e., increase in cortex thickness and the number of cortex layers). Under drought stress, SiO2NPs treatment increased net photosynthetic rates, stomatal conductance, intercellular CO2 concentration, and transpiration. SiO2NPs treatment also led to increase in light use efficiency and instantaneous Rubisco carboxylation rate and decrease in water use efficiency under drought stress. Under drought stress, SiO2NPs treatment resulted in increased activities of antioxidant enzymes (superoxide dismutase, catase, and peroxidase) and concentrations of antioxidants (ascorbate and glutathione), decreasing oxidative damage caused by drought stress. All together, these results suggested that SiO2NPs could be used for seedling culture of forest trees.

Effect of biochar addition and reduced irrigation regimes on growth, physiology and water use efficiency of cotton plants under salt stress

To alleviate the salinity and drought stresses faced in agricultural production, and to improve crop water use efficiency (WUE) in drought-prone regions, novel management strategies are needed. The combination of biochar amendment and reduced irrigation regimes could mitigate the negative effects of salinity and drought stresses and improve WUE of cotton plants. A split-root pot trial was performed in order to investigate the effects of two biochar amendments [wheat straw pellets biochar (WSP) and soft wood pellets biochar (SWP)] combined with three irrigation schemes [full irrigation (FI), deficit irrigation (DI), and partial root-zone drying irrigation (PRD)] on the growth, physiology and WUE of cotton plants under two salinity levels [0 mM NaCl (S0) and 200 mM NaCl (S1)]. The results showed that salt stress depressed plant growth and physiology, and reduced seed cotton yield and lint yield by 19.33–47.22% and 40.43–58.81%, respectively. However, the biochar amendment alleviated salt stress and increased plant dry biomass allocation ratio by 3.85%–12.54%, 5.07%–14.39% and 9.78%–46.62% in boll, seed cotton and lint cotton under S1, respectively, and also increased lint ginning out turn (GOT), harvest index (HI), WUE at plant and yield level (WUEp and WUEy) by 0.21%–28.69%, 5.07%–14.39%, −0.30%–15.71% and 5.83%–32.44%, respectively. Moreover, WSP was superior to SWP in terms of improving plant growth and yield. PRD showed better growth and physiological effects than DI, especially WUEp and WUEy were 6.88%–13.73% and 9.16%–22.78% greater under PRD than under DI. The combined application of biochar and PRD counteracted the decrease in WUE caused by biochar application alone under S0. Collectively, WSP combined with PRD could be a promising strategy in sustainable cotton production under drought and salinity stress.

Nitrogen application rates influence on yield and water productivity of quinoa under saline irrigation water regimes and saline water table

There are areas with high saline water and saline irrigation water in Iran that may be used for quinoa cultivation. In these conditions, proper saline irrigation water regimes and nitrogen application should be determined and used. Therefore, the aim of this experiment is to investigate the effect of different saline irrigation water regimes (100, 75 and 50% of full irrigation, FI) and nitrogen application rates (0, 100, 200 and 300 kg ha−1) on growth and yield of quinoa with water table depth of 0.8 m, salinity of irrigation water and water table of 20 dS m−1. The irrigation of 75% FI and 50% FI decreased the applied water by 19 and 38%, respectively. Further, there was no reducing effect of irrigation water regimes in seed and shoot dry matter yield. Furthermore, groundwater contribution (GWC) increased significantly by 8 and 18% in 75%FI and 50%FI compared with that obtained in full irrigation, and resulted in no extreme water stress under high water table depth (0.8 m). Increasing application of nitrogen fertilizer significantly increased the yield components, ETc and GWC. In addition, reducing irrigation water did not show a significant decrease in water use efficiency (WUE) in high water table depth. However, water productivity increased significantly by decreasing irrigation water. It is concluded that under deficit irrigation, high water table depth could be a valuable source of water supply to meet quinoa water requirements. Moreover, application of nitrogen fertilizer at all levels significantly increased water use efficiency and water productivity.

控水与补水条件下连续热浪对闽楠光合特性和生长速率的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 控水与补水条件下连续热浪对闽楠光合特性和生长速率的影响 DOI: 10.5846/stxb202201190183 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(32171749,31800512);国家重点研发计划子课题项目(2016YFD0600603-2);福建省种业创新与产业化工程项目(ZYCX-LY-202102) Influences of multiple successive heat waves combined with water control and supplement on photosynthetic characteristics and growth rate of Phoebe bournei seedlings Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:全球变暖背景下,亚热带地区极端气候热浪事件发生频率持续增加。高频热浪及其伴随的高温和干旱复合胁迫将严重影响植物的光合特性,抑制植物的生长,甚至造成死亡。然而,目前亚热带树木光合特性及生长对高频热浪及复合胁迫的响应仍不明确。以亚热带阔叶树种闽楠苗木为研究对象进行了热浪模拟实验,关注了补水和控水处理不同水分环境下连续热浪对闽楠光合特性及生长速率的影响。结果表明,补水处理下闽楠净光合速率(Pn)在单次热浪影响下显著下降了34%,同时水分利用效率显著(WUE)下降,但蒸腾速率(Tr)、气孔导度(Gs)和叶片水汽压亏缺(Leafvpd)显著上升(P<0.05)。表明水分充沛的高温环境中闽楠可通过增加蒸腾耗水加速水分蒸散来调节叶片的温度,增强植株光合特性对热浪的抗性。而控水处理下单次热浪处理组Tr和Gs未显著上升,以及Tr与Leafvpd在干湿环境下线性拟合的不同斜率,说明水分胁迫会降低叶片降温的效率,加剧热浪对闽楠光合特性的影响。水分和高温的复合胁迫还延长了闽楠光合特性在热浪后的恢复过程,高温胁迫下闽楠Pn在15 d后恢复至未干扰水平,但复合胁迫组未能恢复。此外,连续发生的热浪存在累加效应,表现为降低闽楠对热浪的抗性,其中闽楠Tr、Gs和WUE在连续热浪处理组变化显著(P<0.05)。但连续发生的热浪事件不会显著影响闽楠光合特性在热浪后的恢复过程,且会增加闽楠的高度,补水处理下连续热浪处理组闽楠苗高相对生长率显著高于其它处理组,但地径相对增长率未见显著差异。该研究结果表明,热浪阶段的水分供给可以增强亚热带树种闽楠的热浪抗性,并加速恢复,但控水处理的干环境下闽楠热浪抗性下降,若该环境下连续热浪事件发生可能增加闽楠苗木死亡的概率。因此,植物对气候变化响应的研究应该增强对复合胁迫或极端气候模式变化的关注。 Abstract:Under the background of global warming, the frequency of extreme climatic heat wave events continues to increase in subtropical region. The high frequency heat wave events severely reduced plants photosynthetic properties, especially when the combined thermal and drought stresses occurred, it will inhibit plant growth, and further lead to plant mortality. However, the response of subtropical tree species photosynthetic characteristics and growth to high-frequency heat waves and their complex stresses is still unclear. In this study, we created a heat wave simulation experiment on subtropical tree species, Phoebe bournei, focusing on the influences of heat waves on the photosynthetic characteristics and growth rates with or without water supplement during heat waves. The results showed that the single heat wave event in wet environment with water supply can resulted in 34% decrease in net photosynthetic rate (Pn) and also decrease in water use efficiency (WUE), but transpiration rate (Tr), stomatal conductance (Gs) and leaf vapor pressure deficit (Leafvpd) showed significant increase (P<0.05). This indicates that the Phoebe bournei in sufficient water environment can regulate leaf temperature via accelerating the water evapotranspiration consumption under high temperature stress, which could enhance the resistance of plant photosynthetic characteristics to heat waves. However, there was no significant increase in Tr and Gs in the single heat wave treatment group in drought habitat without water supplement, as well as the different slopes of the linear fit between Tr and Leafvpd in dry and wet environments. It suggests that without water supply, heat waves can cause drought stress, reduce the efficiency of leaf cooling, and exacerbate the effect of heat wave on photosynthetic characteristics of Phoebe bournei. The combined drought and high temperature stress also prolonged the recovery process of Phoebe bournei photosynthetic characteristics after heat wave, while Pn recovered to the undisturbed level at 15 days later after heat wave influences, but failed to recover in the combined stress group. In addition, there was a cumulative effect when successive heat wave occurred, which showed a reduction of Phoebe bournei resistance to heat waves, evidenced by the significant variation (P<0.05) of Tr, Gs and WUE during multiple successive heat wave events. But the multiple successive heat wave events did not significantly influence the recovery process of photosynthetic characteristics after heat wave, even caused an increasing of plant height. Under the wet environment with water supply, the Phoebe bournei seeding height relative growth rate of cumulative effect of continuous heat wave was significantly higher than other treatments, but no significant difference was observed in the relative growth rate of ground diameter. Our results indicate that the subtropical tree species, Phoebe bournei, has a strong heat wave resistance in wet environment, but such resistance will largely reduce in dry environment, and the successive heat wave events may also increase the probability of seedling mortality in dry environment. Therefore, studies of plant response to climate change should pay more attention on compound environment stresses or changes in extreme climate patterns. 参考文献 相似文献 引证文献

The interactions of iron nutrition, salinity and ultraviolet-B radiation on the physiological responses of wheat (Triticum aestivum L.)

Increasing human population, land degradation and global change is intensifying pressure on agricultural production in marginal environments. Many marginal environments experience multiple stressors, however, few studies have investigated the interaction of more than two stressors. This is the first study examining the interaction of Fe nutrition, salinity and ultraviolet-B (UV-B) radiation in plants. Wheat (Triticum aestivum L. cv. 1862) was grown in a three-way factorial design: iron (75 µM Fe and 3.75 µM Fe as FeCl3), salinity (0 mM and 75 mM NaCl) and UV-B radiation (1 kJ m−2 d−1, and 15 kJ m−2 d−1 biologically effective UV-B) in chelator-buffered solutions. Examination of the stress interactions showed that phytosiderophore release and root Fe accumulation were limited by UV-B and NaCl stress under Fe deficiency. The findings demonstrated Fe dependency of plant responses to salinity and to UV-B, e.g. sufficient Fe is required for UV-B-induced stomatal opening. Other interactions included that elevated salinity alleviated Fe deficiency-induced decreases in water use efficiency. In addition, Fe deficiency increased the accumulation of UV-absorbing compounds under elevated UV-B radiation. UV-B radiation affected belowground morphology and physiology, including a 47 % reduction in phytosiderophore release. This is the first study to demonstrate a role for wavelengths other than photosynthetically active radiation in phytosiderophore release. Our findings demonstrate that aboveground environmental factors such as UV-B radiation can affect important aspects of belowground plant function, and that Fe availability needs to be considered when growing plants in saline or high UV-B radiation environments.

Paclobutrazol improves surface water use efficiency by regulating allometric trait behavior in maize

Paclobutrazol (PBZ) role in drought management of maize is least understood. In maize, root traits are linked with surface water management. Over three years, early and terminal deficit irrigation (EDI and TDI) with or without PBZ were imposed on DKC-9144 and PG-2475 maize varieties. Several allometric parameters viz. stem height, stem diameter, leaf area and root traits along with physiological processes were measured. Implication of these parameters in the management of soil surface irrigation in terms of water use efficiency (WUE) was demonstrated in maize. Increased number of lateral roots and root number density in DKC-9144 provided more surface area for water absorption for better management of EDI. Root growth rates showed a similar pattern with root length, root surface areas, and root numbers in EDI. Elevated expressions of ZmRTCL, ZmRTCS and ZmARF34 in EDI and EDI plus PBZ were associated with seminal roots and root laterals initiation. Under TDI alone or in combination with PBZ, root lengths (BRL, CRL, SRL) and root surface areas varied in DKC-9144 and PG-2475 over control. Furthermore, correlation analysis showed that decrease in WUE under TDI was significantly associated with a reduction in stem thickness and leaf surface area. For WUE_N in TDI and PBZ plus TDI, structural equation modelling proposed, brace root surface area (BRSA_N) as a positive contributor, while a negative contributor was seminal root surface area (SRSA_N). Present study explained the importance of specific root traits and their association with other allometric parameters for improving WUE in DKC-9144 variety of maize and the crop in general.

Spatiotemporal Variability in Water-Use Efficiency in Tianshan Mountains (Xinjiang, China) and the Influencing Factors

Water-use efficiency (WUE) is a crucial physiological index in carbon–water interactions and is defined as the ratio of vegetation productivity to water loss. The variation in climatic variables and drought have the most significant effects on WUE and evapotranspiration (ET). Nevertheless, how WUE varies with climate factors and drought processes in the Tianshan Mountains (TMS) is still poorly understood. In the present work, we analyzed the spatiotemporal variations in WUE, and investigated the correlations between WUE, climate factors, and drought, in the study area. The results showed that, in the TMS during 2000–2020, annual net primary productivity (NPP) ranged from 147.9 to 189.4 gC·m−2, annual ET was in the range of 212.5–285.8 mm, and annual WUE ranged from 0.66 to 0.78 gC·kg−1·H2O. Both NPP and ET exhibited an increasing trend with some fluctuation, whereas WUE showed the opposite tendency during the study period. The obtained results demonstrated that the decrease in WUE was primarily because of the increase in ET. There were obvious differences in WUE, under different land-use types, caused by NPP and ET. However, the interannual variation in WUE showed small fluctuations and the dynamic process of WUE in each land-use type showed good consistency. Temperature and wind speed had a positive influence on WUE in the middle and eastern regions of the TMS. Precipitation also played a mainly positive role in enhancing WUE, especially on the northern slope of the TMS. There was strong spatial heterogeneity of the correlation coefficient (0.68, p &lt; 0.05) between WUE and the temperature vegetation drought index (TVDI). Moreover, the slopes of WUE and TVDI showed good consistency in terms of spatial distribution, suggesting that drought had a significant impact on ecosystem WUE. This work will enhance the understanding of WUE variation, and provide scientific evidence for water resource management and sustainable utilization in the study area.

Vegetation in Arid Areas of the Loess Plateau Showed More Sensitivity of Water-Use Efficiency to Seasonal Drought

Studying the impact of regional or seasonal drought on vegetation water-use efficiency (WUE) can identify an effective theoretical basis by which vegetation can cope with future climate change. Based on remote sensing data and climate grid data, in this study, we calculated the ecosystem WUE and standardized precipitation evapotranspiration index (SPEI), analyzed the temporal and spatial divergence of seasonal drought and WUE, and explored the relationship between WUE and seasonal drought in the Loess Plateau. The results indicate that from 2001 to 2019, the humidity in spring and summer on the Loess Plateau shows an increasing trend, and the aridity in fall also shows an increasing trend. Averaged over four seasons, WUE presents distribution characteristics of “high in the southeast and low in the northwest”, with the highest WUE in summer. However, the geological distribution of the sensitivity of WUE to seasonal drought was significantly different. Spring drought increased WUE, whereas summer drought led to a decrease in WUE. When fall drought was less severe, the WUE increased; WUE response to winter SPEI was negative, but the sensitivity did not change with variation of drought degree. The sensitivity of WUE to the magnitude of seasonal drought was affected by regional dry and wet conditions. A clear seasonal divergence was found in four climate regions, along with increased drought intensity, and the sensitivity of WUE to drought magnitude in arid areas was generally higher than that in semi-arid, semi-humid areas, or humid areas. With this study, we deeply explored how ecosystems deal with the water supply strategy of seasonal drought, which is of great significance in the understanding of the coupling relationship between the carbon–water cycle and climate change.

Presence of N-fixing neighbors increases leaf N and \u03b413C in Castilleja applegatei, a root hemiparasite

Parasitic plants are known for their high transpiration rates and low water use efficiency (WUE), which the N-parasitism hypothesis posits is driven by N limitation. Thus, availability of N-fixing hosts may affect parasite’s WUE and in turn impact the surrounding plant community. Here, I investigate how the availability of an N-fixing host affects the root hemiparasite, Castilleja applegatei, and examines host-mediated effects on community structure and soil moisture. I surveyed plant diversity and percent cover and measured soil moisture in 120 1 × 1 m plots within Sagehen Experimental Forest, CA. Fifty percent of the plots included C. applegatei. In a subset of plots, I measured leaf N, C/N, δ13C, and δ15N in C. applegatei and in one N-fixer (Ceanothus prostratus) and two non-N-fixing plants (Artemisia tridentata and Wyethia mollis). In C. applegatei availability of N-fixing hosts corresponded to a significant increase in leaf %N, a distinct δ15N signature, and an increase in δ13C (which typically signifies an increased WUE). The presence of parasites was associated with a marginally significant decrease in WUE in N-fixing neighbors, but had no effect on the two non-N-fixing species. The presence of parasites did not impact diversity, percent cover, or soil moisture. These results broadly support the N-parasitism hypothesis and indicate that host type can affect parasite’s physiology and therefore have the potential to mediate parasite’s effects in the community; however, community-level impacts were not found here.

Effect of NaCl or Macronutrient-Imposed Salinity on Basil Crop Yield and Water Use Efficiency

Cascade hydroponics, that is, the application of the circular economy concept in greenhouse hydroponic crops, may be considered as an alternative means to increase water and nutrient use efficiency in greenhouses. In such systems, the drained nutrient solution from a crop may be used as input in a second crop. However, the second (secondary) crop in the loop must be a crop that is less sensitive to salinity than the first (primary) crop. In the present study, the salinity tolerance of basil plants grown in rockwool and nutrient film technique (NFT) systems was investigated in order to study the potential of using a basil crop as a secondary crop in a cascade hydroponic system. In total, 4 electrical conductivity (EC) levels of the irrigation nutrient solution were tested (2, 4, 6, and 8 dS m−1), and salinity was imposed by NaCl or by macronutrients. Plant growth varied across the different substrates, with those grown in the NFT system being less affected as opposed to the rockwool-grown basil plants, which showed a significant growth decrease with EC values higher than 4 dS m−1. This relatively low growth pattern was associated with a decrease in water use efficiency (WUE) in the rockwool system. On the contrary, in the NFT system, the continuous flow of the nutrient solution in the root zone of the plants contributed to the alleviation of negative salinity effects, yielding up to 30 kg FM m−2 WUE even for the plants irrigated with the highest salinity treatment (8 dS m−1). The majority of macro- and micronutrients in the leaf tissue of basil were positively affected by the higher levels of conductivity in the nutrient solution. Therefore, basil cultivation could be efficiently incorporated as a secondary crop in a cascade NFT cropping system. This would contribute to drainage management in hydroponics, as the crop could be irrigated through the moderately saline drainage from a primary crop due to either NaCl or high nutrient accumulation in the leachates.