Response of Plants to Water Stress: A Meta-Analysis

Unraveling the impact of water deficit stress on nutritional quality and defense response of tomato genotypes

Water deficit stress triggers various physiological and biochemical changes in plants, substantially affecting both overall plant defense response and thus nutritional quality of tomatoes. The aim of this study was to assess the antioxidant defense response and nutritional quality of different tomato genotypes under water deficit stress. In this study, six tomato genotypes were used and subjected to water deficit stress by withholding water for eight days under glass house conditions. Various physiological parameters from leaves and biochemical parameters from tomato fruits were measured to check the effect of antioxidant defense response and nutritional value. Multi-trait genotype-ideotype distance index (MGIDI) was used for the selection of genotypes with improved defense response and nutritional value under water deficit stress condition. Results indicated that all physiological parameters declined under stress conditions compared to the control. Notably, NBH-362 demonstrated resilience to water deficit stress, improving both defense response and nutritional quality which is evident by an increase in proline (16.91%), reducing sugars (20.15%), total flavonoids (10.43%), superoxide dismutase (24.65%), peroxidase (14.7%), and total antioxidant capacity (29.9%), along with a decrease in total oxidant status (4.38%) under stress condition. Overall, the findings suggest that exposure to water deficit stress has the potential to enhance the nutritional quality of tomatoes. However, the degree of this enhancement is contingent upon the distinct genetic characteristics of various tomato genotypes. Furthermore, the promising genotype (NBH-362) identified in this study holds potential for future utilization in breeding programs.

Abscisic acid and glycine betaine-mediated seed and root priming enhance seedling growth and antioxidative defense in wheat under drought

The extent of drought tolerance in the seedlings of three wheat cultivars (WMRI-1, BARI GOM-33 and BARI GOM-21) was investigated by seed and root priming using abscisic acid (ABA) and glycine betaine (GB). The seeds were primed with ABA (10 and 20 μM) and GB (50 and 100 mM) and grown in pots maintaining control (0 % PEG) and drought (10 % PEG) conditions. Under drought, the root and shoot length, root and shoot biomass were significantly increased in ABA and GB primed seedlings than non-primed seedlings in all cultivars. Among the priming agents, either 20 μM ABA or 50 mM GB triggered better seedling growth in all wheat cultivars. These two levels were then applied with the nutrient solution in the hydroponics following four treatments: Control, Drought, Drought + ABA and Drought + GB. The seedling growth significantly declined in drought, while an improved seedling growth was observed in ABA and GB-treated plants in all cultivars. A considerable increase in lipid peroxidation, proline content, total antioxidant capacity and total flavonoid content in roots and leaves were recorded in all drought conditions, while these values were considerably reduced in ABA and GB treatments. Hierarchical clustering heatmap using stress tolerance index (STI) values showed that Drought + ABA and Drought + GB secured higher STI scores suggesting a greater degree of drought tolerance in all cultivars. In conclusion, seed and root priming of ABA and GB enhanced drought tolerance in the wheat seedlings by improving seedling growth and antioxidative defense suggesting a declined state of oxidative damage.

Seed osmopriming with polyethylene glycol (PEG) enhances seed germination and seedling physiological traits of Coronilla varia L. under water stress

Water stress can adversely affect seed germination and plant growth. Seed osmopriming is a pre-sowing treatment in which seeds are soaked in osmotic solutions to undergo the first stage of germination prior to radicle protrusion. Seed osmopriming enhances germination performance under stressful environmental conditions, making it an effective method to improve plant resistance and yield. This study analyzed the effect of seed osmopriming with polyethylene glycol (PEG) on seed germination and physiological parameters of Coronilla varia L. Priming treatments using 10% to 30% PEG enhanced germination percentage, germination vigor, germination index, vitality index, and seedling mass and reduced the time to reach 50% germination (T50). The PEG concentration that led to better results was 10%. The content of soluble proteins (SP), proline (Pro), soluble sugars (SS), and malondialdehyde (MDA) in Coronilla varia L. seedlings increased with the severity of water stress. In addition, under water stress, electrolyte leakage rose, and peroxidase (POD) and superoxide dismutase (SOD) activities intensified, while catalase (CAT) activity increased at mild-to-moderate water stress but declined with more severe deficiency. The 10% PEG priming significantly improved germination percentage, germination vigor, germination index, vitality index, and time to 50% germination (T50) under water stress. Across the water stress gradient here tested (8 to 12% PEG), seed priming enhanced SP content, Pro content, and SOD activity in Coronilla varia L. seedlings compared to the unprimed treatments. Under 10% PEG-induced water stress, primed seedlings displayed a significantly lower MDA content and electrolyte leakage than their unprimed counterparts and exhibited significantly higher CAT and POD activities. However, under 12% PEG-induced water stress, differences in electrolyte leakage, CAT activity, and POD activity between primed and unprimed treatments were not significant. These findings suggest that PEG priming enhances the osmotic regulation and antioxidant capacity of Coronilla varia seedlings, facilitating seed germination and seedling growth and alleviating drought stress damage, albeit with reduced efficacy under severe water deficiency.

How does water stress affect the bioaccumulation of galanthamine and lycorine, growth performance, phenolic content and defense enzyme activities in summer snowflake (Leucojum aestivum L.)?

Leucojum aestivum L. is an Amaryllidaceae bulbous plant with two alkaloids that have remarkable medicinal potential: galanthamine and lycorine. Although the presence of galanthamine in L. aestivum has commercial value for the pharmaceutical industry and the effect of water stress (WS) applications on secondary metabolite enhancement is well established in a variety of plants, no studies have been carried out to reveal the effectiveness of WS on this beneficial medicinal plant. Objective of the study was to investigate the effects of eight different WS treatments [Control, waterlogging (WL) condition, and drought stress conditions (water deficiency generated by water deficit irrigation-WDI 25%, 50%, and 75%- and polyethylene glycol-PEG 6000 15%, 30%, and 45%-)] on growth parameters, alkaloid levels (galanthamine and lycorine), non-enzymatic antioxidant activities (total phenol-flavonoid content and free radical scavenging activity), and enzymatic antioxidant activities [superoxide dismutase (SOD) and catalase (CAT)] of L. aestivum in a pot experiment. Based on the findings, maximum increases in growth parameters were obtained with PEG-induced WS treatments. Moderate water deficiency (50% WDI) produced the highest levels of galanthamine and lycorine, total phenol-flavonoid content, and antioxidant capacity, along with moderately elevated CAT activity in the bulbs. All WS treatments resulted in increased CAT activity in the bulbs. It was observed that bulbs had higher SOD and CAT activities under WL conditions had lower fresh weights and were close to control in terms of alkaloid levels, total phenol-flavonoid content, and free radical scavenging activity. When all of the outcomes were taken into account, it can be concluded that moderate water-deficit stress (50% WDI) was regarded as the most effective treatment for increasing the pharmaceutical value of L. aestivum.

Graphical abstract

Border cell population size and oxidative stress in the root apex of Triticum aestivum seedlings exposed to fungicides

Fungicides reduce the risk of mycopathologies and reduce the content of mycotoxins in commercial grain. The effect of fungicides on the structural and functional status of the root system of grain crops has not been studied enough. In this regard, we studied the phytocytotoxic effects tebuconazole (TEB) and epoxiconazole (EPO) and azoxystrobin (AZO) in the roots of Triticum aestivum seedlings in hydroponic culture. In the presence of EPO and AZO (but not TEB) inhibition of the root growth was accompanied by a dose-dependent increase in the content of malondialdehyde, carbonylated proteins, and proline in roots. TEB was characterized by a dose-dependent decrease in the total amount of border cells (BCs) and the protein content in root extracellular trap (RET). For EPO and AZO, the dose curves of changes in the total number of BCs were bell-shaped. AZO did not affect the protein content in RET. The protein content in RET significantly decreased by 3 times for an EPO concentration of 1 µg/mL. The obtained results reveal that the BC-RET system is one of the functional targets of fungicides in the root system of wheat seedlings. Studied fungicides induce oxidative stress and structural and functional alterations in the BC-RET system that can affect their toxicity to the root system of crops.

Combining PSII photochemistry and hydraulics improves predictions of photosynthesis and water use from mild to lethal drought

Rising temperatures and increases in drought negatively impact the efficiency and sustainability of both agricultural and forest ecosystems. Although hydraulic limitations on photosynthesis have been extensively studied, a solid understanding of the links between whole plant hydraulics and photosynthetic processes at the cellular level under changing environmental conditions is still missing, hampering our predictive power for plant mortality. Here, we examined plant hydraulic traits and CO2 assimilation rate under progressive water limitation by implementing Photosystem II (PSII) dynamics with a whole plant process model (TREES). The photosynthetic responses to plant water status were parameterized based on measurements of chlorophyll a fluorescence, gas exchange and water potential for Brassica rapa (R500) grown in a greenhouse under fully watered to lethal drought conditions. The updated model significantly improved predictions of photosynthesis, stomatal conductance and leaf water potential. TREES with PSII knowledge predicted a larger hydraulic safety margin and a decrease in percent loss of conductivity. TREES predicted a slower decrease in leaf water potential, which agreed with measurements. Our results highlight the pressing need for incorporating PSII drought photochemistry into current process models to capture cross-scale plant water dynamics from cell to whole plant level.

Investigating the potential of nanobonechar toward climate-smart agriculture

Extreme climates and the unpredictability of the weather are significant obstacles to agricultural productivity. This study is the first attempt to explore the capacity of nanobonechar (NBC) for promoting climate-smart agriculture. A pot experiment was performed on maize (Zea mays L.) under a deficit irrigation system (40, 70, and 100% irrigation rates) using different soil application rates of the NBC (0, 0.5, 1, and 2% wt/wt). Additionally, the CO2-C efflux rate and cumulative CO2-C were measured in an incubation experiment. The results indicated the best performance of the 1% NBC treatment under a 70% irrigation rate in terms of the fresh and dry weights of maize plants. Total PO43- and Ca2+ were significantly higher in the plants grown in the NBC-amended soil as compared to the control, showing a gradual increase with an increase in the NBC application rate. The improved productivity of maize plants under a deficit irrigation system was associated with enhanced water-holding capacity, organic matter, and bioavailability of cations (Ca2+, K+, and Na+) and anions (PO43- and NO3-) in the soils amended with NBC. The CO2-C efflux rate and cumulative CO2-C emissions remain higher in the NBC-amended soil than in the un-amended soil, pertaining to the high contents of soil organic matter emanating from the NBC. We conclude that NBC could potentially be used as a soil amendment for promoting maize growth under a water stress condition.

Study the yield and quality of bitter gourd fruit (Momordica charantia) in inoculation with two species of mycorrhizal fungi and phosphorus fertilizer under different irrigation regimes

Drought is known to be the most important constraint to the growth and yield of agricultural products in the world, and plant symbiosis with arbuscular mycorrhizal fungi (AMF) can be a way to reduce drought stress negative impacts. A two-year experiment to investigate the factorial combination of mycorrhizal fungi (Glomus mosseae, Glomus intraradices, Control) and phosphorus fertilizer (application and non-application of phosphorus) on fruit yield and phenolic acids changes bitter gourd under different irrigation regimes as a split factorial based on a randomized complete block design. Three irrigation regimes, including irrigation after 20%, 50%, and 80% available soil water content depletion (ASWD), were considered in the main plots. The results showed that under water deficit stress, fruit yield and physiological (photosynthesis rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), RWC, total chlorophyll, and root colonization) parameters decreased compared to 20% ASWD, and biochemical (proline, soluble sugar, MDA, CAT, SOD, phenol) parameters and fruit phenolic acids (caffeic acid, coumaric acid, ferulic acid) increased. However, the inoculation of AMF and phosphorus fertilizer in three irrigation regimes decreased MDA content, but physiological and biochemical parameters and fruit phenolic acids were increased. In this study, the factorial combination of AMF and sufficient phosphorus improved the resistance of bitter gourd to water deficit, and this not only improved fruit yield but also increased fruit phenolic acids under 80% ASWD, which can be an innovation in the management of water resources and the production industry of medicinal plants with high antioxidant properties in water deficit areas.

Combined biochar and water-retaining agent application increased soil water retention capacity and maize seedling drought resistance in Fluvisols

Global climate change has accelerated the occurrence of agricultural drought events, which threaten food security. Therefore, improvements in the soil water retention capacity (WRC) and crop drought resistance are crucial for promoting the sustainability of the agricultural environment. In this study, we explored the effects of applying biochar and water-retaining agent (WRA) on soil WRC and crop drought resistance in a Fluvisols, along with their potential mechanisms. We applied two types of biochar (based on wheat and maize straw) and two WRAs (polyacrylamide and starch-grafted sodium acrylate) to Fluvisols with different textures, and then evaluated soil water retention and crop drought physiological resistance. The combined biochar and WRA treatment increased the WRC in both the sandy loam and clay loam Fluvisols. Biochar and WRA increased the relative content of soil hydrophilic functional groups. Compared with the control (CK), the combined application of biochar and WRA increased the field capacity, reduced soil water volatilization under drought conditions, and slowed water infiltration into the Fluvisols. The soil WRC was higher with the wheat straw biochar (WBC) treatment than with the maize straw biochar (MBC) treatment. It was also higher with polyacrylamide treatment than with the starch-grafted sodium acrylate treatment. The combined application of biochar and WRA improved crop drought physiological resistance by significantly increasing the maize seedling potassium (K) and soluble sugar contents, increasing antioxidant enzyme activity, and reducing the malondialdehyde (MDA) content. The results indicate that the application of biochar and WRA alleviated drought stress by increasing the soil WRC and improving crop drought resistance in Fluvisols.

Effect of drought stress and subsequent re-watering on the physiology and nutrition of Pistacia vera and Pistacia atlantica

Arid and semi-arid regions are characterised by extreme conditions including drought stress and salinity. These factors profoundly affect the agricultural sector. The objective of this work is to study the effect of drought and re-watering on leaf gas exchange, chlorophyll fluorescence and mineral nutrition in Pistacia vera and Pistacia atlantica . Water stress was applied to individuals of P. vera and P. atlantica for 23days, followed by rehydration for 7days. The results showed a clear reduction in water relations, leaf gas exchange and chlorophyll content in P. vera . Compared to P. vera , P. atlantica maintained less affected water status, total chlorophyll content, leaf gas exchange and chlorophyll fluorescence, stable Zn and Fe proportion, and even elevated K and Cu. The changes in the chlorophyll fluorescence parameter were manifested particularly at the maximal fluorescence (Fm). In contrast, no change was recorded at the minimal fluorescence (F0). After re-hydration, although water status was fully recovered in both species, stomatal conductance (gs), net photosynthesis (A ) and transpiration rate (E ) remain with lower values than the well-watered seedlings. P. atlantica was better adapted to drought stress than P. vera .

Functional Trait Responses of Sophora alopecuroides L. Seedlings to Diverse Environmental Stresses in the Desert Steppe of Ningxia, China

The seedling stage of plants is a crucial and vulnerable period in population and community dynamics. Despite this, studies on how plant traits respond to different environmental stresses often tend to overlook this early stage. Our study focused on Sophora alopecuroides L. seedlings in Ningxia Yanchi desert steppe, analyzing the effects of sand burial, salinity, and drought on their key aboveground and belowground traits. The results showed that sand burial significantly negatively affected stem biomass (SB), leaf biomass (LB), stem diameter (SD), leaf length (LL), leaf width (LW), leaf area (LA), and total root volume (RV), but positively influenced total root length (RL). As sand burial depth increased, SB, LB, SD, LL, LW, LA, RV, root biomass (RB), RV, and lateral root numbers (LRN) significantly decreased. Salinity stress negatively affected SB, LB, SD, LL, LW, LA, RB, RL, and RV, with these traits declining as the stress concentration increased. Drought stress had a positive effect on SD and LL, with both traits showing an increase as the intensity of the drought stress intensified; however, it adversely affected RL. In Ningxia Yanchi desert steppe, salinity stress had the most significant effect on the traits of S. alopecuroides seedlings, followed by sand burial, with drought having the least significant effect. This study provides essential theoretical support for understanding how S. alopecuroides seedlings cope with environmental stresses in their early life stages.

Divergent patterns and drivers of leaf functional traits of Robinia pseudoacacia and Pinus tabulaeformis plantations along a precipitation gradient in the Loess plateau, China

Changes in precipitation patterns in arid and semi-arid regions can reshape plant functional traits and significantly affect ecosystem functions. However, the synchronous responses of leaf economical, anatomical, photosynthetic, and biochemical traits to precipitation changes and their driving factors have rarely been investigated, which hinders our understanding of plants' ecological adaptation strategies to drought tolerance in arid areas. Therefore, the leaf traits of two typical plantations (Robinia pseudoacacia, RP and Pinus tabulaeformis, PT) along the precipitation gradient in the Loess Plateau, including economical, anatomical, photosynthetic, and biochemical traits, were investigated in this study. The results show that the leaf photosynthetic traits of RP and PT increase along the precipitation gradient, whereas leaf biochemical traits decrease. The anatomical traits of PT decrease with increasing precipitation, whereas no significant variation was observed for RP. Random Forest analysis show that LNC, LDMC, Chl, and PRO are leaf traits that significantly vary with the precipitation gradient in both plantations. Correlation analysis reveals that the traits coordination of RP is better than that of PT. The LMG model was used to determine driving factors. The results suggest that MAP explains the variation of PT leaf traits better (30.38%-36.78%), whereas SCH and SPH contribute more to the variation of RP leaf traits (20.88%-41.76%). In addition, the piecewise Structural Equation Model shows that the climate and soil physical and chemical properties directly affect the selected leaf functional traits of RP, whereas only the soil chemical properties directly affect the selected leaf functional traits of PT. The results of this study contribute to the understanding of the ecological adaptation of plants to environmental gradients and highlight that correlations among leaf traits should be considered when predicting plant adaptation strategies under future global change scenarios.

Antioxidant Response, Phenolic Compounds and Yield of Solanum tuberosum Tubers Inoculated with Arbuscular Mycorrhizal Fungi and Growing under Water Stress

Solanum tuberosum (potato) is one of the most common crops worldwide; however, it is sensitive to water stress, which necessitates the identification of alternative tools to improve their production. Here, we evaluated the inoculation of two arbuscular mycorrhizal fungi (AMF) strains, Claroideoglomus claroideum (CC), Claroideoglomus lamellosum (HMC26), and the MIX (CC + HMC26) in yield and phenolic and antioxidant response using chromatographic and spectroscopic methods in potato crops, at increasing levels of water stress, namely, with 100% (0), 70% (S1), and 40% (S2) soil humidity. Two caffeoylquinic acid isomers were detected and their levels showed a tendency to increase under stress together with the AMF inoculation, reaching up to 19.2 mg kg-1 of 5-caffeoylquinic acid and 7.4 mg kg-1 of caffeoylquinic acid isomer when CC was inoculated, and potato plants grew at the highest water starvation condition (S2). Regarding antioxidant activities, a differentiated response was detected depending on the AMF strain, highlighting the effect of HMC26 on Trolox equivalent antioxidant capacity (TEAC) method and CC in cupric reducing antioxidant capacity (CUPRAC) method, reaching up to 1.5 μmol g-1 of TEAC in plants inoculated with HMC26 and 0.9 μmol g-1 of CUPRAC in plants inoculated with CC, both in potato tubers of plants growing under the S2 stress condition. Meanwhile, the use of AMF did not influence the number and biomass of the tubers, but significant changes in the biochemical properties of tubers were observed. The results suggest that specific AMF adaptations to water stress must be considered when inoculation procedures are planned to improve the yield and quality of tubers in potato crops.

Photosynthesis regulation, cell membrane stabilization and methylglyoxal detoxification seems major altered pathways under cold stress as revealed by integrated multi-omics meta-analysis

Climate change has altered cold weather patterns, resulting in irregular cold weather conditions, and changing the global plant distribution pattern affecting plant development processes resulting in severe yield losses. Although molecular mechanisms and interconnections are quite well studied, a cumulative understanding of plant responses to cold stress (CS) is still lacking. Through meta-analysis, integration of data at the multi-omics level and its correlation with known physiological changes to map and understand the global changes in response to CS was made. Meta-analysis was conducted using the metafor R package program based on physiological parameters like relative electrolytic leakage, malondialdehyde, soluble sugar, proline and antioxidant enzymes activity. Proline and soluble sugars showed the highest (> 1.5 mean fold) change over control thus qualifying as global markers for studying CS. Surprisingly most up-regulated (> 15-fold) DEGs corresponded with the dehydrin family and glyoxalase superfamily proteins. Functional annotations of DEGs corresponded with photosynthesis and glycolysis pathway. Proteins responsible for cell signalling and increased soluble sugars were common in all the datasets studied thus correlating with the transcriptome and proteomic data. Proline and soluble sugars were positively regulated in all the metabolomics datasets. This study supported the earlier known players like proline and soluble sugars. Surprisingly, a new player glyoxalase seems to be contributing in CS.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01367-9.

Deciphering the molecular basis of abiotic stress response in cucumber (Cucumis sativus L.) using RNA-Seq meta-analysis, systems biology, and machine learning approaches

Abiotic stress in cucumber (Cucumis sativus L.) may trigger distinct transcriptome responses, resulting in significant yield loss. More insight into the molecular underpinnings of the stress response can be gained by combining RNA-Seq meta-analysis with systems biology and machine learning. This can help pinpoint possible targets for engineering abiotic tolerance by revealing functional modules and key genes essential for the stress response. Therefore, to investigate the regulatory mechanism and key genes, a combination of these approaches was utilized in cucumber subjected to various abiotic stresses. Three significant abiotic stress-related modules were identified by gene co-expression network analysis (WGCNA). Three hub genes (RPL18, δ-COP, and EXLA2), ten transcription factors (TFs), one transcription regulator, and 12 protein kinases (PKs) were introduced as key genes. The results suggest that the identified PKs probably govern the coordination of cellular responses to abiotic stress in cucumber. Moreover, the C2H2 TF family may play a significant role in cucumber response to abiotic stress. Several C2H2 TF target stress-related genes were identified through co-expression and promoter analyses. Evaluation of the key identified genes using Random Forest, with an area under the curve of ROC (AUC) of 0.974 and an accuracy rate of 88.5%, demonstrates their prominent contributions in the cucumber response to abiotic stresses. These findings provide novel insights into the regulatory mechanism underlying abiotic stress response in cucumber and pave the way for cucumber genetic engineering toward improving tolerance ability under abiotic stress.

Selenium enhances ROS scavenging systems and sugar metabolism increasing growth of sugarcane plants

Selenium (Se) beneficial effect on plants is related to an increase in nitrogen (N) assimilation and its role as an abiotic stress mitigator by reactive oxygen species (ROS) scavenging enhanced by antioxidant metabolism. This study aimed to evaluate sugarcane (Saccharum spp.) growth, photosynthetic and antioxidant responses, and sugar accumulation in response to Se supply. The experimental design was a factorial scheme 2 × 4: two sugarcane varieties (RB96 6928 and RB86 7515) and four Se application rates (0; 5; 10 and 20 μmol L-1) applied as sodium selenate in the nutrient solution. Leaf Se concentration increased under Se application in both varieties. The enzymes SOD (EC 1.15.1.1) and APX (EC 1.11.1.11) showed increase activities under Se application on variety RB96 6928. Nitrate reductase activity increased in both varieties resulting in the conversion of nitrate into higher total amino acids concentration indicating an enhanced N assimilation. This led to an increased concentration of chlorophylls and carotenoids, increased CO2 assimilation rate, stomatal conductance, and internal CO2 concentration. Selenium provided higher starch accumulation and sugar profiles in leaves boosting plant growth. This study shows valuable information regarding the role of Se on growth, photosynthetic process, and sugar accumulation in sugarcane leaves, which could be used for further field experiments. The application rate of 10 μmol Se L-1 was the most adequate for both varieties studied considering the sugar concentration and plant growth.

Organ-specific responses during acclimation of mycorrhizal and non-mycorrhizal tomato plants to a mild water stress reveal differential local and systemic hormonal and nutritional adjustments

MAIN CONCLUSION

Tomato plant acclimation to a mild water stress implied tissue-specific hormonal and nutrient adjustments, being the root one of the main modulators of this response. Phytohormones are key regulators of plant acclimation to water stress. However, it is not yet clear if these hormonal responses follow specific patterns depending on the plant tissue. In this study, we evaluated the organ-specific physiological and hormonal responses to a 14 day-long mild water stress in tomato plants (Solanum lycopersicum cv. Moneymaker) in the presence or absence of the arbuscular mycorrhizal fungus Rhizoglomus irregulare, a frequently used microorganism in agriculture. Several physiological, production, and nutritional parameters were evaluated throughout the experiments. Additionally, endogenous hormone levels in roots, leaves, and fruits at different developmental stages were quantified by ultrahigh-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Water deficit drastically reduced shoot growth, while it did not affect fruit production. In contrast, fruit production was enhanced by mycorrhization regardless of the water treatment. The main tissue affected by water stress was the root system, where huge rearrangements in different nutrients and stress-related and growth hormones took place. Abscisic acid content increased in every tissue and fruit developmental stage, suggesting a systemic response to drought. On the other hand, jasmonate and cytokinin levels were generally reduced upon water stress, although this response was dependent on the tissue and the hormonal form. Finally, mycorrhization improved plant nutritional status content of certain macro and microelements, specially at the roots and ripe fruits, while it affected jasmonate response in the roots. Altogether, our results suggest a complex response to drought that consists in systemic and local combined hormonal and nutrient responses.

Marine fungi showing multifunctional activity against human pathogenic microbes and cancer

Multifunctional drugs have shown great promise in biomedicine. Organisms with antimicrobial and anticancer activity in combination with antioxidant activity need further research. The Red Sea and the Arabian Gulf coasts were randomly sampled to find fungi with multifunctional activity. One hundred strains (98 fungi and 2 lichenized forms) were isolated from 15 locations. One-third of the isolates inhibited clinical bacterial (Staphylococcus aureus, Bacillus subtilis, Vibrio cholerae, Salmonella typhi, S. paratyphi) and fungal pathogens (Talaromycets marneffei, Malassezia globose, Cryptococcus neoformans, Candida albicans, Aspergillus fumigatus) and four cancer cell lines (Hep G2 liver, A-549 lung, A-431skin, MCF 7 breast cancer). Bacterial and cancer inhibition was often accompanied by a high antioxidant activity, as indicated by the principal component analysis (PCA). PCA also indicated that fungal and bacterial pathogens appeared to be inhibited mostly by different marine fungal isolates. Strains with multifunctional activity were found more from the Rea Sea than from the Arabian Gulf coasts. The highest potential for multifunctional drugs were observed for Acremonium sp., Acrocalymma sp., Acrocalymma africana, Acrocalymma medicaginis (activity reported for the first time), Aspergillus sp. Cladosporium oxysporum, Emericellopsis alkaline, Microdochium sp., and Phomopsis glabrae. Lung, skin, and breast cancers were inhibited 85%-97% by Acremonium sp, while most of the isolates showed low inhibition (ca 20%). The highest antifungal activity was observed for Acremonium sp., Diaporthe hubeiensis, Lasiodiplodia theobromae, and Nannizia gypsea. One Acremonium sp. is of particular interest to offer a multifunctional drug; it displayed both antifungal and antibacterial activity combined with high antioxidant activity (DPPH scavenging 97%). A. medicaginis displayed combined antibacterial, anticancer, and antioxidant activity being of high interest. Several genera and some species included strains with both high and low biological activities pointing out the need to study several isolates to find the most efficient strains for biomedical applications.

Spatiotemporal dynamics of the tomato fruit transcriptome under prolonged water stress

Water availability influences all aspects of plant growth and development; however, most studies of plant responses to drought have focused on vegetative organs, notably roots and leaves. Far less is known about the molecular bases of drought acclimation responses in fruits, which are complex organs with distinct tissue types. To obtain a more comprehensive picture of the molecular mechanisms governing fruit development under drought, we profiled the transcriptomes of a spectrum of fruit tissues from tomato (Solanum lycopersicum), spanning early growth through ripening and collected from plants grown under varying intensities of water stress. In addition, we compared transcriptional changes in fruit with those in leaves to highlight different and conserved transcriptome signatures in vegetative and reproductive organs. We observed extensive and diverse genetic reprogramming in different fruit tissues and leaves, each associated with a unique response to drought acclimation. These included major transcriptional shifts in the placenta of growing fruit and in the seeds of ripe fruit related to cell growth and epigenetic regulation, respectively. Changes in metabolic and hormonal pathways, such as those related to starch, carotenoids, jasmonic acid, and ethylene metabolism, were associated with distinct fruit tissues and developmental stages. Gene coexpression network analysis provided further insights into the tissue-specific regulation of distinct responses to water stress. Our data highlight the spatiotemporal specificity of drought responses in tomato fruit and indicate known and unrevealed molecular regulatory mechanisms involved in drought acclimation, during both vegetative and reproductive stages of development.

Mechanisms involved in drought stress tolerance triggered by rhizobia strains in wheat

Rhizobium spp. is a well-known microbial plant biostimulant in non-legume crops, but little is known about the mechanisms by which rhizobia enhance crop productivity under drought stress. This work analyzed the mechanisms involved in drought stress alleviation exerted by Rhizobium leguminosarum strains in wheat plants under water shortage conditions. Two (LBM1210 and LET4910) of the four R. leguminosarum strains significantly improved the growth parameters (fresh and dry aerial weight, FW and DW, respectively), chlorophyll content, and relative water content (RWC) compared to a non-inoculated control under water stress, providing values similar to or even higher for FW (+4%) and RWC (+2.3%) than the non-inoculated and non-stressed control. Some other biochemical parameters and gene expression explain the observed drought stress alleviation, namely the reduction of MDA, H₂O₂ (stronger when inoculating with LET4910), and ABA content (stronger when inoculating with LBM1210). In agreement with these results, inoculation with LET4910 downregulated DREB2 and CAT1 genes in plants under water deficiency and upregulated the CYP707A1 gene, while inoculation with LBM1210 strongly upregulated the CYP707A1 gene, which encodes an ABA catabolic enzyme. Conversely, from our results, ethylene metabolism did not seem to be involved in the alleviation of drought stress exerted by the two strains, as the expression of the CTR1 gene was very similar in all treatments and controls. The obtained results regarding the effect of the analyzed strains in alleviating drought stress are very relevant in the present situation of climate change, which negatively influences agricultural production.

Integrative System Biology Analysis of Transcriptomic Responses to Drought Stress in Soybean (Glycine max L.)

Drought is a major abiotic stressor that causes yield losses and limits the growing area for most crops. Soybeans are an important legume crop that is sensitive to water-deficit conditions and suffers heavy yield losses from drought stress. To improve drought-tolerant soybean cultivars through breeding, it is necessary to understand the mechanisms of drought tolerance in soybeans. In this study, we applied several transcriptome datasets obtained from soybean plants under drought stress in comparison to those grown under normal conditions to identify novel drought-responsive genes and their underlying molecular mechanisms. We found 2168 significant up/downregulated differentially expressed genes (DEGs) and 8 core modules using gene co-expression analysis to predict their biological roles in drought tolerance. Gene Ontology and KEGG analyses revealed key biological processes and metabolic pathways involved in drought tolerance, such as photosynthesis, glyceraldehyde-3-phosphate dehydrogenase and cytokinin dehydrogenase activity, and regulation of systemic acquired resistance. Genome-wide analysis of plants’ cis-acting regulatory elements (CREs) and transcription factors (TFs) was performed for all of the identified DEG promoters in soybeans. Furthermore, the PPI network analysis revealed significant hub genes and the main transcription factors regulating the expression of drought-responsive genes in each module. Among the four modules associated with responses to drought stress, the results indicated that GLYMA_04G209700, GLYMA_02G204700, GLYMA_06G030500, GLYMA_01G215400, and GLYMA_09G225400 have high degrees of interconnection and, thus, could be considered as potential candidates for improving drought tolerance in soybeans. Taken together, these findings could lead to a better understanding of the mechanisms underlying drought responses in soybeans, which may useful for engineering drought tolerance in plants.

Enzyme activity profiling for physiological phenotyping within functional phenomics: plant growth and stress responses

High-throughput profiling of key enzyme activities of carbon, nitrogen, and antioxidant metabolism is emerging as a valuable approach to integrate cell physiological phenotyping into a holistic functional phenomics approach. However, the analyses of the large datasets generated by this method represent a bottleneck, often keeping researchers from exploiting the full potential of their studies. We address these limitations through the exemplary application of a set of data evaluation and visualization tools within a case study. This includes the introduction of multivariate statistical analyses that can easily be implemented in similar studies, allowing researchers to extract more valuable information to identify enzymatic biosignatures. Through a literature meta-analysis, we demonstrate how enzyme activity profiling has already provided functional information on the mechanisms regulating plant development and response mechanisms to abiotic stress and pathogen attack. The high robustness of the distinct enzymatic biosignatures observed during developmental processes and under stress conditions underpins the enormous potential of enzyme activity profiling for future applications in both basic and applied research. Enzyme activity profiling will complement molecular -omics approaches to contribute to the mechanistic understanding required to narrow the genotype-to-phenotype knowledge gap and to identify predictive biomarkers for plant breeding to develop climate-resilient crops.

Morphological and physiological changes in Artemisia selengensis under drought and after rehydration recovery

Changes in global climate and precipitation patterns have exacerbated the existing uneven distribution of water, causing many plants to face the alternate situation of drought and water flooding. We studied the growth and physiological response of the wetland plant Artemisia selengensis to drought and rehydration. In this study, Artemisia selengensis seedlings were subjected to 32.89% (SD), 47.36 % (MD), 60.97% (MID), and 87.18 % (CK) field water holding capacity for 70 days, followed by 14 days of rehydration. The results showed that drought inhibited the increase of plant height, basal diameter, and biomass accumulation under SD and MD, but the root shoot ratio (R/S) increased. Drought stress also decreased the content of total chlorophyll (Chl), chlorophyll a (Chl-a), chlorophyll b (Chl-b), and carotenoid (Car). Soluble sugar (SS) and proline (Pro) were accumulated rapidly under drought, and the relative water content (RWC) of leaves was kept at a high level of 80%. After rehydration, the plant height, basal diameter, biomass, and R/S ratio could not be recovered under SD and MD, but these indicators were completely recovered under MID. The RWC, Chl, Chl-a, Chl-b, Car, and osmotic substances were partially or completely recovered. In conclusion, Artemisia selengensis not only can improve drought resistance by increasing the R/S ratio and osmotic substances but also adopt the compensatory mechanism during rehydration. It is predictable that A. selengensis may benefit from possible future aridification of wetlands and expand population distribution.

What happens after drought ends: synthesizing terms and definitions

Drought is intensifying globally with climate change, creating an urgency to understand ecosystem response to drought both during and after these events end to limit loss of ecosystem functioning. The literature is replete with studies of how ecosystems respond during drought, yet there are far fewer studies focused on ecosystem dynamics after drought ends. Furthermore, while the terms used to describe drought can be variable and inconsistent, so can those that describe ecosystem responses following drought. With this review, we sought to evaluate and create clear definitions of the terms that ecologists use to describe post-drought responses. We found that legacy effects, resilience and recovery were used most commonly with respect to post-drought ecosystem responses, but the definitions used to describe these terms were variable. Based on our review of the literature, we propose a framework for generalizing ecosystem responses after drought ends, which we refer to as 'the post-drought period'. We suggest that future papers need to clearly describe characteristics of the imposed drought, and we encourage authors to use the term post-drought period as a general term that encompasses responses after drought ends and use other terms as more specific descriptors of responses during the post-drought period.

Leaf Eco-Physiological Profile and Berries Technological Traits on Potted Vitis vinifera L. cv Pinot Noir Subordinated to Zeolite Treatments under Drought Stress

In Mediterranean areas, extreme weather conditions such as high diurnal temperatures during the growing season could tweak vine physiology and metabolism, affecting grapes’ quality. Moreover, uncertainty in spatial and temporal distribution precipitation is an issue for the water resources of the vineyards, forcing the winemakers to continuously face an increasing water demand in recent decades, which has led them to non-sustainable choices for ambient (i.e., irrigation solutions). The aspiration of this experiment was to explore the effects of zeolite treatments (clinoptilolite type) on Vitis vinifera L. (potted vines) ecophysiology and berry metabolism under two water regimes. The plants were subordinated to two different predawn water potential regimes (0 ≤ ΨPD ≤ −0.4, WWCtrl and −0.4 ≤ ΨPD ≤ −0.9, WSCtrl), both associated with zeolite treatments (WWt and WSt). Gas exchanges, predawn and midday stem water potential, chlorophyll fluorescence, temperature, and relative water content were overseen on leaves at veraison, maturation, and harvest. Technological analyses were performed on the berries. Moreover, data were analyzed with principal component analysis and Pearson’s correlations. This experiment supplies new evidence that zeolite applications could impact both physiological profiles (higher photosynthesis and stomatal conductance) as well as berry skin metabolism (sugar and size) of vines, giving a better skill to counteract low water availability during the season and maintaining a better hydraulic conductivity.

Research on lncRNA related to drought resistance of Shanlan upland rice

Background

Drought has become the major abiotic stress that causes losses in rice yields and consequently is one of the main environmental factors threatening food security. Long non-coding RNA (lncRNA) is known to play an important role in plant response to drought stress, while the mechanisms of competing endogenous RNA (ceRNA) in drought resistance in upland rice have been rarely reported.

Results

In our study, a total of 191 lncRNAs, 2115 mRNAs and 32 miRNAs (microRNAs) were found by strand-specific sequencing and small RNA sequencing to be differentially expressed in drought-stressed rice. Functional analysis of results indicate that they play important roles in hormone signal transduction, chlorophyll synthesis, protein synthesis and other pathways. Construction of a ceRNA network revealed that MSTRG.28732.3 may interact with miR171 in the chlorophyll biosynthesis pathway and affect the ability of plants to withstand drought stress by regulating Os02g0662700, Os02g0663100 and Os06g0105350. The accuracy of the regulatory network was verified by qRT-PCR.

Conclusion

Our results provide a theoretical basis for future studies on the potential function of lncRNA in plant drought resistance, and they provide new genetic resources for drought-resistant rice breeding.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08546-0.

Root/shoot responses to drought and flooding of bahiagrass at reproductive stage depends on genotype ploidy

Severe water stress is responsible for reducing plant growth and reproduction. This study aimed to evaluate the physiological and biochemical mechanisms associated with the tolerance of two genotipes of bahiagrass (Paspalum notatum Flügge) with different ploidy level to water deficit and flooding at the reproductive stage. Photosynthetic performance of diploid and tetraploid plants was not affected by flooding. In contrast, the water deficit decreased stomatal conductance, increased leaf temperature, and resulted in a decrease in the assimilation rate of the two genotypes. Despite the greater activities of antioxidant enzymes, flooded roots accumulated hydrogen peroxide and malondialdehyde. Roots of plants exposed to water deficit maintained an accumulation of biomass similar to that of control plants; however, with higher levels of total phenol content, total soluble sugars and proline. Diploid plants subjected to flooding had more inflorescences, however, the drought reduced the total number of filled florets per plant. Less starch degradation allows the maintenance and recovery of biomass in the tetraploid genotype, which allows it to maintain its reproductive performance even under drought conditions. Overall, the synthesis of osmoprotectants and activation of antioxidant machinery are important strategies in the tolerance of bahiagrass to water stress at the reproductive stage.

Applications of CRISPR/Cas9 as New Strategies for Short Breeding to Drought Gene in Rice

Recent unpredictable climate change is the main reason for the decline in rice yield. In particular, drought stress is a major constraint in reducing yield and quality for rice at rainfed agriculture areas, such as Asia and South America. CRISPR/Cas9 provides an effective solution for gene function study and molecular breeding due to specific editing of targeted genome sequences. In addition, CRISPR/Cas9 application can significantly reduce the time required to develop new cultivars with improved traits compared to conventional complex and time-consuming breeding. Here, drought-induced gene Oryza sativa Senescence-associated protein (OsSAP) was edited by CRISPR/Cas9. To investigate the possible role of OsSAP in drought stress, genome-editing plants were subjected to drought stress until the soil moisture content reached 20%, and the reactive oxygen species (ROS) scavenging efficiency of genome-editing plants were decreased. When the genome-editing plants were subjected to drought stress, survival rate, shoot length, root length, content of chlorophyll number of tiller, and 1,000-grain weight decreased, and more H₂O₂ and O₂ ^- were detected in leaves. In addition, expression levels of several critical stress-related transcription factors were decreased in the OsSAP genome-editing plant. These results suggest that OsSAP function as a positive regulator during drought stress response in rice. We analyzed the expression of OsSAP and Cas9 in T₀ and T₁ plants as well as T₂ seeds. As the course of generation advancement progressed, Cas9 expression remained stable or weakened but the OsSAP expression was continuously removed from the T₀ plant. The coefficient of variation (CV) in both T₁ plants and T₂ seeds was lower than 5%. Overall, our results suggest that CRISPR/Cas9 could be a novel and important tool for efficiently generating specific and inheritable targeted genome editing in rice, with short breeding cycles.

Response of a Diverse European Soybean Collection to "Short Duration" and "Long Duration" Drought Stress

Drought causes significant damage to a high value crop of soybean. Europe has an increasing demand for soybean and its own production is insufficient. Selection and breeding of cultivars adapted to European growth conditions is therefore urgently needed. These new cultivars must have a shorter growing cycle (specifically for adaptation to North-West Europe), high yield potential under European growing conditions, and sufficient drought resistance. We have evaluated the performance of a diverse collection of 359 soybean accessions under drought stress using rain-out shelters for 2 years. The contrasting weather conditions between years and correspondingly the varying plant responses demonstrated that the consequences of drought for an individual accession can vary strongly depending on the characteristics (e.g., duration and intensity) of the drought period. Short duration drought stress, for a period of four to 7 weeks, caused an average reduction of 11% in maximum canopy height (CH), a reduction of 17% in seed number per plant (SN) and a reduction of 16% in seed weight per plant (SW). Long duration drought stress caused an average reduction of 29% in CH, a reduction of 38% in SN and a reduction of 43% in SW. Drought accelerated plant development and caused an earlier cessation of flowering and pod formation. This seemed to help some accessions to better protect the seed yield, under short duration drought stress. Drought resistance for yield-related traits was associated with the maintenance of growth under long duration drought stress. The collection displayed a broad range of variation for canopy wilting and leaf senescence but a very narrow range of variation for crop water stress index (CWSI; derived from canopy temperature data). To the best of our knowledge this is the first study reporting a detailed investigation of the response to drought within a diverse soybean collection relevant for breeding in Europe.

High-value pleiotropic genes for developing multiple stress-tolerant biofortified crops for 21st-century challenges

The agriculture-based livelihood systems that are already vulnerable due to multiple challenges face immediate risk of increased crop failures due to weather vagaries. As breeders and biotechnologists, our strategy is to advance and innovate breeding for weather-proofing crops. Plant stress tolerance is a genetically complex trait. Additionally, crops rarely face a single type of stress in isolation, and it is difficult for plants to deal with multiple stresses simultaneously. One of the most helpful approaches to creating stress-resilient crops is genome editing and trans- or cis-genesis. Out of hundreds of stress-responsive genes, many have been used to impart tolerance against a particular stress factor, while a few used in combination for gene pyramiding against multiple stresses. However, a better approach would be to use multi-role pleiotropic genes that enable plants to adapt to numerous environmental stresses simultaneously. Herein we attempt to integrate and present the scattered information published in the past three decades about these pleiotropic genes for crop improvement and remodeling future cropping systems. Research articles validating functional roles of genes in transgenic plants were used to create groups of multi-role pleiotropic genes that could be candidate genes for developing weather-proof crop varieties. These biotech crop varieties will help create 'high-value farms' to meet the goal of a sustainable increase in global food productivity and stabilize food prices by ensuring a fluctuation-free assured food supply. It could also help create a gene repository through artificial gene synthesis for 'resilient high-value food production' for the 21st century.

Integrated Analysis of Osmotic Stress and Infrared Thermal Imaging for the Selection of Resilient Rice Under Water Scarcity

The climate change scenario has increased the severity and frequency of drought stress, which limits the growth and yield of rice worldwide. There is a dire need to select drought-tolerant rice varieties to sustain crop production under water scarcity. Therefore, the present study effectively combined morpho-physiological and biochemical approaches with the technology of infrared thermal imaging (IRTI) for a reliable selection of drought-tolerant genotypes. Initially, we studied 28 rice genotypes including 26 advance lines and three varieties for water stress tolerance under net house conditions. Three genotypes NIBGE-DT-02, KSK-133, and NIBGE-DT-11 were selected based on the Standard Evaluation System (SES) scoring for drought tolerance. NIBGE-DT-02 showed tolerance to polyethylene glycol (20%) induced osmotic stress indicated by a minimum reduction in seedling length, biomass, chlorophyll content, and increased leaf proline content as compared to susceptible varieties under a hydroponic system. NIBGE-DT-02 was further evaluated for water withholding at varying growth stages, i.e., 30 and 60 days after transplantation (DAT) in pots under net house conditions. NIBGE-DT-02 showed a significantly lower reduction (35.9%) in yield as compared to a susceptible variety (78.06%) under water stress at 60 DAT with concomitant induction of antioxidant enzymes such as peroxidase, catalase, and polyphenol oxidase. A significant increase (45.9%) in proline content, a low increase (7.5%) in plant temperature, along with a low reduction in relative water content (RWC) (5.5%), and membrane stability index (MSI) (9%) were observed under water stress at 60 DAT as compared to the well-watered control. Pearson correlation analysis showed the strong correlation of shoot length with MSI and root length with RWC in rice genotypes at the later growth stage. Furthermore, Regression analysis indicated a negative correlation between plant temperature of NIBGE-DT-02 and proline, RWC, MSI, and peroxidase enzyme under variable water stress conditions. All these responses collectively validated the adaptive response of selected genotypes under water stress during different growth stages. Tolerant genotypes can be used in breeding programs aimed at improving drought tolerance and can expand rice cultivation. Furthermore, this study provides a foundation for future research directed to utilize IRTI as a fast and non-destructive approach for the selection of potent rice genotypes better adapted to water scarcity from wide germplasm collection.

Genome Editing in Crop Plant Research-Alignment of Expectations and Current Developments

The rapid development of genome editing and other new genomic techniques (NGT) has evoked manifold expectations on purposes of the application of these techniques to crop plants. In this study, we identify and align these expectations with current scientific development. We apply a semi-quantitative text analysis approach on political, economic, and scientific opinion papers to disentangle and extract expectations towards the application of NGT-based plants. Using the sustainable development goals (SDG) of the 2030 agenda as categories, we identify contributions to food security or adaptation to climatic changes as the most frequently mentioned expectations, accompanied by the notion of sustainable agriculture and food systems. We then link SDG with relevant plant traits and review existing research and commercial field trials for genome-edited crop plants. For a detailed analysis we pick as representative traits drought tolerance and resistance against fungal pathogens. Diverse genetic setscrews for both traits have been identified, modified, and tested under laboratory conditions, although there are only a few in the field. All in all, NGT-plants that can withstand more than one stressor or different environments are not documented in advanced development states. We further conclude that developing new plants with modified traits will not be sufficient to reach food security or adaption to climatic changes in a short time frame. Further scientific development of sustainable agricultural systems will need to play an important role to tackle SDG challenges, as well.

Advances in 5-Aminolevulinic Acid Priming to Enhance Plant Tolerance to Abiotic Stress

Priming is an adaptive strategy that improves plant defenses against biotic and abiotic stresses. Stimuli from chemicals, abiotic cues, and pathogens can trigger the establishment of priming state. Priming with 5-aminolevulinic acid (ALA), a potential plant growth regulator, can enhance plant tolerance to the subsequent abiotic stresses, including salinity, drought, heat, cold, and UV-B. However, the molecular mechanisms underlying the remarkable effects of ALA priming on plant physiology remain to be elucidated. Here, we summarize recent progress made in the stress tolerance conferred by ALA priming in plants and provide the underlying molecular and physiology mechanisms of this phenomenon. Priming with ALA results in changes at the physiological, transcriptional, metabolic, and epigenetic levels, and enhances photosynthesis and antioxidant capacity, as well as nitrogen assimilation, which in turn increases the resistance of abiotic stresses. However, the signaling pathway of ALA, including receptors as well as key components, is currently unknown, which hinders the deeper understanding of the defense priming caused by ALA. In the future, there is an urgent need to reveal the molecular mechanisms by which ALA regulates plant development and enhances plant defense with the help of forward genetics, multi-omics technologies, as well as genome editing technology.

Biochemical responses of hairgrass (Deschampsia caespitosa) to hydrological change

Plant growth and development are closely related to water availability. Water deficit and water excess are detrimental to plants, causing a series of damage to plant morphology, physiological and biochemical processes. In the long evolutionary process, plants have evolved an array of complex mechanisms to combat against stressful conditions. In the present study, the duration-dependent changes in ascorbate (AsA) and glutathione (GSH) contents and activities of enzymes involved in the AsA-GSH cycle in hairgrass (Deschampsia caespitosa) in response to water stress was investigated in a pot trial using a complete random block design. The treatments were as follows: (1) heavily waterlogging, (2) moderate waterlogging, (3) light waterlogging, (4) light drought, (5) moderate drought, (6) heavily drought, and (7) a control (CK) with plant be maintained at optimum water availability. The hairgrass plants were subjected to waterlogging or drought for 7, 14, 21 and 28 days and data were measured following treatment. Results revealed that hairgrass subjected to water stress can stimulate enzymatic activities of ascorbate peroxidase (APX), glutathione peroxidase (GPX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and L-galactono-1, 4-lactone dehydrogenase (GalLDH), switched on the ascorbate-glutathione (AsA-GSH) cycle and the L-galactose synthesis, up-regulated the contents of AsA and GSH, and maintained higher ratios of ascorbate to dehydroascorbate (AsA/DHA) and reduced glutathione to oxidized glutathione (GSH/GSSG) to alleviate potential oxidative damage. However, the light waterlogging did not induce hairgrass under stress to switch on the AsA-GSH pathway. In general, the critic substances and enzyme activities in AsA-GSH metabolic pathway increased as the increase of water stress intensity. As the increase of exposure duration, the critic antioxidant substances content and enzyme activities increased first and then maintained a relatively stable higher level. Our findings provide comprehensive information on biochemical responses of hairgrass to hydrological change, which would be a major step for accelerating ecological restoration of degradation alpine marshes in the Qinghai-Tibetan Plateau.

Morpho-Anatomical Traits and Soluble Sugar Concentration Largely Explain the Responses of Three Deciduous Tree Species to Progressive Water Stress

A better understanding of plant drought responses is essential to improve plant water use efficiency, productivity, and resilience to ever-changing climatic conditions. Here, we investigated the growth, morpho-anatomical, physiological, and biochemical responses of Quercus acutissima Carruth., Quercus serrata Murray, and Betula schmidtii Regel to progressive water-stress. Seedlings were subjected to well-watered (WW) and water-stressed (WS) conditions while regularly monitoring the soil volumetric water content, stem diameter (SD), height, biomass, stomatal conductance (gs), intercellular CO2 concentration (Ci), and leaf relative water content (RWC). We also investigated the variation in stomatal pore (SP) area, specific leaf area (SLA), root xylem vessel diameter (VD), and total soluble sugar (TSS) concentration between treatments. After 2 months, WS significantly suppressed SD growth of Q. acutissima and B. schmidtii but had no impact on Q. serrata. Total biomass significantly declined at WS-treated seedlings in all species. WS resulted in a smaller SLA than WW in all species. The SP of WS-treated seedlings of Q. acutissima and B. schmidtii significantly decreased, whereas it increased significantly with time in Q. serrata. Larger vessels (i.e., >100 to ≤ 130) were more frequent at WS for Q. acutissima and B. schmidtii, whereas smaller vessels (i.e., >40 to ≤ 90) were more frequent at WS than at WW for Q. serrata after 8 weeks. Tylosis was more frequent at WS than WW for Q. serrata and B. schmidtii at eighth week. WS seedlings showed lower gs, Ci, and RWC compared with WW-treated ones in Q. acutissima and B. schmidtii. TSS concentration was also higher at WS-treated seedlings in two Quercus species. Overall, principal component analysis (PCA) showed that SLA and SP are associated with WS seedlings of Q. serrata and B. schmidtii and the tylosis frequency, TSS, and VD are associated with WS seedlings of Q. acutissima. Therefore, water-stressed plants from all species responded positively to water stress with increasing experimental duration and stress intensity, and that is largely explained by morpho-anatomical traits and soluble sugar concentration. The present study should enhance our understanding of drought-induced tree growth and short-term tree-seedling responses to drought.

Toxic effects of 2,4,4'- trichlorobiphenyl (PCB-28) on growth, photosynthesis characteristics and antioxidant defense system of Lemna minor L

Polychlorinated biphenyls (PCBs) are a common category of persistent man-made organic pollutants that are widespread in the ambient environment. Although Lemna minor L. is an extensively applied plant for aquatic remediation in ecotoxicology research worldwide, little is known regarding its responses to the potentially toxic effects of PCBs. For this study, a 14-day dissolved exposure was conducted to explore the effects of 2,4,4'- trichlorobiphenyl (PCB-28) on the growth, photosynthesis characteristics and antioxidant defense system of L. minor plants. We found that 100 and 200 μg/L of PCB-28 decreased the fresh weight, chlorophyll and protein content, and activities of superoxide dismutase, peroxidase, glutathione S-transferase, and nitroreductase, whereas plasma membrane permeability, and the malondialdehyde and reactive oxygen species concentrations were increased. However, it was observed that 5 and 20 μg/L of PCB-28 had no significant effects on these physiological indices. The ultra-structure of chloroplast demonstrated that 100 and 200 μg/L PCB-28 severely damaged the chloroplast structures. Moreover, correlation analysis revealed that the content of reactive oxygen species had negative correlations with the fresh weight, chlorophyll and protein content, as well as the activities of superoxide dismutase, peroxidase, glutathione S-transferase, and nitroreductase, but had positive correlations with the malondialdehyde content and plasma membrane permeability. This work provides valuable data toward elucidating the physiology and biochemistry of PCBs induced phytotoxicity.

Remote sensing depicts riparian vegetation responses to water stress in a humid Atlantic region

Riparian areas in the Cantabrian Atlantic ecoregion (northwest Portugal) play a key role in soil formation and conservation, regulation of nutrient and water cycle, creation of landscape aesthetic value and the preservation of biodiversity. The maintenance of their ecological integrity is crucial given the ever increase in multiple anthropogenic (water demand and agriculture) and climatic pressures (droughts and extreme events). We developed a transferable remote sensing approach, taking advantage of the latest freely available technologies (Sentinel-2 and Copernicus Land products), to detect intra-annual and inter-annual changes in riparian vegetation productivity at the river basin scale related to water stress. This study has used the normalized difference vegetation index (NDVI) to investigate riparian vegetation productivity dynamics on three different vegetation types (coniferous, broadleaved and grassland) over the past 5 years (2015-2019). Our results indicated that inter-annual seasonality differed between drier (2017) and wetter (2016) years. We found that intra-annual dynamics of NDVI were influenced by the longitudinal river zonation. Our model ranked first (r²m = 0.73) showed that the productivity of riparian vegetation during the dry season was positively influenced by annual rainfall and by the type of riparian vegetation. The emergent long lags between climatic variation and riparian plant productivity provides opportunities to forecast early warnings of climatically-driven impacts. In addition, the different average productivity levels among vegetation types should be considered when assessing climatic impacts on riparian vegetation. Future applications of Sentinel 2 products could seek to distinguish riparian areas that are likely to be more vulnerable to changes in the annual water balance from those that are more resistant under longer-term changes in climate.

Post-Anthesis Mobilization of Stem Assimilates in Wheat under Induced Stress

Stem reserves in grain crops are considered important in grain filling under post-anthesis stress in the absence/low availability of photosynthetic assimilates. Considerable variation is present among genotypes for stem reserve translocation in wheat. Therefore, this study aimed to exploit the phenotypic variation for stem reserve translocation in wheat under control and chemically induced stress conditions. The phenotypic variation among six parents and their corresponding direct cross combinations was evaluated under induced stress conditions. The results signify the presence of considerable variation between treatments, genotypes, and treatment-genotype interactions. The parent LLR-20 depicted the highest translocation of dry matter and contribution of post-anthesis assimilates under induced-stress conditions. Similarly, cross combinations Nacozari × LLR22, Nacozari × LLR 20, Nacozari × Parula, Nacozari × LLR 21, LLR 22 × LLR 21, and LLR 20 × LLR 21 showed higher source-sink accumulation under induced-stress conditions. The selected parents and cross combinations can be further utilized in the breeding program to strengthen the genetic basis for stress tolerance in wheat.

Genomic Analysis of Serratia plymuthica MBSA-MJ1: A Plant Growth Promoting Rhizobacteria That Improves Water Stress Tolerance in Greenhouse Ornamentals

Water stress decreases the health and quality of horticulture crops by inhibiting photosynthesis, transpiration, and nutrient uptake. Application of plant growth promoting rhizobacteria (PGPR) can increase the growth, stress tolerance, and overall quality of field and greenhouse grown crops subjected to water stress. Here, we evaluated Serratia plymuthica MBSA-MJ1 for its ability to increase plant growth and quality of Petunia × hybrida (petunia), Impatiens walleriana (impatiens), and Viola × wittrockiana (pansy) plants recovering from severe water stress. Plants were treated weekly with inoculum of MBSA-MJ1, and plant growth and quality were evaluated 2 weeks after recovery from water stress. Application of S. plymuthica MBSA-MJ1 increased the visual quality and shoot biomass of petunia and impatiens and increased the flower number of petunia after recovery from water stress. In addition, in vitro characterizations showed that MBSA-MJ1 is a motile bacterium with moderate levels of antibiotic resistance that can withstand osmotic stress. Further, comprehensive genomic analyses identified genes putatively involved in bacterial osmotic and oxidative stress responses and the synthesis of osmoprotectants and vitamins that could potentially be involved in increasing plant water stress tolerance. This work provides a better understanding of potential mechanisms involved in beneficial plant-microbe interactions under abiotic stress using a novel S. plymuthica strain as a model.

Genetic Analysis of Root-to-Shoot Signaling and Rootstock-Mediated Tolerance to Water Deficit in Tomato

Developing drought-tolerant crops is an important strategy to mitigate climate change impacts. Modulating root system function provides opportunities to improve crop yield under biotic and abiotic stresses. With this aim, a commercial hybrid tomato variety was grafted on a genotyped population of 123 recombinant inbred lines (RILs) derived from Solanum pimpinellifolium, and compared with self- and non-grafted controls, under contrasting watering treatments (100% vs. 70% of crop evapotranspiration). Drought tolerance was genetically analyzed for vegetative and flowering traits, and root xylem sap phytohormone and nutrient composition. Under water deficit, around 25% of RILs conferred larger total shoot dry weight than controls. Reproductive and vegetative traits under water deficit were highly and positively correlated to the shoot water content. This association was genetically supported by linkage of quantitative trait loci (QTL) controlling these traits within four genomic regions. From a total of 83 significant QTLs, most were irrigation-regime specific. The gene contents of 8 out of 12 genomic regions containing 46 QTLs were found significantly enriched at certain GO terms and some candidate genes from diverse gene families were identified. Thus, grafting commercial varieties onto selected rootstocks derived from S. pimpinellifolium provides a viable strategy to enhance drought tolerance in tomato.

Seed Priming with Endophytic Bacillus subtilis Modulates Physiological Responses of Two Different Triticum aestivum L. Cultivars under Drought Stress

The protective effects against drought stress of the endophytic bacterium Bacillus subtilis 10-4 were measured by studying the priming response in two wheat (Triticum aestivum L.)—Ekada70 (E70) and Salavat Yulaev (SY)—lines, tolerant and susceptible to drought, respectively. B. subtilis 10-4 improved germination and growth parameters under normal conditions in both cultivars with the most pronounced effect observed in cv. E70. Under drought conditions, B. subtilis 10-4 significantly ameliorated the negative impact of stress on germination and growth of cv. E70, but had no protective effect on cv. SY. B. subtilis 10-4 induced an increase in the levels of photosynthetic chlorophyll (Chl) a, Chl b, and carotenoids (Car) in the leaves of cv. E70, both under normal and drought conditions. In cv. SY plants, bacterial inoculation decreased the contents of Chl a, Chl b, and Car under normal conditions, but pigment content were almost recovered under drought stress. B. subtilis 10-4 increased water holding capacity (WHC) of cv. E70 (but did not affect this parameter in cv. SY) and prevented the stress-induced decline in WHC in both cultivars. Notably, B. subtilis 10-4 increased endogenous salicylic acid (SA) concentration in both cultivars, especially in cv. E70. Moreover, B. subtilis 10-4 reduced drought-induced endogenous SA accumulation, which was correlated with the influence of endophyte on growth, indicating a possible involvement of endogenous SA in the implementation of B. subtilis-mediated effects in both cultivars. Overall, B. subtilis 10-4 inoculation was found to increase drought tolerance in seedlings of both cultivars, as evidenced by decreased lipid peroxidation, proline content, and electrolyte leakage from tissues of wheat seedlings primed with B. subtilis 10-4 under drought conditions.