Response Mechanism of Plants to Drought Stress

The influence of hydrometeorological factors on tree growth in mountainous watersheds of the Qilian mountains in China

To examine the influence of hydrometeorological factors on forest ecosystems, this study focused on the growth response of the Qinghai spruce (Picea crassifolia Kom.) to hydrometeorological factors, such as soil moisture, relative humidity, vapor pressure deficit, temperature, precipitation and wind speed, in a mountainous watershed. The Dayekou watershed, which is situated in the Qilian Mountains, was used to study the increase in stem diameter based on the daily-monthly fluctuations, cumulative growth, and stem diameter expansion in response to hydrometeorological parameters. The stem diameters of six dominant trees (categorized in three classes) were recorded using the Dendrometer DRL26 tree stem diameter growth monitor and combined with hydrometeorological monitoring data. The influence of hydrometeorological factors on stem diameter growth was statistically analyzed. The results indicated that the daily fluctuation of stem diameter growth of Qinghai spruce exhibited a parabolic pattern, which could be divided into three stages: contraction (from 10:00 to 21:00), expanding (from 21:00 to 5:00 the following day), and growth (from 5:00 to 11:00 the following day). The monthly stem diameter growth also exhibited a trend, which could be divided into three stages: initial growth (May), rapid expansion (June-July) and slow growth (August-October). At a 40 cm depth, soil water content, air humidity, and atmospheric pressure all showed positive correlations with stem diameter growth (P < 0.01), while saturated water pressure differential, wind speed, and photosynthetically active radiation showed negative correlations (P < 0.01). Our results demonstrated that relative air humidity, soil moisture, air temperature, and atmospheric pressure at a 40 cm depth had the highest impact on the Qinghai spruce's growth in stem diameter. Changes in these hydrometeorological factors due to potential climate change will affect forest growth in the future.

Metabolomic responses of wheat grains to olive mill wastewater and drought stress treatments

The present research aimed to assess the metabolomic responses of wheat to olive mill wastewater (OMWW) and drought stress treatments. Wheat plants were cultivated under controlled conditions with the following treatments: control (75% field capacity, FC), OMWW (75 ml L-1), drought stress (40% FC, applied 30 days after sowing), and a combined treatment of OMWW and drought stress. Drought stress alone reduced grain yield by 67%, while the OMWW-treated plants resulted in a 29% reduction under stress relative to the control. OMWW application improved soil properties, enhancing organic matter and nutrient levels. Wheat grains from OMWW-treated plants exhibited higher sugar content and related enzyme activities, indicating improved metabolism, with significant increases in starch, fructose, and glucose levels alongside stable invertase and sucrose phosphate synthase activities. The study also noted substantial changes in amino acids, fatty acids, and phenolic acids in plants subjected to OMWW and drought stress. These modifications indicate OMWW's capability to influence vital biochemical pathways and boost antioxidant capacities in wheat. In conclusion, OMWW proves to be an effective soil amendment that mitigates drought stress and contributes to the production of nutrient-rich, resilient wheat, underscoring its potential as a sustainable agricultural practice in water-scarce areas.

Physiological and transcriptomic evaluation of salt tolerance in Egyptian tomato landraces at the seedling stage

BACKGROUND

Tomato (Solanum lycopersicum) is an essential vegetable crop with a wonder fruit used as a good source for human food and health-promoting worldwide. Drought, water salinity, and soil salinity are the commonly known environmental factors that can limit the productivity of various crops between 30% and 50% of final yields. To counter these previous effects, scientists have focused their research on studying how tomato plants at different development stages behave under various saline environmental conditions.

RESULTS

In this study, we used bioinformatics analysis tools to identify the putative genes that are related to salt tolerance in tomatoes based on the percentage of similarity with salt tolerance genes from soybean, rice, wheat, barley, Arabidopsis and other plants. Within these, 254 genes were identified as putatively involved in salt tolerance in tomatoes. Furthermore, the putative tissue expression pattern of these genes under different times from various abiotic stresses was analyzed. Also, the Expression Cube tool was used to predict the putative expression of our target genes at various tissues in fruit development. Then we study the effect of various concentrations from Sodium chloride (NaCl) at different times on the behavior of two Egyptian tomato genotypes through estimate the physiological and metabolic changes such as; soluble sugars, glucose, fructose, total chlorophyll, chlorophyll a, and chlorophyll b contents. Moreover, the relative expression levels of salt tolerance genes in tomato SlAAO3, SlABCG22, SlABF3, SlALDH22A1, SlAPX2, SlAVP1, SlCYP175A, SlNHO1, SlP5CS, SlPIP1, SlTPS1 and SlUGE-1, were investigated in both tomato genotypes under various concentrations from salt tolerance in comparison with the wild-type plants.

CONCLUSIONS

At the end, bioinformatics tools help in the determination of novel genes in tomato that related with tomato plant response to salt stresses. Finally, the findings reported in this article are helpful to assess the two Egyptian tomato genotypes and for understanding the roles of candidate genes for tolerance to saline conditions. And offering insights into future using these genes for generating stress-resistant tomatoes and improving agricultural sustainability.

Identification of key genes and signaling pathways in coconut (Cocos nucifera L.) under drought stress via comparative transcriptome analysis

BACKGROUND

Drought stress has become a pervasive environmental challenge, significantly impacting all stages of plant growth and development under changing climatic conditions worldwide. In coconut, drought stress critically impairs reproductive development, notably reducing the quality of pollen and gametes during fertilization. Therefore, the seedlings of the aromatic coconut variety were subjected to drought stress for varying durations: control (no stress), 7 days, 14 days, and 21 days to find the potential molecular mechanisms and genes related to coconut drought tolerance through transcriptomic analysis. Our study may provide a theoretical basis for investigations into drought stress tolerance that will be useful for further coconut improvement.

RESULTS

We assessed antioxidant enzyme activity and conducted comparative transcriptome analyses of aromatic coconut under different drought conditions (7, 14, and 21 days). Our findings revealed significant rises in superoxide dismutase (SOD), peroxidase (POD) activities and proline (Pro) content across all drought periods compared to control plants, suggesting that these enzymes play a crucial role in the adaptive response of coconuts to drought stress. RNA-seq data identified 280, 729, and 6,698 differentially expressed genes (DEGs) at 7, 14, and 21 days, respectively. Principal Component Analysis (PCA) revealed that coconut samples were scattered and separated across different treatment points, suggesting the presence of differentially expressed genes (DEGs), particularly in the 21 day drought treatment (GH21d). KEGG pathway analysis indicated that DEGs were significantly enriched in pathways related to plant-pathogen interaction, plant hormone signaling, and mitogen-activated protein kinase (MAPK) signaling. Functional annotation of these DEGs revealed key candidate genes involved in several hormone signaling pathways, including abscisic acid (ABA), jasmonates (JA), auxin (AUX), brassinosteroids (BR), ethylene (ET), and gibberellin (GA), along with MAPK pathway which may regulate plant adaptation to drought stress through processes such as plant growth, cell division, stomatal closure, root growth, and stomatal development. This study provides valuable insights into the genetic and molecular basis of drought tolerance in coconuts, paving the way for the improvement of drought-tolerant coconut varieties.

CONCLUSIONS

Under drought stress, the expression of genes related to plant growth, stomatal closure, cell division, stress response, adaptation, and stomatal development appears to play a critical role in drought tolerance in coconut. Our results revealed that multiple genes may contribute to the drought tolerance mechanism in coconut through various hormone signaling pathways, including ABA, JA, auxin, BR, GA, and ethylene. These findings offer new insights into the key molecular mechanisms governing drought tolerance in aromatic coconut. Furthermore, the candidate genes and pathways identified in this study could be valuable for developing strategies to enhance drought tolerance in coconut plants.

CLINICAL TRIAL NUMBER

Not Applicable.

Enhancing water deficit tolerance in canola (Brassica napus L.) through the synergistic application of nano-silicon and sulfur

Water deficit stress is a critical constraint on global crop productivity, particularly in arid and semi-arid regions, where it severely compromises plant growth, yield, and nutritional quality. Sustainable strategies to enhance plant resilience under such conditions are urgently needed. Nano-silicon (Si-NPs) and sulfur (S) have emerged as promising amendments for mitigating abiotic stress, but their synergistic potential in alleviating water deficit stress in oilseed crops like canola (Brassica napus L.) remains underexplored. This study investigated the combined effects of Si-NPs (0, 100, 200, and 300 mg kg⁻1) and sulfur (0, 75, and 150 mg S kg⁻1) on the morphological, physiological, and nutritional responses of canola under three water deficit levels (0.8, 0.6, and 0.4 field capacity). Results demonstrated that water deficit stress significantly reduced photosynthetic efficiency, biomass accumulation, and yield components. However, Si-NPs and S application counteracted these adverse effects. Specifically, 100 mg Si-NPs kg⁻1 increased shoot and root weights by 19.3% and 22.9%, respectively, compared to the control. The most effective treatment-200 mg Si-NPs kg⁻1 combined with 75 mg S kg⁻1-enhanced chlorophyll (1.76 mg g⁻1 FW), carotenoids (0.51 mg g⁻1 FW), phosphorus uptake (0.85%), and silicon accumulation in shoots (4.3%), while reducing lipid peroxidation (malondialdehyde: 23.53 µg g⁻1 FW). These findings highlight the synergistic role of Si-NPs and S in improving drought resilience by enhancing photosynthetic capacity, nutrient homeostasis, and oxidative stress mitigation. This study provides actionable insights for integrating nano-enabled and sustainable nutrient management practices to bolster crop productivity in water-scarce agroecosystems. Future research should validate these results under field conditions and elucidate the molecular mechanisms driving these stress-adaptive responses.

Responses of the physiological characteristics and endophytic bacteria of Urtica cannabina to simulated drought stress

Drought is widespread worldwide and has a negative impact on the growth and development of plants. As a kind of high-quality feed resource with great potential, nettle is also facing the severe test of drought stress. At present, more and more attention has been paid to the strategy of microbial drought resistance, which is expected to bring a turning point for alleviating the survival pressure of nettles under drought. In this study, nettle plants (Urtica cannabina) were obtained from a temperate desert steppe in the Tianshan Mountains, Xinjiang, China. Polyethylene glycol (PEG) was used to simulate a high/low gradient of drought stress. The results indicate that under mild drought stress, drought damage in nettle is reduced through proline (Pro), soluble protein (SP) and soluble sugar (SS) accumulation and increased superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activity. At the same time, the net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) of nettle leaves decreased to resist mild drought stress. However, if the drought is too severe or too prolonged, nettle plants wilt considerably. Under drought stress, the community structure of endophytic bacteria in the nettle plants changed, and the relative abundances of Pseudomonas, Halomonas, Nesterenkonia and Aliihoeflea decreased, while that of Romboutsia increased. Halomonas, Romboutsia, Sphingomonas, Bifidobacterium and Pseudomonas are highly correlated with the physiological characteristics and chlorophyll content of nettle, among which Pseudomonas is the key factor of endophytic bacterial in nettle under drought stress. In this study, the changes of physiological characteristics and endophytic bacterial community of Urtica cannabina under different degrees of drought stress provided a preliminary foundation for field experiments under natural drought conditions and the verification of drought-related microorganisms.

Transcription factor AtWRKY43 enhances drought tolerance by positively regulating the expression of AtSWEET5

Drought exerts negative effects on plant growth and crop productivity. Sugars play a crucial role in enhancing drought tolerance by acting as osmoprotectants. Sugar transporters AtSWEETs are essential for maintaining sugar distribution equilibrium and facilitating effective adaptation to drought stress. In the study, transcriptomic analysis showed that WRKY transcription factor AtWRKY43 plays a key role in modulating gene expression patterns that enhance the plant's ability to accumulate sugars, which in turn supports osmotic adjustment and overall drought stress resilience. AtWRKY43 was identified as a promoter of sugar accumulation through its induction of transcriptional expression of AtSWEET5, thereby influencing drought tolerance. We observed an upregulation in the expression of the gene AtSWEET5 during drought stress. The mutant atsweet5 exhibited increased sensitivity to drought compared to Col-0, possibly due to increased H2O2 content and disrupted sugar homeostasis. Our research highlights the critical roles of AtWRKY43 and AtSWEET5 in modulating drought stress, providing new gene targets for developing crop varieties with enhanced sugar content. Therefore, it is imperative to understand the impact of drought stresses on sugar transport and transporters at both genetic and molecular levels in order to maintain optimal sugar balance in plants experiencing drought stress.

Transcriptome Analysis Reveals the Role of Plant Hormone Signal Transduction Pathways in the Drought Stress Response of Hemerocallis middendorffii

Drought stress is a significant environmental factor that can impede plant growth and ornamental quality. Hemerocallis middendorffii, a drought-tolerant garden plant, has attracted attention for its ornamental value and application prospects. To investigate the molecular mechanism of drought stress resistance of H. middendorffii, this study employed 20% polyethylene glycol (PEG) 6000 to simulate drought stress. Leaves and roots of H. middendorfii were subjected to 24 h treatment and followed by transcriptome sequencing. Analysis revealed 8796 and 3401 differentially expressed genes (DEGs) in leaves and roots. The major biological processes and key molecular pathways activated under drought stress in H. middendorffii were revealed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. The focus of this analysis was on the gene expression changes within plant hormone signal transduction pathway. Additionally, drought-associated transcription factor families such as AP2/ERF, WRKY, MYB, bHLH, NAC, and bZIP were identified among DEGs. Furthermore, potential regulatory relationships of the above transcription factors (TFs) with functional genes in the abscisic acid (ABA) and jasmonic acid (JA) signalling pathways were analysed using correlation network prediction. This research establishes the groundwork for subsequent exploration of drought-responsive gene expression and regulatory patterns in H. middendorfii and provides an importance for the systematic study of its drought-resistant molecular mechanism.

Shaker K+ channel NKT3A enhances potassium uptake and transport in tobacco (Nicotiana tabacum L.) seedlings under low potassium stress

One of the nutrients that is necessary for plant growth and development is potassium (K+). The uneven production and distribution of global potassium resources significantly challenge crop yields and quality. A moderate increase in the potassium content within plants can enhance both crop yield and quality. This study identifies the Shaker K+ channel NKT3A within the model crop, tobacco. The yeast heterologous expression system demonstrated its capability for K+ inward transportation. GUS staining and RT-qPCR analyses of the constructed promoter materials revealed NKT3A's activity during the tobacco seedling stage. Expression levels are higher in the leaf and stems, with low potassium levels inducing upregulation of its expression, also observed in roots. Gene editing technology was employed to construct overexpression and knockout mutants, with subsequent measurement of their phenotypes. Results indicate that NKT3A expression enhances facilitates potassium absorption and transport in tobacco seedlings under low potassium conditions. For the first time, this article identifies the Shaker potassium channel gene NKT3A, which functions as an inward rectifier K+ channel in tobacco. It elucidates the gene's role in regulating potassium distribution under low potassium conditions, thereby deepening our understanding of plant responses in such environments and offering a potential target for enhancing crop potassium use efficiency.

Role of Metal-Based Nanoparticles in Capsicum spp. Plants

Agriculture is a core activity in human civilization, constantly facing challenges with the main objective of increasing crop production; to solve this, different strategies and technologies have been used. Currently, metal-based nanoparticles (MNPs) have great potential to be used as agricultural inputs to mitigate the negative effects on crops caused by different stresses. However, studies about their impact on plants and agroecosystems require a comprehensive understanding of their effects. Chili pepper (Capsicum spp.) is a crop of global economic importance that could benefit from the use of MNPs in order to increase its production. The effects of MNPs depend on factors such as their composition, morphology, size, concentration, and application method. Both in vitro and greenhouse studies have demonstrated improvements in plant growth, response to abiotic stresses, and the induction of resistance to different pathogens. However, results vary considerably from one study to another, probably due to heterogeneity in synthesis, characterization, and application methods. This review examines recent findings about the effects of MNPs on chili pepper crops, focusing on growth, development, bioaccumulation, and response to biotic and abiotic stresses.

Enhancing drought resistance in Dracocephalum moldavica L. through mycorrhizal fungal inoculation and melatonin foliar application

This research focused on improving the drought tolerance of Dracocephalum moldavica, a plant vulnerable to water stress, by exploring the combined effects of melatonin spray and mycorrhizal fungus Glomus intraradices inoculation. The experiment was designed as a factorial randomized study to evaluate the plant's morphological, physiological, and phytochemical responses under different drought conditions (100%, 75%, and 50% field capacity). The findings revealed that the combination of melatonin and mycorrhizal inoculation significantly improved the morphological traits of Moldavian balm under drought conditions. Under severe drought (50% field capacity), chlorophyll a and b levels increased by 26.3% and 35.5%, respectively, when both treatments were applied. Stress indicators, including electrolyte leakage and malondialdehyde content, were substantially reduced with the simultaneous application of melatonin and mycorrhizal symbiosis, indicating decreased cellular damage. Moreover, the combined treatment resulted in the highest activities of the antioxidant enzymes catalase and peroxidase, suggesting that these treatments bolster the plant's oxidative stress defense mechanisms. Additionally, drought stress alone led to an increase in secondary metabolites like phenolic and flavonoid compounds, which were further amplified by the treatments. The study also observed significant alterations in the essential oil composition of the plant. Drought stress increased the levels of α-pinene, 1,8-cineole, and borneol, and these increases were even more pronounced with the combined treatments. Conversely, the levels of geraniol and geranial decreased under drought stress and further with treatment. Overall, this research demonstrates that melatonin and Glomus intraradices inoculation can effectively enhance drought tolerance in Dracocephalum moldavica by improving its physiological characteristics and biochemical composition.

Interaction of beneficial microorganisms and phenolic compounds in hydroponically cultivated tomato plants

The combined effects of applying extracts derived from plant debris and biostimulant microorganisms have not been thoroughly investigated. Furthermore, the interaction between these components and plants remains poorly understood. Utilizing the commercial cherry tomato (Solanum lycopersicum cv. Unidarkwin) as a study model, we conducted a hydroponic experiment in a controlled growth chamber to assess the impact of foliar application of phenolic compounds extracted from Vitis vinifera leaves, combined with the inoculation of Trichoderma harzianum or Bacillus velezensis via roots. Plant growth, gas exchange and root architecture were measured and mineral nutrients, chlorophylls and phenolic compounds were analysed. The results showed that phenolic compounds produced an increase in root fresh weight, by the enhanced root length. This could be related to the improved transpiration rate, sub-stomatal CO2 concentration, phosphorus and iron concentration in the roots. A positive effect was also found by B. velezensis application in root length development that could be related to the increase in hydraulic conductance. However, T. harzianum inoculation only showed higher root diameter and volume in combination to phenolic application, but with no effect on growth. The absence of caffeic acid and sinapic acid in the Hoagland solution used in the B. velezensis treatments and of chlorogenic acid in all treatments with added microorganisms suggested their metabolization. Therefore, our findings establish that the phenolic exudation could regulate the interaction of microorganism with plants resulting in beneficial physiological changes.

Unraveling the role of κ-carrageenan on the combined effect of drought and chromium stress in wheat (Triticum aestivium L.)

Drought (D) and chromium (Cr) stress co-occur in agricultural fields due to the accumulation of excessive Cr in soils from industrial pollution and increasing frequency of water scarcity. Carrageenan (Car), a compound extracted from red seaweed, is an emerging biostimulant with multifaceted roles in plants. This study investigated the role of exogenous Car in mediating tolerance to D-, Cr-, and DCr-stress in wheat seedlings, aiming to elucidate the potential of Car in mitigating toxicity and promoting plant resilience. Wheat seedlings exposed to DCr-stress exhibited reduced growth and biomass production, along with elevated levels of reactive oxygen, carbonyl, and nitrogen species. Moreover, D-stress exacerbated Cr-toxicity, as demonstrated by principal component analysis (PCA), which showed a strong positive correlation between DCr-stress and stress marker parameters. This suggests that DCr-stress resulted in higher Cr uptake and increased oxidative damage compared to individual D- or Cr-stress, making DCr-stress more detrimental than either stress applied alone. However, Car priming ameliorated the toxic effects of DCr-stress and promoted the growth performance of DCr-stressed wheat seedlings. In PCA, the positive correlation of D + Car, Cr + Car, and DCr + Car treatments with growth and plant defense-related parameters suggests that Car-mediated improvement in stress tolerance can be attributed to reduced accumulation of toxic Cr, increased levels of total free amino acids and soluble sugars, enhanced antioxidant enzyme activity, elevated non-enzymatic antioxidant levels, higher phenolic and flavonoid content, and improved metal chelation and detoxification. Our results indicated Car is a potential and cost-effective biostimulant for managing D-, Cr-, or DCr-stress in wheat.

Enhancing drought tolerance in Pisum sativum and Vicia faba through interspecific interactions with a mixed inoculum of Rhizobium laguerreae and non-host beneficial rhizobacteria

Introduction

Harnessing plant growth-promoting rhizobia presents a sustainable and cost-effective method to enhance crop performance, particularly under drought stress. This study evaluates the variability of plant growth-promoting (PGP) traits among three strains of Rhizobium laguerreae LMR575, LMR571, and LMR655, and two native PGP strains Bacillus LMR698 and Enterobacter aerogenes LMR696. The primary objective was to assess the host range specificity of these strains and their effectiveness in improving drought tolerance in three legume species: Pisum sativum, Vicia faba, and Phaseolus vulgaris.

Methods

In-vitro experiments were conducted to assess the PGP traits of the selected strains, including phosphate solubilization, indole-3-acetic acid (IAA) production, and siderophore production. Greenhouse trials were also performed using a mixed inoculum of performing strains to evaluate their effects on plant physiological and biochemical traits under drought conditions.

Results

Significant variability in PGP traits was observed among the strains. R. laguerreae LMR655 exhibited the highest phosphate solubilization (113.85 mg mL-1 PO4 2-), while R. laguerreae LMR571 produced the highest IAA concentration (25.37 mg mL-1). E. aerogenes LMR696 demonstrated 82% siderophore production. Symbiotic interactions varied, with R. laguerreae LMR571 and LMR655 forming associations with P. sativum and V. faba, but none establishing compatibility with P. vulgaris. Greenhouse experiments showed that a mixed inoculum of R. laguerreae LMR571, LMR655, and E. aerogenes LMR696 significantly improved proline, total soluble sugars, proteins, and chlorophyll content under drought stress, with V. faba showing the strongest response.

Discussion

These findings highlight the importance of strain selection based on host specificity and PGP potential. The enhanced drought tolerance observed suggests that tailored microbial inoculants can improve legume resilience in water-limited environments. This study provides valuable insights for optimizing bioinoculant formulations to enhance crop performance under drought stress.

Reductions in mesophyll conductance under drought stress are influenced by increases in cell wall chelator-soluble pectin content and denser microfibril alignment in cotton

Plants commonly undergo leaf morphoanatomy and composition modifications to cope with drought stress, and these tend to reduce mesophyll conductance to CO2 diffusion (gm), a key limitation to photosynthesis. The cell wall appears to play a crucial role in this reduction, yet the specific effect of cell wall component on gm and the underlying regulatory mechanisms of cell wall thickness (Tcw) variation are not well understood. In this study, we subjected cotton plants to varying levels of water deficit to investigate the impact of leaf cell wall component and the arrangement patterns of microfibrils within cell walls on Tcw and leaf gas exchange. Drought stress resulted in a significant thickening of cell walls and a decrease in gm. Concurrently, drought stress increased the content of chelator-soluble pectin and cellulose while reducing hemicellulose content. The alignment of cellulose microfibrils became more parallel and their diameter increased under drought conditions, suggesting a decrease in cell wall effective porosity which coincides with the observed reduction in gm. This research demonstrates that reduced gm typically observed under drought stress is related not only to thickened cell walls, but also to ultra-anatomical and compositional variations. Specifically, increases in cellulose content, diameter, and a highly aligned arrangement of cellulose microfibrils collectively contributed to an increase in Tcw, which, together with increases in chelator-soluble pectin content, resulted in an increased cell wall resistance to CO2 diffusion.

NIN-like proteins NLP8 negatively regulate drought resistance in Arabidopsis by regulating the expression level of PUB23

KEY MESSAGE

NLP8-mediated transcriptional activation of PUB23 expression negatively regulates drought resistance. Drought severely affects crop yields, and nitrate is essential for plant growth and development. However, the precise mechanisms by which nitrate influences drought stress responses are not fully understood. In the study, we investigated the role of the nitrate-responsive transcription factor NLP8 in drought stress. Our results showed that the nlp8 mutant exhibited enhanced drought tolerance. Transcriptome analysis revealed that NLP8 primarily regulates sugar metabolism, lipid metabolism, and nitrogen metabolism under drought conditions. Furthermore, EMSA, yeast one-hybrid, and LUC assays confirmed that NLP8 binds to the PUB23 promoter and activates its expression, thereby participating in drought resistance. The study defines the relationship between nitrate signalling and drought stress and provides insights into how plants regulate nutrient allocation during drought. These findings not only uncover the mechanisms by which plants modulate nutrient utilization under adverse conditions but also provide important insights into the physiological processes involved in plant stress responses.

Molecular investigation of how drought stress affects chlorophyll metabolism and photosynthesis in leaves of C3 and C4 plant species: A transcriptome meta-analysis

Drought stress has a significant impact on photosynthesis in plants, leading to reduced photosynthesis rates and affecting plant growth and yield. Understanding the effects of drought stress on photosynthetic pathways, particularly in C3 and C4 plants, is crucial for maximizing agricultural productivity and maintaining food security. In this study, we analyzed RNA-seq data from leaves of common wheat (Triticum aestivum) and sorghum (Sorghum bicolor), as representatives of C3 and C4, using a meta-analysis approach to investigate the photosynthesis-related genes involved in the response to drought stress. We identified specific genes and components of the photosynthesis pathway that are affected by drought stress. The findings suggest that wheat and sorghum respond differently to drought stress, with sorghum showing a more effective defense system against photoinhibition and damage to photosystems. On the other hand, it seems that in wheat, in order to deal with oxidative stress, the expression of homologous genes of C4 enzyme and genes involved in heme and siroheme synthesis pathway has increased under stress. This is probably due to the higher photoinhibition in C3 photosynthetic system compared to C4. Furthermore, drought stress affected chlorophyll biosynthesis and degradation pathways in both wheat and sorghum, but compared with sorghum, drought stress had a greater inhibitory effect on chlorophyll biosynthesis in wheat, which indicates the difference in their ability to cope with photoinhibition.

Anthocyanin biosynthesis and transport synergistically modulated by RcMYB75 and RcGSTFL11 play a pivotal role in the feedforward loop in response to drought stress

Anthocyanins, the important antioxidants and signaling molecules, are natural polyphenolic compounds widely present in plants and essential for plant defense. However, little is known about the mechanisms underlying plant anthocyanin accumulation in relation to drought stress. This study reveals that drought stress induces significant anthocyanin accumulation in Rosa chinensis, alongside an increase in the expression of the MYB transcription factor (TF) gene RcMYB75 and the glutathione S-transferase (GST) gene RcGSTFL11. When overexpressed, RcMYB75 markedly increases anthocyanin contents in both roses and tobaccos; conversely, reducing its expression significantly lowers anthocyanin contents in rose petals. RcGSTFL11 was confirmed as an anthocyanin transporter and overexpression of RcGSTFL11 can restore the anthocyanin-deficient phenotype in the Arabidopsis tt19 mutant. Transgenic roses overexpressing RcGSTFL11 exhibit enhanced anthocyanin accumulation, while those with downregulated RcGSTFL11 have reduced contents. Transcriptomic analysis indicates that RcMYB75 upregulates the expression of key genes in the anthocyanin biosynthetic pathway and the anthocyanin transport gene RcGSTFL11. Ultimately, we also found that anthocyanin accumulation in these transgenics further enhances plant resistance to drought stress. Taken together, RcMYB75 and RcGSTFL11 promote the synthesis and transport of anthocyanins and play a key role in the feedforward loop responding to drought stress in roses. This study provides insights into the molecular mechanisms by which MYB TFs contribute to anthocyanin biosynthesis and transport, as well as the adaptive strategies of roses in response to drought stress.

Integrated comparative physiological and transcriptomic analyses of Elymus sibiricus L. reveal the similarities and differences in the molecular mechanisms in response to drought and cold stress

Drought and cold crucially affect plant growth and distribution. Plants have evolved complex molecular mechanisms to adapt to such adverse environmental conditions. This study examines two Elymus sibiricus (Es) germplasms differing in resilience to these stresses. Analyzing physiological responses and gene expression changes under drought and cold, it reveals the similarities and differences in their molecular mechanisms that underlie these responses. The results indicate that both drought stress and cold stress severely damage the integrity of the cell membrane in Es. Notably, under cold stress, the accumulation of osmotic regulation substances in Es is more significant, which may be related to the regulation of carbohydrate metabolism (CM)-related genes in cold environments. Furthermore, the response to oxidative stress triggered by cold stress in Es is partially inhibited. The enrichment analysis showed that the DEGs responsive to drought stress in Es were mainly related to the pathway of photosynthesis, whereas the DEGs responsive to cold stress were more associated with the protein processing in endoplasmic reticulum (PPER), highlighting distinct molecular responses. In addition, we discovered that the abscisic acid (ABA) signaling transduction plays a dominant role in mediating the drought resistance mechanism of Es. We have identified 86 key candidate genes related to photosynthesis, Phst, CM, and PPER, including 5 genes that can respond to both drought and cold stress. This study provides a foundation for the molecular mechanisms underlying cold and drought resistance in Es, with insight into its future genetic improvement for stress resistance.

Biochemical and proteomic approaches to investigating effects of IAA-aspartate in pea (Pisum sativum L.) seedlings during osmotic shock

Osmotic shock is the first step of high salt or drought action that involves biochemical and molecular changes during plant response to these unfavorable conditions. Indole-3-acetyl-aspartate (IAA-aspartate, IAA-Asp) is the main amide conjugate of auxin in pea (Pisum sativum L.) tissues. Although the exact molecular mechanism of the IAA-Asp action is unknown, this conjugate's indole-3-acetic acid (IAA)-independent biological activity has been observed during physiological and stress conditions. In this work, we investigated the effect of IAA-Asp alone, as well as in combination with NaCl or polyethylene glycol (PEG) (osmotic shock) on reduced/oxidized glutathione (GSH/GSSG) ratio, activities of enzymes modulating glutathione concentration, protein S-glutathionylation, and IAA homeostasis. We did not observe the hydrolysis of IAA-Asp to IAA in pea seedlings, which, together with other results, suggests that IAA-Asp modulates plant response to abiotic stimuli independently of IAA. Moreover, despite the effect of IAA-Asp on the enzymes responsible for IAA conjugation, no changes in this phytohormone level were visible. Furthermore, 3h plant treatment with IAA-Asp increased the activity of glutathione reductase (GR), which correlates with an elevated GSH/GSSG ratio. On the contrary, more extended (48h) incubation with IAA-Asp diminished the GSH/GSSG ratio and increased the activity of glutathione peroxidase (GPX). IAA-Asp reduced GR activity during salt treatment but did not affect the GSH/GSSG ratio. Similarly, under plant incubation with PEG, IAA-Asp did not change the GSH/GSSG ratio but increased glutathione S-transferase (GST) activity. We also analyzed the effect of IAA-Asp on pea protein S-glutathionylation. Increased S-glutathionylation of heat shock 70 kDa protein (HSP70) was observed after plant treatment with IAA-Asp, PEG, or IAA-Asp combined with PEG. The proteomic analysis also revealed that IAA-Asp diminished S-glutathionylation of lipoxygenase during plant incubation with PEG. Thus, we suggest that IAA-Asp modulates redox status in pea during oxidative stress and under normal physiological conditions.

Evaluation of the rainfed and irrigated conditions on biomass and essential oil yield of German chamomile (Matricaria chamomilla) in response to melatonin foliar application

German chamomile (Matricaria chamomilla L.) is a valuable medicinal plant known for its rich content of bioactive compounds, including chamazulene, α-bisabolol, and α-bisabololoxide A. Drought stress poses a significant challenge to agricultural productivity and negatively affects the growth and yield of chamomile. This study aimed to investigate the effects of foliar-applied melatonin on the antioxidant capacity and secondary metabolite production of M. chamomilla under both rainfed and irrigated conditions. The research was conducted using a randomized complete block design with three replications during the 2022-2023 period. To impose drought stress, we compared rainfed and irrigated treatments, while melatonin was applied at three concentrations (0, 100, and 200 mM). The composition of essential oils was analyzed using gas chromatography-mass spectrometry (GC/MS). Results indicated that the application of melatonin significantly improved essential oil content and plant performance under drought conditions. In rainfed situations, applying 100 mM of melatonin increased the essential oil rate by 45%, reaching 1.45% compared to the control group. Under irrigated conditions, the highest essential oil yield of 0.33 g per plant was also achieved with 100 mM melatonin. The maximum proline content of 4.05 mg/g of fresh weight was found in rainfed cultivation with 200 mM melatonin. Plants receiving irrigation with 200 mM melatonin demonstrated the highest values for relative water content (83.2 mg/g fresh weight), total chlorophyll (3.99 mg/g fresh weight), and dry matter (16.61 g). GC and GC-MS analyses revealed that secondary metabolites ranged from 39.85 to 56.97%, with α-bisabolol, chamazulene, and α-bisabololoxide B being the major components. Path analysis showed strong direct effects of essential oil rate (0.921), proline (1.397), and relative water content (1.115) on dry mass, with R² values reaching 95.4% in the final model. The analysis indicated that all measured traits influenced dry mass, with relative water content directly affecting dry mass and essential oil rate positively influencing both proline and dry mass. Based on these findings, combining rainfed cultivation with melatonin application is a promising and environmentally friendly strategy to enhance drought tolerance, growth, and biochemical content in German chamomile.

Exploring the Role of Non-Structural Carbohydrates (NSCs) Under Abiotic Stresses on Woody Plants: A Comprehensive Review

Global climate change has increased the severity and frequency of abiotic stresses, posing significant challenges to the survival and growth of woody plants. Non-structural carbohydrates (NSCs), including starch and sugars, play a vital role in enabling plants to withstand these stresses, helping to stabilize cellular functions by buffering plant energy demands and facilitating recovery on the alleviation of stress. Despite the recognized multiple functions of NSCs, the contrasting effects of multiple abiotic stresses on NSCs dynamics in woody plants remain poorly understood. This review aims to explore the current knowledge of the contrasting effects of abiotic stress conditions including drought, salinity, heat, water logging, and cold on NSCs dynamics. The roles of NSCs in regulating stress-resilience responses in woody plants are also discussed, along with the challenges in NSC measurement, and options for future research directions are explored. This review is based on comprehensive literature research across different search engines like Scopus, Web of Science, and Google Scholar (2000-2024) using targeted keywords. This study compiles the current research on NSCs functions and provides insights into the adaptive strategies of woody plants in response to changing climate conditions, providing groundwork for future research to improve stress tolerance in woody plants.

Enhancing Tolerance to Combined Heat and Drought Stress in Cool-Season Grain Legumes: Mechanisms, Genetic Insights, and Future Directions

The increasing frequency of concurrent heat and drought stress poses a significant challenge to agricultural productivity, particularly for cool-season grain legumes, including broad bean (Vicia Faba L.), lupin (Lupinus spp.), lentil (Lens culinaris Medik), chickpea (Cicer arietinum L.), grasspea (Lathyrus sativus L.), pea (Pisum sativum L.), and common vetch (Vicia sativa L.). These legumes play a vital role in sustainable agricultural systems due to their nitrogen-fixing ability and high nutritional value. This review synthesizes current knowledge of the impacts and tolerance mechanisms associated with combined heat and drought stresses in these crops. We evaluate physiological and biochemical responses to combined heat and drought stress, focusing on their detrimental effects on growth, development, and yield. Key genetic and molecular mechanisms, such as the roles of osmolytes, antioxidants, and stress-responsive genes, are explored. We also discuss the intricate interplay between heat and drought stress signaling pathways, including the involvement of Ca2+ ions, reactive oxygen species, transcription factor DREB2A, and the endoplasmic reticulum in mediating stress responses. This comprehensive analysis offers new insights into developing resilient legume varieties to enhance agricultural sustainability under climate change. Future research should prioritize integrating omics technologies to unravel plant responses to combined abiotic stresses.

Enhancing drought tolerance in horticultural plants through plant hormones: a strategic coping mechanism

Abiotic stresses are considered as a significant factor restricting horticultural crop productivity and quality. Drought stress is a major environmental constraint among the emerging concerns. Plants have significant susceptibility to drought stress, resulting in a marked decline in production during the last several decades. The development of effective strategies to mitigate drought stress is essential for sustainable agriculture and food security, especially considering the continuous growth of the world population. Several studies suggested that exogenous application of phytohormone to plants can improve drought stress tolerance by activating molecular and physiological defense systems. Phytohormone pretreatment is considered a potential approach for alleviating drought stress in horticultural plants. In addition, melatonin, salicylic acid, jasmonates, strigolactones, brassinosteroids, and gamma-aminobutyric acid are essential phytohormones that function as growth regulators and mitigate the effects of drought stress. These hormones frequently interact with one another to improve the survival of plants in drought-stressed environments. To sum up, this review will predominantly elucidate the role of phytohormones and related mechanisms in drought tolerance across various horticulture crop species.

Effect of crude extract and polysaccharides derived from Fucus spiralis on radish plants Raphanus sativus L. agrophysiological traits under drought stress

Drought is a significant environmental stressor that induces changes in the physiological, morphological, biochemical, and molecular traits of plants, ultimately resulting in reduced plant growth and crop productivity. Seaweed extracts are thought to be effective in mitigating the effects of drought stress on plants. In this study, we investigated the impact of crude extract (CE), and polysaccharides (PS) derived from the brown macroalgae Fucus spiralis (Heterokontophyta, Phaeophyceae) applied at 5% (v/v) and 0.1% (w/v) respectively on radish plants Raphanus sativus L. subjected to varying levels of drought stress, specifically 80% of field capacity (FC) for no stress, 60% FC for moderate stress, and 40% FC for severe stress. Our examination of growth parameters, along with physiological and biochemical characteristics, revealed that both CE and PS increased the fresh weight over the control by 47.43% and 64% at 40% FC and 12.5% and 38% at 60% FC respectively. Under stress (40% FC), the application of CE and PS decreased proline content of radish leaves by 23.45% and 6.46% respectively in comparison with the control. Furthermore, PS treatment caused an increase of the alkaline phosphatase and urease activity in the soil by 182.5% and 34.6% respectively. CE and PS treatments led to decreased sugar content and total phenolics levels. Notably, lipid peroxidation was reduced in stressed plants treated with both CE and PS, with PS treatment yielding lower concentrations (3.75 nmol MDA.g- 1 FW at 40% FC). Overall, F. spiralis extracts interacted through several mechanisms using various compounds to mitigate the negative effects of drought stress on radish plants. These results demonstrate that seaweed extracts could be adopted in integrated production systems to boost food productivity under harsh climatic conditions.

Understanding the impacts of drought on peanuts (Arachis hypogaea L.): exploring physio-genetic mechanisms to develop drought-resilient peanut cultivars

Peanut is a vital source of protein, particularly in the tropical regions of Asian and African countries. About three-quarters of peanut production occurs worldwide in arid and semi-arid regions, making drought an important concern in peanut production. In the US about two-thirds of peanuts are grown in non-irrigated lands, where drought accounts for 50 million USD loss each year. The looming threat of climate change exacerbates this situation by increasing erratic rainfall. Drought not only reduces yield but also degrades product quality. Peanuts under drought stress exhibit higher levels of pre-harvest aflatoxin contamination, a toxic fungal metabolite detrimental to both humans and animals. One way to sustain peanut production in drought-prone regions and address pre-harvest aflatoxin contamination is by developing drought-tolerant peanut cultivars, a process that can be accelerated by understanding the underlying physiological and genetic mechanisms for tolerance to drought stress. Different physiological attributes and genetic regions have been identified in drought-tolerant cultivars that help them cope with drought stress. The advent of precise genetic studies, artificial intelligence, high-throughput phenotyping, bioinformatics, and data science have significantly improved drought studies in peanuts. Yet, breeding peanuts for drought tolerance is often a challenge as it is a complex trait significantly affected by environmental conditions. Besides technological advancements, the success of drought-tolerant cultivar development also relies on the identification of suitable germplasm and the conservation of peanut genetic variation.

Applying microbial biostimulants and drought-tolerant genotypes to enhance barley growth and yield under drought stress

With climate change, the frequency of regions experiencing water scarcity is increasing annually, posing a significant challenge to crop yield. Barley, a staple crop consumed and cultivated globally, is particularly susceptible to the detrimental effects of drought stress, leading to reduced yield production. Water scarcity adversely affects multiple aspects of barley growth, including seed germination, biomass production, shoot and root characteristics, water and osmotic status, photosynthesis, and induces oxidative stress, resulting in considerable losses in grain yield and its components. In this context, the present review aims to underscore the importance of selecting drought-tolerant barley genotypes and utilizing bio-inoculants constructed from beneficial microorganisms as an agroecological approach to enhance barley growth and production resilience under varying environmental conditions. Selecting barley genotypes with robust physiological and agronomic tolerance can mitigate losses under diverse environmental conditions. Plant Growth Promoting Rhizobacteria (PGPR) play a crucial role in promoting plant growth through nutrient solubilization, nitrogen fixation, phytohormone production, exopolysaccharide secretion, enzyme activity enhancement, and many other mechanisms. Applying drought-tolerant genotypes with bio-inoculants containing PGPR, improves barley's drought tolerance thereby minimizing losses caused by water scarcity.

SAL1 gene: a promising target for improving abiotic stress tolerance in plants a mini review

Global climate change poses a significant risk to agricultural productivity due to its diverse impacts on agricultural ecosystems, such as increased temperatures and altered precipitation patterns, all of which can adversely affect crop productivity. To overcome these challenges, plants have evolved intricate mechanisms to regulate stress responses and enhance stress tolerance. The SAL1 gene, which encodes a phosphatase enzyme, has emerged as a key player in plant stress responses. In this review, we provide an overview of the SAL1 gene, its functional significance, and its potential applications for improving stress tolerance in crops. To address the escalating global food demand amidst climate change challenges, it is imperative to pursue innovative strategies aimed at enhancing crop tolerance against abiotic stress.

Water deficit and aphid resilience on wheat: examining Sitobion avenae F. and their bacterial symbionts interplay under controlled laboratory conditions

BACKGROUND

Climate change has far-reaching effects on food security and agriculture, affecting crop yields and food distribution. Agriculture relies heavily on water for irrigation and production, making it vulnerable to water scarcity. Additionally, climate change can affect crop pest insects, leading to increased global crop losses, particularly in cereals, an important component of the human diet. Aphids are major crop pests and have a symbiotic relationship with bacterial endosymbionts that can contribute to their success as pests under a climate change scenario. To test the effect of drought on aphids, we examined varying levels of water deficit and endosymbiont composition on the grain aphid (Sitobion avenae) performance on wheat under controlled laboratory conditions. We measured the intrinsic rate of population increase (rm), the body weight of adult aphids, and the pre-reproductive period for different genotypes of the grain aphid (including Chilean superclones) under different irrigation regimes. We also analyzed the relative abundance of their endosymbionts under the different water treatments.

RESULTS

Our findings revealed that water deficit affects each aphid genotype differently, impacting various traits. For instance, the body weight of adult aphids was notably affected by different water treatments, with aphids grown under intermediate water deficit (IW) being significantly bigger. The relative abundance of endosymbionts also varied among genotypes and water treatments-specifically Regiella insecticola had a noticeably higher abundance under IW (P < 0.05).

CONCLUSION

This study provides valuable insights into the impact of water deficit on aphid performance and the role of endosymbionts in mitigating the effects of water deficit. © 2024 Society of Chemical Industry.

Impact of arbuscular mycorrhizal fungi on maize rhizosphere microbiome stability under moderate drought conditions

With an alarming increase in global greenhouse gas emissions, unstable weather conditions are significantly impacting agricultural production. Drought stress is one of the frequent consequences of climate change that affects crop growth and yield. Addressing this issue is critical to ensure stable crop productivity under drought conditions. Arbuscular mycorrhizal fungi (AMF) establish symbiotic relationships with plants and enhance their resistance to adverse conditions. Effects of arbuscular mycorrhizal associations on the rhizosphere microbiome and root transcriptome under drought conditions have not been explored. Here, we investigated the effects of AMF and drought stress on rhizosphere microorganisms and root transcriptome of maize plants grown in chernozem soil. We used high-throughput sequencing data of bacterial 16S rRNA and fungal internal transcribed spacer regions (ITS) to identify rhizosphere microorganisms. Transcriptomic data were used to assess gene expression in maize plants under different treatments. Our results show that AMF maintains the composition of maize rhizosphere microorganisms under drought stress. In particular, the bacterial and fungal phyla maintained were Actinomycetes and Ascomycota, respectively. Transcriptomic data indicated that AMF influenced gene expression in maize plants under drought stress. Under drought stress, the expression of SWEET13, CHIT3, and RPL23A was significantly higher in the presence of AMF than it was without AMF inoculation, indicating better sugar transport, reduced malondialdehyde accumulation, and improved water use efficiency in AMF-inoculated maize plants. These findings suggest that AMF can enhance the resistance of maize to moderate drought stress by stabilising plant physical traits, which may help maintain the structure of the rhizosphere microbial community. This study provides valuable theoretical insights that should aid the utilization of AMF in sustainable agricultural practices.

Identification of the xyloglucan endotransglycosylase/hydrolase genes and the role of PagXTH12 in drought resistance in poplar

The xyloglucan endotransglycosylase/hydrolase (XTH) gene family plays a crucial role in plant cell wall remodeling, facilitating growth and structural changes. However, the divergence of paralogous genes among different species of Populus remains inadequately understood. This study investigates the phylogenetic relationships and expression characteristics of XTH genes in two Populus species: Populus trichocarpa and Populus alba × P. glandulosa '84K'. Forty-one XTHs were identified in P. trichocarpa and 38 and 33 members in the subgenome A and G of '84K' poplar, respectively. Gene expression analysis demonstrated differences among paralogous genes within the same subgenome and between orthologous genes across species, likely influenced by variations in promoter regions. Notably, XTH12 showed a specific response to drought stress among various abiotic stresses. In a population of 549 Populus individuals, functional SNPs in XTH12's coding region did not affect its conserved ExDxE catalytic site, highlighting its irreplaceable function. Furthermore, validation through qRT-PCR and ProPagXTH12::GUS activity, alongside PagXTH12-overexpression poplar lines, substantiated the role of PagXTH12 in modulating the balance between plant biomass and drought resistance. Overall, this research provides valuable insights into the biological functions of XTHs in plant environmental adaptability and offers strategies for targeted regulation of tree growth and stress resistance.

Genetic Diversity and Drought Stress Tolerance of a Global Collection of Pearl Millet at Germination and Early Seedling Growth Stages

Pearl millet {Pennisetum glaucum (L.) R. Br} is a C4 panicoid cereal millet crop grown in arid and semi-arid regions in Africa and Asia for food and fodder. This study involves the evaluation of the genetic diversity of 28 worldwide germplasm collection of pearl millet by genetic markers polymorphism and drought tolerance indices. The genetic diversity was expressed by 51 alleles of 9 ISSR markers that showed 96.43% total polymorphism and 11.76 alleles per marker. Cluster analysis of ISSR markers polymorphism divided the 28 genotypes into four clusters partially in agreement with their origin. The application of drought stress simulated by 20% PEG6000 treatment, retarded the germination percentage, and reduced shoot and root length, seedling fresh and dry weights. Drought tolerance indices (DTIs) were calculated based on the response of the seedling traits under drought stress compared to the control seedlings. ANOVA revealed statistically significant variation among the genotypes (P ≤ 0.05), except for seedling fresh weight (P = 0.17 > 0.05) under control conditions and seedling dry weight (P = 0.99 > 0.05) under drought conditions. Genotypes having higher DTIs for three traits are regarded drought resistant, i.e., those from India, Ethiopia, Pakistan, and Nigeria. The calculated heritability values indicated that seedlings dry weight is the least trait affected by drought stress whereas root length is the most influenced trait. Hierarchical clustering, based on the DTI values, also grouped the genotypes partially concomitant to their origin. The correlation analysis demonstrated a modest positive correlation between shoot length and root length. A low correlation of r ≤ 0.12 was observed between the morphological DTI matrix and the genetic matrix. Nevertheless, high levels of genetic diversity were identified among the examined genotypes that may face genetic erosion by climatic constraints, and a high potential for creating agronomically superior cultivars by crossing widely divergent genotypes.

The Crossregulation Triggered by Bacillus Strains Is Strain-Specific and Improves Adaptation to Biotic and Abiotic Stress in Arabidopsis

Plants are sessile organisms that overcome environmental stress by activating specific metabolic pathways, leading to adaptation and survival. In addition, they recruit beneficial bacterial strains to further improve their performance. As plant-growth-promoting rhizobacteria (PGPR) are able to trigger multiple targets to improve plant fitness, finding effective isolates for this purpose is of paramount importance. This metabolic activation involves the following two stages: the priming pre-challenge with no evident changes, and the post-challenge, which is characterized by a faster and more intense response. Eight Bacillus strains, obtained in a previous study, were tested for their ability to improve plant growth, and to protect Arabidopsis thaliana plants against biotic and abiotic stress. After the 16S rRNA gene sequencing, three isolates were selected for their ability to improve growth (G7), and to protect against biotic and abiotic stress (H47, mild protection, with a similar intensity for biotic and abiotic stress; L44, the highest protection to both); moreover the expression of Non-Expresser of Protein Resistance Gene 1 (NPR1) and Protein resistance (PR1) as markers of the Salicylic Acid (SA) pathway, and lipooxygenase (LOX2) and plant defensin gene (PDF1) as markers of the Ethylene/Jasmonic Acid (Et/Ja) pathway, was determined 24 h after the stress challenge and compared to the expression in non-stressed plants. The results indicated that (i) the three strains prime Arabidopsis according to the more marked and faster increases in gene expression upon stress challenge, (ii) all three strains activate the SA-mediated and the Et/Ja-mediated pathways, therefore conferring a wide protection against stress, and (iii) PR1 and PDF1, traditionally associated to Systemic Acquired Resistance (SAR) and Induced Systemic Resistance (ISR) protection against pathogenic stress, are also overexpressed under abiotic stress conditions. Therefore, it appears that the priming of the plant adaptive metabolism is strain-dependent, although each stress factor determines the intensity in the response of the expression of each gene; hence, the response is determined by the following three factors: the PGPR, the plant, and the stress factor.

Phytostabilization of Soils Contaminated with Cadmium by Peristrophe bivalvis

This study aims to investigate the ability of cadmium (Cd) accumulation in Peristrophe bivalvis cultivated in a pot experiment for 60 days at various Cd amounts of 0, 20, 60, and 100 mg/kg. Throughout the experiment, no toxic effects were observed, and the presence of Cd did not inhibit the growth of the plants. A linear correlation coefficient (P < 0.05) showed that there was a significant decrease in leaf stomata opening due to Cd stress. After treatment with a high concentration of Cd in the root rather than the shoot (P < 0.05), the plant's Cd accumulation increased significantly. P. bivalvis demonstrated reduced translocation factor (TF) and bioconcentration factor (BAF) values < 1; nevertheless, by the end of the experiment, the enhanced Cd uptake value on concentration showed the maximum value of 1.56 mg/plant. The results suggest that P. bivalvis had a tolerance and phytostabilization ability for Cd.

Identification of crucial drought-tolerant genes of barley through comparative transcriptomic analysis and yeast-based stress assay

Drought is a persistent and serious threat to crop yield and quality. The identification and functional characterization of drought tolerance-related genes is thus vital for efforts to support the genetic improvement of drought-tolerant crops. Barley is highly adaptable and renowned for its robust stress resistance, making it an ideal subject for efforts to explore genes related to drought tolerance. In this study, two barley materials with different drought tolerance were subjected to soil drought treatment, including a variety with strong drought tolerance (Hindmarsh) and a genotype with weaker drought tolerance (XZ5). Transcriptomic sequencing data from the aboveground parts of these plants led to the identification of 1,206 differentially expressed genes associated with drought tolerance. These genes were upregulated in Hindmarsh following drought stress exposure but downregulated or unchanged in XZ5 under these same conditions, or were unchanged in Hindmarsh but downregulated in XZ5. Pathway enrichment analyses suggested that these genes are most closely associated with defense responses, signal recognition, photosynthesis, and the biosynthesis of various secondary metabolites. Using protein-protein interaction networks, the ankyrin repeat domain-containing protein 17-like isoform X2 was predicted to impact other drought tolerance-related protein targets in Hindmarsh. In MapMan metabolic pathway analyses, genes found to be associated with the maintenance of drought tolerance in Hindmarsh under adverse conditions were predicted to include genes involved in the abscisic acid, cytokinin, and gibberellin phytohormone signaling pathways, genes associated with redox homeostasis related to ascorbate and glutathione S-transferase, transporters including ABC and AAAP, transcription factors such as AP2/ERF and bHLH, the heat shock proteins HSP60 and HSP70, and the sucrose non-fermenting-1-related protein kinase. Heterologous HvSnRK2 (one of the identified genes, which encodes the sucrose non-fermenting-1-related protein kinase) gene expression in yeast conferred significant drought tolerance, highlighting the functional importance of this gene as one linked with drought tolerance. This study revealed the drought tolerance mechanism of Hindmarsh by comparing transcriptomes while also providing a set of candidate genes for genetic efforts to improve drought tolerance in this and other crop species.

Improvement of maize drought tolerance by foliar application of zinc selenide quantum dots

Maize (Zea mays L.) is an important cereal crop grown in arid and semiarid regions of the world. During the reproductive phase, it is more frequently exposed to drought stress, resulting in lower grain yield due to oxidative damage. Selenium and zinc oxide nanoparticles possess inherent antioxidant properties that can alleviate drought-induced oxidative stress by the catalytic scavenging of reactive oxygen species, thereby protecting maize photosynthesis and grain yield. However, the effect of zinc selenide quantum dots (ZnSe QDs) under drought stress was not been quantified. Hence, the aim of this study was to quantify the (i) toxicity potential of ZnSe QDs and (ii) drought mitigation potential of ZnSe QDs by assessing the transpiration rate, photosynthetic rate, oxidant production, antioxidant enzyme activity and seed yield of maize under limited soil moisture levels. Toxicity experiments were carried out with 0 mg L-1 to 500 mg L-1 of ZnSe QDs on earthworms and azolla. The results showed that up to 20 mg L-1, the growth rates of earthworms and azolla were not affected. The dry-down experiment was conducted with three treatments: foliar spray of (i) water, (ii) ZnSe QDs (20 mg L-1), and (iii) combined zinc sulfate (10 mg L-1) and sodium selenate (10 mg L-1). ZnSe or Se applications under drying soil reduced the transpiration rate compared to water spray by partially closing the stomata. ZnSe application at 20 mg L-1 at the tasselling stage significantly increased the photosynthetic rate (25%) by increasing catalase (98%) and peroxidase (85%) enzyme activity and decreased the hydrogen peroxide (23%) content compared to water spray, indicating that premature leaf senescence was delayed under rainfed conditions. ZnSe spray increased seed yield (26%) over water spray by increasing the number of seeds cob-1 (42%). The study concluded that foliar application of ZnSe (20 mg L-1) could decrease drought-induced effects in maize.

Drought-tolerant fungal microbes, Aspergillus oryzae and Aspergillus fumigatus, elevate physiohormonal and antioxidant responses of maize under drought stress

Introduction

Temporary and extended drought stress accelerates phytohormones and reactive oxygen species (ROS) in plants, however, the fate of the plants under stress is mostly determined by the metabolic and molecular reprogramming, which can be modulated by the application of habitat-adapted fungi that triggers resistance to stress upon symbiotic association.

Methods

The present research exhibited the exploitation of the newly isolated, drought habitat-adapted fungal endophytic consortium of SAB (Aspergillus oryzae) and CBW (Aspergillus fumigatus), on maize under drought stress. SAB and CBW primarily hosted the root tissues of Conyza bonariensis L., which have not been reported earlier, and sufficiently produced growth-promoting metabolites and antioxidants.

Results

SAB and CBW adeptly inhabited the maize roots. They promoted biomass, primary metabolites, osmolytes (protein, sugar, lipids, proline, phenolics, flavonoids), and IAA production while reducing tannins, ABA, and H2O2 contents and increasing antioxidant enzyme activities. In addition, the enhanced adventitious root development at the root/stem interface, and elongated main root development optimum stomatal activity of SAB- and CBW-inoculated maize plants were observed under drought stress. SAB and CBW modulated the expression of the ZmBSK1, ZmAPX, and ZmCAT1 genes in the maize shoot and root tissues under drought stress vs. control, signifying an essential regulatory function for SAB/CBW-induced drought stress tolerance via phytohormonal signaling pathway leading to the antioxidant upregulation.

Discussion

These findings imply that the exogenous administration of the SAB/CBW consortium might be a rather efficient strategy that contributes to optimizing the physio-hormonal attributes and antioxidant potential to alleviate the drought stress in maize.

Dual Roles of Heterotrophic Ammonia-Oxidizing Bacteria in Enhancing Compensatory Growth upon Post-Drought in Maize

This study investigates the mechanisms driving maize compensatory growth upon post-drought, to reveal how the root's original cytokinins are regulated by the two-fold roles of heterotrophic bacteria with ammonia-oxidizing (HAOB) capabilities. The HAOB' dual roles encompass influencing root cytokinin synthesis and transport through nitrification and a direct pathway. Experiment 1 involved introducing the application of varying amounts of NO3- to the roots to examine how nitrification affects cytokinin roots-to-leaves transport. Results demonstrate that the 30-40 mmol·L-1 NO3- concentration had ideal effects on enhancing post-drought growth in maize by facilitating cytokinin synthesis and transport. In experiment 2, an HAOB strain, S2_8_1, was utilized and NO3- was supplemented alongside HAOB inoculation to assess the joint impacts of nitrification and the direct pathway on the production and transportation of cytokinins. Results demonstrate that the HAOB strain S2_8_1 increases nitrification rates in rhizosphere soil, thereby promoting the transport of cytokinins from roots to leaves. In addition, the HAOB strain promotes root cytokinin transport to leaves autonomously, showcasing its direct pathway. Inoculation with the HAOB strain increased leaf cytokinin content and improved water use efficiency compared to the addition of NO3-; however, the combination of NO3- and HAOB strains resulted in a synergistic effect and further improvement. These findings elucidate how HAOB can enhance maize compensatory growth through its dual roles, presenting promising applications in agriculture.

The interaction effect of water deficit stress and nanosilicon on phytochemical and physiological characteristics of hemp (Cannabis sativa L.)

Different practical approaches have been employed to attenuate the destructive impacts of water deficit stress on plants, such as utilization of humic acid, salicylic acid, algae extract, mulching, and microorganisms, as well as silicon application. Nanosilicon significantly moderates the ruinous effects of abiotic and biotic stress in plants through some physiological processes. In this study, the interaction effect of drought stress and nanosilicon on phytochemical and physiological characteristics of hemp (Cannabis sativa L.) was investigated, wherein the four-week-old seedlings were subjected to irrigation treatments at four levels, including 100% (control), 80% (mild stress), 60% (moderate stress), and 40% (severe stress) of field capacity and nanosilicon at three concentrations (0, 0.5, and 1.5 mM) was foliar applied every 10 days in a factorial completely randomized design experiment with three replications for 30 days. Phytochemical and physiological analyses such as photosynthetic pigments, total phenolic and flavonoid content, and antioxidant enzyme activities were conducted. The results indicated that the highest content of Cannabidiol and Tetrahydrocannabinol was achieved using 1.5 mM (1.89%) and 0.5 mM (0.63%) nanosilicon treatments, respectively, under moderate stress. The plants subjected to severe drought stress without nanosilicon application displayed the lowest values of chlorophyll a (0.50 mg/g FW) and b (0.20 mg/g FW). The use of nanosilicon excited the activation of antioxidant enzymes, wherein the plants treated with nanosilicon and drought stress exhibited significantly higher SOD, POD, and APX activities compared to the control. Under all drought stress levels, foliar application of nanosilicon at the highest concentration decreased proline content. The results proposed that the application of 1.5 mM nanosilicon, as a more efficient concentration, improved drought tolerance in hemp plants.

Comparative Study on the Response of Hyssop (Hyssopus officinalis L.), Salvia (Salvia officinalis L.), and Oregano (Origanum vulgare L.) to Drought Stress Under Foliar Application of Selenium

Drought is one of the most important abiotic factors limiting plant productivity. Although the aromatic plants of the Lamiaceae family often grow in arid regions, drought tolerance varies greatly among the different species of this family. The effect of induced drought stress can be reduced by the application of selenium. The current study aims to compare the growth and biochemical responses of three species of the Lamiaceae family (hyssop, salvia, and oregano) to drought stress and the possibility of reducing the effect of stress in these plants by foliar treatment with selenium. Drought stress reduced the fresh and dry biomass of hyssop (by 35% and 15%), salvia (by 45% and 41%), and oregano (by 51% and 32%). Se treatment did not affect the growth of plants under drought stress, but it improved relative water content in hyssop and salvia under moderate drought conditions. A reduction in the content of chlorophyll a and chlorophyll b (in hyssop and salvia). In addition, an increase in the content of hydrogen peroxide (in oregano and salvia), malondialdehyde, and proline in plants cultivated under drought conditions was observed. Se treatment led to reduced levels of hydrogen peroxide and malondialdehyde, along with an increase in chlorophyll a content (in hyssop and oregano) and proline content. The response of the antioxidant system depended on the plant species. Hyssop exhibited a significant increase in glutathione peroxidase, superoxide dismutase, and peroxidase activities. Oregano showed enhanced catalase activity. Salvia experienced a sharp increase in ascorbic acid content. Se treatment stimulated the accumulation of phenolic compounds and increased glutathione peroxidase activity in all studied species.

Drought Tolerance in Plants: Physiological and Molecular Responses

Drought, a significant environmental challenge, presents a substantial risk to worldwide agriculture and the security of food supplies. In response, plants can perceive stimuli from their environment and activate defense pathways via various modulating networks to cope with stress. Drought tolerance, a multifaceted attribute, can be dissected into distinct contributing mechanisms and factors. Osmotic stress, dehydration stress, dysfunction of plasma and endosome membranes, loss of cellular turgidity, inhibition of metabolite synthesis, cellular energy depletion, impaired chloroplast function, and oxidative stress are among the most critical consequences of drought on plant cells. Understanding the intricate interplay of these physiological and molecular responses provides insights into the adaptive strategies plants employ to navigate through drought stress. Plant cells express various mechanisms to withstand and reverse the cellular effects of drought stress. These mechanisms include osmotic adjustment to preserve cellular turgor, synthesis of protective proteins like dehydrins, and triggering antioxidant systems to counterbalance oxidative stress. A better understanding of drought tolerance is crucial for devising specific methods to improve crop resilience and promote sustainable agricultural practices in environments with limited water resources. This review explores the physiological and molecular responses employed by plants to address the challenges of drought stress.

The role of salicylic acid in modulating phenotyping in spring wheat varieties for mitigating drought stress

Climate change-related droughts that recur frequently are one of the biggest obstacles to wheat (Triticum aestivum L.) productivity. Worldwide, attempts are being done to establish drought-resistant cultivars. However, progress is slow since drought tolerance is a complex trait controlled by numerous genes, and its expression is influenced by the environment. Phenotypic, biochemical physiological, and genotyping approaches are highlighted as critical research components for leveraging genetic variation in eight wheat genotypes. Treatments included eight spring wheat genotypes (IPK_040, IPK_046, IPK_050, IPK_071, IPK_105, WAS_007, WAS_024 and WAS_031), normal irrigation (NI), drought stress (D) (30% field capacity (FC)), normal irrigation with 0.5 mM SA (NSA), and drought treated with SA (DSA). The results revealed that there was a reduction in relative water content, an increase membrane leakage, and leaf chlorophyll content under drought stress. SA induced the defense responses against drought by increasing the osmolytes and the antioxidative enzymes activities. Compared to the NI group, the DSA treatment improved the water regulation, antioxidant capacity, and drought stress resistance. SA significantly reduced the deleterious effects of water stress on phenotyping more in WAS_ 024 and IPK_ 105 genotypes. The most responsive genotypes to salicylic acid were IPK_ 046 among the IPK genotypes, whereas WAS_031 genotype was amongst WAS genotypes based on the morpho-physiological traits. The findings of this study give a solid foundation for assessing drought resistance in T. aestivum and developing cultivation-specific water management methods.

Drought stress mitigation through bioengineering of microbes and crop varieties for sustainable agriculture and food security

Climate change and agriculture are intrinsically connected and sudden changes in climatic conditions adversely impact global food production and security. The climate change-linked abiotic stressors like drought and high temperatures are resulting in crop failure. The most severe abiotic stress drought significantly affect the stomatal closure, production of reactive oxygen species, transpiration, photosynthesis or other physiological processes and plant morphology, and adversely affect plant growth and crop yield. Therefore, there is an exigent need for cost effective and eco-friendly modern technologies to induce drought tolerance in crop plants leading to climate-adapted sustainable agricultural practices for sustained food production. Among many options being pursued in this regard, the use of plant growth promoting microbes (PGPMs) is the most sustainable approach to promote drought stress resilience in crop plants leading to better plant growth and crop productivity. These PGPMs confer drought resistance via various direct or indirect mechanisms including production of antioxidants, enzymes, exopolysaccharides, modulation of phytohormones level, osmotic adjustment by inducing the accumulation of sugars, along with increases in nutrients, water uptake and photosynthetic pigments. However, several technological and ecological challenges limit their use in agriculture and sometimes treatment with plant beneficial microbes fails to produce desired results under field conditions. Thus, development of synthetic microbial communities or host mediated microbiome engineering or development of transgenic plants with the capacity to express desired traits may promote plant survival and growth under drought stress conditions. The present review critically assesses research evidence on the plant growth and stress resilience promoting potentials of PGPMs and their genes as an approach to develop drought resilient plants leading to increased crop productivity. Effective collaboration among scientific communities, policymakers and regulatory agencies is needed to create strong frameworks that both promote and regulate the utilization of synthetic microbial communities and transgenic plants in agriculture.

Magnesium Hydride Confers Osmotic Tolerance in Mung Bean Seedlings by Promoting Ascorbate-Glutathione Cycle

Despite substantial evidence suggesting that hydrogen gas (H2) can enhance osmotic tolerance in plants, the conventional supply method of hydrogen-rich water (HRW) poses challenges for large-scale agricultural applications. Recently, magnesium hydride (MgH2), a hydrogen storage material in industry, has been reported to yield beneficial effects in plants. This study aimed to investigate the effects and underlying mechanisms of MgH2 in plants under osmotic stress. Mung bean seedlings were cultured under control conditions or with 20% polyethylene glycol (PEG)-6000, with or without MgH2 addition (0.01 g L-1). Under our experimental conditions, the MgH2 solution maintained a higher H2 content and longer retention time than HRW. Importantly, PEG-stimulated endogenous H2 production was further triggered by MgH2 application. Further results revealed that MgH2 significantly alleviated the inhibition of seedling growth and reduced oxidative damage induced by osmotic stress. Pharmacological evidence suggests the MgH2-reestablished redox homeostasis was associated with activated antioxidant systems, particularly the ascorbate-glutathione cycle. The above observations were further supported by the enhanced activities and gene transcriptional levels of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase. Overall, this study demonstrates the importance of MgH2 in mitigating osmotic stress in mung bean seedlings, providing novel insights into the potential agricultural applications of hydrogen storage materials.

LpNAC5 positively regulates drought, salt and alkalinity tolerance of Lilium pumilum

NACs (NAM、ATAF1/2、CUC1/2), as a large family of plant transcription factors, are widely involved in abiotic stress responses. This study aimed to isolate and clone a novel stress-responsive transcription factor LpNAC5 from Lilium pumilum bulbs. Drought, salt, alkali, and ABA stresses induced the expression of LpNAC5. Transgenic tobacco plants overexpressing LpNAC5 were generated using the Agrobacterium-mediated method to understand the role of this factor in stress response. These plants exhibited increased tolerance to drought, salt, and alkali stresses. The tobacco plants overexpressing LpNAC5 showed strong drought, salt, and alkaline tolerance. Under the three abiotic stresses, the activities of antioxidant enzymes were enhanced, the contents of proline and chlorophyll increased, and the contents of malondialdehyde decreased. The functional analysis revealed that LpNAC5 enabled plants to positively regulate drought and salt stresses. These findings not only provided valuable insights into stress tolerance mechanisms in L. pumilum but also offered a potential genetic resource for breedi.

Alteration in certain growth, biochemical, and anatomical indices of grapevine (Vitis vinifera) in response to the foliar application of auxin under water deficit

Drought-induced stress represents one of the most economically detrimental natural phenomena impacting grapevine (Vitis vinifera ) development, yield, and fruit characteristics. Also, auxin is one of the most important plant growth regulators that can reduce damage caused by stress in plants. In this study, the impact of exogenously sprayed auxin (0, 50, and 200mgL-1 ) on growth, biochemical, and anatomical parameters was investigated in two grapevine varieties (cvs. 'Rashe' and 'Fakhri') under water deficit. According to our findings, water deficit led to a notable decrease in growth, protein content, and anatomical parameters; but significantly enhanced electrolyte leakage. Grapevines exposed to water deficit exhibited substantial increases in total phenolic compounds and antioxidant activity. Applying 50mgL-1 napthalene acetic acid (NAA) reduced the effects of water deficit in both grapevine cultivars by decreasing electrolyte leakage (15% in 'Rashe' and 20% in 'Fakhri'), and accumulating protein content (22% 'Rashe' and 32% 'Fakhri'), total phenolic compounds (33%'Rashe' and 40% 'Fakhri'), and antioxidant capacity (11% 'Rashe' and 39% 'Fakhri'); anantomical parameters were also improved. However, application of 200mgL-1 NAA had adverse effects on growth and biochemical traits of grapevines, with a more pronounced impact on root growth and anatomical parameters compared to other NAA concentrations. In conclusion, the application of 50mgL-1 NAA enhanced grapevine growth, enabling them to better thrive under water deficit.

The drought-induced plasticity of mineral nutrients contributes to drought tolerance discrimination in durum wheat

Drought is a major challenge for the cultivation of durum wheat, a crucial crop for global food security. Plants respond to drought by adjusting their mineral nutrient profiles to cope with water scarcity, showing the importance of nutrient plasticity for plant acclimation and adaptation to diverse environments. Therefore, it is essential to understand the genetic basis of mineral nutrient profile plasticity in durum wheat under drought stress to select drought-tolerant varieties. The research study investigated the responses of different durum wheat genotypes to severe drought stress at the seedling stage. The study employed an ionomic, molecular, biochemical and physiological approach to shed light on distinct behaviors among different genotypes. The drought tolerance of SVEMS16, SVEVO, and BULEL was related to their capacity of maintaining or increasing nutrient's accumulation, while the limited nutrient acquisition capability of CRESO and S.CAP likely resulted in their susceptibility to drought. The study highlighted the importance of macronutrients such as SO42-, NO3-, PO43-, and K+ in stress resilience and identified variant-containing genes potentially influencing nutritional variations under drought. These findings provide valuable insights for further field studies to assess the drought tolerance of durum wheat genotypes across various growth stages, ultimately ensuring food security and sustainable production in the face of changing environmental conditions.

Multi-omics integration analysis reveals the molecular mechanisms of drought adaptation in homologous tetraploid alfalfa(Medicago sativa 'Xinjiang-Daye')

Drought stress is a predominant abiotic factor leading to decreased alfalfa yield. Genomic ploidy differences contribute to varying adaptation mechanisms of different alfalfa cultivars to drought conditions. This study employed a multi-omics approach to characterize the molecular basis of drought tolerance in a tetraploid variant of alfalfa (Medicago sativa, Xinjiang-Daye). Under drought treatment, a total of 4446 genes, 859 proteins, and 524 metabolites showed significant differences in abundance. Integrative analysis of the multi-omics data revealed that regulatory modules involved in flavonoid biosynthesis, plant hormone signalling transduction, linoleic acid metabolism, and amino acid biosynthesis play crucial roles in alfalfa adaptation to drought stress. The severity of drought led to the substantial accumulation of flavonoids, plant hormones, free fatty acids, amino acids, and their derivatives in the leaves. Genes such as PAL, 4CL, CHI, CHS, PP2C, ARF_3, and AHP_4 play pivotal regulatory roles in flavonoid biosynthesis and hormone signalling pathways. Differential expression of the LOX gene emerged as a key factor in the elevated levels of free fatty acids. Upregulation of P5CS_1 and GOT1/2 contributed significantly to the accumulation of Pro and Phe contents. ERF19 emerged as a principal positive regulator governing the synthesis of the aforementioned compounds. Furthermore, observations suggest that Xinjiang-Daye alfalfa may exhibit widespread post-transcriptional regulatory mechanisms in adapting to drought stress. The study findings unveil the critical mechanisms by which Xinjiang-Daye alfalfa adapts to drought stress, offering novel insights for the improvement of alfalfa germplasm resources.

Inside-out: Synergising leaf biochemical traits with stomatal-regulated water fluxes to enhance transpiration modelling during abiotic stress

As the global climate continues to change, plants will increasingly experience abiotic stress(es). Stomata on leaf surfaces are the gatekeepers to plant interiors, regulating gaseous exchanges that are crucial for both photosynthesis and outward water release. To optimise future crop productivity, accurate modelling of how stomata govern plant-environment interactions will be crucial. Here, we synergise optical and thermal imaging data to improve modelled transpiration estimates during water and/or nutrient stress (where leaf N is reduced). By utilising hyperspectral data and partial least squares regression analysis of six plant traits and fluxes in wheat (Triticum aestivum), we develop a new spectral vegetation index; the Combined Nitrogen and Drought Index (CNDI), which can be used to detect both water stress and/or nitrogen deficiency. Upon full stomatal closure during drought, CNDI shows a strong relationship with leaf water content (r2 = 0.70), with confounding changes in leaf biochemistry. By incorporating CNDI transformed with a sigmoid function into thermal-based transpiration modelling, we have increased the accuracy of modelling water fluxes during abiotic stress. These findings demonstrate the potential of using combined optical and thermal remote sensing-based modelling approaches to dynamically model water fluxes to improve both agricultural water usage and yields.