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Fenugreek (Trigonella foenum-graecum L.) is a valuable medicinal plant in farm and pharmaceutical industry, and on the other hand, drought stress is one of the major problems of crop production in most countries. To explore the effect of drought stress on fenugreek, we first examined three levels of water deficit (− 3.0, − 5.0, − 7.0 Bar water potentials using polyethylene glycol) and assessed plant responses to polyethylene glycol-induced stress. In the second experiment, the effect of different concentrations of melatonin (50, 100, 300 and 500 µM) on the alleviation of detrimental effects of water stress was investigated in the highest level of drought stress (− 7 Bar PEG). The finding in the first experiment (drought stress applying) demonstrated that water deficit decreased length, fresh and dry weight of shoot and root, chlorophyll content and antioxidant enzyme activities, such as ascorbate peroxidase, catalase, superoxide dismutase and peroxidase, and also led to an increase in proline content. Also, melatonin treatment (especially 100 mM) improved photosynthetic performance by increase in net photosynthesis (PN) and transpiration rate (E), reducing chlorophyll degradation but increasing the antioxidant enzyme activities. These results revealed that fenugreek tolerated water deficit by increasing the endogenous melatonin and trigonelline, as well as the general physiological responses. [ABSTRACT FROM AUTHOR]

Plant yield and productivity are being impacted significantly by global climate change. Since water scarcity is one of the main risks to agriculture's future, developing plants that can withstand water stress is crucial. The peach is an essential fruit crop for examining how plants respond to drought stress, which lowers crop performance through yield and quality losses. Melatonin, a versatile, beneficial stress-relieving hormone, can be used to alter how plants respond to environmental stresses. The current investigation examined how melatonin may improve early peach seedlings' resistance to drought stress. Our findings revealed a significant decrease in plant biomass and photosynthetic activity and increased oxidative damage under drought stress. Melatonin application promotes plant development and reduces oxidative damage by increasing photosynthetic activity and chlorophyll contents. Melatonin also increases soluble sugars and proline contents. Furthermore, an increase in the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) was also recorded in peach seedlings. According to the results of our investigation, melatonin applied at a concentration of 100 µM had the highest effect on increasing plant survival under drought stress and contributed to the development of a practical approach for peaches under drought stress conditions. [ABSTRACT FROM AUTHOR]

The paper studied the effects of drought stress, selenium (Se) supply and their combination on growth and physiological characteristics of wheat ( Triticum aestivum L. cv Shijiazhuang NO. 8) seedlings. The experimental design included two water treatments (well-watered, 75% of maximum field capacity; drought stress, 30% of maximum field capacity) and two Se levels (0; 0.5 mg/kg) to determine whether Se can modify the negative impacts of drought stress on seedling growth and physiological traits. Drought stress caused a marked decline in growth parameters and soluble protein content, whereas it induced an increase in root activity, proline content and the activities of peroxidase (POD) and catalase (CAT) of leaf tissue. On the other hand, Se supply induced an increase in biomass accumulation only under well-watered condition. Under drought stress, Se supply increased free proline content, root activity and the activities of POD and CAT in leaf tissue, but did not significantly affect on growth parameters. These results implied that drought stress brought harmful effects on wheat seedlings, and that Se supply was favorable for biomass accumulation of wheat seedlings under well-watered condition. However, it did not significantly affect on biomass accumulation under drought stress, although it increased root activity and activities of some antioxidant index in experimental periods. [ABSTRACT FROM AUTHOR]

The plants produced by in vitro methods are free of any microflora contrary to natural systems where plants are colonized by symbiotic fungi. The present paper reports the experiments carried out to evaluate the role of arbuscular endomycorrhizal fungi in development of micropropagated strawberries and their photosynthetic activity (measured by chlorophyll fluorescence) under drought conditions. Mycorrhization strongly affected growth and tolerance to water deficiency of the plants cultivated in greenhouse. Wilting of not-mycorrhized plants was accompanied by drastic increase of Fo and Tfm and decrease of Fm. At the same time, the value of these parameters for mycorrhized plants did not change. Drastic decrease in the value of parameters Fv/Fm, Fv/Fo and Fo/Fm for plants without AMF appeared at the end of dry period. Rise of Fs and decrease Rfd was noted only for not-mycorrhized plants. The plants colonized by fungi, fully recovered their photosynthetic activity when watering was restored. [ABSTRACT FROM AUTHOR]

Since global drought events have been occurring more frequently, identification of the key mechanisms underlying adaptive responsiveness to drought stress is urgently needed to improve the drought resistance of plants. In this study, a simulated drought stress experiment (five gradients (0, − 0.1, − 0.3, − 0.5, and − 0.7 MPa) × four exposure times (7, 14, 21, and 28 days)) was performed to study the growth, photosynthesis and physio-biochemical parameters of Paspalum wettsteinii. The results indicate that mild drought stress (− 0.1 MPa) significantly increased the growth, photosynthesis, antioxidant (superoxide dismutase, catalase, and peroxidase), and osmotic adjustment (proline, soluble sugar, and soluble protein contents) capacities. In contrast, extreme drought stress (− 0.7 MPa) markedly decreased the growth, photosynthesis, antioxidant, and osmotic adjustment capacities but increased the intercellular CO2 concentration and malondialdehyde capacity. The responses to moderate (− 0.3 MPa) and severe (− 0.5 MPa) drought stress depended on the exposure time. Short-term drought stress promoted photosynthesis and increased the antioxidant and osmotic adjustment capacities, but these parameters were inhibited with increases in the exposure time. Overall, these findings highlight that the increases in photosynthesis, antioxidant and osmotic adjustment capacities and the decrease in lipid peroxidation capacity contribute to the adaptation of P. wettsteinii to drought stress. This study provides new insight into the adaptive responsiveness of P. wettsteinii to drought stress. [ABSTRACT FROM AUTHOR]

Drought stress is a factor affecting plant growth in the arid regions of Tunisia. The experiment was performed on two species: Hedysarum coronarium (H. coronarium; Sulla coronaria) and Hedysarum carnosum (H. carnosum; Sulla carnosa) which were subjected to two water regimes (60 and 100% of field capacity). The aim was to study the photochemical stability of PSII (using the fluorescence transient OJIP in light- and dark-adapted states) and gas exchange under drought stress. Results revealed that drought stress affected the majority of the studied physiological parameters: a sharp decrease in relative water content, total chlorophyll content, and gas exchange in both species during the first month of treatment followed by a more or less constant phase (2 months) and a decrease to the lowest levels of the studied parameters. Nevertheless, H. coronarium plants maintained relatively higher stomatal conductance, photosynthesis activity, transpiration rate, and total chlorophyll content under drought stress conditions. In addition, a change in fluorescence intensity as a function of time was noted in both species. The effect of drought stress was also invested on the different fluorescence intensities of the transitions J, I, and P and consequently on the different oxidation–reduction states of PSII electron acceptors. Drought stress had no effect on the fluorescence level O, whereas the effect which was observed at the J transition level was much higher at the I and P levels. In addition, H. coronarium was more able to protect its PSII from water-deficit stress as consequently was more drought-tolerant compared to the endemic species of H. carnosum in arid climate. Overall, our study contributed to the understanding of the mechanisms of adaptation and stability of PSII under drought stress in H. carnosum and H. coronarium. [ABSTRACT FROM AUTHOR]

Lipoxygenase (LOX, EC1.13.11.12) catalyzes the oxygenation of polyunsaturated fatty acids and further generates oxylipins via enzymatic or non-enzymatic pathways, thus participating in the regulation of growth and development, stress response, and other processes. The objective of this research was to characterize the function and evaluate the mechanism of lipoxygenase gene AfLOX4's role in enhancing drought tolerance. Transcriptomic data were generated and analyzed for the LOX gene, under different concentrations of drought (polyethylene glycol-6000) (PEG6000) and abscisic acid (ABA) stress treatment, to determine their effects on the expression of the AfLOX4 gene and its role in plant physiology. The localization of the AfLOX4 protein was detected through protoplast transformation. The expression of AfLOX4 in Amorpha fruticosa tissues was determined by quantitative real-time PCR (qRT-PCR). Six LOX genes of A. fruticosa that showed an upregulated pattern under different concentrations of drought (PEG6000) stress were found via transcriptomic analysis and were named AfLOX1 ~ 6. The AfLOX4 protein was localized in the cytoplasm. AfLOX4 was expressed in the stems, roots, flowers, and leaves of Amorpha fruticosa L., and its expression level was the highest in leaves. The expression of AfLOX4 increased with the prolongation of stress time under different stresses. After ABA treatment, the germination rate of tobacco lines overexpressing AfLOX4 was significantly increased, while under NaHCO3 stress, the tolerance of tobacco plants overexpressing AfLOX4 was higher than that of wild-type tobacco. The tobacco with overexpression of the AfLOX4 gene detected by the natural drought method had a higher survival rate in the drought stress recovery experiment, and improved the drought tolerance of tobacco. This study reveals the function of the AfLOX4 gene in resisting drought stress and lays a solid theoretical foundation for the genetic improvement of Amorpha fruticosa L. plant varieties, as well as improvement of resource utilization. [ABSTRACT FROM AUTHOR]

Understanding the water relationship and biochemical changes in response to drought can aid in drought tolerance in wheat, which is critical for future yield stability. The current study investigated the mechanisms of drought tolerance in wheat, considering water relations, biochemical properties, and yield of two wheat varieties: drought-susceptible BARI Gom 25 and drought-tolerant BARI Gom 26. Drought decreased relative water content (RWC), leaf water potential (LWP), xylem exudation rate (XER), leaf chlorophyll content, flag leaf phosphorus (P), and grain yield. Conversely, drought stress increased various osmolytes: proline, soluble sugar, malondialdehyde (MDA), and flag leaf potassium ion (K+). Under drought conditions, BARI Gom 26 outperformed BARI Gom 25 in terms of LWP, RWC, and XER. However, drought increased the electrolyte leakage (EL) and MDA in BARI Gom 25. BARI Gom 26 had higher proline concentration, soluble sugar accumulation, cell membrane integrity, chlorophyll concentration, and K+ in drought conditions than BARI Gom 25. These responses were most noticeable during the reproductive stages. However, BARI Gom 26 could compensate for drought-induced reductions in agronomic parameters, including grain yield, by maintaining superior osmotic adjustment in the leaves, as evidenced by increased proline, MDA, cell membrane stability, and K+ accumulation. [ABSTRACT FROM AUTHOR]

Recent biotechnological advances have made it possible to obtain glyphosate-resistant corn genotypes and, therefore, the large-scale use of products for weed management. Usage of this systemic, non-selective herbicide can accentuate the water deficit effects in prolonged drought periods during the initial development of some crops. This work aimed to study the physiological and biochemical effects of glyphosate on RR corn plants under water deficit conditions. Cultivars were screened, and then the glyphosate effects on RR corn plants under water deficit were tested in an experiment with four cultivars (two tolerant and two susceptible), two water regimes (30 and 80% of available water), and two rates of glyphosate application (with and without). Water deficit affected all traits evaluated in glyphosate-resistant corn cultivars, reducing leaf area, and shoot and root dry biomass by more than 60%. Our results show that the application of glyphosate in RR corn plants can be carried out without negatively impacting corn plants under moderate water deficit up to 44 days after emergence. In the absence of water deficit, glyphosate increased the leaf area of RR corn plants compared to those that did not receive the product. The glyphosate application negatively impacted the length and root volume of RR corn hybrids in the two water regimes evaluated. [ABSTRACT FROM AUTHOR]

Identification of genes playing a role in stress tolerance has great importance in the elucidation of biotic and abiotic plant stress pathways. In this study, comparative analysis was carried out for genes (bZIP60 and bZIP28) activated during ER stress response in plant root and leaf tissues. The relative water content (RWC) of the plant leaves grown under stress factors, di-thio-threitol (DTT) and polyethylene glycol (PEG) were measured at critical periods. Expression analysis of bZIP60 and bZIP28 genes involved at ER stress pathways was evaluated through RT-PCR assay at determined intervals of time, (in Nimet cultivar of alfalfa) under the artificial ER stress implemented by DTT and drought stress by PEG. According to the results, it was determined that DTT reduced the functionality of these two genes involved in ER stress pathways. The most critical time for plants in drought (PEG) tolerance was 8th h after treatment, in which the expression of bZIP60 in leaves was increased compared to other applications (about 42 times). Furthermore, according to the findings, the two studied gene regions, bZIP60 have a more active role in the stress pathways than bZIP28; and the leaf tissues were more affected than the root tissues under the stress conditions. [ABSTRACT FROM AUTHOR]

Physiological integration may be an important ecological strategy for clonal plants living in heterogeneous environments. The physiological integration between Zoysia japonica parent and offspring ramets under different experimental water conditions was examined. We applied four treatments: (1) both the parents and offspring were well watered, (2) both experienced drought, (3) the parents were well watered and the offspring experienced drought, and (4) the parents experienced drought and the offspring were well watered. The growth, chlorophyll content, photosynthesis, chlorophyll fluorescence, and antioxidant enzymes of Zoysia japonica were measured. The chlorophyll contents, chlorophyll a/b ratio, and photosynthetic parameters (Pn, Gs) of offspring ramets were not reduced when parents under well-watered conditions and offspring ramets under drought conditions suggested that the physiological support provided by parents enabled their offspring to maintain photosynthetic efficiencies. The support provided to the offspring by their parents was also obvious in the antioxidant systems and proline accumulation of Zoysia japonica in heterogeneous water environments. Physiological integration was not detected when the parents experienced drought and the offspring were well watered. The parents provided physiological support to their offspring and did not expense significant benefits through physiological integration when parents were well watered and offspring experienced drought. When the opposite conditions were true, physiological integration did not exist. [ABSTRACT FROM AUTHOR]

To compare C. monogyna seed germination and the seedling emergence of two populations from Quchan and Bardaskan in Khorasan-e-Razavi-I province in north east of Iran, experiments were carried out. From the results, the highest germination percentages for Quchan (98%) and Bardaskan (97%) populations were observed at alternating 25/15 and 30/20 °C day/night temperatures, respectively. Germination percentage of both populations was 42–92% over a wide range of constant temperatures (10–35 °C). The NaCl concentration of 399.5 and 443.6 mM caused 50% inhibition of germination for Quchan and Bardaskan populations, respectively. The osmotic potential for 50% inhibition of germination was − 0.63 for Quchan and − 0.66 MPa for Bardaskan populations. The maximum emergence of Quchan (74%) and Bardaskan (80%) populations were recorded in the seeds placed at 0.5 cm with emergence failure at 5 cm soil depth. In another experiment in which seeds were after-ripened at different depths of soil in the field, seed germination was lower on the soil surface and 20 cm soil depth compared to 2, 5, 10 and 15 cm depth; and the highest seed emergence in the field was observed at 5 cm soil depth, 270 days after seed burial. The information of this study would be useful for determining the potential of this parasitic species to spread to new areas and arrange management strategies in different environmental conditions. [ABSTRACT FROM AUTHOR]

5-Aminolevulinic acid (ALA), as a precursor of plant chlorophyll synthesis, can alleviate damage to photosynthesis and thus improve the drought resistance of plants, but the mechanism behind this is still obscure, especially its correlation with functional gene transcription and noncoding RNA regulation. The leaves were collected from Aikang-58 wheat seedlings subjected to drought stress and exogenous ALA application for ultrastructure observation and gene transcription analysis. The results indicated that drought stress attenuated the photosynthesis evidenced by the decrease of net photosynthetic rate (Pn) and stomatal conductance (gs), damaged the chloroplast ultrastructure by destroying the thylakoid matrix, degrading the chlorophyll, and leading to lipid peroxidation of the cells due to the toxicity of free radicals, causing lipids to dissociate and combine with osmium acid to form plastoglobuli. Under drought stress, exogenous ALA pretreatment can increase the transcript abundance of the chlorophyll synthesis-related genes. Moreover, exogenous ALA increased psb28 transcript abundance under drought stress, to alleviate the damage to the chloroplast ultrastructure and photosynthesis. Our data revealed the possible gene transcriptional regulation patterns in response to drought stress and exogenous ALA alleviation. [ABSTRACT FROM AUTHOR]

The influence of drought stress on barley (Hordeum vulgare) has been investigated. The experiments were conducted with seedlings of barley—by the application of combined drought and temperature stresses. Here we showed that combination of drought and high temperature inflicted more severe damage to plants than the drought and low temperature stress. The temperature stress triggered more drastic changes in plant morphology/physiology and biochemistry than the drought stress. Interestingly, plants exposed to high temperature exhibited significant reduction of shoot and root aldehyde oxidase (AO) activity. Moreover, increased temperature resulted in lower levels of reactive oxygen species (ROS), while drought stress had an opposite effect on ROS accumulation and AO activity. This is the first demonstration of inhibition of plant AO and ROS in response to heat stress. The combined heat and drought stresses resulted in increased activity of catalase (CAT) and superoxide dismutase (SOD) in roots but not in shoots. Our findings indicate that heat and drought stresses may induce activation of different antioxidant enzymatic defense mechanisms and heat stress significantly affects enzymes responsible for the ROS accumulation in plants. [ABSTRACT FROM AUTHOR]

Prolonged drought stress could accelerate plant death. In this study the mechanisms of the acetic acid to increase the survival rate of cotton under drought stress were studied. Twenty-day-old cotton seedlings were grown for 9 days in the presence or absence of acetic acid under natural drought conditions in which the relative water content (RWC) of the soil decreased below 60% at 6 days after treatment (DAT). The water potential, photosynthesis (Pn), chlorophyll (Chl) content, stomatal conductance (Cond), and transpiration (Tr) of the control plants started to decrease at 6 DAT. However, acetic acid treatment caused a decrease in Cond and Tr at 3 DAT. Abscisic acid (ABA) and jasmonic acid (JA) contents and the expression of ABA biosynthesis genes (NCED2, NCED3, and NCED9) and JA biosynthesis genes (GhAOS6, GhLOX3, and GhOPR11) in cotton leaves were increased by acetic acid treatment at 3 DAT, and these variables were increased in control and acetic acid-treated plants at 6 and 9 DAT. These results indicate that acetic acid can increase ABA and JA contents by upregulating the expression of their biosynthesis genes, thus decreasing the Cond and Tr, and therefore, increasing the RWC of the soil and increasing the survival of cotton under drought stress. [ABSTRACT FROM AUTHOR]

As one of the main indicators of nutritional values of foxtail millet, grain protein contents (GPCs) of seeds can be affected by soil water conditions. Studies in this report indicated that intensified drought in filling stage increased the GPCs. To gain better insight into the interaction mechanism between the GPCs and soil water deficits, the proteomic profiles of mature seeds under three drought stress levels (moderate drought-W2; combined drought-W1; severe drought-W0) were conducted on two varieties, Longgu6 (LG6) and Huangjinmiao (HJM) by two-dimensional electrophoresis, with acidic (pH 4–7) gels. There were 83 protein spots in total identified successfully in two comparison groups (W1 vs W2 and W0 vs W2), associated with four major biochemical and metabolic pathways, including storage protein, amino acid and protein metabolisms, energy metabolism, response to stress and defense, and chaperones. Further analysis revealed that the increase of GPCs in LG6 under both W0 and W1 may be owing to the up-regulated storage proteins and the up-regulated protein response to drought stress. The levels of DEPs related to protein and amino acid biosynthesis and starch metabolism increased greatly in LG6 under W1, and this may also result in the high GPC level of seeds in LG6 under W1. Protein biosynthesis was up-regulated and drought stress-related pathways were enhanced in HJM under W1, thereby resulting in the increase of GPC in HJM under W1. These results will contribute to the existing knowledge on the complexity of protein changes leading to the GPC changes in response to drought. [ABSTRACT FROM AUTHOR]

Proline accumulation in roots and shoots is one of the most evident responses to environmental stresses such as drought, which is currently one of the main threats for agriculture. Based on this response, in this work, we hypothesize that proline accumulation is dependent on root-to-shoot communication through light perception. Thus, we used exaggerated light response ( hp1) and phytochrome-deficient ( au) mutants of tomato, which were combined through self-grafting and reciprocal grafting and subjected to drought stress, for posterior determination of shoot and root growth and proline content. Light-affected proline metabolism, as hp1, had the highest accumulation, while au presented the lowest proline values. Reciprocal grafting showed that hp1 and MT as scion or rootstock improved MT and au proline content, respectively, indicating shoot-to-root and root-to-shoot communication modulate the metabolism of this compatible osmolyte. Dry weight, leaf area, and root area presented similar patterns to proline content, indicating the importance of this compound for plant growth under stress conditions. These results provide a new perspective on light mediation of long-distance proline translocation in stressed plants. [ABSTRACT FROM AUTHOR]

Functionality of the photosynthetic system under water stress is of major importance in drought tolerance. Oat ( Avena sativa L.) doubled haploid (DH) lines obtained by pollination of F oat crosses with maize were used to assess the differences in plant genotypic response to soil drought. The investigations were based on the measurements of gas exchange and chlorophyll a fluorescence kinetics. Drought was applied to 17-day-old seedlings by withholding water for 14 days and subsequent plant recovery. Non-stressed optimally watered plants served as controls. Yield components were determined when plants reached full maturity. It was shown differences among the oat lines with respect to drought stress susceptibility (SI) and stress tolerance index mean productivity and drought susceptibility index. Sensitivity to drought of individual DH lines was significantly different, as demonstrated by the correlation between drought susceptibility index and yield components, such as dry weight (GW) or grain number (GN) of the harvested plants. GW and GN were lower in drought-sensitive genotypes exposed to drought stress compared to those resistant to drought. The principal component analysis allow to separate three groups of lines differing in their sensitivity to drought stress and indicated that tolerance to drought in oat has a common genetic background. [ABSTRACT FROM AUTHOR]

Desiccation, a major environmental stress, affects water potential and turgor in the plants leading to physiological imbalance. Though bryophytes have the ability to endure desiccation, the adverse environmental conditions may cause them to dry irreversibly. In the present study, desiccation tolerance mechanism of Brachythecium procumbens (Mitt.) A. Jaeger was analysed in terms of its antioxidative response and photosynthetic pigments. Plants of B. procumbens were subjected to desiccation stress for varying durations (24-96 h) along with control (0 h) at room temperature. Monitoring was done using antioxidant enzyme activities, photosynthetic pigments, chlorophyll stability index, as well as, relative water content. The antioxidative enzymes-superoxide dismutase and peroxidase-showed higher activity in desiccated plants as compared to control and increased significantly with duration of desiccation. However, the activity of catalase decreased during desiccation. The amount of chlorophyll increased up to 48 h of desiccation treatment as compared to control, whereas in rehydrated samples, relatively lower value was obtained. Majority of bryophytes may withstand a certain level of desiccation for at least a few days, but some are much more tolerant than that. The bryophyte system studied showed basic difference in enzyme activities and chlorophyll under different periods of desiccation. Hence, drought-tolerant genera need to be identified and propagated so that some pioneer colonizers of the ecosystem are naturally conserved. [ABSTRACT FROM AUTHOR]

Wild progenitors of common wheat are a potential source of tolerance to biotic and abiotic stresses. We conducted a glasshouse pot experiment to study genotypic differences in response to drought stress in a collection of 180 accessions of Aegilops and Triticum along with one tolerant and one sensitive control variety. Several physiological traits and chlorophyll fluorescence parameters were evaluated. Our findings indicated that drought significantly reduced shoot fresh (59.45%) and dry (50.83%) weights, stomatal conductance (41.52%) and maximum photosynthetic capacity (41.06%), but increased initial fluorescence (28.10%). Drought stress also decreased the chlorophyll content, relative water content and maximum quantum efficiency by 14.90, 12.13 and 11.42%, respectively. Principal component analysis of the 182 individuals identified three components that explained 57.61 and 61.68% of the total variation in physiological and photosynthetic traits under control and stress conditions, respectively. When grouped into the 12 species tested, the three top components explained 78.22% of the total variation under drought. The means comparison, stress tolerance index and biplot analysis identified five accessions with superior tolerance to drought. Remarkably, four species of wild relatives- Ae. cylindrica (DC genome), Ae. crassa (DM genome), Ae. caudata (C genome) and T. urartu (A genome)-responded well to drought stress with a lower percentage decline for most traits and high values for the first two components. The potential of these species offers further opportunities for analysis at the molecular and cellular levels to confront with drought stress through a physiological mechanism. [ABSTRACT FROM AUTHOR]

The accumulation level of soluble carbohydrates in fibers during flowering may affect the final fiber length in upland cotton ( Gossypium hirsutum L.). The objective of this study was to determine the relationship of carbohydrate levels and carbon metabolism enzyme activities in fibers to fiber elongation under water deficit stress. A pot study was conducted in 2013 with treatments consisting of control (well-watered) and water stress using two cotton genotypes differing in drought tolerance, namely S011 (drought sensitive) and T886 (drought tolerant). Water stress treatment was designed as withholding water from the pots until stomatal closure followed by limited water supply for 25 days where water-stressed plants received 40% of optimum quantity of water. The results showed that the glucose, fructose, sucrose and starch concentrations decreased in water-stressed fibers compared to the control. The degree of decline in hexose and total soluble sugar concentrations under water deficit stress was higher in the sensitive genotype (S011) than the tolerant genotype (T886). Similar changes were also observed in vacuolar invertase (VIN) and sucrose synthase (SuSy) activities. The reduction in hexose concentration might be due to decreased sucrose-cleaving enzyme activities especially VIN activity. The study showed that drought stress decreased VIN and SuSy activities, and hence hexose concentration in fiber cells, which resulted in a slower fiber elongation compared to the control. [ABSTRACT FROM AUTHOR]

Drought stress produces many physiological and biochemical changes in plant affecting its life cycle and production. Oxidative damage and antioxidant defense responses are two components of plant to survive under drought stress. Nitric oxide (sodium nitroprusside, SNP) and brassinosteroid (24-epibrassinolide, EBL) were used in this experiment as single and combined application as foliar spray to study the mitigating effect of drought stress in two tomato genotypes EC-625652 (drought susceptible) and EC-620419 (drought tolerant). Drought stress produced harmful effect on number of leaves plant, RWCL, fruit set percent, days to first fruit set, number of cluster plant, lycopene content, fruit diameter and fruit yield. Plant produces reactive oxygen species (ROS), such as HO in response to drought stress. Exogenous application of SNP and EBL, both in single and combined application, mitigated the deleterious effects of drought and improved drought tolerance by increasing SOD activity, fruit yield, and other physiological processes. [ABSTRACT FROM AUTHOR]