Water Deficit Conditions Research Articles

Understanding Water Utilization Mechanisms in Degrading Bamboo Shoots: A Cytological and Physiological Study.

Degradation of shoots, characterized by stunted growth and signs of water deficit, is common in bamboo stands. However, the specific mechanisms underlying water utilization in degrading shoots remain unclear. This study sought to address this gap by harvesting bamboo shoots and culms of Phyllostachys edulis 'Pachyloen', employing cytological and physiological techniques to compare water utilization mechanisms between healthy and degrading shoots, and investigating the water supply to bamboo shoots by the parent bamboo. The water pressure in the degrading shoots was markedly lower compared to that of the healthy shoots, and it declined as the degradation progressed, resulting in reduced water content and the cessation of guttation in the degrading shoots. In conditions of water deficit, the percentage of free water in bamboo shoots decreased while the percentages of bound and semi-bound water increased, with the proportion of semi-bound water reaching as high as 88.13% in the late stages of degradation. The water potential of parent bamboo culms of different ages varied at different times of the day and during different growth stages of bamboo shoots, showing a strong association with the development of bamboo shoots. Conversely, the correlation between changes in the water potential of bamboo shoots and their degradation patterns was found to be comparatively minimal. The weakening of the connection between the bamboo shoots and the parent bamboo culms may play a significant role in the degradation of the bamboo shoots. This is evidenced by a decrease in the fluorescence intensity of the nucleus in bamboo shoots and the degradation of genetic material. This study lays the foundation for future research into the mechanisms of bamboo shoot degradation.

Ecophysiological Recovery of Micropropagated Olive Cultivars: Field Research in an Irrigated Super-High-Density Orchard

This research focuses on the seasonal patterns of the ecophysiological recovery of four olive cultivars (Arbequina, Coratina, Frantoio, and Urano), both micropropagated and self-rooted, grown in a mature, irrigated, super high-density (SHD) orchard under Mediterranean conditions (Southern of Italy). The aim was to observe the impact of the micropropagation method on the ecophysiological responses. Ecophysiological parameters, including leaf water potential (LWP), stomatal conductance (gs), net photosynthetic rate (Pn), and transpiration rate (E) were assessed. Self-rooted trees consistently exhibited superior gs, E, and Pn recovery compared to the micropropagated ones. ‘Arbequina’ maintained elevated levels of Pn under water-deficit conditions. ‘Coratina’ exhibited increases in gs and E after irrigation. ‘Frantoio’ demonstrated recovery capabilities, with lower LWP and higher Pn under stress. ‘Urano’ micropropagated trees achieved higher gs values in mid-summer, while self-rooted trees sustained higher Pn later in the season. This field research highlighted the important role of the propagation method in optimizing the physiological performance of olive cultivars in SHD orchards. Furthermore, it highlighted the necessity of long-term studies on the effects of propagation methods and their interactions with other farming practices.

Influence of silicon application on the growth of corn under conditions of water stress

The low availability of water in the soil is one of the precursors of stress in the plant, responsible for the decrease in growth and losses in crop productivity, by hindering the maintenance of essential metabolic processes. Many experimental results have demonstrated the effect of silicon (Si) as an attenuator of environmental stresses in plants. Thus, the objective of this research was to evaluate the growth of the corn crop subjected to water stress and the application of silicon in the semi-arid region of Alagoas. The experimental design used was in strips with four replications, schematized in subdivided plots. The culture was subjected to a combination of five water stress conditions (1, 4, 7, 10 and 13 days of intervals of irrigation) and two conditions of availability of Si (with and without Si). The following plant variables were analyzed: canopy height, stem diameter and leaf area index. It was found that the longer the irrigation interval, the lower the growth of plants. The application of Si provided higher rates of leaf area. The use of Si in plant fertilization in water deficit conditions is a viable alternative.

Effects of arbuscular mycorrhizal fungi in the rhizosphere of two olive (Olea europaea) varieties Arbequina and Barnea under water deficit conditions.

One strategy to improve olive (Olea europaea ) tree drought tolerance is through the symbiosis of arbuscular mycorrhizal fungi (AMF), which helps alleviate water deficit through a combination of morphophysiological effects. Cuttings of olive varieties Arbequina (A) and Barnea (B) were grown with (+AMF) or without (-AMF) inoculum in the olive grove rhizosphere soil. One year after establishment, pots were exposed to four different water regimes: (1) control (100% of crop evapotranspiration); (2) short-period drought (20days); (3) long-period drought (25days); and (4) rewatering (R). To evaluate the influence of AMF on tolerance to water stress, stem water potential, stomatal conductance and the biomarkers for water deficit malondialdehyde, proline, soluble sugars, phenols, and flavonoids were evaluated at the end of the irrigation regimes. Stem water potential showed higher values in A(+) and B(+) in all water conditions, and the opposite was true for stomatal conductance. For proline and soluble sugars, the stem water potential trend is repeated with some exceptions. AMF inoculum spore communities from A(+ and -) and B(+ and -) were characterised at the morphospecies level in terms of richness and abundance. Certain morphospecies were identified as potential drought indicators. These results highlight that the benefits of symbiotic relationships between olive and native AMF can help to mitigate the effects of abiotic stress in soils affected by drought.

Synergistic effects of melatonin and 24-epibrassinolide on chickpea water deficit tolerance

BackgroundWater deficiency stress reduces yield in grain legumes, primarily due to a decrease in the pods number. Melatonin (ML) and 24-epibrassinolide (EBL) are recognized for their hormone-like properties that improve plant tolerance to abiotic stresses. This study aimed to assess the impact of different concentrations of ML (0, 100, and 200 µM) and EBL (0, 3, and 6 µM) on the growth, biochemical, and physiological characteristics of chickpea plants under water-stressed conditions.ResultsThe study's findings indicated that under water-stressed conditions, a decrease in seed (30%) and pod numbers (31%), 100-seed weight (17%), total chlorophyll content (46%), stomatal conductance (33%), as well as an increase in H2O2 (62%), malondialdehyde content (40%), and electrolyte leakage index (40%), resulted in a 40% reduction in chickpea plants grain yield. Our findings confirmed that under water-stressed conditions, seed oil, seed oil yield, and seed protein yield dropped by 20%, 55%, and 36%, respectively. The concurrent exogenous application of ML and EBL significantly reduces oxidative stress, plasma membrane damage, and reactive oxygen species (ROS) content. This treatment also leads to increased yield and its components, higher pigment content, enhanced oil and protein yield, and improved enzymatic and non-enzymatic antioxidant activities such as catalase, superoxide dismutase, polyphenol oxidase, ascorbate peroxidase, guaiacol peroxidase, flavonoid, and carotenoid. Furthermore, it promotes the accumulation of osmoprotectants such as proline, total soluble protein, and sugars.ConclusionsOur study found that ML and EBL act synergistically to regulate plant growth, photosynthesis, osmoprotectants accumulation, antioxidant defense systems, and maintain ROS homeostasis, thereby mitigating the adverse effects of water deficit conditions. ML and EBL are key regulatory network components in stressful conditions, with significant potential for future research and practical applications. The regulation metabolic pathways of ML and EBL in water-stressed remains unknown. As a result, future research should aim to elucidate the molecular mechanisms by employing genome editing, RNA sequencing, microarray, transcriptomic, proteomic, and metabolomic analyses to identify the mechanisms involved in plant responses to exogenous ML and EBL under water deficit conditions. Furthermore, the economical applications of synthetic ML and EBL could be an interesting strategy for improving plant tolerance.

Zinc foliar application may alleviate drought stress in wheat species through physiological changes

Drought is the greatest threat to food security in the climate change scenario, which affects crop plants' growth and development by disturbing the plant's physiological and biochemical processes. Zinc (Zn) is an essential micronutrient in many metabolic processes and may improve plant tolerance to water deficit conditions besides its nutritional value.This study investigated the reaction of several wheat species with different ploidy levels to foliar Zn application under water stress. Water stress significantly reduced grain yield (GY), leaf relative water contents (RWC), chlorophyll (Chla and Chlb), and carotenoid (Car) contents. Water stress also impacted several other physiological characteristics by increasing leaf hydrogen peroxide (HP), free proline (Prl), malondialdehyde (MDA) contents, soluble protein (PC), sodium content (Na+), and antioxidant enzymes, including peroxidase (Pox), ascorbate peroxidase (Aes) and catalase (Cat). Remarkably, the Zn application alleviated yield reduction caused by water stress. Moreover, the Zn application increased grains' Zn, potassium content (K+), and K+/Na+ ratio, RWC, Chl, Car contents, Pox, Aes, and Cat activities while significantly reducing MDA, HP, and Na+ contents compared with the control treatment. Pox, Aes, and Cat activities increased to higher concentrations in 6x and 4x than in 2x, indicating that the 6x and 4x species responded better to water stress. Wild and landrace varieties of 4x, such as T. dicoccum, T. ispahanicum, and T. dicoccoides, showed better water stress tolerance than the landrace varieties of 2x and 6x species. These species may be a valuable genetic source for improving modern bread and durum wheat to water stress.

Simulation of water content in the soil, canopy growth and biomass production for the maize crop, in different conditions of water replenishment with the aquacrop model

Simulation models for crop production are tools increasingly used to aid decision making and resource optimization, such as irrigation. In this sense, this study aimed to evaluate the performance of the AquaCrop model in the simulation of water content in the soil, canopy growth and biomass production for the maize crop under different water replenishment conditions, in the western border region in the State of Rio Grande do Sul - Brazil. It was used data from climate, soil, crop and management from two experiments developed in the 2017/18 and 2018/19 seasons in the municipality of Alegrete. The irrigation treatments corresponded to layers of 0, 50, 75, 100 and 125% of ETc for the first cultivation period, and 0%; 50, 75 and 100%, suppressed by 50% in the reproductive period of the crop; and 100% of ETc for the second cultivation period. The performance index, used in the evaluation, classified the AquaCrop model as “excellent” for the simulation of canopy cover and biomass production, and “very good” for the simulation of water content in the soil. The model presented a tendency to underestimate canopy coverage under deficit conditions and to overestimate it under irrigation conditions. For the production of biomass and water content in the soil, the model tended to overestimate the results of treatments under conditions of water deficit.

Exogenous Sodium Nitroprusside Affects the Redox System of Wheat Roots Differentially Regulating the Activity of Antioxidant Enzymes under Short-Time Osmotic Stress.

Nitric oxide (NO) is a multifunctional signalling molecule involved in the regulation of plant ontogenesis and adaptation to different adverse environmental factors, in particular to osmotic stress. Understanding NO-induced plant protection is important for the improvement of plant stress tolerance and crop productivity under global climate changes. The root system is crucial for plant survival in a changeable environment. Damages that it experiences under water deficit conditions during the initial developmental periods seriously affect the viability of the plants. This work was devoted to the comparative analysis of the pretreatment of wheat seedlings through the root system with NO donor sodium nitroprusside (SNP) for 24 h on various parameters of redox homeostasis under exposure to osmotic stress (PEG 6000, 12%) over 0.5-24 h. The active and exhausted solutions of SNP, termed as (SNP/+NO) and (SNP/-NO), respectively, were used in this work at a concentration of 2 × 10-4 M. Using biochemistry and light microscopy methods, it has been revealed that osmotic stress caused oxidative damages and the disruption of membrane cell structures in wheat roots. PEG exposure increased the production of superoxide (O2•-), hydrogen peroxide (H2O2), malondialdehyde (MDA), and the levels of electrolyte leakage (EL) and lipid peroxidation (LPO). Stress treatment enhanced the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), the excretion of proline, and the rate of cell death and inhibited their division. Pretreatment with (SNP/+NO) decreased PEG-induced root damages by differently regulating the antioxidant enzymes under stress conditions. Thus, (SNP/+NO) pretreatment led to SOD, APX, and CAT inhibition during the first 4 h of stress and stimulated their activity after 24 h of PEG exposure when compared to SNP-untreated or (SNP/-NO)-pretreated and stress-subjected plants. Osmotic stress triggered the intense excretion of proline by roots into the external medium. Pretreatment with (SNP/+NO) in contrast with (SNP/-NO) additionally increased stress-induced proline excretion. Our results indicate that NO is able to mitigate the destructive effects of osmotic stress on the roots of wheat seedlings. However, the mechanisms of NO protective action may be different at certain periods of stress exposure.

Análisis de mecanismos bioquímico-fisiológicos involucrados en las respuestas a sequía en soja

Water deficit limits soybean crop productivity and reduces yield stability. Many parameters have been associated with tolerance to water deficit, where the control of leaf water loss is by far the most important. Since most of the water loss occurs through the stomata, the objective of this thesis was to deepen the understanding of the response to water deficit in soybeans through the control of stomatal closure and to determine how this can affect the water consumption of soybeans and its tolerance to water deficit. To achieve this, we delved into the study of stomatal closure control. We focused on the role of nitric oxide (•NO) as a key molecule in the control of stomatal opening/closing. •NO kinetic accumulation was analyzed from the establishment of the hydric deficit, and its association with stomatal closure was assessed. Our work showed an endogenous •NO accumulation at the guard cell level before stomatal closure, which allowed us to postulate that in the early perception of stress there is an accumulation of •NO that inhibits stomatal closure, potentially through blocking responses to ABA. This initial fine control of the stomatal closure by •NO would be decisive to define the final responses of water loss/consumption during the establishment of the water deficit. Furthermore, we developed an empirical mathematical model in soybean that describes the kinetics of water consumption under water deficit conditions of a controlled plant-pot-substrate growth system. The model defined two parameters that determine the water consumption curve, t0.5 (time at which the system lost half of the maximum amount of potentially evapotranspirable water) and Gw(t0.5) (stomatal conductance at t0.5). A correspondence analysis between t0.5 and Gw(t0.5), and the genetic structure of two soybean populations, indicated the existence of genetic associations with consumption phenotypes based on these parameters. On the other hand, using data from the drought susceptibility index (DSI) in the field, generated by previous work on one of the populations of this thesis, and through a correspondence analysis, a grouping between the model parameter t0.5 and DSI is observed. This would indicate that the developed phenotyping strategy could also be useful in the characterization of genotypes at the field level.

Melatonin mitigates drought stress by increasing sucrose synthesis and suppressing abscisic acid biosynthesis in tomato seedlings.

The increasing prevalence of drought events poses a major challenge for upcoming crop production. Melatonin is a tiny indolic tonic substance with fascinating regulatory functions in plants. While plants can respond in several ways to alleviate drought stress, the processes underpinning stress sensing and signaling are poorly understood. Hereafter, the objectives of this investigation were to explore the putative functions of melatonin in the regulation of sugar metabolism and abscisic acid biosynthesis in drought-stressed tomato seedlings. Melatonin (100 μM) and/or water were foliar sprayed, followed by the plants being imposed to drought stress for 14 days. Drought stress significantly decreased biomass accumulation, inhibited photosynthetic activity, and stimulated senescence-associated gene 12 (SAG12) expression. Melatonin treatment effectively reversed drought-induced growth retardation as evidenced by increased leaf pigment and water balance and restricted abscisic acid (ABA) accumulation. Sugar accumulation, particularly sucrose content, was higher in drought-imposed seedlings, possibly owing to higher transcription levels of sucrose non-fermenting 1-related protein kinase 2 (SnKR2.2) and ABA-responsive element binding factors 2 (AREB2). Melatonin addition further uplifted the sucrose content, which coincided with increased activity of sucrose synthase (SS, 130%), sucrose phosphate synthase (SPS, 137%), starch degradation encoding enzyme β-amylase (BAM, 40%) and α-amylase (AMY, 59%) activity and upregulated their encoding BAM1(10.3 folds) and AMY3 (8.1 folds) genes expression at day 14 relative to the control. Under water deficit conditions, melatonin supplementation decreased the ABA content (24%) and its biosynthesis gene expressions. Additionally, sugar transporter subfamily genes SUT1 and SUT4 expression were upregulated by the addition of melatonin. Collectively, our findings illustrate that melatonin enhances drought tolerance in tomato seedlings by stimulating sugar metabolism and negatively regulating ABA synthesis.

Drought and mycorrhizal inoculation affect growth and morphology of Australian stormwater biofilter plants

This study evaluated the effect of mycorrhizal inoculation on six common Australian biofilter plant species using a pot experiment. We divided 120 pots planted with six common biofilter species into four treatments: control water-deficit, inoculated water-deficit, control well-watered, and inoculated well-watered. Inoculated treatments were inoculated with a commercially available blend of arbuscular mycorrhizal fungi spores. While well-watered pots were watered to pot capacity daily, water-deficit pots were subjected to a simulated drought that lasted six weeks until harvesting. All plants inoculated with arbuscular mycorrhizal fungi developed greater total root surface area, plant biomass, and plant relative growth rate. Which are associated with better stormwater nutrient removal. Mycorrhizal inoculation also increased the average root diameter, total length, and surface area of thick roots (diameter > 1 mm) of six species, which are essential to maintain the infiltration rates and hydraulic functions of biofilter systems. Moreover, an increase in shoot biomass following inoculation was also observed across six species, potentially contributing to higher water loss and stormwater volume reduction. Although the water-deficit condition greatly limited the effects of mycorrhizal inoculation on other morphological traits, we still observed the benefits of inoculation on total root length and surface area in well-watered J. pallidus and C. appressa. As drought stress imposes limitations on the effects of inoculation, we recommend inoculation should be carried out in advantageous times, such as during wet periods before the drought season for the optimal colonization and plant biomass and morphological responses. Additionally, selecting mycorrhizae-responsive species like C. appressa, J. pallidus, and G. sieberiana can result in favorable outcomes.

Unraveling the complexities of drought stress in cotton: a multifaceted analysis of selection criteria and breeding approaches

Abiotic stress tolerance breeding programs present a spectrum of perspectives, yet definitive solutions remain elusive, with each approach carrying its own set of advantages and disadvantages. This study systematically evaluates extant methodologies, comparing plant performance across varied genotypes and selection traits under optimal and stress conditions. The objective is to elucidate prevailing ambiguities. Ten homozygous lines (F8 generation) were assessed using a randomized block design alongside five control varieties, with four replicates cultivated under well-watered and deficit water conditions. It is noteworthy that six of the ten homozygous lines were cultivated exclusively under well-watered conditions (F3 to F7), while four lines experienced deficit water conditions (F3 to F7). All five control varieties underwent cultivation under both conditions. These findings underscore the necessity for tailored breeding programs attuned to specific environmental exigencies, recognizing that individual traits manifest divergent responses to varying conditions. It is evident that certain traits exhibit marked disparities under well-watered conditions, while others evince heightened differentiation under water deficit conditions. Significantly, our analysis reveals a pronounced interaction between irrigation regimes and selection traits, which serves to underscore the nuanced interplay between genotype and environmental stress.

Sweet Cherry Plants Prioritize Their Response to Cope with Summer Drought, Overshadowing the Defense Response to Pseudomonas syringae pv. syringae.

Disease severity and drought due to climate change present significant challenges to orchard productivity. This study examines the effects of spring inoculation with Pseudomonas syringae pv. syringae (Pss) on sweet cherry plants, cvs. Bing and Santina with varying defense responses, assessing plant growth, physiological variables (water potential, gas exchange, and plant hydraulic conductance), and the levels of abscisic acid (ABA) and salicylic acid (SA) under two summer irrigation levels. Pss inoculation elicited a more pronounced response in 'Santina' compared to 'Bing' at 14 days post-inoculation (dpi), and those plants inoculated with Pss exhibited a slower leaf growth and reduced transpiration compared to control plants during 60 dpi. During differential irrigations, leaf area was reduced 14% and 44% in Pss inoculated plants of 'Bing' and 'Santina' respectively, under well-watered (WW) conditions, without changes in plant water status or gas exchange. Conversely, water-deficit (WD) conditions led to gas exchange limitations and a 43% decrease in plant biomass compared to that under WW conditions, with no differences between inoculation treatments. ABA levels were lower under WW than under WD at 90 dpi, while SA levels were significantly higher in Pss-inoculated plants under WW conditions. These findings underscore the influence on plant growth during summer in sweet cherry cultivars that showed a differential response to Pss inoculations and how the relationship between ABA and SA changes in plant drought level responses.

Identifying Bioactive Compounds in Common Bean (Phaseolus vulgaris L.) Plants under Water Deficit Conditions

Deficit irrigation (DI) strategies are becoming increasingly common in areas where water resources are limited. The application of moderate levels of DI can result in water savings with a small reduction in yield but with a higher quality of the product. The aim of this work was to evaluate the effect of applying a certain level of water deficit (40% water holding capacity) on the yield and quality of the common bean (Phaseolus vulgaris L.), specifically the cultivar ‘Triunfo-70’. Bioactive compounds were investigated by applying an LC-MS-based untargeted metabolomics approach as an analytical tool for identifying novel markers associated with a water deficit in beans. The results showed that beans harvested 30 days after DI application experienced water stress, as indicated by the decrease in the leaf water potential and gas exchange values (stomatal conductance and photosynthesis). In addition, the number of pods per plant was significantly reduced by the DI treatment. The water deficit induced significant alterations in various bioactive compounds (including organic acids, polyphenols, hydroxybenzoic acids, lipids, and phospholipids) when compared to the control treatment. Additionally, twelve new biomarkers were identified in this study for the first time in the common bean under DI. These findings suggested that DI acted as an elicitor, increasing phenylpropanoid metabolism, while concurrently reducing the production of compounds associated with fatty acid metabolism. Additionally, new metabolites were tentatively identified in common beans. This study represents the successful application of the untargeted metabolomics approach to finding bioactive secondary metabolites in beans under different irrigation conditions.

Water deficit response in nodulated soybean roots: a comprehensive transcriptome and translatome network analysis

BackgroundSoybean establishes a mutualistic interaction with nitrogen-fixing rhizobacteria, acquiring most of its nitrogen requirements through symbiotic nitrogen fixation. This crop is susceptible to water deficit; evidence suggests that its nodulation status—whether it is nodulated or not—can influence how it responds to water deficit. The translational control step of gene expression has proven relevant in plants subjected to water deficit.ResultsHere, we analyzed soybean roots’ differential responses to water deficit at transcriptional, translational, and mixed (transcriptional + translational) levels. Thus, the transcriptome and translatome of four combined-treated soybean roots were analyzed. We found hormone metabolism-related genes among the differentially expressed genes (DEGs) at the translatome level in nodulated and water-restricted plants. Also, weighted gene co-expression network analysis followed by differential expression analysis identified gene modules associated with nodulation and water deficit conditions. Protein-protein interaction network analysis was performed for subsets of mixed DEGs of the modules associated with the plant responses to nodulation, water deficit, or their combination.ConclusionsOur research reveals that the stand-out processes and pathways in the before-mentioned plant responses partially differ; terms related to glutathione metabolism and hormone signal transduction (2 C protein phosphatases) were associated with the response to water deficit, terms related to transmembrane transport, response to abscisic acid, pigment metabolic process were associated with the response to nodulation plus water deficit. Still, two processes were common: galactose metabolism and branched-chain amino acid catabolism. A comprehensive analysis of these processes could lead to identifying new sources of tolerance to drought in soybean.

Endophyte-Mediated Populus trichocarpa Water Use Efficiency Is Dependent on Time of Day and Plant Water Status

Endophytes are potential partners for improving the resource use efficiency of bioenergy feedstock systems such as short rotation coppice Populus species. Endophytes isolated from members of the Salicaceae family have broad host compatibility and can improve water use efficiency (WUE) through decreases in stomatal conductance. However, the literature is inconsistent with regard to the environmental conditions and temporal patterns of these benefits. This study investigated how endophyte-mediated changes in Populus trichocarpa ‘Nisqually-1’ stomatal conductance and WUE shift with time and scale in response to water deficit stress. Leaf gas exchange and aboveground productivity were used to evaluate the carbon and water balance of greenhouse-grown plants in response to endophyte inoculation and water deficit. Differences in stomatal conductance between control and inoculated plants were more pronounced (39.7% decrease, Welch two-sample t [14.34 adjusted degrees of freedom] = –2.358, P = 0.033) under water deficit conditions in the late morning during a period of higher light intensity. The decrease in stomatal conductance accompanied a substantial increase in intrinsic WUE (iWUE) for water deficit inoculated plants. However, increases in iWUE did not result in improvements in aboveground productivity or shoot biomass WUE for water deficit inoculated plants. This decoupling between iWUE and aboveground productivity may be an indicator of assimilate allocation to microbial metabolism as an additional carbon sink or a shift in carbon allocation toward belowground biomass. Future work should take a whole plant approach that accounts for diurnal patterns in incident irradiance to evaluate the impact of endophyte inoculation on host WUE and stress tolerance.

Selenium and its nanoparticles modulate the metabolism of reactive oxygen species and morpho-physiology of wheat (Triticum aestivum L.) to combat oxidative stress under water deficit conditions

BackgroundWheat (Triticum aestivum L.) is one of the most important cereal crop species worldwide, but its growth and development are adversely influenced by drought stress. However, the application of trace elements is known to improve plant physiology under water-limited conditions. In this study, the effects of drought stress on wheat plants were investigated, with a focus on potential mitigation by foliar application of selenium nanoparticles (Se(np)) and sodium selenate (Na2SeO4). The experiment was conducted in a net house using a completely randomized design with four replications. The treatments involved three levels of drought stress (mild, moderate, and severe) started at 30 days after sowing (DAS), with foliar sprays of Se(np) and Se (both 25 µM) initiated at 27 DAS and repeated 4 times at 7-day intervals until 55 DAS.ResultsDrought stress significantly reduced plant growth, whereas Se(np) and Se sprays enhanced it. Drought stress induced chlorophyll degradation, increased malondialdehyde and hydrogen peroxide levels, impaired membrane stability, and caused electrolyte leakage. Severe drought stress reduced the levels of antioxidants (e.g., proline, ascorbate, and glutathione by 4.18-fold, 80%, and 45%) and the activities of antioxidant enzymes (ascorbate peroxidase, dehydroascorbate reductase, and others). Conversely, treatment with Se(np) and Se restored these parameters, for example, 1.23-fold higher total chlorophyll content with Se(np) treatment, 26% higher APX activity with Se treatment, 15% lower electrolyte leakage with Se treatment in wheat plants under severe drought stress. This Se-associated enhancement facilitated rapid scavenging of reactive oxygen species and reduced methylglyoxal toxicity, thereby diminishing oxidative stress and positively affecting the morphophysiological and biochemical responses of the plants under drought.ConclusionsDrought-stressed wheat plants exhibited reductions in physiological processes, including water uptake and photosynthetic activity. However, Se(np) and Se applied at 25 µM mitigated the detrimental effects of drought. The application of Se(np) was notably more effective than the application of Se in mitigating drought stress, indicating the potential of the application of Se(np) as a sustainable agricultural practice under water-limited conditions.

Interactive effect of rhizobacterium Bacillus sp. strain MRD-17 and macro-nutrients on the amelioration of drought stress in mustard (Brassica juncea L.)

ABSTRACT Drought is a major abiotic stress in mustard. In the present investigation, the interactive effects of rhizobacterium Bacillus sp. MRD-17 and nutrients nitrogen, phosphorus, and potassium (N, P, K), 100% and 50% of the recommended dose of fertiliser (RDF) on shoot-root growth and nutrient uptake by mustard under well-watered (−0.33 bar) and water deficit (−8 bar) conditions were determined. Drought stress for 30 days, reduced root growth, but rhizobacterial inoculation under drought and nutrient stress improved root viability (73%, and 39%, respectively) and architecture, nitrate reductase (20% and 12%, respectively) and glutamine synthetase activity (21% and 14%, respectively), shoot nitrogen, phosphorus, and potassium and seed K content. The protective effects of Bacillus sp. MRD-17 to mustard under drought stress was also accompanied by decreased acid phosphatase activity. However, rhizobacterial and macro-nutrient interactions had no impact on seed N and P content on drought and nutrient-stressed plants. Therefore, in terms of plant growth and nutrient uptake, the efficiency of Bacillus sp. MRD-17 was dependent on the soil nutrient status. Furthermore, rhizobacterial application might facilitate a higher uptake of water and nutrients by the plant from the soil and thus sustain crop productivity under water and nutrient stress scenarios.

Physiological Indices for the Selection of Drought-Tolerant Safflower Genotypes for Cultivation in Marginal Areas

Safflower is known as a tolerant plant to abiotic stress factors. This study was conducted to introduce some physiological indices to improve drought-tolerant safflower genotypes for cultivation in marginal and arid areas. Six safflower genotypes were studied for two years (2017–2019) in the East Azarbaijan Agricultural and Natural Resources Research and Education Centre of Iran under non-stressed and low-water conditions from flowering to seed maturity. The occurrence of water deficits led to a significant decrease in relative water content (RWC), stomatal conductance (gs), osmotic adjustment (Oadj), water potential (WP) and agronomic water use efficiency (WUEa) and an increase in the water stress index (CWSI). In addition, the values of these traits differed significantly between the safflower genotypes. The correlations between the physiological traits and seed yield were significant. The regression relationships between seed yield and the above traits showed that CWSI, WP and WUEa had a strong relationship with seed yield under normal (R2 = 0.854, 0.801 and 0.856, respectively) and water deficit conditions (R2 = 0.931, 0.877 and 0.900, respectively). It can be concluded that the CWSI, WP and WUEa indices are able to select high-yielding and drought-tolerant safflower genotypes for the late season. Among the components of seed yield, the number of capitula per plant (r = 0.86) and seeds per capitula (r = 0.92), which were positively and significantly correlated with seed yield, played the main roles in the formation of seed yield. The Golemehr and Mec.295 genotypes achieved higher seed yields under normal (4676 and 4961 kg h−1, respectively) and water deficit conditions (3211 and 3385 kg h−1, respectively) and can be recommended for cultivation in marginal and arid areas.

Unveiling Drought-Resilient Latin American Popcorn Lines through Agronomic and Physiological Evaluation.

Water stress can lead to physiological and morphological damage, affecting the growth and development of popcorn. The objective of this study was to identify the yield potential of 43 popcorn lines derived from a Latin American germplasm collection, based on agronomic and physiological traits, under full irrigation (WW) and water deficit conditions (WS), aiming to select superior germplasm. The evaluated agronomic traits included the ear length and diameter, number of grains per row (NGR) and rows per ear (NRE), grain yield (GY), popping expansion (EC), volume of expanded popcorn per hectare (VP), grain length (GL), width, and thickness. The physiological traits included the chlorophyll, anthocyanin, and flavonoid content in the leaves. The genetic variability and distinct behavior among the lines for all the agronomic traits under WW and WS conditions were observed. When comparing the water conditions, line L292 had the highest mean for the GY, and line L688 had the highest mean for the EC, highlighting them as the most drought-tolerant lines. A water deficit reduced the leaf greenness but increased the anthocyanin content as an adaptive response. The GY trait showed positive correlations with the VP, NGR, and GL under both water conditions, making the latter useful for indirect selection and thus of great interest for plant breeding targeting the simultaneous improvement of these traits.