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According to classic stomatal optimization theory, plant stomata are regulated to maximize carbon assimilation for a given water loss. A key component of stomatal optimization models is marginal water-use efficiency (mWUE), the ratio of the change of transpiration to the change in carbon assimilation. Although the mWUE is often assumed to be constant, variability of mWUE under changing hydrologic conditions has been reported. However, there has yet to be a consensus on the patterns of mWUE variabilities and their relations with atmospheric aridity. We investigate the dynamics of mWUE in response to vapor pressure deficit (VPD) and aridity index using carbon and water fluxes from 115 eddy covariance towers available from the global database FLUXNET. We demonstrate a non-linear mWUE-VPD relationship at a sub-daily scale in general; mWUE varies substantially at both low and high VPD levels. However, mWUE remains relatively constant within the mid-range of VPD. Despite the highly non-linear relationship between mWUE and VPD, the relationship can be informed by the strong linear relationship between ecosystem-level inherent water-use efficiency (IWUE) and mWUE using the slope, m*. We further identify site-specific m* and its variability with changing site-level aridity across six vegetation types. We suggest accurately representing the relationship between IWUE and VPD using Michaelis–Menten or quadratic functions to ensure precise estimation of mWUE variability for individual sites.

Maize is vital in Ethiopia, particularly in Jimma. However, the benefits of deficit irrigation (DI) under varying nitrogen rates (NRs) for maize remain unknown. A 3-year field experiment assessed maize response to different NRs (N0=0 kg ha−1 , N23=23 kg ha−1 , N46=46 kg ha−1 , N69=69 kg ha−1 , and N92=92 N kg ha−1) under three DI levels (I50=50 , I75=75 , and I100=100% ETc). Factors such as rain-fed findings, soil testing, and local recommendations were considered in determining these rates. The results showed significant effects of DI, NR, and their interactions on grain yield, biomass, water-use efficiency (WUE), nitrogen-use efficiency (NUE), and harvest index (HI). Without nitrogen, 50% DI led to a greater than 50% reduction in yield and biomass compared with that at I100×N0. However, WUE and HI increased at I50×N92 compared with I100×N0. Increasing irrigation and nitrogen levels improved yield and biomass. Optimal WUE was achieved with irrigation close to 75% ETc without compromising yields. Agronomic yield significantly improved with NR above 92 kg N ha−1 under mild deficit and full irrigation, but higher rates did not provide additional benefits under severe deficit conditions. The economically optimum nitrogen rate ranged from 78 to 80 kg N ha−1 for irrigation levels ranging from 50% to 100% ETc. The study suggests that applying 80 kg N ha−1 with 75%–100% ETc levels is the best approach to enhance maize yield and achieve economic benefits. Further research is needed to explore DIs below 50% and above 100% ETc, as well as nitrogen fertilization rates above 92 kg ha−1 , in order to optimize maize production in the region. Practical Applications: This study examined the benefits of deficit irrigation and fluctuating nitrogen rates for maize production in Jimma, Ethiopia. By adopting deficit irrigation strategies and adjusting nitrogen rates, producers can reduce water withdrawal by approximately 25%. This approach optimizes both water-use efficiency and nitrogen-use efficiency without compromising yields. Increasing irrigation and nitrogen rates above I100×N92 improves agronomic yield, whereas reducing them below I50×N46 significantly decreases yield and WUE. Economically optimum nitrogen rates range from 78 to 80 kg N ha−1 with 50%–100% full irrigation. Balancing input costs and potential benefits is crucial for optimizing irrigation and nitrogen rates for maize production. To maximize agronomic yield, full irrigation with 92 kg N ha−1 (less than 96 kg N ha−1) is advisable. To optimize water use, 75% of full irrigation with 92 kg N ha−1 is recommended. To optimize nitrogen (economic yield) and achieve higher net returns, fully irrigating the maize crop with 80 kg ha−1 of nitrogen fertilization is advised. Farmers should adapt these findings to local conditions, considering factors such as soil characteristics, nitrogen price, and water price, and should consult local experts. Further research is needed to explore the effects of more or less than 50% full irrigation and of nitrogen doses exceeding 92 kg ha−1. [ABSTRACT FROM AUTHOR]

Miscanthus is a perennial grass that can yield substantial amounts of biomass in land areas considered marginal. In the Coastal Plain region of North Carolina, marginal lands are typically located in coarse‐textured soils with low nutrient retention and water‐holding capacity, and high erosivity potential. Little is known about miscanthus water use under these conditions. We conducted a study to better understand the efficiency with which miscanthus uses natural resources such as water and radiant energy to produce harvestable dry biomass in comparison to corn, a typical commodity crop grown in the region. We hypothesized that under non‐limiting soil water conditions, miscanthus would have greater available energy and water use rates owing to its greater leaf area, thus leading to greater agronomic yields. Conversely, these effects would be negated under drought conditions. Our measurements showed that miscanthus intercepted more radiant energy than corn, which led to greater albedo (by 0.05), lower net radiation (by 4% or 0.4 MJ m−2 day−1), and lower soil heat flux (by 69% or 1.0 MJ m−2 day−1) than corn on average. Consequently, miscanthus had greater available energy (by 7% or 0.6 MJ m−2 day−1) and water use rates (by 14% or 0.5 mm day−1) than corn throughout the growing season on average, which partially confirmed our hypothesis. Greater water use rates and radiation interception by miscanthus did not translate to greater water‐use (1.5 g kg−1 vs. 1.6 g kg−1) and radiation‐use (0.9 g MJ−1 vs. 1.1 g MJ−1) efficiencies than corn. Compared to literature values, our data indicated that water and radiation availability were not limiting at our study site. Thus, it is likely that marginal land features present at the Coastal Plain region such as low soil fertility and high air temperatures throughout the growing season may constrain agronomic yields even if soil water and radiant energy are non‐limiting. [ABSTRACT FROM AUTHOR]

Drought is one of the most adverse factors affecting plant growth and productivity. Identifying elite genotypes and their ideotypic traits conferring high yield potential and drought tolerance is critical in selecting and breeding drought‐tolerant wheat cultivars. In this study, we conducted field experiments at the Xinxiang Agricultural Comprehensive Experimental station in the North China Plain from 2018 to 2020 and assessed 209 wheat cultivars released since the 1940s under irrigated and nonirrigated conditions. Then, we selected drought‐tolerant cultivars by classifying them into four groups based on yield response to drought stress and several drought indices. Finally, the key ideotypic traits associated with high yield potential and drought tolerance were identified. Results indicated that the grain yield of the 209 cultivars decreased on average by 10.4% and 9.4% under nonirrigated treatment in 2018–2019 and 2019–2020, respectively, relative to full irrigation. The high‐yielding cultivars under both irrigation treatments are characterised by a compact plant type, larger thousand‐grain weight, larger chlorophyll content, higher leaf photosynthesis, shorter plant height and stay‐green traits. The stomatal and nonstomatal limitations are strongly associated with genotype yield performance, elucidating a potential mechanism underlying drought tolerance. Drought tolerance and yield stability of wheat cultivars have been improved through breeding over the past 70 years. Our findings enhance understanding of drought tolerance and identify genotypes and traits beneficial for breeding high‐yielding and drought‐tolerant cultivars. [ABSTRACT FROM AUTHOR]

Premise: Increases in genome size in plants—often associated with larger, low‐density stomata and greater water‐use efficiency (WUE)—could affect plant ecophysiological and hydraulic function. Variation in plant genome size is often due to polyploidy, having occurred repeatedly in the austral sedge genus Schoenus in the Cape Floristic Region (CFR), while species in the other major schoenoid genus in the region, Tetraria, have smaller genomes. Comparing these genera is useful as they co‐occur at the landscape level, under broadly similar bioclimatic conditions. We hypothesized that CFR Schoenus have greater WUE, with lower maximum stomatal conductance (gwmax) imposed by larger, less‐dense stomata. Methods: We investigated relationships between genome size and stomatal parameters in a phylogenetic context, reconstructing a phylogeny of CFR‐occurring Schoeneae (Cyperaceae). Species' stomatal and functional traits were measured from field‐collected and herbarium specimens. Carbon stable isotopes were used as an index of WUE. Genome size was derived from flow‐cytometric measurements of leafy shoots. Results: Evolutionary regressions demonstrated that stomatal size and density covary with genome size, positively and negatively, respectively, with genome size explaining 72–75% of the variation in stomatal size. Larger‐genomed species had lower gwmax and C:N ratios, particularly in culms. Conclusions: We interpret differences in vegetative physiology between the genera as evidence of more‐conservative strategies in CFR Schoenus compared to the more‐acquisitive Tetraria. Because Schoenus have smaller, reduced leaves, they likely rely more on culm photosynthesis than Tetraria. Across the CFR Schoeneae, ecophysiology correlates with genome size, but confounding sources of trait variation limit inferences about causal relationships between traits. [ABSTRACT FROM AUTHOR]

Hemiparasitic Cassytha filiformis commonly infects native host (Dillenia suffruticosa and Melastoma malabathricum) and introduced host (Acacia auriculiformis and Acacia mangium) species in threatened heath forests in Brunei. This study aims to investigate the impact of parasitism on the ecophysiology of these host species. This study addresses the research gap in understanding the ecophysiology of C. filiformis–host associations, particularly when native and introduced hosts were infected. We generated CO2 and light response curves to examine the effects of increasing CO2 and light levels of infected and uninfected hosts and examined gaseous exchange, mineral nutrients, and secondary bioactive compounds of host–parasite associations. Infected hosts were negatively impacted by C. filiformis as exhibited in the CO2 and light response curves, with C. filiformis–native host association performing better than introduced species. There were no significant differences in photosynthetic parameters between infected and uninfected hosts, except in D. suffruticosa. Certain nutrient contents showed significant differences, but total N, Ca, and K in uninfected hosts were similar to infected hosts. Total phenols and tannins were significantly higher in introduced hosts than native hosts. Our findings asserted that this hemiparasitic vine relies on both its photosynthetic efficiency and nutrient acquisition from its hosts. The parasitism did not significantly hinder the ecophysiological performance of infected hosts, suggesting a plausible co‐existence between the hosts and C. filiformis. This study provides essential ecophysiological information for future research on how C. filiformis can establish itself without negatively impacting the co‐habitating native hosts. [ABSTRACT FROM AUTHOR]

Rainfed mungbean crops in Queensland Australia frequently experience terminal drought (drought stress in the final stages of reproductive development), highlighting the importance of drought-tolerant varieties for sustainable mungbean production. Given there is limited information on the relative drought tolerance of current mungbean varieties in Australia, the study of genetic variations and mechanisms of drought tolerance in summer mungbean can provide a basis for developing drought-tolerant mungbean varieties. This study evaluated the physiological, biochemical, and phenological traits underpinning yield attributes associated with drought tolerance in selected mungbean varieties. Four new mungbean varieties (AVTMB#1 to 4) and the Australian commercial line (Jade-AU) were grown in tall (75 cm) polyvinyl chloride (PVC) lysimeters where drought stress was imposed at the early flowering stage (R1) and maintained until maturity. Drought stress significantly impacted all the varieties. Averaged across all the varieties, drought stress was associated with a reduction in stomatal conductance (gs) and photosynthetic rate (Asat) by 78% and 86%, respectively, compared to well-watered plants. Internal carbon dioxide concentration (Ci), the effective quantum yield of photosystem II (ΦPSII) and maximum light-use efficiency of light-acclimated photosystem II (PSII) centres (Fv'/Fm') were also decreased, while excitation pressure (1-qP) increased with drought treatment. A positive correlation (r = 0.60) existed between seed yield and ΦPSII assessed at R1, while a weak correlation with Fv'/Fm' (r = 0.24) was observed. Excitation pressure (1-qP) at the R1 stage was negatively correlated with seed yield (r = −0.66). Therefore, leaf fluorescence measures, viz., 1-qP and ΦPSII, were recommended for use in screening mungbean varieties for drought tolerance. The varieties, AVTMB#1 and AVTMB#4, respectively achieved 39 and 38% greater seed yields relative to the commercial variety, Jade-AU, under terminal drought conditions. [ABSTRACT FROM AUTHOR]

Global climate change is leading to increased frequency of extreme climatic events, higher temperatures and water scarcity. Tef (Eragrostis tef (Zucc.) Trotter) is an underutilized C4 cereal crop that harbors a rich gene pool for stress resilience and nutritional quality. Despite gaining increasing attention as an "opportunity" crop, physiological responses and adaptive mechanisms of tef to drought stress have not been sufficiently investigated. This study was aimed to characterize the dynamic physiological responses of tef to drought. Six selected tef genotypes were subjected to high-throughput whole-plant functional phenotyping to assess multiple physiological responses to contrasting water regimes. Drought stress led to a substantial reduction in total, shoot and root dry weights, by 59%, 62% and 44%, respectively (averaged across genotypes), and an increase of 50% in the root-to- shoot ratio, relative to control treatment. Drought treatment induced also significant reductions in stomatal conductance, transpiration, osmotic potential and water-use efficiency, increased chlorophyll content and delayed heading. Tef genotypes exhibited diverse water-use strategies under drought: water-conserving (isohydric) or non-conserving (anisohydric), or an intermediate strategy, as well as variation in drought-recovery rate. Genotype RTC-290b exhibited outstanding multifaceted drought-adaptive performance, including high water-use efficiency coupled with high productivity under drought and control treatments, high chlorophyll and transpiration under drought, and faster drought recovery rate. This study provides a first insight into the dynamic functional physiological responses of tef to water deficiency and the variation between genotypes in drought-adaptive strategies. These results may serve as a baseline for further studies and for the development of drought-resistant tef varieties. [ABSTRACT FROM AUTHOR]

Summary: Aerosols could significantly influence ecosystem carbon and water fluxes, potentially altering their interconnected dynamics, typically characterized by water‐use efficiency (WUE). However, our understanding of the underlying ecophysiological mechanisms remains limited due to insufficient field observations.We conducted 4‐yr measurements of leaf photosynthesis and transpiration, as well as 3‐yr measurements of stem growth (SG) and sap flow of poplar trees exposed to natural aerosol fluctuation, to elucidate aerosol's impact on plant WUE.We found that aerosol improved sun leaf WUE mainly because a sharp decline in photosynthetically active radiation (PAR) inhibited its transpiration, while photosynthesis was less affected, as the negative effect induced by declined PAR was offset by the positive effect induced by low leaf vapor pressure deficit (VPDleaf). Conversely, diffuse radiation fertilization (DRF) effect stimulated shade leaf photosynthesis with minimal impact on transpiration, leading to an improved WUE. The responses were further verified by a strong DRF on SG and a decrease in sap flow due to the suppresses in total radiation and VPD.Our field observations indicate that, contrary to the commonly assumed coupling response, carbon uptake and water use exhibited dissimilar reactions to aerosol pollution, ultimately enhancing WUE at the leaf and canopy level. [ABSTRACT FROM AUTHOR]

Global warming and waterlogging stress due to climate change are expected to continue influencing agricultural production worldwide. In the field, two or more environmental stresses usually happen simultaneously, inducing more complex responses in plants compared with individual stresses. Our aim was to clarify how the two key factors (temperature and water) interacted and influenced physiological response and plant growth in tomatoes under ambient temperature, moderately elevated temperature, waterlogging stress, and moderately elevated temperature and waterlogging stress. The results showed that leaf photosynthesis was inhibited by waterlogging stress but enhanced by elevated temperature, as shown by both the light- and temperature-response curves. The elevated temperature decreased leaf water-use efficiency, but enhanced plant growth and fresh and dry weights of plants under both normal water supply and waterlogging stress conditions. Elevated temperature generally decreased the anthocyanin and flavonol index in tomato leaves compared with the control temperature, regardless of water status. The increase in the optimal temperature was more pronounced in plants under normal irrigation than under waterlogging stress. Waterlogging stress significantly inhibited the root length, and leaf number and area, while the moderately elevated temperature significantly enhanced the leaf number and area. Overall, the moderately elevated temperature offset the effects of waterlogging stress on tomato plants, as shown by leaf gas exchange, plant size, and dry matter accumulation. Our study will improve the understanding of how tomatoes respond to increasing temperature and excess water. [ABSTRACT FROM AUTHOR]

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Economic growth in Spain has largely relied on certain water-intensive sectors including construction, leisure, and agriculture; but considerable heterogeneity is found across the country's regions, both in terms of water stress and economic structure. Using Data Envelopment Analysis and a panel Tobit model, we analyze the determinants of water efficiency in Spain, differentiating by groups of agents (companies, households, and municipalities) and paying particular attention to inter-regional differences and specifically the sectoral structure of the various regions. To the best of our knowledge, such an analysis has never before been conducted with a focus on Spain's economy. Moreover, we emphasize the importance of considering the circular aspects of water management by including treated wastewater and recycled water in our analysis. We argue that this approach provides more credible and accurate measures of efficiency as well as more robust results around the key driving and explanatory factors. Our analysis reveals that water efficiency has a very significant inertia component with respect to one-year and even two-year lags, and this is found to react positively to water scarcity. Moreover, water efficiency depends on income in a nonlinear way, and it is sensitive to the economic structures of the diverse regions, with more efficient regions tending to export more at the national level. In terms of policy implications, our results provide an empirical basis from which to advocate for water tariffication as a means to spur efficiency. [ABSTRACT FROM AUTHOR]

Popular evapotranspiration (ET) partitioning methods make assumptions that might not be well‐suited to dryland ecosystems, such as high sensitivity of plant water‐use efficiency (WUE) to vapor pressure deficit (VPD). Our objectives were to (a) create an ET partitioning model that can produce fine‐scale estimates of transpiration (T) in drylands, and (b) use this approach to evaluate how climate controls T and WUE across ecosystem types and timescales along a dryland aridity gradient. We developed a novel, semi‐mechanistic ET partitioning method using a Bayesian approach that constrains abiotic evaporation using process‐based models, and loosely constrains time‐varying WUE within an autoregressive framework. We used this method to estimate daily T and weekly WUE across seven dryland ecosystem types and found that T dominates ET across the aridity gradient. Then, we applied cross‐wavelet coherence analysis to evaluate the temporal coherence between focal response variables (WUE and T/ET) and environmental variables. At yearly scales, we found that WUE at less arid, higher elevation sites was primarily limited by atmospheric moisture demand, and WUE at more arid, lower elevation sites was primarily limited by moisture supply. At sub‐yearly timescales, WUE and VPD were sporadically correlated. Hence, ecosystem‐scale dryland WUE is not always sensitive to changes in VPD at short timescales, despite this being a common assumption in many ET partitioning models. This new ET partitioning method can be used in dryland ecosystems to better understand how climate influences physically and biologically driven water fluxes. Plain Language Summary: We developed a new model to better understand how plants use and lose water in drylands and applied it to seven dryland sites. Our model partitions evapotranspiration—the total water lost to the atmosphere from the Earth's surface— into its components. Evapotranspiration consists of both evaporation from wet surfaces, such as wet soil, and the water lost from plants when they photosynthesize. Currently, models assume a strong relationship between the efficiency with which plants use water ("water‐use efficiency") and the dryness of the atmosphere, but this violates what we know about how plants function in drylands. For example, in drylands many plants are adapted to very dry conditions and their water use can be less sensitive to increasing atmospheric dryness compared to plants from wet environments. Using this new model, we found that plant water‐use efficiency is only correlated with atmospheric dryness some of the time and that evapotranspiration is primary controlled by water lost from plants. This model allows us to better understand the importance of timescale and ecosystem type in governing plant water‐use dynamics and more accurately assess the potential impact of changing climate conditions on dryland water fluxes and ecosystem processes. Key Points: A new evapotranspiration partitioning model (DEPART) was developed using eddy covariance flux tower measurements in a Bayesian frameworkThis method produces daily estimates of transpiration and weekly estimates of plant water‐use efficiency at the ecosystem scaleThis method reveals water‐use efficiency is limited by moisture supply in more arid climates and moisture demand in less arid climates [ABSTRACT FROM AUTHOR]

Sustainable Development Goal 6 (SDG 6) is closely linked to the sustainable management of water resources and sanitation worldwide. SDG 6.4, in particular, aims to significantly improve water-use efficiency across all sectors by 2030. It is important to acknowledge the significant role that behavioural aspects of water users in an agricultural context play in contributing to water-use efficiency. This systematic review aims to provide an up-to-date synthesis of the current knowledge of water-use behaviours in agriculture to stay on track in achieving SDG 6. This systematic literature review investigates the factors influencing water-use behaviour among agricultural water users globally. Using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) method, we retrieved a total of 867 records, of which 47 matched the eligibility criteria. The 47 relevant studies were primarily conducted in the United States and China with key themes including sustainable agricultural practices, technology adoption for productivity, climate change adaptation, and modelling and uncertainty in water conservation. Additionally, the review identified six distinct water-use behaviours investigated from 2020 to 2024, which were each driven by its unique set of factors. Overall, the findings from the systematic review indicate that there has been a geographical gap in research efforts over the past five years, and it is important for water-use behaviour-related research to be extended to other countries that are water-stressed. Furthermore, the researchers recommend that future studies should develop comprehensive behavioural models and adopt holistic approaches to better understand and promote sustainable water-use behaviours in agriculture. These efforts are vital for achieving sustainable water management and broader SDGs. [ABSTRACT FROM AUTHOR]

Justification: Water-use efficiency (WUE) is the amount of carbon assimilated as biomass or grain produced per unit of water the crop uses, and it is considered a critical factor in maintaining the balance between carbon gain and water loss during photosynthesis, particularly in the face of global warming and drought challenges. Improving agricultural WUE is essential for sustainable crop production in water-scarce regions. Objective: This article explores the significance of WUE enhancement in agriculture, especially under drought conditions, and discusses various strategies to optimize WUE for improved crop productivity. Methods: We searched the scientific literature for articles on water-use efficiency published between 2010 and 2023 and selected the 42 most relevant studies for a comprehensive overview of strategies, technologies, and approaches to investigate sustainable agricultural practices to improve water-use efficiency in agriculture, particularly focusing on agronomic methods such as mulching, cover crops, canopy management, deficit irrigation, and irrigation modernization. Results: This review highlights several practical techniques for enhancing WUE, including sustainable irrigation practices, crop-specific agronomic strategies, and innovative technological solutions. By adopting these approaches, farmers can improve water management efficiency, reduce crop vulnerability to water stress, and ultimately enhance agricultural sustainability. In conclusion, improving water-use efficiency is an essential factor for ensuring food security in the face of climate change and water scarcity. By implementing innovative strategies and exploiting the power of technology, we can enhance WUE in agriculture, optimize crop production, conserve natural resources, and contribute to a more sustainable future. [ABSTRACT FROM AUTHOR]

How tropical plants cope with water availability has important implications for forest resilience, as severe drought events are expected to increase with climate change. Tree size has emerged as a major axis of drought vulnerability. To understand how Amazon tree species are distributed along size-linked gradients of water and light availability, we tested the niche acclimation hypothesis that there is a developmental gradient in ontogenetic shift in embolism resistance and tree water-use efficiency among tree species that occurs along the understory-overstory gradient. We evaluated ontogenetic differences in the intrinsic water-use efficiency (iWUE) and xylem hydraulic traits of abundant species in a seasonal tropical forest in Brazil. We found that saplings of dominant overstory species start with a high degree of embolism resistance to survive in a dense understory environment where competition for water and light among smaller trees can be intense during the prolonged dry season. Vulnerability to embolism consistently changed with ontogeny and varied with tree species' stature (maximum height): mature individuals of larger species displayed increased vulnerability, whereas smaller species displayed unchanging or even increased resistance at the mature stage. The ability to change drought-resistance strategies (vulnerability to embolism) through ontogeny was positively correlated with ontogenetic increase in iWUE. Ecologically, overstory trees appear to shift from being hydraulically drought resilient to persisting under dry soil surface layer conditions to being more likely physiological drought avoiders as adults when their roots reach wetter and deeper soil layers.

Abstract Background Afforestation of non-forestland is a new measure by the European Union to enhance climate mitigation and biodiversity. Hybrid aspen (Populus tremula L. × P. tremuloides Michx.) is among the suitable tree species for afforestation to produce woody biomass. However, the best performing genotypic material for intensive biomass production and its physiological adaptation capacity is still unclear. We compared 22 hybrid aspen genotypes growth and leaf physiological characteristics (stomatal conductance, net photosynthesis, intrinsic water-use efficiency) according to their geographical north- or southward transfer (European P. tremula parent from 51° to 60° N and North American P. tremuloides parent from 45° to 54° N) to hemiboreal Estonia (58° N) in a completely randomized design progeny trial. We tested whether the growth ranking of genotypes of different geographical origin has changed from young (3-year-old) to mid-rotation age (13-year-old). The gas exchange parameters were measured in excised shoots in 2021 summer, which was characterised with warmer (+ 4 °C) and drier (17% precipitation from normal) June and July than the long-term average. Results We found that the northward transfer of hybrid aspen genotypes resulted in a significant gain in growth (two-fold greater diameter at breast height) in comparison with the southward transfer. The early selection of genotypes was generally in good accordance with the middle-aged genotype ranking, while some of the northward transferred genotypes showed improved growth at the middle-age period in comparison with their ranking during the early phase. The genotypes of southward transfer demonstrated higher stomatal conductance, which resulted in higher net photosynthesis, and lower intrinsic water-use efficiency (iWUE) compared with northward transfer genotypes. However, higher photosynthesis did not translate into higher growth rate. The higher physiological activity of southern transferred genotypes was likely related to a better water supply of smaller and consequently more shaded trees under drought. Leaf nitrogen concentration did not have any significant relation with tree growth. Conclusions We conclude that the final selection of hybrid aspen genotypes for commercial use should be done in 10–15 years after planting. Physiological traits acquired during periods of droughty conditions may not fully capture the growth potential. Nonetheless, we advocate for a broader integration of physiological measurements alongside traditional traits (such as height and diameter) in genotype field testing to facilitate the selection of climate-adapted planting material for resilient forests.

Wheat crops underpin contemporary global food security. Predominant wheat production zones in China include the Huang‐Huai‐Hai‐Plain and the Mid‐Lower Reaches of the Yangtze River, although climatic effects on productive potential across these regions vary markedly in space and time. Here, we conducted field experiments during the wheat season of 2015–2018 to examine environmental effects on growth, with fertilization and irrigation provided at levels ensuring that nutrient and water stress exposure was minimal. Yields in Huang‐Huai‐Hai‐Plain and the Mid‐Lower Reaches of the Yangtze River averaged 8950 and 4818 kg ha−1, respectively. Yield variation across regions was primarily related to spike number per unit area and grain number per spike. Maturity biomass was higher in Huang‐Huai‐Hai‐Plain; this translated into higher grain yields. Lower temperature and longer growing duration between emergence and jointing in Huang‐Huai‐Hai‐Plain afforded higher tillering and spike numbers, whereas higher growth rates from jointing to maturity resulted in higher biomass production in Huang‐Huai‐Hai‐Plain compare with the Mid‐Lower Reaches of Yangtze River. Growth rate, grain numbers and yield were positively correlated with the ratio of daily intercepted solar radiation to mean temperature during jointing to anthesis, termed photothermal quotient. Collectively, our results suggest that growth rate accounted for more variation in biomass production compared with growth duration, and the photothermal conditions in the Mid‐Lower Reaches of the Yangtze River were restrictive for spike development and yield formation. Our results help disentangle drivers of crop growth through the development of agro‐environmental conceptual frameworks, enabling a better understanding of yield variability in space and time. [ABSTRACT FROM AUTHOR]

The influence of water regimes on plants is crucial for integrating bush tea (Athrixia phylicoides DC.) into strategies in Sub-Saharan Africa to tackle food and nutritional insecurity by considering physiological aspects, nutritional yield, nutritional water productivity, and metabolite composition. The objective of the study was to determine the physiological aspects, including leaf gas exchange and chlorophyll fluorescence, nutritional yield, nutritional water productivity, and metabolite composition of bush tea under varying water regimes. The tunnel experiment was laid out in a randomized complete block design (RCBD) with treatments consisting of three water regimes: 100% of crop water requirement (ETa), 30% of ETa, and a control (no irrigation), all replicated three times. The morphological aspects were recorded on a weekly basis. However, yield, nutrient content, nutritional water productivity (NWP), and phytochemical composition were determined at harvest. The phytochemical analysis by liquid chromatography mass spectrometry (LC-MS), coupled with visualization of the detected chemical spaces through molecular networking, indicated Athrixia phylicoides DC. to be rich in various bioactive compound derivatives, including methyl chlorogenate, flavonoids, tartaric acid, caffeoylquinic acid, and glutinane. The results showed that 30% ETa enhanced plant growth, nutrient content, and nutritional water productivity compared to other water treatments. Nevertheless, 100% ETa yielded more (95.62 kg ha−1) than 30% ETa (60.61 kg ha−1) and control (12.12 kg ha−1). The accumulation of chlorogenic acids was higher under 30% ETa compared to 100% ETa and control. Therefore, this study is the first to determine the accumulation of various bioactive compounds in bush tea leaf extracts under varying water regimes. This confirms that in areas with low water availability, bush tea is well adapted for production without limiting nutrients. [ABSTRACT FROM AUTHOR]

For sustainable management of urban forests, information regarding species-specific responses of urban trees is essential to determine suitable trees for planting and to maintain the existing trees amid the worsening climate. One approach is to study plant growth and water use and their changes with weather variations in various tree species and sites. Here, we measured leaf photosynthesis (A), transpiration (E), and stomatal conductance (gs) of Samanea saman, Tabebuia rosea, and Millingtonia hortensis, which were found in a new and an old park in Bangkok. Additionally, we investigated how these parameters and water-use efficiency (WUE), the ratio between A and E, varied with atmospheric conditions, represented by leaf-to-air vapor pressure deficit (VPDLA). Results indicated decreasing gas exchange rates with increasing VPDLA in all species, signifying stomatal closure under drying air. In all cases, changes of A and E with VPDLA were similar to those in gs, except for E of T. rosea in the new park that showed no response. Of all species, only M. hortensis displayed similar response patterns with VPDLA across sites, implying its capacity to adapt to various settings. Interestingly, regardless of the periods since establishments of the parks, WUE of these species responded similarly to VPDLA. This finding may imply that, regardless of their sizes, these trees may retain the capacity of carbon dioxide absorption provided the same unit of water use, despite the changing climate. Nevertheless, further investigations involving more species and sites with various periods since establishment should be performed to confirm these results. [ABSTRACT FROM AUTHOR]

Background: Afforestation of non-forestland is a new measure by the European Union to enhance climate mitigation and biodiversity. Hybrid aspen (Populus tremula L. × P. tremuloides Michx.) is among the suitable tree species for afforestation to produce woody biomass. However, the best performing genotypic material for intensive biomass production and its physiological adaptation capacity is still unclear. We compared 22 hybrid aspen genotypes growth and leaf physiological characteristics (stomatal conductance, net photosynthesis, intrinsic water-use efficiency) according to their geographical north- or southward transfer (European P. tremula parent from 51° to 60° N and North American P. tremuloides parent from 45° to 54° N) to hemiboreal Estonia (58° N) in a completely randomized design progeny trial. We tested whether the growth ranking of genotypes of different geographical origin has changed from young (3-year-old) to mid-rotation age (13-year-old). The gas exchange parameters were measured in excised shoots in 2021 summer, which was characterised with warmer (+ 4 °C) and drier (17% precipitation from normal) June and July than the long-term average. Results: We found that the northward transfer of hybrid aspen genotypes resulted in a significant gain in growth (two-fold greater diameter at breast height) in comparison with the southward transfer. The early selection of genotypes was generally in good accordance with the middle-aged genotype ranking, while some of the northward transferred genotypes showed improved growth at the middle-age period in comparison with their ranking during the early phase. The genotypes of southward transfer demonstrated higher stomatal conductance, which resulted in higher net photosynthesis, and lower intrinsic water-use efficiency (iWUE) compared with northward transfer genotypes. However, higher photosynthesis did not translate into higher growth rate. The higher physiological activity of southern transferred genotypes was likely related to a better water supply of smaller and consequently more shaded trees under drought. Leaf nitrogen concentration did not have any significant relation with tree growth. Conclusions: We conclude that the final selection of hybrid aspen genotypes for commercial use should be done in 10–15 years after planting. Physiological traits acquired during periods of droughty conditions may not fully capture the growth potential. Nonetheless, we advocate for a broader integration of physiological measurements alongside traditional traits (such as height and diameter) in genotype field testing to facilitate the selection of climate-adapted planting material for resilient forests. [ABSTRACT FROM AUTHOR]

Reducing the nitrogen (N) application rate and improving water-use efficiency (WUE) are extremely important for sustainable agricultural development in wheat–maize rotation systems in the North China Plain (NCP). We conducted a three-year experiment to investigate the effects of the N application rate on the water-use characteristics of wheat–maize rotation systems in the NCP. The experiment consisted of four N application rates: 250, 167, 84, and 0 kg hm−2, denoted by N3, N2, N1, and N0, respectively. The results showed the following: For the 0–60 cm soil layer, N deficiency could lead to reduced soil water use (SWU) in wheat seasons, but in maize seasons, N deficiency showed no significant effects on SWU in the 0–60 cm layer. For the 60–140 cm soil layer, N deficiency could lead to reduced SWU in wheat seasons, but in maize seasons, the effects of N deficiency on SWU in the 60–140 cm layer varied with the SWC in the 0–60 cm layer. Throughout the three-year experiment, the evapotranspiration (ET), leaf area index (LAI), yield, and WUE of plants receiving low N treatments decreased with the growing season due to the negative effects of low N treatment (N1 and N0) on the soil. The LAI, total ET, grain yield, and WUE were all positively correlated with each other for both wheat and maize. Considering grain yield and WUE, a single-season N application rate of 167 kg hm−2 (N2 treatment) in the NCP could meet the growth needs of the wheat–maize rotation system. [ABSTRACT FROM AUTHOR]

The response of plants to increasing atmospheric CO2 depends on the ecological context where the plants are found. Several experiments with elevated CO2 (eCO2) have been done worldwide, but the Amazonian forest understory has been neglected. As the central Amazon is limited by light and phosphorus, understanding how understory responds to eCO2 is important for foreseeing how the forest will function in the future. In the understory of a natural forest in the Central Amazon, we installed four open‐top chambers as control replicates and another four under eCO2 (+250 ppm above ambient levels). Under eCO2, we observed increases in carbon assimilation rate (67%), maximum electron transport rate (19%), quantum yield (56%), and water use efficiency (78%). We also detected an increase in leaf area (51%) and stem diameter increment (65%). Central Amazon understory responded positively to eCO2 by increasing their ability to capture and use light and the extra primary productivity was allocated to supporting more leaf and conducting tissues. The increment in leaf area while maintaining transpiration rates suggests that the understory will increase its contribution to evapotranspiration. Therefore, this forest might be less resistant in the future to extreme drought, as no reduction in transpiration rates were detected. Summary statement: The Amazonian understory plants demonstrate a remarkable response to elevated CO2, including an increase in leaf area and a higher investment in the maximum electron transport rate. These findings suggest enhanced carbon storage and water flux, stressing the important role of the understory in the overall functioning of the forest ecosystem. [ABSTRACT FROM AUTHOR]

The response of plants to increasing atmospheric CO2 depends on the ecological context where the plants are found. Several experiments with elevated CO2 (eCO2) have been done worldwide, but the Amazonian forest understory has been neglected. As the central Amazon is limited by light and phosphorus, understanding how understory responds to eCO2 is important for foreseeing how the forest will function in the future. In the understory of a natural forest in the Central Amazon, we installed four open‐top chambers as control replicates and another four under eCO2 (+250 ppm above ambient levels). Under eCO2, we observed increases in carbon assimilation rate (67%), maximum electron transport rate (19%), quantum yield (56%), and water use efficiency (78%). We also detected an increase in leaf area (51%) and stem diameter increment (65%). Central Amazon understory responded positively to eCO2 by increasing their ability to capture and use light and the extra primary productivity was allocated to supporting more leaf and conducting tissues. The increment in leaf area while maintaining transpiration rates suggests that the understory will increase its contribution to evapotranspiration. Therefore, this forest might be less resistant in the future to extreme drought, as no reduction in transpiration rates were detected. Summary statement: The Amazonian understory plants demonstrate a remarkable response to elevated CO2, including an increase in leaf area and a higher investment in the maximum electron transport rate. These findings suggest enhanced carbon storage and water flux, stressing the important role of the understory in the overall functioning of the forest ecosystem. [ABSTRACT FROM AUTHOR]

As a crucial basic natural resource, water resources are the cornerstone for sustainable national economic development. This paper takes the 2014 pilot water rights trading policy (WRT) as an entry point and uses a difference-in-differences (DID) model to test the policy effect of WRT on water-use efficiency (WUE) based on panel data for 30 Chinese provinces from 2005 to 2021. The study shows that WRT can significantly improve the regional WUE, and these results remain valid after a series of robustness tests, such as the parallel trend test, placebo test, and PSM-DID. Mechanistic analysis revealed that WRT can produce the Porter effect, which affects the WUE through technological innovation. The results of the heterogeneity analysis based on the synthetic control method (SCM) showed that WRT effectively improved WUE in Jiangxi, Henan, Ningxia, Hubei, and Guangdong, but did not achieve the expected effect in Inner Mongolia or Gansu. This paper provides solid empirical support for assessing the effectiveness of WRT and accelerating the process of establishing a unified national WRT market in China by 2025. [ABSTRACT FROM AUTHOR]

Background and Aims Variation in architectural traits related to the spatial and angular distribution of leaf area can have considerable impacts on canopy-scale fluxes contributing to water-use efficiency (WUE). These architectural traits are frequent targets for crop improvement and for improving the understanding and predictions of net ecosystem carbon and water fluxes. Methods A three-dimensional, leaf-resolving model along with a range of virtually generated hypothetical canopies were used to quantify interactions between canopy structure and WUE by examining its response to variation of leaf inclination independent of leaf azimuth, canopy heterogeneity, vegetation density and physiological parameters. Key Results Overall, increasing leaf area index (LAI), increasing the daily-averaged fraction of leaf area projected in the sun direction (G avg) via the leaf inclination or azimuth distribution and increasing homogeneity had a similar effect on canopy-scale daily fluxes contributing to WUE. Increasing any of these parameters tended to increase daily light interception, increase daily net photosynthesis at low LAI and decrease it at high LAI, increase daily transpiration and decrease WUE. Isolated spherical crowns could decrease photosynthesis by ~60 % but increase daily WUE ≤130 % relative to a homogeneous canopy with equivalent leaf area density. There was no observed optimum in daily canopy WUE as LAI, leaf angle distribution or heterogeneity was varied. However, when the canopy was dense, a more vertical leaf angle distribution could increase both photosynthesis and WUE simultaneously. Conclusions Variation in leaf angle and density distributions can have a substantial impact on canopy-level carbon and water fluxes, with potential trade-offs between the two. These traits might therefore be viable target traits for increasing or maintaining crop productivity while using less water, and for improvement of simplified models. Increasing canopy density or decreasing canopy heterogeneity increases the impact of leaf angle on WUE and its dependent processes. [ABSTRACT FROM AUTHOR]

In regions where water is a limited resource, lettuce production can be challenging. To address this, water management strategies like deficit irrigation are used to improve water-use efficiency in agriculture. Associating this strategy with silicon (Si) application could help maintain adequate levels of agricultural production even with limited water availability. Two lettuce crop cycles were conducted in a completely randomized design, with a factorial scheme (2 × 3), with three irrigation levels (60%, 80% and 100%) of crop evapotranspiration (ETc), and with and without Si application. To explore their combined effects, morphological, productive, physiological and nutritional parameters were evaluated in the crops. The results showed that deficit irrigation and Si application had a positive interaction: lettuce yield of the treatment with 80% ETc + Si was statistically similar to 100% ETc without Si in the first cycle, and the treatment with 60% ETc + Si was similar to 100% ETc without Si in the second cycle. Photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate and total chlorophyll content increased under water-stress conditions with Si application; in the first cycle, the treatment with 80% ETc + Si increased by 30.1%, 31.3%, 7.8%, 28.46% and 50.3% compared to the same treatment without Si, respectively. Si application in conditions of water deficit was also beneficial to obtain a cooler canopy temperature and leaves with higher relative water content. In conclusion, we found that Si applications attenuate water deficit effects and provide a strategy to ameliorate the yield and water productivity in lettuce crops, contributing to more sustainable practices in agriculture. [ABSTRACT FROM AUTHOR]

Key message: Eucalyptus grandis and Red-Gum hybrid plantlets differ in the photosynthetic responses to long and short-term water restriction, leading to different adaptation mechanisms to cope with stress. Eucalypts are the most planted forest species in Uruguay and face frequent drought events, which impact plantlet's establishment. Information needs to be included regarding the behavior of promising clones in such conditions. This work aimed to analyze the effects of short and long-term water restriction (WR) on photosynthetic parameters and whether they enable the plant to cope with water shortage. One clone of Eucalyptus grandis (GG) and interspecific hybrids of E. grandis × E. camaldulensis (GC) and E. grandis × E. tereticornis (GT) were subjected to WR defined by soil water potential. At 6 and 16 weeks after treatment imposition, chlorophyll (%Chl) carotenoids (%Carot), maximum net assimilation rate (Amax), stomatal conductance (gS), leaf transpiration rate (E), light saturation point (LSP) and quantum efficiency (ΦPSII) were assessed. Our results showed that the clones behaved differently. GG minimized water loss significantly to avoid the stress condition through strong stomatal regulation while GC and GT adapted their photosynthetic structure and thus were able to cope with water shortage. Unexpectedly, GT increased Amax significantly under short-term WR, suggesting an early adaptation mechanism to WR. In the long-term WR condition, both hybrids increased %Chl, ΦPSII and Amax while reducing gS and water uptake. These results suggest that Red-Gum hybrids experienced a "priming" effect of a sublethal dose of WR that enabled them to cope with drought stress in the long term. [ABSTRACT FROM AUTHOR]

This article, titled "Editorial: New generation agronomy for net-zero greenhouse gas emissions," discusses the importance of agronomy in addressing the challenges posed by climate change. It emphasizes the need for agriculture to strive for net-zero emissions and explores innovative agronomic practices that can reduce greenhouse gas emissions while sustaining food security. The article highlights the benefits of tailored fertilizer mixes, conservation tillage, and optimized planting patterns in reducing emissions and enhancing resource efficiency. It also discusses the challenges faced in implementing sustainable practices, such as the need for technological advancements, infrastructure improvements, and supportive policy frameworks. The article concludes by emphasizing the urgency to adopt new-generation agronomic practices and the importance of collaborative efforts across sectors to achieve sustainable agricultural systems. [Extracted from the article]

Photosynthesis is extremely sensitive to drought and decreases due to co-occurring stomatal, mesophyll, and biochemical limitations. Few studies have shown the effects of a drought cycle (drought-rewatering) on photosynthesis and water-use efficiency (WUE) in cotton. Here, the dynamics of photosynthesis in upland (Gossypium hirsutum) and pima (G. barbadense) cotton were analyzed during a drought cycle. While both species decreased net CO2 assimilation rate (PN) to a similar extent under drought, in pima cotton rewatering rapidly restored PN, the stomatal conductance (gs), the maximum carboxylation rate (Vcmax), and the maximum electron transport rate above the control level. Meanwhile, the response of leaf intrinsic WUE (WUEi) to drought and recovery was different between the two cotton species, which was mainly co-regulated by Vcmax and gs. In conclusion, pima and upland cotton exhibit different response patterns of PN and WUEi during the whole process of drought and recovery.

PremiseGenetic variation influences the potential for evolution to rescue populations from impacts of environmental change. Most studies of genetic variation in fitness-related traits focus on either vegetative or floral traits, with few on floral scent. How vegetative and floral traits compare in potential for adaptive evolution is poorly understood.MethodsWe measured variation across source populations, planting sites, and genetic families for vegetative and floral traits in a hybrid zone. Seeds from families of Ipomopsis aggregata, I. tenuituba, and F1 and F2 hybrids of the two species were planted into three common gardens. Measured traits included specific leaf area (SLA), trichomes, water-use efficiency (WUE), floral morphology, petal color, nectar, and floral volatiles.ResultsVegetative traits SLA and WUE varied greatly among planting sites, while showing weak or no genetic variation among source populations. Specific leaf area and trichomes responded plastically to snowmelt date, and SLA exhibited within-population genetic variation. All aspects of floral morphology varied genetically among source populations, and corolla length, corolla width, and sepal width varied genetically within populations. Heritability was not detected for volatiles due to high environmental variation, although one terpene had high evolvability, and high emission of two terpenes, a class of compounds emitted more strongly from the calyx than the corolla, correlated genetically with sepal width. Environmental variation across sites was weak for floral morphology and stronger for volatiles and vegetative traits. The inheritance of three of four volatiles departed from additive.ConclusionsResults indicate stronger genetic potential for evolutionary responses to selection in floral morphology compared with scent and vegetative traits and suggest potentially adaptive plasticity in some vegetative traits.

A meta-analysis was conducted with the aim of exploring the influence of irrigation on potato yield, evapotranspiration (ET), and water-use efficiency (WUE) in northern China, considering factors such as irrigation methods, growing region, irrigation water-use efficiency (IWUE), irrigation frequency, soil types, and nitrogen (N) fertilizer rate. Overall, irrigation significantly increased potato yield and ET by an average of 45 and 54% compared to non-irrigation, respectively, but did not significantly increase the WUE. The increase in potato yield under irrigation is the most evident in aeolian sandy soil in northeast China and northwest China. Drip irrigation demonstrated the highest positive impact on both yield and WUE. Optimal yields were achieved with an irrigation amount ranging from 100 to 200 mm, while the highest WUE was observed with an irrigation amount of 30–50 mm. When the amount of irrigation exceeded 100 mm, the irrigation significantly resulted in decreased WUE compared to non-irrigation. The relative increase in yield per unit of irrigation amount and IWUE gradually decreased and eventually stabilized when the irrigation amount exceeded 100 mm. Therefore, the yield and WUE perform best when the irrigation amount is below 100 mm and the irrigation frequency is less than three times for sprinkling and flood irrigation methods. The greatest increases in yield and WUE under irrigation were found under a moderate N rate (150–250 kg N ha−1). Additionally, the relative increase in yield per unit of irrigation amount decreases gradually as the organic matter content increases. These findings suggest that the optimal benefits from irrigation might be realized when the irrigation amount is below 100 mm, with a moderate nitrogen fertilizer application and an irrigation frequency of three times. However, it is essential to consider local environmental factors such as the growing region, soil types, and organic carbon content. [ABSTRACT FROM AUTHOR]

Background and aims: Plants in severely phosphorus (P)-impoverished environments in southwest Australia are highly P efficient. In a Eucalyptus patens forest on P-impoverished soils in this region, leaf P concentrations ([P]) are very low in common species, which release carboxylates to acquire P. We hypothesised that these species exhibit a high photosynthetic P-use efficiency (PPUE). Being mycorrhizal and releasing carboxylates, the eucalypts would be very strong competitors, also against N2-fixing neighbours. Therefore, we hypothesised that the dominant species show relatively low leaf nitrogen concentrations ([N]) and a high photosynthetic N-use efficiency (PNUE). Conversely, we expected these species to have a low intrinsic water-use efficiency (iWUE). We also tested the hypothesis that E. patens would not show P-toxicity symptoms at high P availability, and its carboxylate release would not decline at high P supply. Methods: We selected common species such as Eucalyptus patens, E. marginata, Corymbia calophylla, Banksia grandis and Bossiaea aquifolium. We analysed their leaf [P], [N], photosynthesis rates, stomatal conductance, PPUE, PNUE, δ13C, WUE and iWUE. We grew E. patens seedlings in nutrient solution with increasing P supply and measured their carboxylate-exudation rates to test if it declined at high P supply. Results: Eucalyptus patens released large amounts of carboxylates without a decrease in carboxylate release with increasing P supply. Eucalyptus patens and co-occurring common species had similarly low leaf [P] and [N], high PPUE and PNUE, but low WUE and iWUE, when compared with literature values. Conclusions: The low leaf [N] of dominant species was compensated for by high stomatal conductance. This strategy would be viable only in habitats with abundant water. Therefore, P-efficient water-inefficient species would be restricted in their distribution to habitats with high water availability and not be 'Darwinian demons'. [ABSTRACT FROM AUTHOR]

Multidimensional trait frameworks are increasingly used to understand plant strategies for growth and survival. However, it is unclear if frameworks developed at a global level can be applied in local communities and how well these frameworks—based largely on plant morphological traits—align with plant physiology and response to stress.We tested the ability of an integrated framework of plant form and function to characterise seedling trait variation and drought response among 22 grasses and forbs common in a semi‐arid grassland. We measured above‐ground and below‐ground traits, and survival to explore how drought response is linked to three trait dimensions (resource conservation, microbial collaboration, and plant size) associated with the framework as well as non‐morphological dimensions (e.g. physiological traits) that are under‐represented in global trait frameworks.We found support for three globally‐recognised axes representing trade‐offs in strategies associated with tissue investment (leaf nitrogen, leaf mass per area, root tissue density), below‐ground resource uptake (root diameter, specific root length), and size (shoot mass). However, in contrast to global patterns, above‐ground and below‐ground resource conservation gradients were oppositely aligned: root tissue density was positively correlated with leaf N rather than leaf mass per area. This likely reflects different investment strategies of annual and perennial herbaceous species, as fast‐growing annual species invested in lower density roots and less nitrogen‐rich leaves to maximise plant‐level carbon assimilation. Species with longer drought survival minimised water loss through small above‐ground size and low leaf‐level transpiration rates, and drought survival was best predicted by a principal component axis representing plant size.Contrary to our expectations, drought survival in seedlings did not align with the conservation or collaboration axes suggesting that seedlings with different functional strategies can achieve similar drought survival, as long as they minimise water loss. Our results also show that within local communities, expected trait relationships could be decoupled as some plant groups achieve similar performance through different trait combinations. The effectiveness of species mean trait values in predicting drought response highlights the value of trait‐based methods as a versatile tool for understanding ecological processes locally across various ecosystems. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Leaf ecophysiological traits are known to change with leaf and tree age. In the present study, we measured the effect of leaf and tree age on leaf ecophysiological and morphological traits of nitrogen-fixing Alnus nepalensis (D. Don) which is a pioneer tree species in degraded lands. Three naturally occurring A. nepalensis forest stands, namely young (5–8 years old), mature (40–55 years old), and old (130–145 years old), were considered in this study. We also investigated the seasonal variations in leaf ecophysiological and morphological traits during leaf flushing, fully expanded, and leaf senescence phenological stages. The ecophysiological and morphological traits were compared between leaf and tree ages using a linear mixed-effect model (LMM) and Tukey’s HSD test. Fully expanded leaves and young trees demonstrate ecophysiological traits consistent with acquisitive resource-use strategies. Our results revealed that net photosynthetic capacity (Aarea and Amass), leaf stomatal conductance (gswarea and gswmass), transpiration rate (Earea and Emass), specific leaf area (SLA), predawn and midday water potential (Ψ), leaf total chlorophyll concentration, photosynthetic N- and P-use efficiency (PNUE and PPUE) were higher in younger trees than mature and old trees. We found lower water-use efficiency (WUE) and intrinsic water-use efficiency (WUEi) in young trees than in mature and old ones. Mass-based net photosynthetic capacity (Amass) was positively correlated with PNUE, PPUE, transpiration rate, stomatal conductance, SLA and chlorophyll concentrations but negatively correlated with WUE and WUEi. However, mass-based leaf nitrogen (N) and phosphorus (P) concentrations were the highest in fully expanded leaves and did not vary with tree age despite N concentration being negatively correlated with SLA. Overall, this study provides valuable insights into the age-related changes in leaf ecophysiological traits of A. nepalensis. The findings underscore the importance of considering tree age when studying plant ecophysiology and highlight the acquisitive resource-use strategies employed by young trees for rapid growth and establishment. [ABSTRACT FROM AUTHOR]

We investigated the effects of variety, planting density, and irrigation amount on grain yield, water-use efficiency (WUE), and evapotranspiration (ETc). The trial was conducted in Tong Liao, Inner Mongolia, from 2021 to 2022, with compact variety Dika159 (DK159) and conventional variety Zhengdan958 (ZD958) as the test materials. The planting density was set to 6.0 × 104 plants/ha (D1, local farmer planting density) and 9.0 × 104 plants/ha (D2), with five irrigation levels: 450 mm (W450, irrigation amount used by local farmers, CK); 360 mm (W360); 270 mm (W270); 180 mm (W180); and 90 mm (W90). The results indicate that the yield and WUE of variety DK159 increased by 7.48% and 5.00%, compared to ZD958, respectively. Increasing planting density enhanced yield by 13.32–15.57% in maize yield and 9.55–11.47% in WUE. Maize yield exhibited a trend of increasing linearly with the irrigation amount before reaching a plateau, reaching a maximum (16.62–17.39 t/ha) and high WUE (2.45–2.49 kg/m3) with DK159-D2-W270. The highest water consumption intensity occurred during the silking stage to the milk stage for different densities and varieties. The results indicate that selecting compact varieties, increasing planting density, and optimizing irrigation amount through integrated drip irrigation and water fertilizer can effectively improve maize yield and WUE. [ABSTRACT FROM AUTHOR]

Seasonal changes in carbon (C), nitrogen (N), and phosphorus (P) stoichiometry and water-use efficiency (WUE) in the needles of Pinus armandii were investigated. The needles of P. armandii were sampled in January, May, August, and November 2021. The results showed that (1) the needle δ13C values of young P. armandii forests were higher than those of middle-aged P. armandii forests, and these differences were significant in winter. (2) Both young and middle-aged P. armandii forests were restricted by N and P, and P. armandii was more restricted by N in summer, autumn, and winter. (3) Needle δ13C values were significantly positively correlated with P and negatively correlated with N, C/P, and N/P in young P. armandii forests; P. armandii (especially young stands) can compensate for decreases in N-use efficiency by increasing WUE. The C, N, and P content and their stoichiometric ratios were affected by a combination of season, stand age, and WUE. This study contributes to an in-depth understanding of the adaptive mechanisms of nutrients and WUE in P. armandii in the subtropical region. Our findings also have implications for the management of P. armandii plantations in the study area. [ABSTRACT FROM AUTHOR]

Key message: Superior F1 mulberry genotypes with high leaf yield, quality, and moderate to high stability were identified for optimal and sub-optimal input conditions. Mulberry (Morus spp.) is a highly heterozygous, perennial tree widely grown for its foliage to feed monophagous silkworms (Bombyx mori L.) and fruits for human consumption across the globe. The present study evaluated twenty-one F1 mulberry genotypes for the selection of superior ones based on leaf yield, yield attributes, leaf quality, and stability over two years under optimal and sub-optimal input (irrigation and fertilizer) conditions. Based on pooled data analysis over four crop seasons, it was found that six mulberry genotypes, D16, D21, D22, D23, D28, and D67, had leaf yields (663–840 g/plant) statistically similar to or better than the Vishala check (663 g/plant) under optimal conditions. Similarly, under sub-optimal conditions, seven genotypes, D16, D21, D22, D23, D24, D28 and D34, showed significantly higher leaf yields (418–596 g/plant) than Vishala (415 g/plant). The δ13C (a surrogate trait of water-use efficiency) of five mulberry genotypes, D16, D21, D24, D28, and D34, varied from – 28.21 to – 28.98 and was similar to the AGB8 check (– 28.87). Total soluble sugar, protein, chlorophyll content, and the silkworm moulting percentage and single larval weight for the seven genotypes D16, D21, D22, D23, D24, D28, and D34 were statistically similar to or better than Vishala under both optimal and sub-optimal conditions. The additive main effects and the multiplicative interaction-based simultaneous selection index showed that these seven genotypes had moderate to high stability and high leaf-yielding ability over the seasons under both optimal and sub-optimal conditions. DNA fingerprint profiles of these selected genotypes have been developed for their molecular identification. Under this context, these seven genotypes might be further tested under advanced evaluation trials to identify the best one regarding leaf yield and quality under optimal and sub-optimal conditions. [ABSTRACT FROM AUTHOR]

Episodes of drought-induced decline in tree growth and mortality are becoming more frequent as a result of climate warming and enhanced water stress in semi-arid areas. However, the ecophysiological mechanisms underlying the impact of drought on tree growth remains unresolved. In this study, earlywood and latewood tree-ring growth, δ13C, and δ18O chronologies of Picea mongolica from 1900 to 2013 were developed to clarify the intra- and inter-annual tree-ring growth responses to increasingly frequent droughts. The results indicate that annual basal area increment residuals (BAIres), which removed tree age and size effects, have significantly decreased since 1960. However, the decreasing trend of earlywood BAIres was higher than that of latewood. Climate response analysis suggests that the dominant parameters for earlywood and latewood proxies (BAIres, δ13C and δ18O) were drought-related climate variables (Palmer drought severity index, temperature, relative humidity, and vapor pressure deficit). The most significant period of earlywood and latewood proxies’ responses to climate variables were focused on June–July and July–August, respectively. BAIres, and δ13C were significantly affected by temperature and moisture conditions, whereas δ18O was slightly affected. Decreasing stomatal conductance due to drought outweighed the influence of increasing CO2 on intrinsic water use efficiency (iWUE), and ultimately led to a decline in BAIres. Compared to latewood, the faster decreasing BAIres and smaller increasing iWUE of earlywood suggested trees were more vulnerable to water stress in the early growing season. Our study provides insights into the inter- and intra-annual mechanisms of tree-ring growth in semi-arid regions under rising CO2 and climate change. [ABSTRACT FROM AUTHOR]

High soybean yields generally requires fields to have an adequate supply of boron (B). However, there remains uncertainty around how different cultivars might respond to differing levels of available B. The objective of this study was to evaluate the effect of B fertilisation on physiological efficiencies, yield, and export of B in various soybean cultivars. A randomised block experiment was carried out under field conditions in Region, Brazil consisting of 10 soybean cultivars and two levels of B fertilisation (without application and with application of 3 kg ha−1 of B). Water-use efficiency, instantaneous carboxylation efficiency, B content in the seed, export of B, and grain yield were evaluated. There was a significant interaction between B fertilisation x genotypes for all variables evaluated. In general, B fertilisation improved physiological and nutritional characteristics, increasing grain yield and B seed content on average by 21% and 35%, respectively. The soybean cultivars 7110 and Soyoro showed increases in all physiological and agronomic variables evaluated with B fertilisation. The results of this research confirm that B fertilisation improves the physiological and agronomic performance of the majority of soybean genotypes evaluated. [ABSTRACT FROM AUTHOR]

Wheat, being the third largest U.S. crop and the principal food grain, faces significant risks from climate extremes such as drought. This necessitates identifying and developing methods for early water-stress detection to prevent yield loss and improve water-use efficiency. This study investigates the potential of hyperspectral imaging to detect the early stages of drought stress in wheat. The goal is to utilize this technology as a tool for screening and selecting drought-tolerant wheat genotypes in breeding programs. Additionally, this research aims to systematically evaluate the effectiveness of various existing sensors and methods for detecting early stages of water stress. The experiment was conducted in a durum wheat experimental field trial in Maricopa, Arizona, in the spring of 2019 and included well-watered and water-limited treatments of a panel of 224 replicated durum wheat genotypes. Spectral indices derived from hyperspectral imagery were compared against other plant-level indicators of water stress such as Photosystem II (PSII) and relative water content (RWC) data derived from proximal sensors. Our findings showed a 12% drop in photosynthetic activity in the most affected genotypes when compared to the least affected. The Leaf Water Vegetation Index 1 (LWVI1) highlighted differences between drought-resistant and drought-susceptible genotypes. Drought-resistant genotypes retained 43.36% more water in leaves under well-watered conditions compared to water-limited conditions, while drought-susceptible genotypes retained only 15.69% more. The LWVI1 and LWVI2 indices, aligned with the RWC measurements, revealed a strong inverse correlation in the susceptible genotypes, underscoring their heightened sensitivity to water stress in earlier stages. Several genotypes previously classified based on their drought resistance showed spectral indices deviating from expectations. Results from this research can aid farmers in improving crop yields by informing early management practices. Moreover, this research offers wheat breeders insights into the selection of drought-tolerant genotypes, a requirement that is becoming increasingly important as weather patterns continue to change. [ABSTRACT FROM AUTHOR]

Photosynthesis is extremely sensitive to drought and decreases due to co-occurring stomatal, mesophyll, and biochemical limitations. Few studies have shown the effects of a drought cycle (drought-rewatering) on photosynthesis and water-use efficiency (WUE) in cotton. Here, the dynamics of photosynthesis in upland (Gossypium hirsutum) and pima (G. barbadense) cotton were analyzed during a drought cycle. While both species decreased net CO2 assimilation rate (PN) to a similar extent under drought, in pima cotton rewatering rapidly restored PN, the stomatal conductance (gs), the maximum carboxylation rate (Vcmax), and the maximum electron transport rate above the control level. Meanwhile, the response of leaf intrinsic WUE (WUEi) to drought and recovery was different between the two cotton species, which was mainly co-regulated by Vcmax and gs. In conclusion, pima and upland cotton exhibit different response patterns of PN and WUEi during the whole process of drought and recovery. [ABSTRACT FROM AUTHOR]

Forests are highly relevant for the water dynamics of mountain areas. This study assesses the water balance of two mountainous watersheds in Austria (Rindbach and Schmittental) with similar average annual precipitation patterns but different parent material, i.e., limestone in Rindbach versus greywacke in Schmittental. The biogeochemical mechanistic ecosystem model Biome-BGC with parameter settings developed for the central European tree species was obtained to assess the energy, nutrient, and water cycle as relevant for tree growth (=carbon cycle). The seasonal precipitation pattern, the snow accumulation, the evapotranspiration, the transpiration, the water-use efficiency, and the outflow are investigated. For the period 1960 to 2022, no precipitation trends are detectable, but a temperature increase of 1.9 °C in Rindbach and 1.6 °C in Schmittental is evident, leading to a declining snow accumulation. The model simulations suggest that transpiration and evapotranspiration rates increase with increasing LAI, indicating higher rates in Rindbach compared to Schmittental. The water use efficiency increases up to an LAI = 3 m2 m−2 and declines afterwards. The water balance variables follow the same pattern, i.e., with increasing LAI, the water outflow at the Rindbach catchment declines from 78% to 29% and from 72% to 31% in Schmittental. This confirms that forest cover is important to reduce water outflow and thus enhances the protection function of mountain forests. [ABSTRACT FROM AUTHOR]

Poplar plantations play an active role in windbreak and sand-fixation and timber production in water-limited areas, but the large-scale plantations are experiencing degradation, characterized by short trees, small size, and dieback. Moreover, the potential impacts of plantation degradation on ecohydrological processes in soil-plant systems remain unclear. We continuously measured soil water content (SWC), hydrogen and oxygen isotopic compositions in the soil water and plant xylem water, carbon isotopic compositions in the leaf, and sap flow velocity of poplar trees under various degraded plantations (no degraded, ND; lightly degraded, LD; severely degraded, SD) during the 2021 growing season (May–September). We also investigated tree root systems at a depth of 0–200 cm. Our results showed that as plantation degradation intensified, the root weight density at different depths decreased and the root proportion of the shallow layer (0–40 cm) increased. Although the SWC of the shallow layer did not change in the degraded plantations, the SWCs at middle layer (40–80 cm) and deep layer (80–200 cm) were higher in the LD and SD plantations than in the ND plantations, which might be related to reduced transpiration of degraded plantations. The Bayesian mixing model showed that all plantations can shift the water source from shallow to deep layers in the process of soil wetting to drying. Evidence from leaf carbon isotopes suggested that degraded plantations increased the sensitivity of intrinsic water-use efficiency to SWC. Our findings demonstrate that the normal growth of poplar plantations is prone to soil desiccation of deep layers due to high transpiration demand in water-limited areas, and degraded poplar plantations alleviate deep soil water depletion due to low transpiration. For rain-fed poplar plantations, proper thinning and measures of reducing soil evaporation may be necessary to avoid water excess consumption from deep soils.

Abstract Water‐use efficiency (WUE) is an under‐researched but very important drought tolerance trait in forage breeding. This research estimated quantitative genetic parameters of morpho‐physiological traits linked to agronomic water‐use efficiency (WUEA) and its proxy measures based on δ13C (WUEi) or gas exchange (evapotranspiration, WUEAET, or stomatal conductance WUEASC) of genotypes from half‐sib families of Lolium perenne L. (PRG) in a simulated summer drought cycle. Principal component analysis (PCA) of trait data distinguished a group of PRG genotypes where high WUEA and dry matter yield was associated with deep rooting, leaf hydration at more negative leaf osmotic and water potential, and reduced soil moisture depletion. Plants with this trait association sustained net assimilation and postdefoliation regrowth in drought. However, WUEi, WUEASC, and WUEAET were poorly correlated with most traits of interest at p 0.7;p

Cyclocarya paliurus has been traditionally used as a functional food in China. A hydroponic experiment was conducted to determine the effects of N and P additions on photosynthesis and chlorophyll fluorescence (ChlF) of C. paliurus seedlings. N and P additions significantly altered photosynthesis and ChlF in the seedlings, but responses of these parameters to the N and P concentrations varied at different developmental stages. The greatest net photosynthetic rate (PN) and actual photochemical efficiency of PSII (ФPSII) occurred in the treatment of 150.0 mg(N) L-1 and 25.0 mg(P) L-1 addition, whereas the highest maximum quantum yield of PSII (Fv/Fm) and water-use efficiency (WUE) were recorded with 150.0 mg(N) L-1 and 15.0 mg(P) L-1 on the 60th day after treatment. Significantly positive correlations of PN with leaf relative chlorophyll content, transpiration rate, WUE, Fv/Fm, and ΦPSII, as well as the ФPSII with the Fv/Fm, were found. Our results indicated that an optimal addition of N and P nutrients depends on their coupling effects on the photosynthetic capacity and PSII photochemistry.