Impact of exogenously applied trehalose on leaf biochemistry, achene yield and oil composition of sunflower under drought stress

Inter-subspecies diversity of maize to drought stress with physio-biochemical, enzymatic and molecular responses

Background

Drought is the most significant factor limiting maize production, given that maize is a crop with a high water demand. Therefore, studies investigating the mechanisms underlying the drought tolerance of maize are of great importance. There are no studies comparing drought tolerance among economically important subspecies of maize. This study aimed to reveal the differences between the physio-biochemical, enzymatic, and molecular mechanisms of drought tolerance in dent (Zea mays indentata), popcorn (Zea mays everta), and sugar (Zea mays saccharata) maize under control (no-stress), moderate, and severe drought stress.

Methods

Three distinct irrigation regimes were employed to assess the impact of varying levels of drought stress on maize plants at the V14 growth stage. These included normal irrigation (80% field capacity), moderate drought (50% field capacity), and severe drought (30% field capacity). All plants were grown under controlled conditions. The following parameters were analyzed: leaf relative water content (RWC), loss of turgidity (LOT), proline (PRO) and soluble protein (SPR) contents, membrane durability index (MDI), malondialdehyde (MDA), and hydrogen peroxide (H2O2) content, the antioxidant enzyme activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT). Additionally, the expression of heat shock proteins (HSPs) was examined at the transcriptional and translational levels.

Results

The effects of severe drought were more pronounced in sugar maize, which had a relatively high loss of RWC and turgor, membrane damage, enzyme activities, and HSP90 gene expression. Dent maize, which is capable of maintaining its RWC and turgor in both moderate and severe droughts, and employs its defense mechanism effectively by maintaining antioxidant enzyme activities at a certain level despite less MDA and H2O2 accumulation, exhibited relatively high drought tolerance. Despite the high levels of MDA and H2O2 in popcorn maize, the up-regulation of antioxidant enzyme activities and HSP70 gene and protein expression indicated that the drought coping mechanism is activated. In particular, the positive correlation of HSP70 with PRO and HSP90 with enzyme activities is a significant result for studies examining the relationships between HSPs and other stress response systems. The discrepancies between the transcriptional and translational findings provide an opportunity for more comprehensive investigations into the role of HSPs in stress conditions.

Exogenous glycine betaine alleviates water-deficit stress in Indian pennywort (Centella asiatica) under greenhouse conditions

Centella asiatica (Indian pennywort) is a green leafy vegetable containing centelloside' (triterpenoid), a key phytochemical component in traditional medicine. Being a glycophytic species, they exhibit decline in growth performance and yield traits when subjected to water-deficit (WD) conditions. Glycine betaine (GB) is a low molecular-weight organic metabolite that plays a crucial role in abiotic stress conditions in higher plants. The objective of this study was to investigate the potential of GB in alleviating water-deficit stress (in terms of morphological and physiological responses) in two different genotypes of Indian pennywort, "Nakhon Pathom" (NP; high centelloside-yielding genotype) and "Pathum Thani" (PT; low centelloside-yielding genotype). The genotypes of Indian pennywort were propagated by stolon cutting and transplanted into plastic bags containing 2 kg of garden soil. At the flower-initiation stage (30 days after transplantation), uniform plant material was treated exogenously with 0 (control), 25, and 50 mM GB at 100 mL per plant (one-time foliar spray) and then divided into two groups, 1) well watered (WW; irrigated daily with 400 mL fresh water; 98% field capacity) and 2) water deficit (WD; withheld water for 14 days; 72% field capacity). Foliar application of GB (25 mM) significantly improved leaf osmotic potential in NP under WD conditions via osmotic adjustment by free proline and fructose. Differences in leaf temperature (Tleaf) between WD and WW in NP were maximized (+ 1.93 °C) and the gap of Tleaf was reduced in the case of 25-50 mM GB application. Similarly, crop water stress index (CWSI) in NP and PT plants under WD condition was significantly increased by 1.95- and 1.86-fold over the control, respectively; however, it was significantly decreased by exogenous GB application. Increasing Tleaf and CWSI in drought-stressed plants was closely related to stomatal closure, leading to reduced gas exchange parameters, i.e., stomatal conductance (gs), transpiration rate (E), net photosynthetic rate (Pn), and intercellular CO2 concentration (Ci), and consequently decreased plant biomass and total centelloside yield. Overall physiological, morphological, and secondary metabolite traits were enhanced in NP under WD conditions using 25 mM GB exogenous application compared with the control. The study highlights the significance of GB in Indian pennywort production under limited water irrigation (water deficit) with higher vegetable yield and phytochemical stabilization.

Effects of wheat intercropping on growth and occurrence of Fusarium wilt in watermelon

Watermelon is commonly affected by Fusarium wilt in a monoculture cropping system. Wheat intercropping alleviates the affection of Fusarium wilt of watermelon. The objective of this study was to determine the effects of wheat and watermelon intercropping on watermelon growth and Fusarium wilt. Our results showed that wheat and watermelon intercropping promoted growth, increased chlorophyll content, and photosynthesis of watermelon. Meanwhile, wheat and watermelon intercropping inhibited watermelon Fusarium wilt occurrence, decreased spore numbers, increased root vigor, increased antioxidant enzyme activities, and decreased malondialdehyde (MDA) content in watermelon roots. Additionally, wheat and watermelon intercropping enhanced the bacterial colonies and total microbes growth in soil, decreased fungi and Fusarium oxysporum f. sp. niveum (FON) colonies, and increased soil enzyme activities in watermelon rhizosphere soil. Our results indicated that wheat and watermelon intercropping enhanced watermelon growth and decreased the incidence of Fusarium wilt in watermelon. These effects could be due to intercropping inducing physiological changes, regulating soil enzyme activities, and/or modulating soil microbial communities.

Alleviating chromium-induced oxidative stress in Vigna radiata through exogenous trehalose application: insights into growth, photosynthetic efficiency, mineral nutrient uptake, and reactive oxygen species scavenging enzyme activity enhancement

Trehalose serves as a crucial osmolyte and plays a significant role in stress tolerance. The influence of exogenously added trehalose (1 and 5 mM) in alleviating the chromium (Cr; 0.5 mM) stress-induced decline in growth, photosynthesis, mineral uptake, antioxidant system and nitrate reductase activity in Vigna radiata was studied. Chromium (Cr) significantly declined shoot height (39.33%), shoot fresh weight (35.54%), shoot dry weight (36.79%), total chlorophylls (50.70%), carotenoids (29.96%), photosynthesis (33.97%), net intercellular CO2 (26.86%), transpiration rate (36.77%), the content of N (35.04%), P (35.77%), K (31.33%), S (23.91%), Mg (32.74%), and Ca (29.67%). However, the application of trehalose considerably alleviated the decline. Application of trehalose at both concentrations significantly reduced hydrogen peroxide accumulation, lipid peroxidation and electrolyte leakage, which were increased due to Cr stress. Application of trehalose significantly mitigated the Cr-induced oxidative damage by up-regulating the activity of reactive oxygen species (ROS) scavenging enzymes, including superoxide dismutase (182.03%), catalase (125.40%), ascorbate peroxidase (72.86%), and glutathione reductase (68.39%). Besides this, applied trehalose proved effective in enhancing ascorbate (24.29%) and reducing glutathione content (34.40%). In addition, also alleviated the decline in ascorbate by Cr stress to significant levels. The activity of nitrate reductase enhanced significantly (28.52%) due to trehalose activity and declined due to Cr stress (34.15%). Exogenous application of trehalose significantly improved the content of osmolytes, including proline, glycine betaine, sugars and total phenols under normal and Cr stress conditions. Furthermore, Trehalose significantly increased the content of key mineral elements and alleviated the decline induced by Cr to considerable levels.

Effect of naringenin based nanocomposites and pure naringenin on cumin (Cuminum cyminum L.) under drought stress

Key message

Naringenin based nanocomposite alleviate the harmful effects of drought stress in Cuminum cyminum and enhance carefully the plant tolerance against drought condition with different mechanisms.

Abstract

In the recent years, drought stress is considered as one of the most important stressful conditions for agricultural plants. Reducing the effects of drought on plants is a crucial need nowadays, which calls for innovative methods. Naringenin is one of the most known plant flavonoids with antioxidant properties. In the present work, a naringenin based nanocomposite containing carboxymethylcellulose (CMC) as carrier (CMC-Nar) with an average size of 65 nm were synthesized by coacervation method. In order to investigate the effect of CMC nanocomposites containing naringenin (CMC-Nar) and pure naringenin in modulating the effects of drought stress, cultivation of Cuminum cyminum (varieties: Isfahan and Kashan) was carried out in greenhouse conditions. Drought stress was imposed as 30% of the field capacity. Various physiological, biochemical, and phytochemical assays were performed after treating the plants in drought conditions (30%). The results indicated that treatment of nanocomposites (CMC-Nar) and pure naringenin at drought conditions increased growth and photosynthetic parameters such as germination, shoot and root fresh weight, shoot dry weight, and chlorophyll content of the Cumin. Stress markers such as malondialdehyde, H2O2, and electrolyte leakage decreased under the treatment of narinjenin and especially nanocomposites (CMC-Nar) under drought conditions. Moreover, under same condition and treatments, some biochemical parameters including soluble sugar and total protein increased but the activity of antioxidant enzymes and the level of free amino acids has gone down. Compatible Solutes (Proline and glycine betaine) also increased. There was an increase in phytochemical parameters such as total phenols, flavonoids, anthocyanin, and tannins under naringenin and nanocomposites (CMC-Nar) treatment in drought conditions. In general, nanocomposites and pure naringenin reduced the harmful effects of drought stress, and the ameliorating impacts of nanocomposites (CMC-Nar) are more than pure naringenin. According to the results: In most cases, the impact of drought stress was modulated to a greater extent by (CMC-Nar) nanocomposites in the Isfahan variety compared to the Kashan variety. This research tries to propose a new method to reduce the effects of drought stress on Cuminum cyminum.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-024-01460-7.

Current views of drought research: experimental methods, adaptation mechanisms and regulatory strategies

Drought stress is one of the most important abiotic stresses which causes many yield losses every year. This paper presents a comprehensive review of recent advances in international drought research. First, the main types of drought stress and the commonly used drought stress methods in the current experiment were introduced, and the advantages and disadvantages of each method were evaluated. Second, the response of plants to drought stress was reviewed from the aspects of morphology, physiology, biochemistry and molecular progression. Then, the potential methods to improve drought resistance and recent emerging technologies were introduced. Finally, the current research dilemma and future development direction were summarized. In summary, this review provides insights into drought stress research from different perspectives and provides a theoretical reference for scholars engaged in and about to engage in drought research.

RING-type E3 ligase BnaJUL1 ubiquitinates and degrades BnaTBCC1 to regulate drought tolerance in Brassica napus L

Drought stress poses a persistent threat to field crops and significantly limits global agricultural productivity. Plants employ ubiquitin-dependent degradation as a crucial post-translational regulatory mechanism to swiftly adapt to changing environmental conditions. JUL1 is a RING-type E3 ligase related to drought stress in Arabidopsis. In this study, we explored the function of BnaJUL1 (a homologous gene of JUL1 in Brassica napus) and discovered a novel gene BnaTBCC1 participating in drought tolerance. First, we utilised BnaJUL1-cri materials through the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 system. Second, we confirmed that BnaJUL1 regulated drought tolerance through the drought tolerance assay and transcriptome analysis. Then, we identified a series of proteins interacting with BnaJUL1 through yeast library screening, including BnaTBCC1 (a tubulin binding cofactor C domain-containing protein); whose homologous gene TBCC1 knockdown mutants (tbcc1-1) exhibited ABA-sensitive germination in Arabidopsis, we then confirmed the involvement of BnaTBCC1 in drought tolerance in both Arabidopsis and Brassica. Finally, we established that BnaJUL1 could ubiquitinate and degrade BnaTBCC1 to regulate drought tolerance. Consequently, our study unveils BnaJUL1 as a novel regulator that ubiquitinates and degrades BnaTBCC1 to modulate drought tolerance and provided desirable germplasm for further breeding of drought tolerance in rapeseed.

Cyto and Genoprotective Potential of Tannic Acid Against Cadmium and Nickel Co-exposure Induced Hepato-Renal Toxicity in BALB/c Mice

Tannic acid (TA) is a metal chelating polyphenol that plays a crucial role in metal detoxification, but its modulatory role in co-exposure of these heavy metals' exposure needs to be explored. Cadmium (Cd) and nickel (Ni) are inorganic hazardous chemicals in the environment. Humans are prone to be exposed to the co-exposure of Cd and Ni, but the toxicological interactions of these metals are poorly defined. Present study was undertaken to study the preventive role of TA in Cd-Ni co-exposure-evoked hepato-renal toxicity in BALB/c mice. In the current investigation, increased oxidative stress in metal intoxicated groups was confirmed by elevated peroxidation of the lipids and significant lowering of endogenous antioxidant enzymes. Altered hepato-renal serum markers, DNA fragmentation, and histological alterations were also detected in the metal-treated groups. Present study revealed that Cd is a stronger toxicant than Ni and when co-exposure was administered, additive, sub-additive, and detrimental effects were observed. Prophylactic treatment with TA significantly reinstated the levels of lipid peroxidation (LPO), non-enzymatic, and enzymatic antioxidants. Moreover, it also restored the serum biomarker levels, DNA damage, and histoarchitecture of the given tissues. TA due to its metal chelating and anti-oxidative properties exhibited cyto- and genoprotective potential against Cd-Ni co-exposure-induced hepatic and renal injury.

Trehalose alleviates the inhibition of adventitious root formation caused by drought stress in cucumber through regulating ROS metabolism and activating trehalose and plant hormone biosynthesis

Trehalose (Tre) plays a vital role in response to drought stress in plants but its regulatory mechanism remains unclear. Here, this study explores the mechanism of re-regulated drought tolerance during cucumber adventitious root formation. Our results indicate that 2 mM Tre displays remarkable drought alleviation in the aspect of root number, root length, fresh weight, and dry weight. Under drought stress, Tre could inhibit greatly the MDA, H2O2, and O2- accumulation, enhance obviously the activities of SOD, POD, and CAT enzymes and up-regulate significantly the transcript levels of SOD, POD, and CAT genes. Furthermore, Tre treatment also promotes Tre metabolism during drought stress: significantly increases starch and Tre contents and decreases glucose content, the biosynthesis enzymatic activity of the Tre metabolic pathway including TPS and TPP are enhanced and the activity of degradation enzyme THL is decreased, and corresponding genes TPS1, TPS2, TPPA, and TPPB are up-regulated. Tre significantly reversed the decrease caused by PEG in IAA, ethylene, ABA, and BR contents and the increase caused by PEG in GA3 and KT contents. Collectively, Tre appears to be the effective treatment in counteracting the negative effects of drought stress during adventitious root formation by regulating ROS, Tre metabolisms and plant hormones.

Deciphering the mechanisms, hormonal signaling, and potential applications of endophytic microbes to mediate stress tolerance in medicinal plants

The global healthcare market in the post-pandemic era emphasizes a constant pursuit of therapeutic, adaptogenic, and immune booster drugs. Medicinal plants are the only natural resource to meet this by supplying an array of bioactive secondary metabolites in an economic, greener and sustainable manner. Driven by the thrust in demand for natural immunity imparting nutraceutical and life-saving plant-derived drugs, the acreage for commercial cultivation of medicinal plants has dramatically increased in recent years. Limited resources of land and water, low productivity, poor soil fertility coupled with climate change, and biotic (bacteria, fungi, insects, viruses, nematodes) and abiotic (temperature, drought, salinity, waterlogging, and metal toxicity) stress necessitate medicinal plant productivity enhancement through sustainable strategies. Plants evolved intricate physiological (membrane integrity, organelle structural changes, osmotic adjustments, cell and tissue survival, reclamation, increased root-shoot ratio, antibiosis, hypersensitivity, etc.), biochemical (phytohormones synthesis, proline, protein levels, antioxidant enzymes accumulation, ion exclusion, generation of heat-shock proteins, synthesis of allelochemicals. etc.), and cellular (sensing of stress signals, signaling pathways, modulating expression of stress-responsive genes and proteins, etc.) mechanisms to combat stresses. Endophytes, colonizing in different plant tissues, synthesize novel bioactive compounds that medicinal plants can harness to mitigate environmental cues, thus making the agroecosystems self-sufficient toward green and sustainable approaches. Medicinal plants with a host set of metabolites and endophytes with another set of secondary metabolites interact in a highly complex manner involving adaptive mechanisms, including appropriate cellular responses triggered by stimuli received from the sensors situated on the cytoplasm and transmitting signals to the transcriptional machinery in the nucleus to withstand a stressful environment effectively. Signaling pathways serve as a crucial nexus for sensing stress and establishing plants' proper molecular and cellular responses. However, the underlying mechanisms and critical signaling pathways triggered by endophytic microbes are meager. This review comprehends the diversity of endophytes in medicinal plants and endophyte-mediated plant-microbe interactions for biotic and abiotic stress tolerance in medicinal plants by understanding complex adaptive physiological mechanisms and signaling cascades involving defined molecular and cellular responses. Leveraging this knowledge, researchers can design specific microbial formulations that optimize plant health, increase nutrient uptake, boost crop yields, and support a resilient, sustainable agricultural system.

Dynamic characteristics and functional analysis provide new insights into the role of GauERF105 for resistance against Verticillium dahliae in cotton

BACKGROUND

The cotton industry suffers significant yield losses annually due to Verticillium wilt, which is considered the most destructive disease affecting the crop. However, the precise mechanisms behind this disease in cotton remain largely unexplored.

METHODS

Our approach involved utilizing transcriptome data from G. australe which was exposed to Verticillium dahliae infection. From this data, we identified ethylene-responsive factors and further investigated their potential role in resistance through functional validations via Virus-induced gene silencing (VIGS) in cotton and overexpression in Arabidopsis.

RESULTS

A total of 23 ethylene response factors (ERFs) were identified and their expression was analyzed at different time intervals (24 h, 48 h, and 72 h post-inoculation). Among them, GauERF105 was selected based on qRT-PCR expression analysis for further investigation. To demonstrate the significance of GauERF105, VIGS was utilized, revealing that suppressing GauERF105 leads to more severe infections in cotton plants compared to the wild-type. Additionally, the silenced plants exhibited reduced lignin deposition in the stems compared to the WT plants, indicating that the silencing of GauERF105 also impacts lignin content. The overexpression of GauERF105 in Arabidopsis confirmed its pivotal role in conferring resistance against Verticillium dahliae infection. Our results suggest that WT possesses higher levels of the oxidative stress markers MDA and H2O2 as compared to the overexpressed lines. In contrast, the activities of the antioxidant enzymes SOD and POD were higher in the overexpressed lines compared to the WT. Furthermore, DAB and trypan staining of the overexpressed lines suggested a greater impact of the disease in the wild-type compared to the transgenic lines.

CONCLUSIONS

Our findings provide confirmation that GauERF105 is a crucial candidate in the defense mechanism of cotton against Verticillium dahliae invasion, and plays a pivotal role in this process. These results have the potential to facilitate the development of germplasm resistance in cotton.

Genomics and Physiology of Chlorophyll Fluorescence Parameters in Hordeum vulgare L. under Drought and Salt Stresses

To map the genomic regions and control chlorophyll fluorescence attributes under normal, salinity-, and drought-stress conditions in barley (Hordeum vulgare L.) at the seedling stage, an experiment was conducted in 2019-2020 using 106 F8 lines resulting from the cross between Badia × Kavir. Initially, the different chlorophyll fluorescence parameters were evaluated. Under drought stress, the highest decrease was related to REo/CSm (59.56%), and the highest increase was related to dV/dto (77.17%). Also, under salinity stress, the highest decrease was related to Fv/Fo (59.56%), and the highest increase was related to DIo/RC (77.17%). Linkage maps were prepared using 152 SSR polymorphic markers, 72 ISSR alleles, 7 IRAP alleles, 29 CAAT alleles, 27 Scot alleles, and 15 iPBS alleles. The obtained map accounted for 999.2 centi-Morgans (cM) of the barley genome length (92% of the whole barley genome). The results indicated the importance of chromosomes 3, 2, and 7 in controlling ABS/CSm, Area, ETo/CSm, Fm, Fv, and ETo/RC under drought stress. qEToRCD-7, as a major QTL, controlled 18.3% of ETo/RC phenotypic variation under drought stress. Under salinity stress, the regions of chromosomes 2 and 7 (102 cM and 126 cM) controlled the parameters ABS/CSo, Fm, Fo, Fv, TRo/SCo, Area, ETo/CSm, and ETo/CSo. The results showed that chlorophyll fluorescence is an important parameter in the study of drought and salinity effects on barley. This is the first report of the investigation of changes in the genetic structure of quantitative genes controlling the fluorescence parameters associated with barley response to drought and salinity stresses in the Iranian barley RILs population. According to the obtained results, it is possible to use HVPLASC1B and EBmac0713 in normal conditions, ISSR21-2 and ISSR30-4 in drought conditions, and Bmac0047, Scot5-B, CAAT6-C, and ISSR30iPBS2076-4 in saline stress conditions to select genotypes with higher photosynthetic capacity in marker-assisted selection programs.

Crucial roles of trehalose and 5-azacytidine in alleviating salt stress in tomato: Both synergistically and independently

Trehalose may improve plant stress tolerance by regulating gene expression under different abiotic stresses. DNA methylation is involved in plant growth and development, but also in response to abiotic stresses. 5-azacytidine is a widely used inhibitor of DNA methylation. In this study, tomato (Solanum lycopersicum L. 'Ailsa Craig') was used as experimental material to explore the effects of trehalose and DNA methylation on the growth and development in tomato seedlings under salt stress. 10 mM trehalose, 50 μM 5-azacytidine, and their combined treatments could significantly increase growth parameters in tomato under salt stress, indicating trehalose and 5-azacytidine might play crucial roles in alleviating salt stress both synergistically and independently. Additionally, trehalose significantly down-regulated the expression of DNA methylase genes (SlDRM5, SlDRM1L1, SlCMT3 and SlCMT2) and up-regulated the expression of DNA demethylases genes under salt stress, suggesting that trehalose might regulate DNA methylation under salt stress condition. Under salt stress, trehalose and 5-azacytidine treatments enhanced antioxidant enzyme activity and induced antioxidant enzyme gene expression in tomato seedlings. Meanwhile, trehalose and 5-azacytidine increased ABA content by regulating the expression of ABA metabolism-related genes, thereby enhancing salt tolerance in tomato. Altogether, these results suggest that trehalose conferred salt tolerance in tomato seedlings probably by DNA demethylation and enhancing antioxidant capability and ABA accumulation.

Simultaneous application of salicylic acid and silicon in aerial parts of Scrophularia striata L. in response to drought stress

Plants respond to water shortage by regulating biochemical pathways which result in the biosynthesis of osmotic compounds. Active metabolites and compatible osmolytes control the inhibition of oxygen free radicals and dehydration. The physiological response of scrophularia striata to drought stress, a factorial completely randomized design (FCRD) experiment was conducted in three replication. Drought stress was induced at two levels (100% and 50% field capacity), and salicylic acid (SA) and silicon (Si) and Ecotype were also used at two levels of (0 and 100 PPM), (0 and 1 g/L) and (Ilam and Abdanan) respectively. Data analysis results indicated that the H2O2 content, Malondialdehyde (MDA), glycine betaine (GB) and the activity of the enzyme glutathione reductase (GR; EC 1.6.4.2) of aerial parts increased during the entire stress exposure period. Although the SA + Si + stress + ecotype interaction increased the content of soluble carbohydrate s and the GR activity in aerial parts of Ilam and Abdanan ecotypes, this interaction led to a decrease in MDA, H2O2 in Ilam ecotypes. The interaction between the stress + SA + Si + ecotype led to an increase in the phenylalanine ammonialyase (PAL; EC 4.3.1.5) activity in the Abdanan ecotype, but no important difference was observed. As compared to the control treatment, the content of Polyphenol increased, The interaction between ecotype + stress + Si caused to increased the of proline content in the Abadanan ecotype. The results showed that the increase in antioxidant defense and compatible osmolytes due to the use of SA and Si can improve the drought tolerance in S.striata.

Exploring the Heat Shock Transcription Factor (HSF) Gene Family in Ginger: A Genome-Wide Investigation on Evolution, Expression Profiling, and Response to Developmental and Abiotic Stresses

Ginger is a valuable crop known for its nutritional, seasoning, and health benefits. However, abiotic stresses, such as high temperature and drought, can adversely affect its growth and development. Heat shock transcription factors (HSFs) have been recognized as crucial elements for enhancing heat and drought resistance in plants. Nevertheless, no previous study has investigated the HSF gene family in ginger. In this research, a total of 25 ZoHSF members were identified in the ginger genome, which were unevenly distributed across ten chromosomes. The ZoHSF members were divided into three groups (HSFA, HSFB, and HSFC) based on their gene structure, protein motifs, and phylogenetic relationships with Arabidopsis. Interestingly, we found more collinear gene pairs between ZoHSF and HSF genes from monocots, such as rice, wheat, and banana, than dicots like Arabidopsis thaliana. Additionally, we identified 12 ZoHSF genes that likely arose from duplication events. Promoter analysis revealed that the hormone response elements (MEJA-responsiveness and abscisic acid responsiveness) were dominant among the various cis-elements related to the abiotic stress response in ZoHSF promoters. Expression pattern analysis confirmed differential expression of ZoHSF members across different tissues, with most showing responsiveness to heat and drought stress. This study lays the foundation for further investigations into the functional role of ZoHSFs in regulating abiotic stress responses in ginger.

Effects of exogenous glycine betaine and cycloleucine on photosynthetic capacity, amino acid composition, and hormone metabolism in Solanum melongena L

Although exogenous glycine betaine (GB) and cycloleucine (Cyc) have been reported to affect animal cell metabolism, their effects on plant growth and development have not been studied extensively. Different concentrations of exogenous glycine betaine (20, 40, and 60 mmol L^-1) and cycloleucine (10, 20, and 40 mmol L^-1), with 0 mmol L^-1 as control, were used to investigate the effects of foliar spraying of betaine and cycloleucine on growth, photosynthesis, chlorophyll fluorescence, Calvin cycle pathway, abaxial leaf burr morphology, endogenous hormones, and amino acid content in eggplant. We found that 40 mmol L^-1 glycine betaine had the best effect on plant growth and development; it increased the fresh and dry weight of plants, increased the density of abaxial leaf hairs, increased the net photosynthetic rate and Calvin cycle key enzyme activity of leaves, had an elevating effect on chlorophyll fluorescence parameters, increased endogenous indoleacetic acid (IAA) content and decreased abscisic acid (ABA) content, and increased glutamate, serine, aspartate, and phenylalanine contents. However, cycloleucine significantly inhibited plant growth; plant apical dominance disappeared, plant height and dry and fresh weights decreased significantly, the development of abaxial leaf hairs was hindered, the net photosynthetic rate and Calvin cycle key enzyme activities were inhibited, the endogenous hormones IAA and ABA content decreased, and the conversion and utilization of glutamate, arginine, threonine, and glycine were affected. Combined with the experimental results and plant growth phenotypes, 20 mmol L^-1 cycloleucine significantly inhibited plant growth. In conclusion, 40 mmol L^-1 glycine betaine and 20 mmol L^-1 cycloleucine had different regulatory effects on plant growth and development.

The impact of boron nutrient supply in mulberry (Morus alba) response to metabolomics, enzyme activities, and physiological parameters

Boron (B) is essential for normal and healthy plant growth. Therefore, Boron stress is a common abiotic stress that limits plant growth and productivity. However, how mulberry copes with boron stress remains unclear. In this study, seedlings of the Morus alba cultivar, Yu-711, were treated with five different concentrations of boric acid (H₃BO₃), including deficient (0 and 0.02 mM), sufficient (0.1 mM) and toxic (0.5 and 1 mM) levels. Physiological parameters, enzymatic activities and non-targeted liquid chromatography-mass spectrometry (LC-MS) technique were employed to evaluate the effects of boron stress on the net photosynthetic rate (Pn), chlorophyll content, stomatal conductance (Gs), transpiration rate (Tr), intercellular CO₂ concentration (Ci) and metabolome signatures. Physiological analysis revealed that Boron deficiency and toxicity induced a decline in P_n, C_i, G_s, T_r, and chlorophyll content. Also, enzymatic activities, including catalase (CAT) and superoxide dismutase (SOD), decreased, while POD activity increased in response to Boron stress. Osmotic substances such as soluble sugars, soluble proteins, and proline (PRO) presented elevated levels under all Boron concentrations. Metabolome analysis indicated that differential metabolites, including amino acids, secondary metabolites, carbohydrates, and lipids, played a key role in Yu-711's response to Boron stress. These metabolites were mainly involved in amino acid metabolism, biosynthesis of other secondary metabolites, lipid metabolism, metabolism of cofactors and vitamins, and metabolism of other amino acids pathways. Our findings reveal the various metabolites pathways in mulberry response to boron nutrient supply and may serve as fundamental knowledge in breeding resistance mulberry plants, so that it can cope with climate changes.

Physiological, biochemical, and metabolic changes in diploid and triploid watermelon leaves during flooding

BACKGROUND

Flooding is a major stress factor impacting watermelon growth and production globally. Metabolites play a crucial role in coping with both biotic and abiotic stresses.

METHODS

In this study, diploid (2X) and triploid (3X) watermelons were investigated to determine their flooding tolerance mechanisms by examining physiological, biochemical, and metabolic changes at different stages. Metabolite quantification was done using UPLC-ESI-MS/MS and a total of 682 metabolites were detected.

RESULTS

The results showed that 2X watermelon leaves had lower chlorophyll content and fresh weights compared to 3X. The activities of antioxidants, such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), were higher in 3X than in 2X. 3X watermelon leaves showed lower O₂ production rates, MDA, and hydrogen peroxide (H₂O₂) levels in response to flooding, while higher ethylene production was observed. 3X had higher levels of dehydrogenase activity (DHA) and ascorbic acid + dehydrogenase (AsA + DHA), but both 2X and 3X showed a significant decline in the AsA/DHA ratio at later stages of flooding. Among them, 4-guanidinobutyric acid (mws0567), an organic acid, may be a candidate metabolite responsible for flooding tolerance in watermelon and had higher expression levels in 3X watermelon, suggesting that triploid watermelon is more tolerant to flooding.

CONCLUSION

This study provides insights into the response of 2X and 3X watermelon to flooding and the physiological, biochemical, and metabolic changes involved. It will serve as a foundation for future in-depth molecular and genetic studies on flooding response in watermelon.

Drought tolerance of Aspergillus violaceofuscus and Bacillus licheniformis and their influence on tomato growth and potassium uptake in mica amended tropical soils under water-limiting conditions

Drought is a significant abiotic stress that alters plant physiology and ultimately affects crop productivity. Among essential plant nutrients, potassium (K) is known to mitigate the deleterious effect of drought on plant growth. If so, K addition or inoculation of potassium solubilizing microorganisms (KSMs) that are tolerant to drought should promote plant growth during water stress. Therefore, in this study, K solubilizing Aspergillus violaceofuscus and Bacillus licheniformis, isolated from saxicolous environments, were tested for their capacity to tolerate drought using different molecular weights (~4000, 6000, and 8000 Da), and concentrations (0, 250, 500, 750, 1000, and 1250 mg/L) of polyethylene glycol (PEG) under in vitro conditions. The results showed that high concentrations (750 and 1000 mg/L) of PEG with different molecular weight considerably improved bacterial cell numbers/fungal biomass and catalase (CAT) and proline activities. Moreover, the ability of KSMs alone or in combination to impart drought tolerance and promote plant growth in the presence and absence of mica (9.3% K₂O) supplementation was tested in Alfisol and Vertisol soil types under greenhouse conditions. The results revealed that the tomato plants inoculated with KSMs individually or dually with/without mica improved the physiological and morphological traits of the tomato plants under drought. Generally, tomato plants co-inoculated with KSMs and supplemented with mica were taller (2.62 and 3.38-fold) and had more leaf area (2.03 and 1.98-fold), total root length (3.26 and 8.86-fold), shoot biomass (3.87 and 3.93-fold), root biomass (9.00 and 7.24-fold), shoot K content (3.08 and 3.62-fold), root K content (3.39 and 2.03-fold), relative water content (1.51 and 1.27-fold), CAT activity (2.11 and 2.14-fold), proline content (3.41 and 3.28-fold), and total chlorophyll content (1.81 and 1.90-fold), in unsterilized Alfisol and Vertisol soil types, respectively, than uninoculated ones. Dual inoculation of the KSMs along with mica amendment, also improved the endorrhizal symbiosis of tomato plants more than their individual inoculation or application in both soil types. These findings imply that the A. violaceofuscus and B. licheniformis isolates are promising as novel bioinoculants for improving crop growth in water-stressed and rainfed areas of the tropics in the future.

Chitosan-based Schiff base-metal (Fe, Cu, and Zn) complexes mitigate the negative consequences of drought stress on pomegranate fruits

Drought is one of the major environmental stresses that impairs fruit productivity and quality. The proper management of minerals can, however, assist plant to maintain their growth even under drought incidents, and is considered one of the encouraging approaches to refine the drought tolerance of plants. The beneficial effects of chitosan (CH)-based Schiff base-metal complexes (e.g., CH-Fe, CH-Cu and CH-Zn) in reducing the harmful impacts of different levels of drought stress on the growth and productivity of 'Malase Saveh' pomegranate cultivar were examined. All CH-metal complexes displayed favorable effects on the yield- and growth-related attributes of pomegranate trees cultivated under well-watered and different drought situations, with the best effects were observed with CH-Fe application. Specifically, leaves of CH-Fe-treated pomegranate plants showed higher concentrations of photosynthetic pigments [chlorophyll a (Chl a), Chl b, Chl a+b, and carotenoids by 28.0, 29.5, 28.6 and 85.7%, respectively] and microelements (Fe by 27.3%), along with increased levels of superoxide dismutase (by 35.3%) and ascorbate peroxidase (by 56.0%) enzymatic activities relative to those of CH-Fe-non-treated pomegranate plants under intense drought stress. CH-Fe-treated drought-stressed pomegranate leaves showed high increment of abscisic acid (by 25.1%) and indole-3-acetic acid (by 40.5%) relative to CH-Fe-non-treated pomegranates. The increased contents of total phenolics, ascorbic acid, total anthocyanins, and titratable acidity (by 24.3, 25.8, 9.3 and 30.9%, respectively) in the fruits of CH-Fe-treated drought-stressed pomegranates indicated the advantageousness of CH-Fe on the enhancement of fruit nutritional qualities. Collectively, our results prove the explicit functions of these complexes, particularly CH-Fe, in the control of drought-induced negative effects on pomegranate trees grown in semi-arid and dry areas.

The battle of crops against drought: Genetic dissection and improvement

With ongoing global climate change, water scarcity-induced drought stress remains a major threat to agricultural productivity. Plants undergo a series of physiological and morphological changes to cope with drought stress, including stomatal closure to reduce transpiration and changes in root architecture to optimize water uptake. Combined phenotypic and multi-omics studies have recently identified a number of drought-related genetic resources in different crop species. The functional dissection of these genes using molecular techniques has enriched our understanding of drought responses in crops and has provided genetic targets for enhancing resistance to drought. Here, we review recent advances in the cloning and functional analysis of drought resistance genes and the development of technologies to mitigate the threat of drought to crop production.

Targeted and untargeted metabolomics reveals deep analysis of drought stress responses in needles and roots of Pinus taeda seedlings

Drought stress is one of major environmental stresses affecting plant growth and yield. Although Pinus taeda trees are planted in rainy southern China, local drought sometime occurs and can last several months, further affecting their growth and resin production. In this study, P. taeda seedlings were treated with long-term drought (42 d), and then targeted and untargeted metabolomics analysis were carried out to evaluate drought tolerance of P. taeda. Targeted metabolomics analysis showed that levels of some sugars, phytohormones, and amino acids significantly increased in the roots and needles of water-stressed (WS) P. taeda seedlings, compared with well-watered (WW) pine seedlings. These metabolites included sucrose in pine roots, the phytohormones abscisic acid and sacylic acid in pine needles, the phytohormone gibberellin (GA4) and the two amino acids, glycine and asparagine, in WS pine roots. Compared with WW pine seedlings, the neurotransmitter acetylcholine significantly increased in needles of WS pine seedlings, but significantly reduced in their roots. The neurotransmitters L-glutamine and hydroxytyramine significantly increased in roots and needles of WS pine seedlings, respectively, compared with WW pine seedlings, but the neurotransmitter noradrenaline significantly reduced in needles of WS pine seedlings. Levels of some unsaturated fatty acids significantly reduced in roots or needles of WS pine seedlings, compared with WW pine seedlings, such as linoleic acid, oleic acid, myristelaidic acid, myristoleic acid in WS pine roots, and palmitelaidic acid, erucic acid, and alpha-linolenic acid in WS pine needles. However, three saturated fatty acids significantly increased in WS pine seedlings, i.e., dodecanoic acid in WS pine needles, tricosanoic acid and heptadecanoic acid in WS pine roots. Untargeted metabolomics analysis showed that levels of some metabolites increased in WS pine seedlings, especially sugars, long-chain lipids, flavonoids, and terpenoids. A few of specific metabolites increased greatly, such as androsin, piceatanol, and panaxatriol in roots and needles of WS pine seedlings. Comparing with WW pine seedlings, it was found that the most enriched pathways in WS pine needles included flavone and flavonol biosynthesis, ABC transporters, diterpenoid biosynthesis, plant hormone signal transduction, and flavonoid biosynthesis; in WS pine roots, the most enriched pathways included tryptophan metabolism, caffeine metabolism, sesquiterpenoid and triterpenoid biosynthesis, plant hormone signal transduction, biosynthesis of phenylalanine, tyrosine, and tryptophan. Under long-term drought stress, P. taeda seedlings showed their own metabolomics characteristics, and some new metabolites and biosynthesis pathways were found, providing a guideline for breeding drought-tolerant cultivars of P. taeda.

Physiological and molecular insight of microbial biostimulants for sustainable agriculture

Increased food production to cater the need of growing population is one of the major global challenges. Currently, agro-productivity is under threat due to shrinking arable land, increased anthropogenic activities and changes in the climate leading to frequent flash floods, prolonged droughts and sudden fluctuation of temperature. Further, warm climatic conditions increase disease and pest incidences, ultimately reducing crop yield. Hence, collaborated global efforts are required to adopt environmentally safe and sustainable agro practices to boost crop growth and productivity. Biostimulants appear as a promising means to improve growth of plants even under stressful conditions. Among various categories of biostimulants, microbial biostimulants are composed of microorganisms such as plant growth-promoting rhizobacteria (PGPR) and/or microbes which stimulate nutrient uptake, produce secondary metabolites, siderophores, hormones and organic acids, participate in nitrogen fixation, imparts stress tolerance, enhance crop quality and yield when applied to the plants. Though numerous studies convincingly elucidate the positive effects of PGPR-based biostimulants on plants, yet information is meagre regarding the mechanism of action and the key signaling pathways (plant hormone modulations, expression of pathogenesis-related proteins, antioxidants, osmolytes etc.) triggered by these biostimulants in plants. Hence, the present review focuses on the molecular pathways activated by PGPR based biostimulants in plants facing abiotic and biotic challenges. The review also analyses the common mechanisms modulated by these biostimulants in plants to combat abiotic and biotic stresses. Further, the review highlights the traits that have been modified through transgenic approach leading to physiological responses akin to the application of PGPR in the target plants.

Exogenous α-Tocopherol Regulates the Growth and Metabolism of Eggplant (Solanum melongena L.) under Drought Stress

The present investigation was designed to improve drought stress tolerance in eggplant (Solanum melongena L.) through the exogenous application of α-tocopherol (TOC). For exogenous application, two modes, i.e., foliar spray (FS) and pre-sowing seed treatment (PS), were used. Water deficiency treatment (50% field capacity (FC)) was applied on 32-day-old seedlings of two eggplant cultivars, i.e., Janak and Black Beauty. Five levels of TOC (0 mg/L, 50 mg/L PS, 100 mg/L PS, 50 mg/L FS, and 100 mg/L FS) were applied as PS and FS. Pre-sowing seed treatment was conducted before seed sowing, while FS treatment after 30 days of drought stress treatment. After 15 days of TOC as an FS application, it was observed that drought stress significantly reduced plant growth (5-15%) and chlorophyll contents (4-10%), while it increased proline (4-6%), glycine betaine (GB) (5-10%), malondialdehyde (MDA) (10.8%), hydrogen peroxide (15-16%), relative membrane permeability (RMP) (5-8%), and the activities of peroxidase (7-8%) and superoxide dismutase (12-15%) in both eggplant cultivars. The TOC application (FS and PS) exhibited a positive role in overcoming the adverse effect of water stress on eggplants. Plant growth increased (15-18%) as a result of the application of TOC, which could be linked with improved chlorophyll, ascorbic acid (AsA), GB, proline, total soluble proteins (TSP), and the activities of peroxidase (POD) and superoxide dismutase (SOD) activities. The reactive oxygen species H₂O₂ was also decreased by TOC application. Overall, TOC as a foliar spray was more effective in improving the accumulation of proline, GB, AsA, and activities of SOD and POD enzymes, while PS treatment was more effective in reducing RMP and improving the TSP of eggplant. Cv. Black Beauty was comparatively better in root dry weight, chlorophyll a and b, and MDA contents, while cv. Janak in RMP, AsA, TSP, and activity of the POD enzyme. It can be inferred that the application of TOC was useful in counteracting the harmful effects of drought stress on both cultivars of eggplants.

Effects of a heavy metal (cadmium) on the responses of subtropical coastal tree species to drought stress

With global climate change and increased industrialization, drought and heavy metals have become common abiotic stress factors for coastal vegetation. In this study, we investigated the ecophysiological responses of the seedlings of three subtropical coastal tree species (Barringtonia racemosa, Hibiscus tiliaceus, and Terminalia neotaliala) to drought stress (D), cadmium addition (Cd), and their combined effects (Cd + D). The results showed that, for all three plant species, treatment D significantly decreased A_max, Y(II), qP, and ETR; increased the concentrations of PRO, soluble sugars, ABA, MDA, and O₂^-; and increased the activity of Rubisco. The concentrations of soluble sugars, MDA, and O₂^- were similar for treatments D and Cd; the only difference was that qP, A_max, and ETR values of B. racemosa and the A_max value of H. tiliaceus were significantly lower in treatment Cd than in control. The concentrations of PRO, soluble sugars, ABA, and MDA were significantly lower for treatment Cd + D than for treatment D. The O₂^- concentration was positively correlated with the concentrations of soluble sugars and PRO, indicating that osmoregulation was important for the responses of the plants to oxidative stress. ABA was positively correlated with MDA, indicating that ABA was involved in the response to oxidative stress. These results, which show that Cd may weaken the physiological responses of coastal plants to drought stress by increasing ABA accumulation, may provide guidance for coastal ecosystem management in South China.

Comparative analysis of physiological responses to environmental stress in Hedysarum scoparium and Caragana korshinskii seedlings due to roots exposure

Hedysarum scoparium and Caragana korshinskii seedlings were used as the test materials to carry out the roots exposure stress model test. By comparing the physiological growth indexes in the leaves of the tested plants, the stress resistance ability was evaluated. The results showed (1) root exposure resulted in excessive oxygen free radicals, which resulted in membrane lipid peroxidation and increased MDA content in two plants. The increase of MDA content in H. scoparium was greater than that in C. korshinskii. (2) H. scoparium mainly regulate their own adaptation to the stress by regulating carotenoids. C. korshinskii adjusts itself to adapt to the stress by regulating chlorophyll. (3) H. scoparium resist this stress mainly by regulating their respiration rate. (4) H. scoparium mainly through the mobilization of proline, by adjusting the proline concentration to reduce their water potential; C. korshinskii reduced its water potential mainly by regulating the concentration of soluble sugar to adapt to the stress. (5) H. scoparium and C. korshinskii activated peroxidase (H. scoparium) and catalase (C. korshinskii) to clean up intracellular peroxides, respectively. To sum up, under the same root exposure ratio, there were significant differences in physiological regulation and morphological indexes between H. and C. korshinskii, but their stress resistance mechanisms were quite different.

Combined physiological and metabolomic analysis reveals the effects of different biostimulants on maize production and reproduction

Plant biostimulants (PBs) are a potential strategy to improve crop growth and grain quality. In the present study, 100 mg/L trehalose, chitosan, humic acid and gamma-aminobutyric acid treatments were applied to analyze the effects of maize production and reproductive characteristics. The contents of nitrogen, phosphorus and potassium and grain quality were significantly affected by the PBs, but not yield. The seed germination rate of all PB treatments was significantly reduced, but the drought resistance of progeny seedlings was significantly improved, with humic acid having the strongest effect. Liquid chromatography mass spectrometry analysis indicated that the disruption of the tricarboxylic acid cycle, probably due to the blockage of intermediate anabolism, reduced the supply of energy and nutrients in the early stages of germination, thus inhibiting seed germination, while the increased resistance of the offspring seedlings may be due to the up-regulation of the synthesis of unsaturated fatty acids and alkaloids by humic acid treatment. This study revealed the similarity and heterogeneity of the effects of different PBs on nutrient accumulation, yield characteristics and grain quality of maize, providing guidance for the application of PBs in intensive and sustainable agricultural production.

Comparison of lauric acid and 12-hydroxylauric acid in the alleviation of drought stress in peach (Prunus persica (L.) Batsch)

Water shortage is a key factor that can restrict peach tree growth. Plants produce fatty acids and the fatty acid derivatives lauric acid (LA) and 12-hydroxylauric acid (LA-OH), which are involved in abiotic stress responses, but the underlying stress response mechanisms remain unclear. In this study, physiological examination revealed that in Prunus persica (L.) Batsch, pretreatment with 50 ppm LA-OH and LA reduced drought stress, efficiently maintained the leaf relative water content, and controlled the relative conductivity increase. Under drought stress, LA-OH and LA treatments prevented the degradation of photosynthetic pigments, increased the degree of leaf stomatal opening and enhanced the net photosynthetic rate. Compared with drought stress, LA-OH and LA treatment effectively increased the net photosynthetic rate by 204.55% and 115.91%, respectively, while increasing the Fv/Fm by 2.75% and 7.75%, respectively, but NPQ decreased by 7.67% and 37.54%, respectively. In addition, the level of reactive oxygen species increased under drought stress. The content of O₂ ^- in LA-OH and LA treatment decreased by 12.91% and 11.24% compared to CK-D, respectively, and the content of H₂O₂ decreased by 13.73% and 19.94%, respectively. At the same time, the content of malondialdehyde (MDA) decreased by 55.56% and 58.48%, respectively. We believe that the main reason is that LA-OH and LA treatment have improved the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). The application of exogenous LA increased the levels of soluble sugars, soluble proteins, proline and free amino acids under drought stress, and maintained the osmotic balance of cells. Compared with CK-D treatment, it increased by 24.11%, 16.89%, 29.3% and 15.04%, respectively. At the same time, the application of exogenous LA-OH also obtained similar results. In conclusion, exogenous LA-OH and LA can alleviate the damage to peach seedlings caused by drought stress by enhancing the photosynthetic and antioxidant capacities, increasing the activities of protective enzymes and regulating the contents of osmotic regulators, but the molecular mechanism is still in need of further exploration.

Trehalose-Induced Regulations in Nutrient Status and Secondary Metabolites of Drought-Stressed Sunflower (Helianthus annuus L.) Plants

Trehalose regulates key physio-biochemical parameters, antioxidants, and the yield of plants exposed to a dry environment. A study was conducted to assess the regulatory roles of exogenously applied trehalose in drought-stressed sunflower plants. Two cultivars of sunflowers (Hysun 33 and FH 598) were subjected to drought stress (60% field capacity) and varying (0, 10, 20, and 30 mM) concentrations of trehalose. The data indicated that water stress significantly reduced the shoot length, root length, total soluble proteins, shoot Ca²⁺, root P, relative water content (RWC), and achene yield per plant. The foliar spray of trehalose was effective at improving plant growth, RWC, total soluble proteins, total soluble sugars, the activities of enzymatic antioxidants, Ca²⁺ (shoot and root), root K⁺, and the yield attributes. Exogenously supplemented trehalose considerably suppressed relative membrane permeability (RMP), but did not alter ascorbic acid, malondialdehyde, the total phenolics, shoot K⁺, or P (shoot and root) in both sunflower cultivars. The cv. Hysun 33 had better ascorbic acid, total soluble sugars, non-reducing sugars, shoot P, and root P than the other cultivar, whereas cv. FH 598 was relatively better at regulating RMP, malondialdehyde, peroxidase, and root Ca²⁺ concentration. Overall, exogenously supplemented trehalose, particularly at 10 mM, was effective at improving the physiochemical parameters and yield of sunflower plants under stress conditions. Therefore, a better performance of sunflower cv. Hysun 33 under drought stress can be suggested as a trehalose-induced enhancement of yield and oxidative defense potential.

Impact of Biochar Application at Water Shortage on Biochemical and Physiological Processes in Medicago ciliaris

The application of biochar is mostly used to improve soil fertility, water retention capacity and nutrient uptake. The present study was conducted in order to study the impact of biochar at water deficiency conditions on the physiological and biochemical processes of Medicago ciliaris seedlings. Seedlings were cultivated under greenhouse conditions in pots filled with a mixture of soil and sand mixed in the presence or absence of 2% biochar. Plants of uniform size were subjected after a pretreatment phase (72 days) either to low (36% water holding capacity, water potential low) or high soil water potential (60% water holding capacity, water potential high). Pots were weighed every day to control and maintain a stable water holding capacity. In Medicago ciliaris, drought led to a significant reduction in plant growth and an increase in the root/shoot ratio. The growth response was accompanied by a decreased stomatal conductance and a reduction of the net CO₂ assimilation rate and water use efficiency. The associated higher risk of ROS production was indicated by a high level of lipid peroxidation, high antioxidant activities and high proline accumulation. Soil amendment with biochar enhanced the growth significantly and supported the photosynthetic apparatus of Medicago ciliaris species by boosting chlorophyll content and A_net both under well and insufficient watered plants and water use efficiency in case of water shortage. This increase of water use efficiency was correlated with the biochar-mediated decrease of the MDA and proline contents in the leaves buffering the impact of drought on photosynthetic apparatus by increasing the activity of enzymatic antioxidants SOD, APX, GPOX and GR and non-enzymatic antioxidants, such as AsA and DHAsA, giving the overall picture of a moderate stress response. These results confirmed the hypothesis that biochar application significantly reduces both the degree of stress and the negative impact of oxidative stress on Medicago ciliaris plants. These results implied that this species could be suitable as a cash pasture plant in the development of agriculture on dry wasteland in a future world of water shortages.

Endophytic Fungal Consortia Enhance Basal Drought-Tolerance in Moringa oleifera by Upregulating the Antioxidant Enzyme (APX) through Heat Shock Factors

Global climate change has imposed harsh environmental conditions such as drought. Naturally, the most compatible fungal consortia operate synergistically to enhance plant growth and ecophysiological responses against abiotic strains. Yet, little is known about the interactions between phytohormone-producing endophytic fungal symbionts and plant growth under drought stress. The existing research was rationalized to recognize the role of newly isolated drought-resistant, antioxidant-rich endophytic fungal consortia hosting a xerophytic plant, Carthamus oxycantha L., inoculated to Moringa oleifera L. grown under drought stress of 8% PEG (polyethylene glycol-8000). Under drought stress, the combined inoculation of endophytic strain Microdochium majus (WA), Meyerozyma guilliermondi (TG), and Aspergillus aculeatus (TL3) exhibited a significant improvement in growth attributes such as shoot fresh weight (1.71-fold), shoot length (0.86-fold), root length (0.65-fold), dry weight (2.18-fold), total chlorophyll (0.46-fold), and carotenoids (0.87-fold) in comparison to control (8% PEG). Primary and secondary metabolites were also increased in M. oleifera inoculated with endophytic consortia, under drought stress, such as proteins (1.3-fold), sugars (0.58-fold), lipids (0.41-fold), phenols (0.36-fold), flavonoids (0.52-fold), proline (0.6-fold), indole acetic acid (IAA) (4.5-fold), gibberellic acid (GA) (0.7-fold), salicylic acid (SA) (0.8-fold), ascorbic acid (ASA) (1.85-fold), while abscisic acid (ABA) level was decreased (−0.61-fold) in comparison to the control (8% PEG). Under drought stress, combined inoculation (WA, TG, TL3) also promoted the antioxidant activities of enzymes such as ascorbate peroxidase (APX) (3.5-fold), catalase (CAT) activity (1.7-fold), and increased the total antioxidant capacity (TAC) (0.78-fold) with reduced reactive oxygen species (ROS) such as H2O2 production (-0.4-fold), compared to control (8% PEG), and stomatal aperture was larger (3.5-fold) with a lesser decrease (-0.02-fold) in water potential. Moreover, combined inoculation (WA, TG, TL3) up regulated the expression of MolHSF3, MolHSF19, and MolAPX genes in M. oleifera under drought stress, compared to the control (8% PEG), is suggestive of an important regulatory role for drought stress tolerance governed by fungal endophytes. The current research supports the exploitation of the compatible endophytic fungi for establishing the tripartite mutualistic symbiosis in M. oleifera to alleviate the adverse effects of drought stress through strong antioxidant activities.

Melatonin: First-line soldier in tomato under abiotic stress current and future perspective

Melatonin is a natural, multifunctional, nontoxic, regulatory, and ubiquitous biomolecule, having low molecular weight and pleiotropic effects in the plant kingdom. It is a recently discovered plant master regulator which has a crucial role under abiotic stress conditions (salinity, drought, heat, cold, alkalinity, acid rain, ozone, and metals stress). In the solanaceous family, the tomato is highly sensitive to abiotic stresses that affect its growth and development, ultimately hampering production and productivity. Melatonin acts as a strong antioxidant, bio-stimulator, and growth regulator, facilitating photosynthesis, delaying leaf senescence, and increasing the antioxidant enzymes system through direct scavenging of reactive oxygen species (ROS) under abiotic stresses. In addition, melatonin also boosts morphological traits such as vegetative growth, leaf photosynthesis, root architecture system, mineral nutrient elements, and antioxidant activities in tomato plants, confirming their tolerances against salinity, drought, heat, cold, alkalinity, acid rain, chemical, pathogen, and metals stress. In this review, an attempt has been made to summarize the potential role of melatonin for tomato plant endurance towards abiotic stresses, along with the known relationship between the two.

Trehalose alleviates salt tolerance by improving photosynthetic performance and maintaining mineral ion homeostasis in tomato plants

Trehalose (Tre), which was an osmoprotective or stabilizing molecule, played a protective role against different abiotic stresses in plants and showed remarkable perspectives in salt stress. In this study, the potential role of Tre in improving the resistance to salt stress in tomato plants was investigated. Tomato plants (Micro Tom) were treated with Hoagland nutrient solution (CK), 10 mM Tre (T), 150 mM sodium chloride (NaCl, S), and 10 mM Tre+150 mM NaCl (S+T) for 5 days. Our results showed that foliar application of Tre alleviated the inhibition of tomato plant growth under salt stress. In addition, salt stress decreased the values of net photosynthetic rate (Pn, 85.99%), stomata conductance (gs, 57.3%), and transpiration rate (Tr, 47.97%), but increased that of intercellular carbon dioxide concentration (Ci, 26.25%). However, exogenous application of Tre significantly increased photosynthetic efficiency, increased the activity of Calvin cycle enzymes [ribulose diphosphate carboxylase/oxygenase (Rubisco), fructose-1,6-bisphosphate aldolase (FBA), fructose-1, 6-bisphosphatase (FBPase), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and transketolase (TK)], up-regulated the expression of genes encoding enzymes, induced stomatal opening, and alleviated salt-induced damage to the chloroplast membrane and structure. In the saline environment, photosynthetic electron transport was restricted, resulting the J-I-P phase to decrease. At the same time, the absorption, capture, and transport energies per excited cross-section and per active reaction center decreased, and the dissipation energy increased. Conversely, Tre reversed these values and enhanced the photosystem response to salt stress by protecting the photosynthetic electron transport system. In addition, foliage application with Tre significantly increased the potassium to sodium transport selectivity ratio (S _K-Na ) by 16.08%, and increased the levels of other ions to varying degrees. Principal component analysis (PCA) analysis showed that exogenous Tre could change the distribution of elements in different organs and affect the expressions of SlSOS1, SlNHX, SlHKT1.1, SlVHA, and SlHA-A at the transcriptional level under salt stress, thereby maintaining ion homeostasis. This study demonstrated that Tre was involved in the process of mitigating salt stress toxicity in tomato plants and provided specific insights into the effectiveness of Tre in mediating salt tolerance.

Impacts of Ascorbic Acid and Alpha-Tocopherol on Chickpea (Cicer arietinum L.) Grown in Water Deficit Regimes for Sustainable Production

Drought is a major abiotic stress forced by the changing climate that affects plant production and soil structure and functions. A study was conducted to explore the impacts of ascorbic acid (AsA) and α-tocopherol (α-toc) on the agro-physiological attributes and antioxidant enzymes of chickpea grown in water deficit regions. The results of the soil analysis showed that the electrical conductivity (EC) and pH were decreased from 521 mS/m and 7.08 to 151 mS/m and 6.6 in 20-day drought regimes, respectively. Agronomic outcomes showed that exogenous application of AsA and α-toc increased the germination rate index (GRI), mean germination time (MGT), germination energy (GE), water use efficiency (WUE), germination percentage (GP), and seed vigor index (SVI). However, all the above attributes experienced a decline under 10- and 20-day drought stress. Similarly, the Chl. a, Chl. b, carotenoids, proline, protein, sugar, glycine betaine, and hydrogen peroxide contents were significantly increased. Meanwhile, malondialdehyde, glutathione reductase, and enzymatic antioxidants (APOX, SOD, and POD) increased during 10- and 20-day drought, except CAT, which decreased during drought. The exogenous fertigation of these growth regulators improved the photosynthetic pigments and enzymatic and non-enzymatic antioxidants in stressed plants. The current research concludes that simultaneous dusting of AsA and α-toc could be an efficient technique to mitigate the antagonistic impacts of drought, which might be linked to the regulation of antioxidant defense systems.

Improving Drought Stress Tolerance in Ramie (Boehmeria nivea L.) Using Molecular Techniques

Ramie is one of the most significant fiber crops and contributes to good quality fiber. Drought stress (DS) is one of the most devastating abiotic factors which is accountable for a substantial loss in crop growth and production and disturbing sustainable crop production. DS impairs growth, plant water relation, and nutrient uptake. Ramie has evolved a series of defense responses to cope with DS. There are numerous genes regulating the drought tolerance (DT) mechanism in ramie. The morphological and physiological mechanism of DT is well-studied; however, modified methods would be more effective. The use of novel genome editing tools like clustered regularly interspaced short palindromic repeats (CRISPR) is being used to edit the recessive genes in crops to modify their function. The transgenic approaches are used to develop several drought-tolerant varieties in ramie, and further identification of tolerant genes is needed for an effective breeding plan. Quantitative trait loci (QTLs) mapping, transcription factors (TFs) and speed breeding are highly studied techniques, and these would lead to the development of drought-resilient ramie cultivars. The use of hormones in enhancing crop growth and development under water scarcity circumstances is critical; however, using different concentrations and testing genotypes in changing environments would be helpful to sort the tolerant genotypes. Since plants use various ways to counter DS, investigating mechanisms of DT in plants will lead to improved DT in ramie. This critical review summarized the recent advancements on DT in ramie using novel molecular techniques. This information would help ramie breeders to conduct research studies and develop drought tolerant ramie cultivars.

Taurine modulates dynamics of oxidative defense, secondary metabolism, and nutrient relation to mitigate boron and chromium toxicity in Triticum aestivum L. plants

The present study was undertaken to appraise the efficacy of exogenous taurine in alleviating boron (B) and chromium (Cr) toxicity. Taurine protects cell membranes from lipid peroxidation due to its function as a ROS scavenger. However, there exists no report in the literature on the role of taurine in plants under abiotic stresses. The present investigation indicated the involvement of exogenous taurine in mediating plant defense responses under B and Cr toxicity. Wheat plants manifested a significant drop in growth, chlorophyll molecules, SPAD values, relative water content, nitrate reductase activity, and uptake of essential nutrients under B, Cr, and combined B-Cr toxicity. Plants showed significant oxidative damage due to enhanced cellular levels of superoxide radicals (O₂^•-), hydrogen peroxide (H₂O₂), malondialdehyde (MDA), relative membrane permeability, and activity of lipoxygenase (LOX). Additionally, a significant negative correlation existed in B and Cr levels with the uptake of essential nutrients. Taurine substantially improved growth, photosynthetic pigments, and nutrient uptake by regulating ROS scavenging, secondary metabolism, and ions homeostasis under stress. Taurine protected plants from the detrimental effects of B and Cr by upregulating the production of nitric oxide, hydrogen sulfide, glutathione, and phenolic compounds.

Programming an Orthogonal Self-Assembling Protein Cascade Based on Reactive Peptide-Protein Pairs for In Vitro Enzymatic Trehalose Production

Trehalose is an important rare sugar that protects biomolecules against environmental stress. We herein introduce a dual enzyme cascade strategy that regulates the proportion of cargos and scaffolds, to maximize the benefits of enzyme immobilization. Based upon the self-assembling properties of the shell protein (EutM) from the ethanolamine utilization (Eut) bacterial microcompartment, we implemented the catalytic synthesis of trehalose from soluble starch with the coimmobilization of α-amylase and trehalose synthase. This strategy improved enzymatic cascade activity and operational stability. The cascade system enabled the efficient production of trehalose with a yield of ∼3.44 g/(L U), 1.5 times that of the free system. Moreover, its activity was maintained over 12 h, while the free system was almost completely inactivated after 4 h, demonstrating significantly enhanced thermostability. In conclusion, an attractive self-assembly coimmobilization platform was developed, which provides an effective biological process for the enzymatic synthesis of trehalose in vitro.

Trehalose Alleviated Salt Stress in Tomato by Regulating ROS Metabolism, Photosynthesis, Osmolyte Synthesis, and Trehalose Metabolic Pathways

Trehalose plays a critical role in plant response to salinity but the involved regulatory mechanisms remain obscure. Here, this study explored the mechanism of exogenous trehalose-induced salt tolerance in tomato plants by the hydroponic test method. Our results indicated that 10 mM trehalose displayed remarkable plant biomass by improving growth physiology, which were supported by the results of chlorophyll fluorescence and rapid light-response curve. In the salinity environment, trehalose + NaCl treatment could greatly inhibit the decrease of malondialdehyde level, and it increases the contents of other osmotic substances, carbohydrates, K+, and K+/Na+ ratio. Meanwhile, trehalose still had similar effects after recovery from salt stress. Furthermore, trehalose pretreatment promoted trehalose metabolism; significantly increased the enzymatic activity of the trehalose metabolic pathway, including trehalose-6-phosphate synthase (TPS), trehalose-6-phosphate phosphatase (TPP), and trehalase (TRE); and upregulated the expression of SlTPS1, SlTPS5, SlTPS7, SlTPPJ, SlTPPH, and SlTRE under saline conditions. However, the transcriptional levels of SlTPS1, SlTPS5, and SlTPS7 genes and the activity of TPS enzyme were reversed after recovery. In addition, we found that hydrogen peroxide (H2O2) and superoxide anion (O2 -) were accumulated in tomato leaves because of salt stress, but these parameters were all recovered by foliar-applied trehalose, and its visualization degree was correspondingly reduced. Antioxidant enzyme activities (SOD, POD, and CAT) and related gene expression (SlCu/Zn-SOD, SlFe-SOD, SlMn-SOD, SlPOD, and SlCAT) in salt-stressed tomato leaves were also elevated by trehalose to counteract salt stress. Collectively, exogenous trehalose appeared to be the effective treatment in counteracting the negative effects of salt stress.

Mechanistic Insights Into Trehalose-Mediated Cold Stress Tolerance in Rapeseed (Brassica napus L.) Seedlings

Cold stress (CS) severely affects several physiological, biochemical, and molecular mechanisms and limits the growth and production of rapeseed (Brassica napus L.). Trehalose (Tre) acts as a growth modulator, which is extensively used to improve the tolerance to multiple plant stresses. Further, Tre also serves as an external force in inducing plant signaling molecules, regulating the expression of stress-responsive genes, and enhancing the CS tolerance in plants. Nevertheless, the importance of exogenous Tre in improving the CS tolerance in rapeseed is still unclear. Therefore, the current study was designed to get mechanistic insights into Tre-mediated CS tolerance in rapeseed seedlings. To explore the Tre role, we designed four treatments [control (CK), CK + 20 mM L^-1 Tre, Cold, and Cold + 20 mM L^-1 Tre] and three CS conditions (4, 0, and -4°C). The results showed that Tre treatments significantly mitigated the adverse effects of CS on the seedlings and increased the survival rate of Tre-treated seedlings under CS conditions. The exogenous Tre dramatically increased the contents of osmoprotectants, including the soluble sugar (SS), soluble protein (SP), and proline (Pro), and the activities of antioxidant enzymes, such as catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and ascorbate peroxidase (APX) were also increased under CS conditions. Additionally, Tre decreased the malondialdehyde (MDA) contents to protect the rapeseed seedlings. Moreover, Tre also remarkably augmented the expression levels of antioxidant genes (CAT12, POD34, and FSD7), CS-responsive marker genes (CBF1, CBF2, CBF4, COR6.6, COR15, COR25, COL1, and KIN1), and Tre-biosynthesis genes (TPS4, TPS8, and TPS9). Briefly, exogenous Tre not only regulates the antioxidant and osmotic balance, but it also significantly participates in Tre metabolism and signaling network to improve the CS tolerance in rapeseed. Thus, Tre-induced supervisory connections between physiological or/and biochemical attributes provide information to dissect the mechanisms of Tre-mediated CS tolerance.

Integration of the Physiology, Transcriptome and Proteome Reveals the Molecular Mechanism of Drought Tolerance in Cupressus gigantea

Drought stress can dramatically impair woody plant growth and restrict the geographical distribution of many tree species. To better understand the dynamics between the response and mechanism of Cupressus gigantea to drought and post-drought recovery, a comparative analysis was performed, relying on physiological measurements, RNA sequencing (RNA-Seq) and two-dimensional gel electrophoresis (2-DE) proteins. In this study, the analyses revealed that photosynthesis was seriously inhibited, while osmolyte contents, antioxidant enzyme activity and non-enzymatic antioxidant contents were all increased under drought stress in seedlings. Re-watering led to a recovery in most of the parameters analyzed, mainly the photosynthetic parameters and osmolyte contents. Transcriptomic and proteomic profiling suggested that most of the differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) were specifically altered, and a few were consistently altered. Drought induced a common reduction in the level of DEGs and DEPs associated with photosynthesis. Notably, DEGs and DEPs involved in reactive oxygen species (ROS) scavenging, such as ascorbate oxidase and superoxide dismutase (SOD), showed an inverse pattern under desiccation. This study may improve our understanding of the underlying molecular mechanisms of drought resistance in C. gigantea and paves the way for more detailed molecular analysis of the candidate genes.

Leaf extract of neem (Azadirachta indica) alleviates adverse effects of drought in quinoa (Chenopodium quinoa Willd.) plants through alterations in biochemical attributes and antioxidants

The influence of varying concentrations (0, 1, 3, 4, 5, 6, 8, and 10 % v/v) of neem (Azadirachta indica) leaf extract on drought stressed (40 % field capacity) quinoa (Chenopodium quinoa Willd.) plants was assessed. During the current study two cultivars of quinoa (V7 and V9) were used. This study revealed that water stress adversely affects the fresh and dry weight of shoots and roots as well as chlorophyll pigments (a and b) of both quinoa cultivars. In contrast, drought stress enhanced glycinebetaine (GB), free proline, phenolic content, hydrogen peroxide (H2O2), activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) enzymes, and relative membrane permeability (RMP). However, application of neem leaf extract improved the accumulation of key osmoprotectants like proline, GB and activities of enzymatic antioxidants. Our findings showed 5 % neem leaf extract is an effective treatment in counteracting the oxidative damage caused by water stress, thereby improving overall plant growth. Of both cultivars of quinoa, the response of cv. V9 to stress as well as foliar applied neem was relatively more promising.

Water Deficit Stress Tolerance Potential of Newly Developed Wheat Genotypes for Better Yield Based on Agronomic Traits and Stress Tolerance Indices: Physio-Biochemical Responses, Lipid Peroxidation and Antioxidative Defense Mechanism

Changing environmental conditions, fresh water shortages for irrigation and the rapid increase in world population have created the problems of food insecurity and malnutrition. Different strategies, including the development of water stress-tolerant, high-yielding genotypes through breeding are used to fulfil the world food demand. The present study was conducted for the selection of high-yielding, drought-tolerant wheat genotypes, considering different morpho-physio-biochemical, agronomic and yield attributes in relation to the stress tolerance indices (STI). The experiment was carried out in field in a split-plot arrangement. Water deficit stress was maintained based on the number of irrigations. All genotypes showed a differential decreasing trend in different agronomic traits. However, the increasing or decreasing trend in leaf photosynthetic pigments, non-enzymatic and enzymatic antioxidants under limited water supply also found to be genotype-specific. Genotypes MP1, MP3, MP5, MP8 and MP10 performed better regarding the yield performance under water deficit stress, which was associated with their better maintenance of water relations, photosynthetic pigments and antioxidative defense mechanisms. In conclusion, the physio-biochemical mechanisms should also be considered as the part of breeding programs for the selection of stress-tolerant genotypes, along with agronomic traits, in wheat.

Improving crop drought resistance with plant growth regulators and rhizobacteria: Mechanisms, applications, and perspectives

Drought is one of the main abiotic stresses that cause crop yield loss. Improving crop yield under drought stress is a major goal of crop breeding, as it is critical to food security. The mechanism of plant drought resistance has been well studied, and diverse drought resistance genes have been identified in recent years, but transferring this knowledge from the laboratory to field production remains a significant challenge. Recently, some new strategies have become research frontiers owing to their advantages of low cost, convenience, strong field operability, and/or environmental friendliness. Exogenous plant growth regulator (PGR) treatment and microbe-based plant biotechnology have been used to effectively improve crop drought tolerance and preserve yield under drought stress. However, our understanding of the mechanisms by which PGRs regulate plant drought resistance and of plant-microbiome interactions under drought is still incomplete. In this review, we summarize these two strategies reported in recent studies, focusing on the mechanisms by which these exogenous treatments regulate crop drought resistance. Finally, future challenges and directions in crop drought resistance breeding are discussed.

Integrative small RNA and transcriptome analysis provides insight into key role of miR408 towards drought tolerance response in cowpea

Drought stress response studies and overexpression of vun-miR408 proved it to be essential for abiotic stress tolerance in cowpea. Small RNA and transcriptome sequencing of an elite high-yielding drought-tolerant Indian cowpea cultivar, Pusa Komal revealed a differential expression of 198 highly conserved, 21 legume-specific, 14 less-conserved, and 10 novel drought-responsive microRNAs (miRNAs) along with 3391 (up-regulated) and 3799 (down-regulated) genes, respectively, in the leaf and root libraries. Among the differentially expressed miRNAs, vun-miR408-3p, showed an up-regulation of 3.53-log₂-fold change under drought stress. Furthermore, laccase 12 (LAC 12) was identified as the potential target of vun-miR408-3p using 5' RNA ligase-mediated rapid amplification of cDNA ends. The stable transgenic cowpea lines overexpressing artificial vun-miR408-3p (OX-amiR408) displayed enhanced drought and salinity tolerance as compared to the wild-type plants. An average increase of 30.17% in chlorophyll, 26.57% in proline, and 27.62% in relative water content along with lesser cellular H₂O₂ level was observed in the transgenic lines in comparison with the wild-type plants under drought stress. Additionally, the scanning electron microscopic study revealed a decrease in the stomatal aperture and an increase in the trichome density in the transgenic lines. The expression levels of laccase 3 and laccase 12, the potential targets of miR408, related to lipid catabolic processes showed a significant reduction in the wild-type plants under drought stress and the transgenic lines, indicating the regulation of lignin content as a plausibly essential trait related to the drought tolerance in cowpea. Taken together, this study primarily focused on identification of drought-responsive miRNAs and genes in cowpea, and functional validation of role of miR408 towards drought stress response in cowpea.

Nanoencapsulation improves the protective effects of a nitric oxide donor on drought-stressed Heliocarpus popayanensis seedlings

Despite the important role played by nitric oxide (NO) in plants subjected to abiotic stress, NO donors application to induce drought tolerance in neotropical tree seedlings has not yet been tested. It is also worth investigating whether NO bioactivity in drought-stressed seedlings could be potentiated by NO donors nanoencapsulation. The aim of the current study is to evaluate the effects of chitosan nanoparticles (NPs) containing S-nitroso-mercaptosuccinic acid (S-nitroso-MSA) on drought-stressed seedlings of neotropical tree species Heliocarpus popayanensis Kunth in comparison to free NO donor and NPs loaded with non-nitrosated MSA. Nanoencapsulation slowed down NO release from S-nitroso-MSA, and nanoencapsulated S-nitroso-MSA yielded 2- and 1.6-fold higher S-nitrosothiol levels in H. popayanensis roots and leaves, respectively, than the free NO donor. S-nitroso-MSA has prevented drought-induced CO₂ assimilation inhibition, regardless of nanoencapsulation, but the nanoencapsulated NO donor has induced earlier ameliorative effect. Both NO and MSA have decreased oxidative stress in H. popayanensis roots, but this effect was not associated with antioxidant enzyme induction, with higher seedling biomass, or with proline and glycine betaine accumulation. Nanoencapsulated S-nitroso-MSA was the only formulation capable of increasing leaf relative water content in drought-stressed plants (from 32.3% to 60.5%). In addition, it induced root hair formation (increase by 36.6% in comparison to well-hydrated plants). Overall, results have evidenced that nanoencapsulation was capable of improving the protective effect of S-nitroso-MSA on H. popayanensis seedlings subjected to drought stress, a fact that highlighted the potential application of NO-releasing NPs to obtain drought-tolerant tree seedlings for reforestation programs.

Physiological evaluation for salt tolerance in green and purple leaf color rice cultivars at seedling stage

Anthocyanin, a water-soluble pigment found in plants, has been reported to be associated with abiotic stress tolerance including salt stress. For a better understanding of the role of anthocyanin in response to salt stress, two salt-tolerant rice genotypes having different leaf anthocyanin content, one having green ('Pokkali'; PK) and the other purple leaves ('Niew Dam 019'; ND 019), were used in this study. After being subjected to salt stress (150 mM NaCl) for 5 d, the 3-week-old rice genotypes PK and ND 019 exhibited significant physiological responses (water content, Na⁺/K⁺ ratio, osmolyte accumulation, osmotic adjustment, antioxidant capacity, membrane damage and chlorophyll) and expression of ion transporter genes, indicating overall salt tolerance ability. However, the green-leaved rice variety, PK, had better root-to-shoot Na⁺ exclusion mechanism than the purple-leaved variety, ND 019 as evidenced by lower Na⁺ accumulation in leaves compared to ND 019 despite the fact that they accumulated the similar level of Na⁺ in roots. On the other hand, ND 019 accumulated higher concentration of osmolytes leading to more enhanced osmotic adjustment. These results revealed that Na⁺ ion exclusion was the prominent salt tolerance mechanism in the green-leaved PK whereas in the purple-leaved ND 019 osmotic adjustment was the more significant strategy. Under salt stress, there was no remarkable change in anthocyanin in PK while a reduction was found in ND 019. Thus, it could be proposed that anthocyanin did not play a vital role in protecting the purple-leaved rice, ND 019 from salt stress during seedling stage.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-021-01114-y.

Sugar beet extract rich in glycine betaine modulates oxidative defense system and key physiological characteristics of maize under water-deficit stress

Now-a-days, plant-based extracts, as a cheap source of growth activators, are being widely used to treat plants grown under extreme climatic conditions. So, a trial was conducted to assess the response of two maize (Zea mays L.) varieties, Sadaf (drought tolerant) and Sultan (drought sensitive) to foliar-applied sugar beet extract (SBE) under varying water-deficit conditions. Different SBE (control, 1%, 2%, 3% & 4%) levels were used in this study, and plants were exposed to water-deficit [(75% and 60% of field capacity (FC)] and control (100% FC) conditions. It was observed that root and shoot dry weights (growth), total soluble proteins, RWC-relative water contents, total phenolics, chlorophyll pigments and leaf area per plant decreased under different water stress regimes. While, proline, malondialdehyde (MDA), RMP-relative membrane permeability, H2O2-hydrogen peroxide and the activities of antioxidant enzymes [CAT-catalase, POD-peroxidase and SOD-superoxide dismutase] were found to be improved in water stress affected maize plants. Exogenous application of varying levels of SBE ameliorated the negative effects of water-deficit stress by enhancing the growth attributes, photosynthetic pigments, RWC, proline, glycinebetaine (GB), activities of POD and CAT enzymes and levels of total phenolics, whereas it reduced the lipid peroxidation in both maize varieties under varying water stress levels. It was noted that 3% and 4% levels of SBE were more effective than the other levels used in enhancing the growth as well as other characteristics of the maize varieties. Overall, the sugar beet extract proved to be beneficial for improving growth and metabolism of maize plants exposed to water stress.

Glycinebetaine mitigates drought stress-induced oxidative damage in pears

Glycinebetaine (GB) is an osmoprotectant found in plants under environmental stresses that incorporates drought and is associated with drought tolerance in several plants, such as the woody pear. However, how GB improves drought tolerance in pears remains unclear. In the current study, we explored the mechanism by which GB enhances drought tolerance of whole pear plants (Pyrus bretschneideri Redh. cv. Suli) supplied with exogenous GB. The results showed that on the sixth day after withholding water, levels of O₂·⁻, H₂O₂, malonaldehyde (MDA) and electrolyte leakage in the leaves were substantially increased by 143%, 38%, 134% and 155%, respectively. Exogenous GB treatment was substantially reduced O₂·⁻, H₂O₂, MDA and electrolyte leakage (38%, 24%, 38% and 36%, respectively) in drought-stressed leaves. Furthermore, exogenous GB induced considerably higher antioxidant enzyme activity in dry-stressed leaves than drought-stressed treatment alone on the sixth day after withholding water, such as superoxide dismutase (SOD) (201%) and peroxidase (POD) (127%). In addition, these GB-induced phenomena led to increased endogenous GB levels in the leaves of the GB 100 + drought and GB 500 + drought treatment groups by 30% and 78%, respectively, compared to drought treatment alone. The findings obtained were confirmed by the results of the disconnected leaf tests, in which GB contributed to a substantial increase in SOD activity and parallel dose- and time-based decreases in MDA levels. These results demonstrate that GB-conferred drought resistance in pears may be due in part to minimizing symptoms of oxidative harm incurred in response to drought by the activities of antioxidants and by reducing the build-up of ROS and lipid peroxidation.

Effect of potassium fertilizer on the growth, physiological parameters, and water status of Brassica juncea cultivars under different irrigation regimes

Abiotic stress, especially a lack of water, can significantly reduce crop yields. In this study, we evaluated the physiological and biochemical effects of potassium sulfate (K2SO4) fertilizer and varied irrigation regimes on the economically significant oilseed crop, Brassica juncea L, under open field conditions. Two cultivars (RH-725 and RH-749) of B. juncea were used in a randomized complete block design experiment with three replicates. Irrigation regimes consisted of a control (double irrigation: once at the 50% flowering and another at 50% fruiting stages), early irrigation (at 50% flowering only), late irrigation (at 50% fruiting only) and stress (no irrigation). The K2SO4 applications were: control (K0, no fertilization); K1, 10 kg ha-1; and K2, 20 kg ha-1. We measured growth via fresh and dry plant weight, plant height, root length, and leaf area. All the growth parameters were higher in RH-749. The physiological attributes, including the membrane stability index and relative water content, were higher at the 50% flowering stage in RH-749. The amount of antioxidant enzymes (catalase (CAT), guaiacol peroxidase (POX), ascorbate peroxidase (APX), and superoxide dismutase (SOD)) was enhanced when both plants were fertilized during water stress. All of these enzymes had higher activity in RH-749. The total chlorophyll content and photosynthesis rate were considerably higher in RH-749, which leaked fewer electrolytes and maintained a less destructive osmotic potential under limited water conditions. The results indicated that it is water-stress tolerant when given a high concentration of K2SO4, which alleviated the adverse effects of water stress on growth and physiology.