Water-limited Conditions Research Articles

Coupled DSSAT and HYDRUS-1D Simulation of the Farmland–Crop Water Cycling Process in the Dengkouyangshui Irrigation District

(1) Background: Effective water management in agricultural systems poses a significant challenge, particularly in the Dengkouyangshui irrigation district. Inefficiencies and insufficient detail in water usage across crop growth stages have resulted in suboptimal water cycling. Recent infrastructure improvements and technological interventions necessitate a reevaluation of water usage, especially concerning changes in irrigation and seepage dynamics. (2) Methods: This study addresses these concerns by employing an integrated modeling approach that combines the DSSAT with the HYDRUS-1D soil hydrology model to simulate complex interactions among soil, crop growth, and irrigation practices within the district. Observational data were used to calibrate and validate the integrated model, including soil moisture, LAI, and crop yields from the 2022 and 2023 agricultural seasons. (3) Results: The simulation results strongly align with the empirical data, highlighting the ability of the model to capture the intricate dynamics of soil–water–atmosphere–plant interactions. (4) Conclusions: The soil’s retention and moisture-holding characteristics exhibited resilience during periods without water supplementation, with measurable declines in soil moisture at various depths, indicating the soil’s capacity to support crops in water-limited conditions. This study delineates water consumption by maize crops throughout their growth cycle, providing insights into evapotranspiration partitioning and quantifying seepage losses. An in-depth analysis of water balances at different growth stages informs irrigation strategies, suggesting optimal volumes to enhance efficiency during critical crop development phases. This integrative modeling approach is valuable for providing actionable data to optimize the water cycling process and improve agricultural sustainability in the Dengkouyangshui irrigation district.

Enhancing crop productivity and resilience by promoting soil organic carbon and moisture in wheat and maize rotation

Soils with high organic carbon (SOC) have been shown to enhance crop yields while minimizing climate-induced losses. However, the resilience impacts and mechanisms by which high SOC enhances crop performance have not been fully explored. Here, eight-year rotations of winter wheat and summer maize managed with chemical fertilizer input alone (CF) or with cattle manure (OM) or with peat and vermiculite (PV) were conducted, and various soil properties were measured alongside crop growth, nitrogen (N) uptake, and grain yield, with seasons categorized as dry or normal based on precipitation amounts. The OM and PV treatments increased SOC by 57% and 78% relative to the CF, respectively, and improved soil nutrient availability and the soil quality index. Soil moisture content in the 0–30 cm layer increased by 3.5–26.6%, but was less influenced in the 30–90 cm soil layers. Annual yield of wheat plus maize increased by 13% and 12% in OM and PV compared to the CF, and the yield sustainability index increased by 29% and 17%. Yield gains were more pronounced in dry compared to normal seasons, ranging from 19% to 28% and 12–15% for wheat. At least in part, the relative advantages of OM and PV treatments under drying conditions were associated with accelerated growth and N uptake rate from sowing to stem elongation for wheat and maize. Among the factors influencing yield in the present study, soil moisture exerted the greatest positive total effect on yield. Overall, the results highlight that enhanced SOC resulting from combined application of organic amendments and mineral fertilizer was positively associated with yield by promoting soil quality and water availability, with a more pronounced benefit under water-limited conditions.

Tree post-drought recovery: scenarios, regulatory mechanisms and ways to improve.

Efficient post-drought recovery of growth and assimilation enables a plant to return to its undisturbed state and functioning. Unlike annual plants, trees suffer not only from the current drought, but also from cumulative impacts of consecutive water stresses which cause adverse legacy effects on survival and performance. This review provides an integrated assessment of ecological, physiological and molecular evidence on the recovery of growth and photosynthesis in trees, with a view to informing the breeding of trees with a better ability to recover from water stress. Suppression of recovery processes can result not only from stress damage but also from a controlled downshift of recovery as part of tree acclimation to water-limited conditions. In the latter case, recovery processes could potentially be activated by turning off the controlling mechanisms, but several obstacles make this unlikely. Tree phenology, and specifically photoperiodic constraints, can limit post-drought recovery of growth and photosynthesis, and targeting these constraints may represent a promising way to breed trees with an enhanced ability to recover post-drought. The mechanisms of photoperiod-dependent regulation of shoot, secondary and root growth and of assimilation processes are reviewed. Finally, the limitations and trade-offs of altering the photoperiodic regulation of growth and assimilation processes are discussed.

Multi-hormonal analysis and aquaporins regulation reveal new insights on drought tolerance in grapevine

Disentangling the factors that foster the tolerance to water stress in plants could provide great benefits to crop productions. In a two-year experiment, two new PIWI (fungus resistant) grapevine varieties, namely Merlot Kanthus and Sauvignon Kretos (Vitis hybrids), grown in the field, were subjected to two different water regimes: weekly irrigated (IR) or not irrigated (NIR) for two months during the summer. The two varieties exhibited large differences in terms of performance under water-limiting conditions. In particular, Merlot Kanthus strongly decreased stem water potential (Ψs) under water shortage and Sauvignon Kretos maintained higher Ψs values accompanied by generally high stomatal conductance and net carbon assimilation, regardless of the treatment. We hypothesized differences in the hormonal profile that mediate most of the plant responses to stresses or in the regulation of the aquaporins that control the water transport in the leaves. In general, substantial differences were found in the abundance of different hormonal classes, with Merlot Kanthus reporting higher concentrations of cytokinins while Sauvignon Kretos higher concentrations of auxins, jasmonate and salicylic acid. Interestingly, under water stress conditions ABA modulation appeared similar between the two cultivars, while other hormones were differently modulated between the two varieties. Regarding the expression of aquaporin encoding genes, Merlot Kanthus showed a significant downregulation of VvPIP2;1 and VvTIP2;1 in leaves exposed to water stress. Both genes have probably a role in influencing leaf conductance, and VvTIP2;1 has been correlated with stomatal conductance values. This evidence suggests that the two PIWI varieties are characterized by different behaviour in response to drought. Furthermore, the findings of the study may be generalized, suggesting the involvement of a complex hormonal cross-talk and aquaporins in effectively influencing plant performance under water shortage.

Genetic Potential of Newly Developed Maize Hybrids under Different Water-Availability Conditions in an Arid Environment.

Drought is a crucial environmental stress that tremendously impacts maize production, particularly under abrupt climate changes. Consequently, breeding drought-tolerant and high-yielding maize hybrids has become decisive in sustaining its production and ensuring global food security under the global fast-growing population. The present study aimed to explore drought tolerance and agronomic performance of newly developed maize inbred lines and their hybrids. Ten newly developed maize inbred lines were crossed with two high-yielding testers using a line × tester mating design. The developed twenty hybrids alongside two high-yielding commercial hybrids were evaluated under water-deficit (5411 m3/ha) and well-watered (7990 m3/ha) conditions in dry summer climate conditions. Highly significant variations were detected among the evaluated hybrids for all studied agronomic traits under well-watered and water-deficit conditions. The inbred lines L10 and L6 were particularly notable, demonstrating the most significant negative general combining ability (GCA) effects for earliness, which is crucial for stress avoidance in both environmental settings. Inbred lines L11, L7, L6, and L1 also showed the highest positive and most significant GCA effects for key yield traits, indicating their potential as parents in breeding programs. The crosses L-10×T-1 and L-6×T-2 were outstanding for their heterotic effects on earliness in days to tasseling and silking. Similarly, the crosses L-4×T-2 and L-1×T-1 excelled in plant and ear heights under both irrigation regimes. The hybrids L-1×T-2 and L-7×T-1 demonstrated superior heterosis for chlorophyll content, number of rows per ear, and overall grain yield. Additionally, hybrids L-11×T-1 and L-11×T-2 exhibited remarkable heterotic effects for the number of grains per row, number of rows per ear, 100-kernel weight, and grain yield, highlighting their potential in breeding for productivity. Based on drought tolerance indices and cluster analysis, the cross combinations L-11×T-1, L-11×T-2, L-7×T-1, and L-1×T-2 were classified as the most drought-tolerant crosses. The principal component analysis highlighted traits such as days to tasseling, days to silking, chlorophyll content, plant height, ear height, number of grains per row, number of rows per ear, and 100-kernel weight can be taken as selection criteria for improving grain yield in maize breeding programs under limited water conditions. Based on the summarized results, the identified genetic materials could be considered promising under both conditions and hold potential for future breeding programs.

Summer heat induced the decline of Pinus taiwanensis forests at its southern limit in humid Subtropical China

Warming-induced aridity has caused forest decline and mortality for many sites with water-limiting conditions. However, equatorward rear-edge Pinus taiwanensis trees at the Daiyun Mountains in humid subtropical China are also suffering die-backs and decline, but the roles played by heat or drought stress still remain unclear. Here, we compared the tree-ring radial width, anatomical features, stable carbon isotope (δ13C) and intrinsic water use efficiency (iWUE) between die-back and healthy trees to elucidate potential causes driving the decline. Die-back trees showed sustained growth reductions and produced tracheids with thinner cell walls over the recent decade, indicative of reduced carbon assimilation. The climate response pattern and Vaganov-Shashkin (V-S) model indicated the critical role of summer (June-August) temperature in recent growth decline. Long-term higher wood δ13C and iWUE within die-back trees indicated that actual growth decline already started several decades earlier. This conservative growth strategy was at the cost of low efficiency of photosynthesis due to chronic stomatal closure. When the lethal heatwaves arrived, these weakened trees were not able to access sufficient carbonhydrates to maintain metabolism, causing a distinct decline and mortality. We concluded that recent decline in Pinus taiwanensis trees was mainly caused by long-term carbon starvation.

Higher order polyploids exhibit enhanced desiccation tolerance in the grass Microchloa caffra.

Desiccation tolerance evolved recurrently across diverse plant lineages to enable survival in water limited conditions. Many resurrection plants are polyploid and several groups have hypothesized that polyploidy contributed to the evolution of desiccation tolerance. However, due to the vast phylogenetic distance between resurrection plant lineages, the rarity of desiccation tolerance, and the prevalence of polyploidy in plants, this hypothesis has been difficult to test. Here, we surveyed natural variation in morphological, reproductive, and desiccation tolerance traits across several cytotypes of a single species to test for links between polyploidy and increased resilience. We sampled multiple natural populations of the resurrection grass Microchloa caffra across an environmental gradient ranging from mesic to xeric in South Africa. We describe two distinct ecotypes of M. caffra that occupy different extremes of the environmental gradient and exhibit consistent differences in ploidy, morphological, reproductive, and desiccation tolerance traits in both field and common growth conditions. Interestingly, plants with more polyploid genomes exhibited consistently higher recovery from desiccation, were less reproductive, and larger than plants with smaller genomes and lower ploidy. These data suggest that selective pressures in increasingly xeric sites may play a role in maintaining and increasing desiccation tolerance that are mediated by changes in ploidy.

Molecular basis of distinct responses to drought between rice and wheat genotypes

The water-intensive cultivation of rice in flooded conditions poses a great challenge to global water resources, particularly in the face of climate change. Wheat requires significantly less water than rice with fairly high yields. A main research question is whether there are any drought adaptive mechanisms in rice similar to those existing in wheat. We report a study, where precise moisture stress was imposed at the vegetative stage using a high-throughput drought simulator phenomics facility. Variability in stress response was captured through untargeted metabolome analysis. In the first experiment, using two rice cultivars with contrasting drought responses (IR64 and Apo) and a wheat cultivar, Weebill, we found distinct variations in regulation of metabolite levels under well-watered or water-limited conditions, both between and within species. Several biosynthetic pathways, including those of polyamines, flavonoids, flavones, and specific metabolites like sphinganine-1-phosphate and anthranilate were enhanced under water-limited conditions. These metabolites were more abundant in wheat than in rice. Among the rice cultivars, Apo had higher abundance of metabolites than IR64. Regulatory patterns governing these metabolic pathways provided basis for stress responses of the tolerant rice cultivar and wheat. A second experiment was conducted to screen rice germplasm lines for acquired tolerance traits contrasting for drought responsiveness. Eight genotypes (four sensitive and four tolerant ones) were selected to validate the candidate metabolites from the first experiment. In the third experiment, an RT-PCR analysis of the key regulatory genes governing the metabolic pathways was conducted, using plant materials from both experiments. The results of this third experiment provided a strong validation for the relevance of these metabolic pathways under stress in rice. We identified promising rice genotypes that exhibited fold change levels of stress resistance metabolites comparable to those of the wheat cultivar Weebill. This study helped identify key candidate metabolites that can be either developed as markers or as elicitors, and genotypes that can be used as trait donor lines for rice improvement.

Soil water distribution and water productivity in red cabbage crop using superabsorbent polymeric hydrogels under different drip irrigation regimes

The water issue has emerged as a significant barrier to agricultural productivity, particularly in dry and semiarid agro-ecologies, particularly during the winter season. Superabsorbent hydrogels have been identified as effective tools for improving crop and water productivity in arid locations by enhancing moisture retention. The application of hydrogel to soil is commonly done as a basal application, and its effectiveness is heavily influenced by the moisture level present in the soil. Therefore, a two-year field study was carried out to study the effects of various hydrogels and their application techniques and to assess the efficacy of recently developed cross–linked hydrogels (SPG 1118 and Pusa hydrogel) on soil water distribution (both spatial and temporal), water productivity and profitability of red cabbage. The experiment consisted of two irrigation regimes [full irrigation (100% ETc) and limited irrigation (75% ETc)] assisted in main plots, with two type of hydrogels (Pusa Hydrogel and SPG 1118) and two methods of application [root dipping and soil application of hydrogels and Control with no application of hydrogel] assisted in sub plots. The field experiment was conducted using spilt plot design with three replications. The analysis of soil water distribution patterns reveals that the utilization of hydrogels has resulted in a notable increase of 3–6% in soil water content (SWC) under full irrigation conditions, as compared to plots subjected to limited water conditions. In comparison to plots without hydrogel application, the plots treated with SPG 1118 and Pusa hydrogel exhibited enhanced soil water content of 5–6% and 2–4%, respectively. Additionally, the application of hydrogels in the root dipping showed increased water availability in the crop's root zone compared to soil application in throughout the crop season. Thus, hydrogels with reduced irrigation application resulted in significantly higher crop water productivity (14%) and irrigation water productivity (8 – 14%) compared to full irrigation levels. Likewise, root dipping of SPG 1118 led in considerable improvement in CWP (12–14%) and IWP (11–12%) over no hydrogel applied plots. In relation to profitability, the adoption of full irrigation in conjunction with SPG 1118 hydrogel resulted in an 8% increase in the benefit cost ratio compared to the control plots. Hence, the use of the unique SPG 1118 hydrogel through direct application to the roots, whether under conditions of full or limited irrigation, presents an inventive approach to address the growing issues of water shortages and sustainability in countries experiencing water stress.

Genetic Improvement of Drought Tolerance in a Mega-Rice Variety Improved White Ponni through Marker-Assisted Backcross Breeding

In the ever-changing climatic conditions, it has become important to enhance rice productivity to ensure global food security. Drought is one of the major limiting factors in rice pro- duction. Drought during the reproductive stage results in maximum or complete yield loss. Efforts have been taken to develop drought-tolerant rice lines by introgressing three major drought-effect QTLs, viz. qDTY1.1, qDTY2.1, and qDTY3.1, from Apo into a susceptible popular rice variety, Improved White Ponni (IWP). Backcross inbred lines of IWP × Apo were developed through the marker-assisted backcross breeding approach. Foreground analysis using linked markers resulted in the identification of 17 progenies carrying two or more QTLs, and the recurrent parent genome recoveries of these lines were >95.6% using 72 genome-wide SSR markers distributed throughout all chromosomes. Upon phenotypic evaluation of 17 IWP BILs, the water limited condition resulted in the identification of improved lines by recording the yield and the yield-related parameters. The promising performance of IWP BILs in terms of spikelet fertility (63.3%) and grain yield per plant (>10 g) under drought stress indicated the positive effects of introgressed qDTYs, while IWP recorded complete yield loss (94.2%). Out of the cultivars considered, the best-performing lines which truly exhibited drought tolerance, with more increased yield than the recurrent parent under water-limited conditions, and the effects of these QTLs and their interactions were examined in this research work.

Evaluating Yield, Nutritional Quality, and Environmental Impact of Quinoa Straws across Mediterranean Water Environments.

Quinoa (Chenopodium quinoa Willd.) is a promising and versatile crop due to its remarkable adaptability to diverse environments and the exceptional nutritional value of its seeds. Nevertheless, despite the recent extensive research on quinoa seeds, the straw associated with this crop has received comparatively little attention. The valorisation of this by-product provides an opportunity to improve the overall outcomes of quinoa cultivation. In this work, three quinoa varieties were evaluated for two years (2019 and 2020) under three different Mediterranean water environments (irrigation, fresh rainfed, and hard rainfed), aiming to assess the straw yield and nutritional quality and to study the changes in the crop nutritional uptake associated with different water environmental conditions. The nutritional analysis included the quantification of the ash, crude protein, crude fat, minerals (P, K, Ca, Mg), and fibre (gross fibre (GF), acid detergent fibre (ADF), neutral detergent fibre (NDF), acid detergent lignin (ADL), hemicellulose, cellulose) contents. As the results reveal, most of the parameters evaluated were susceptible to change mainly with the water environment but also with the genotype (or their interaction), including the yield, crude protein, relative feed value (RFV), and mineral content, which generally decreased under water-limiting conditions. Moreover, a comparative analysis revealed that straw Ca, Mg, and K contents were generally higher than in seeds. Overall, this study demonstrates that quinoa straw quality is genotypic and environmentally dependent, and these factors should be considered when aiming at improving straw feed value for livestock nutrition.

Biochar amendment modulates xylem ionic constituents and ABA signaling: its implications in enhancing water-use efficiency of maize (Zea mays L.) under reduced irrigation regimes

While biochar amendment is known to enhance plant productivity and water-use efficiency (WUE), particularly under water-limited conditions, the specific mechanisms driving these benefits remain largely elusive. Thus, the present study was conducted to elucidate the synergistic effects of biochar and reduced irrigation on maize (Zea mays L.) plants, focusing on xylem composition, root-to-shoot signaling, stomatal behavior, and WUE. Maize plants were cultivated in split-root pots filled with clay loam soil, amended by either wheat-straw (WSB) or softwood (SWB) biochar at 2% (w/w). Plants received full (FI), deficit (DI), or alternate partial root-zone drying (PRD) irrigation from the fourth leaf to the grain-filling stage. Our results revealed that WSB amendment significantly enhanced plant water status, biomass accumulation, and WUE under reduced irrigation, particularly when combined with PRD. Although reduced irrigation inhibited photosynthesis, it enhanced WUE by modulating stomatal morphology and conductance. Biochar amendment combined with reduced irrigation significantly increased xylem K+, Ca2+, Mg2+, NO3-, Cl-, PO43-, and SO42- while decreased Na+, which in turn lowered xylem pH. Moreover, biochar amendment and especially WSB amendment further resulted in increased abscisic acid (ABA) contents in both leaf and xylem sap under reduced irrigation conditions due to changes in xylem ionic constituents and pH. The synergistic interactions between xylem components and ABA led to refined adjustments in stomatal size and density, thereby affecting stomatal conductance and ultimately improving WUE of maize plants at different scales. The combined application of WSB and PRD can therefore emerge as a promising approach for improving the overall plant performance of maize plants with increased stomatal adaptations and WUE especially under water-limited conditions.

Spatiotemporal metabolic responses to water deficit stress in distinct leaf cell-types of poplar.

The impact of water-deficit (WD) stress on plant metabolism has been predominantly studied at the whole tissue level. However, plant tissues are made of several distinct cell types with unique and differentiated functions, which limits whole tissue 'omics'-based studies to determine only an averaged molecular signature arising from multiple cell types. Advancements in spatial omics technologies provide an opportunity to understand the molecular mechanisms underlying plant responses to WD stress at distinct cell-type levels. Here, we studied the spatiotemporal metabolic responses of two poplar (Populus tremula× P. alba) leaf cell types -palisade and vascular cells- to WD stress using matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI). We identified unique WD stress-mediated metabolic shifts in each leaf cell type when exposed to early and prolonged WD stresses and recovery from stress. During water-limited conditions, flavonoids and phenolic metabolites were exclusively accumulated in leaf palisade cells. However, vascular cells mainly accumulated sugars and fatty acids during stress and recovery conditions, respectively, highlighting the functional divergence of leaf cell types in response to WD stress. By comparing our MALDI-MSI metabolic data with whole leaf tissue gas chromatography-mass spectrometry (GC-MS)-based metabolic profile, we identified only a few metabolites including monosaccharides, hexose phosphates, and palmitic acid that showed a similar accumulation trend at both cell-type and whole leaf tissue levels. Overall, this work highlights the potential of the MSI approach to complement the whole tissue-based metabolomics techniques and provides a novel spatiotemporal understanding of plant metabolic responses to WD stress. This will help engineer specific metabolic pathways at a cellular level in strategic perennial trees like poplars to help withstand future aberrations in environmental conditions and to increase bioenergy sustainability.

Mutation in Arabidopsis mitochondrial Pentatricopeptide repeat 40 gene affects tolerance to water deficit

Main ConclusionThe Arabidopsis Pentatricopeptide repeat 40 (PPR40) insertion mutants have increased tolerance to water deficit compared to wild-type plants. Tolerance is likely the consequence of ABA hypersensitivity of the mutants.Plant growth and development depend on multiple environmental factors whose alterations can disrupt plant homeostasis and trigger complex molecular and physiological responses. Water deficit is one of the factors which can seriously restrict plant growth and viability. Mitochondria play an important role in cellular metabolism, energy production, and redox homeostasis. During drought and salinity stress, mitochondrial dysfunction can lead to ROS overproduction and oxidative stress, affecting plant growth and survival. Alternative oxidases (AOXs) and stabilization of mitochondrial electron transport chain help mitigate ROS damage. The mitochondrial Pentatricopeptide repeat 40 (PPR40) protein was implicated in stress regulation as ppr40 mutants were found to be hypersensitive to ABA and high salinity during germination. This study investigated the tolerance of the knockout ppr40-1 and knockdown ppr40-2 mutants to water deprivation. Our results show that these mutants display an enhanced tolerance to water deficit. The mutants had higher relative water content, reduced level of oxidative damage, and better photosynthetic parameters in water-limited conditions compared to wild-type plants. ppr40 mutants had considerable differences in metabolic profiles and expression of a number of stress-related genes, suggesting important metabolic reprogramming. Tolerance to water deficit was also manifested in higher survival rates and alleviated growth reduction when watering was suspended. Enhanced sensitivity to ABA and fast stomata closure was suggested to lead to improved capacity for water conservation in such environment. Overall, this study highlights the importance of mitochondrial functions and in particular PPR40 in plant responses to abiotic stress, particularly drought.

Syntrichia ruralis: emerging model moss genome reveals a conserved and previously unknown regulator of desiccation in flowering plants.

Water scarcity, resulting from climate change, poses a significant threat to ecosystems. Syntrichia ruralis, a dryland desiccation-tolerant moss, provides valuable insights into survival of water-limited conditions. We sequenced the genome of S. ruralis, conducted transcriptomic analyses, and performed comparative genomic and transcriptomic analyses with existing genomes and transcriptomes, including with the close relative S. caninervis. We took a genetic approach to characterize the role of an S. ruralis transcription factor, identified in transcriptomic analyses, in Arabidopsis thaliana. The genome was assembled into 12 chromosomes encompassing 21 169 protein-coding genes. Comparative analysis revealed copy number and transcript abundance differences in known desiccation-associated gene families, and highlighted genome-level variation among species that may reflect adaptation to different habitats. A significant number of abscisic acid (ABA)-responsive genes were found to be negatively regulated by a MYB transcription factor (MYB55) that was upstream of the S. ruralis ortholog of ABA-insensitive 3 (ABI3). We determined that this conserved MYB transcription factor, uncharacterized in Arabidopsis, acts as a negative regulator of an ABA-dependent stress response in Arabidopsis. The new genomic resources from this emerging model moss offer novel insights into how plants regulate their responses to water deprivation.

Unpacking the point of no return under drought in poplar: insight from stem diameter variation.

A specific, robust threshold for drought-induced tree mortality is needed to improve the prediction of forest dieback. Here, we tested the relevance of continuous measurements of stem diameter variations for identifying such a threshold, their relationship with hydraulic and cellular damage mechanisms, and the influence of growth conditions on these relationships. Poplar saplings were grown under well-watered, water-limited, or light-limited conditions and then submitted to a drought followed by rewatering. Stem diameter was continuously measured to investigate two parameters: the percentage loss of diameter (PLD) and the percentage of diameter recovery (DR) following rewatering. Water potentials, stomatal conductance, embolism, and electrolyte leakage were also measured, and light microscopy allowed investigating cell collapse induced by drought. The water release observed through loss of diameter occurred throughout the drought, regardless of growth conditions. Poplars did not recover from drought when PLD reached a threshold and this differed according to growth conditions but remained linked to cell resistance to damage and collapse. Our findings shed new light on the mechanisms of drought-induced tree mortality and indicate that PLD could be a relevant indicator of drought-induced tree mortality, regardless of the growth conditions.

Effect of deficit irrigation combined with Bacillus simplex on water use efficiency and growth parameters of maize during vegetative stage

The production of crops depending on many factors including water, nutrient, soil types, climate and crops types, water stress and drought is in one of the important factors affecting crop productivity. The experiment was conducted in pots to evaluate the effect of biofertilizers (Bacillus simplex) with deficit irrigations on the early development and growth of maize crop under greenhouse condition. Pre sowing seed was inoculated with strain of bacteria (B+/B-) and different irrigation levels (no stress: 100% (I1) and deficit irrigation: 75 (I2), 50 (I3), 25 (I4) % of required water amount to reach pot capacity) was performed. Data was collected on different morphological characteristics and root characteristic of maize crop. Highest plant height (125 cm), stem diameter (18.02 mm), leaf area (350 cm− 2), plant weight (180.42 g in fresh, 73.58 g in dry), root length (92.83 cm) root ((91.70 g in fresh, (28.66 g in dry) weight were recorded in pots applied with 100% irrigation followed by 75%. Bacillus treated plants showed significant increase in leaf area (214.20 cm− 2), plant fresh weight (91.65 g) and dry weight (42.05 g), root length (79.20 cm), root fresh (53.52 g) and dry weight (16.70 g) compared with control (without bacteria). Likewise highest relative water content of leaf was observed with I3 followed by I2 and I1 respectively. Highest water use efficiency was recorded as 0.67 g pot− 1 mm− 1 in I1 with B + treatment. Likewise, Bacillus inoculated pots resulted in increased water use efficiency (0.44 g pot− 1 mm− 1) compared with no application (0.36 g pot− 1 mm− 1). It can be endorsed from the outcome that Bacillus inoculation increased plant biomass, root biomass of maize and water use efficiency during early growth stage of maize despite of water stress and can be used under limited water condition for crop combating during moderate to lower stress conditions.

Biostimulants do not affect the performance of urban plant species grown under drought stress

Urban areas often have low soil water availability due to their impervious surfaces reducing rainfall infiltration. These water-limited conditions may be exacerbated by the projected increases in drought events caused by climate change. As a result, plants that grow in urban areas are vulnerable to drought stress. There are a range of practices that can be used to help mitigate drought stress, including the use of biostimulants. This study aimed to determine whether biostimulant application (1) improves plant performance and (2) mitigates the drought stress on urban plant species. To address these aims, we selected six woody and three graminoid plant species that are commonly planted in Australian urban areas and exposed them to different watering (drought-stressed, well-watered) and biostimulant (control, humic acid, protein hydrolysate, seaweed extract) treatments. We then measured their assimilation rate, growth metrics and biomass allocation. We found that drought stress reduced the assimilation rates and shoot growth of the study species. However, this did not translate into a biomass reduction because the drought-stressed plants reallocated resources towards root biomass. We found no evidence to suggest biostimulant application mitigated the impacts of drought stress on plant performance. Further, the only effect biostimulant application had on plant performance irrespective of the watering treatment was that the seaweed biostimulant increased the plant height growth of the woody species. These results show that the biostimulants used in this study will have a limited effect on the performance of plant species commonly planted in Australian urban areas.

Decoding the effects of drought stress on popcorn (Zea mays var. everta) flowering combining proteomics and physiological analysis

Under conditions of soil water limitation and adequate irrigation, we conducted an investigation into the growth dynamics, gas exchange performance, and proteomic profiles of two inbred popcorn lines—L71, characterized as drought-tolerant, and L61, identified as drought-sensitive. Our goal was to uncover the mechanisms associated with tolerance to soil water limitation during the flowering. The plants were cultivated until grain filling in a substrate composed of perlite and peat within 150cm long lysimeter, subjected to two water conditions (WC): i) irrigated (WW) at lysimeter capacity (LC - 100%), and ii) water-stressed (WS). Under WS conditions, the plants gradually reached 45% of LC and were maintained at this level for 10 days. Irrespective of the WC, L71 exhibited the highest values of dry biomass in both shoot and root systems, signifying its status as the most robust genotype. The imposed water limitation led to early senescence, chlorophyll degradation, and increased anthocyanin levels, with a more pronounced impact observed in L61. Traits related to gas exchange manifested differences between the lines only under WS conditions. A total of 1838 proteins were identified, with 169 differentially accumulated proteins (DAPs) in the tolerant line and 386 DAPs in the sensitive line. Notably, differences in energy metabolism, photosynthesis, oxidative stress response, and protein synthesis pathways were identified as the key distinctions between L71 and L61. Consequently, our findings offer valuable insights into the alterations in proteomic profiles associated with the adaptation to soil water limitation in popcorn.

Heterosis and Diallel Analysis for Grain Yield, Yield Attributes and Physiological Traits in Barley (Hordeum vulgare L.)

The present study was carried out during November–April, 2019–2020 and 2020–21 with eight diverse barley genotypes and their developed 28F1s (half diallel, excluding reciprocals) to ascertain gene effects, hetrosis and correlations for grain yield, yield attributes and physiological traits under water limited conditions of Bundelkhand region. Days to heading and days to maturity exhibited general mean values of 86 days and 127 days, respectively. The parental genotypes, DWRB180, RD2794 and RD2899 showed early spike emergence and maturity. The cross combinations, namely DWRB160 /DWRB180, DWRB180/RD2907 and BH946/RD2552 were promising for flag leaf length and width. The GCA effects were significant and prevalent for all the characters, except days to heading, plant height and tillers count. The parents, DWRB160 (5.29**) and BH902 (1.59**) depicted high GCA effects for 1000 grain weight. The parents, DWRB180, RD2552, and BH946 exhibited significant positive GCA effects for leaf area index and chlorophyll fluorescence, whereas the genotypes, RD2907, BH946 and RD2899 showed higher GCA effects for chlorophyll content. Grain yield exhibited significant positive correlations with flag leaf width (0.60**), tillers per meter (0.35*), grains per spike (0.39*), harvest index (0.53**), chlorophyll content (0.69**), leaf area index (0.49**) and chlorophyll fluorescence (0.68**). The parents, BH946, DWRB180 and RD2907 and the hybrids, RD2552/DWRB180, BH902/RD2794, DWRB160/DWRB180 and BH946/RD2907 were found promising for yield and yield attributes in the dry agro-ecology of Bundelkhand region. The crosses, DWRB160/BH902 and DWRB160/BH946 can be explored for developing superior segregants for malt barley breeding.