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Climate change combined with drought stress, as a consequence of this global phenomenon, is among the most unfavorable factors that could limit the growth and production of crops worldwide and pose a serious threat to the production of sustainable crops. Since several plant physiological and biochemical relationships under drought conditions remain unknown, it may be possible to obtain more drought-tolerant plants by knowing these details. An effective management strategy involves the use of exogenous substances, increasing the expression of resistant genes, and increasing the production of enzymes that help the plant to withstand damaging environmental conditions such as drought. Experimental treatments consisted of four levels of irrigation regimes and foliar application of abscisic acid (ABA) at two concentrations, with three replicates. The results showed that drought in 30–40% field capacity increased the antioxidant activity by DPPH, ABTS, FRAP, and TAOC methods; and the antioxidant enzymes of catalase (CAT), superoxide dismutase (SOD), peroxidase (POX), and ascorbate peroxidase (APX), significantly. Foliar application of ABA on Lavandula angustifolia cv. Munstead improved plant metabolism under stress conditions, mildly. So that, the interaction between drought and ABA had a synergistic effect on antioxidant activity and related enzymes. The expression of CAT, POD, and APX genes decreased under drought stress, while spraying ABA ameliorated this decrease. The expression of the SOD gene tended to decline, and no drought treatment along with 15 μM ABA spraying revealed the highest expression. Hormone spraying, on the other hand, had a positive effect on this expression under stress compared to the control (no spraying). Overall, despite the unknown details of how radical scavenging functions in plants and the associated expression, these results suggest that ABA treatment reduced the inhibitory effects of drought stress and increased the tolerance of lavender under stress conditions. [ABSTRACT FROM AUTHOR]

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 crucial obstacle in the research of plant science is to distinguish between superior genotypes and its selection. Machine vision can recognize the better genotype precisely, effortlessly and in asymptomatic manner. Genotype differentiation based on machine vision by using thermal imaging parameters is evaluated and elaborated in this article. The main objective of this study is to assess better performance and select superior genotypes based on the common thermal indicators. Mungbean and chickpea crops were studied and measured in greenhouse conditions with well-watered and water stress treatments. An algorithm is developed for extracting parameters from thermal images and implemented in a Python tool using OpenCV (cv2), Pandas packages. The genotypes of the crops were contrasted for drought tolerance to be able to differentiate drought responses with thermal imaging. The result of the experiments express that crops are differentiated between treatments and discriminated among genotypes within a treatment. These results were validated with the soil moisture data, which was collected on simultaneous day of the image captured. [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]

Drought stress induced by inconsistency in rainfall lowers the agricultural productivity and necessitates the employment of a drought-tolerance mitigation strategy that involves fertigating plants with a range of biochemicals. The influence of foliar applied exogenous nitrogen (N), potassium (K), and water-soluble fertilizers (NPK) for the reduction of drought stress in wheat (Triticum aestivum L.) was investigated in the current study under field drought stress conditions. The biological yield, yield and yield components, relative water content, chlorophyll content, and leaf osmotic potential of both cultivars were significantly (P ≤ 0.05) reduced by drought stress. In drought treatments, application of K@2% and water-soluble fertilizer NPK@2% significantly (P ≤ 0.05) improved these parameters. In drought-stressed plants, the addition of K and water-soluble NPK increased the accumulation of osmolytes and soluble carbohydrates while lowering malondialdehyde (MDA) levels. Under drought conditions, water-soluble NPK treatments resulted in a considerable increase in yield in GJW 463. Drought stress alleviation and yield increase in wheat cultivars were attributed to better osmotic adjustment, antioxidant activity and favorable water status under stress circumstances, due to K and NPK treatment. Supplemental fertilization with exogenous water-soluble nutrients K and NPK is an effective way to protect and improve drought tolerance and increase wheat grain output in drought-prone locations. Our results demonstrate that application of exogenous water-soluble NPK as a supplemental fertilizer protects wheat and promotes drought tolerance. [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]

Biological invasions have modified the terrestrial biota worldwide, reducing biodiversity, and causing economic loss. Copernicia prunifera (Carnauba), a palm tree native to the semi-arid region of Brazil (Caatinga ecosystem), has high economic and social importance, but has been impacted by the invasive climbing shrub Cryptostegia madagascariensis (Madagascar rubber vine). We evaluated physiological, biochemical, and nutritional responses in mature plants of both species in two locations: Catuana (where there is an intense water-deficit during the dry season) and Minguaú (where there is high salinity and sodicity, and excess water throughout the year). Our results show that competitive interaction between the two species is mainly defined by their adaptability to abiotic soil constraints. C. prunifera is better adapted to severe water-deficit conditions, but its ecophysiological performance is not sufficient to withstand invasion by C. madagascariensis. The invader is more competitive in flooded, salt-affected soils, and is not severely impacted even with high sodium accumulation in its leaves. Our results also show that the negative impacts on C. prunifera intensify at the final stage of infestation, when the shading caused by C. madagascariensis restricts access to solar radiation and accelerates leaf senescence. However, the impact on C. prunifera precedes the permanent shading, as evidenced by the inhibition of net assimilation of CO2 under intermediate levels of infestation. These results reinforce the vulnerability of carnauba populations in the Caatinga ecosystem, which may be severely impacted without the development of technologies to mitigate the impact of invasion. [ABSTRACT FROM AUTHOR]

During drought stress, plant cells reorganize their proteomes to counteract the adverse impacts of stress. Given that the intracellular environment differs between drought-stressed cells and cells under optimal growth conditions, it has been proposed that the physicochemical characteristics of proteins could also differ under stress. To test this hypothesis, we determined whether the number of proteins resistant to aggregation increases under drought stress conditions in sugarcane, a relevant agricultural species. To do this, we used nanoLC-MS/MS proteomic analysis to identify and count the number of aggregation-resistant proteins produced by sugarcane in response to drought stress. We found that the number of these types of proteins was almost three times higher under drought stress than under control conditions, most of which were predicted to be intrinsically disordered proteins. Under drought stress, we also detected many proteins that are recognized as drought stress-responsive proteins, including enzymes involved in the oxidative response. Interestingly, we found that although most of these enzymes are globular proteins, several of them are predicted to be intrinsically disordered proteins. These results back the idea that, in sugarcane, drought stress can trigger the induction of aggregation-resistant proteins. We propose that the accumulation of aggregation-resistant proteins could be part of the drought stress response, making our approach a potentially useful strategy for discovering novel drought-responsive proteins in other plant models. [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]

Drought stress severely affects plant growth and productivity. Black gram is an extensively cultivated legume crop worldwide. Its production has not improved much in the last decade as it is adversely affected by biotic and abiotic stresses among which drought is a major factor. Salicylic acid (SA) pre-treatment to a Vigna mungo variety significantly increases chlorophyll, proline, carbohydrate, and total phenolic content. APX, GPX and SOD activities also increase and CAT activity decreased. At molecular level, induced expression of various stress-related genes, i.e. heat shock protein (Hsp), calmodulin (CAM), malate dehydrogenase (MD), metallothionein (MT), mitogen-activated protein kinase (MAPK), tryptophan synthase (TSN), zinc finger (ZF), phenylalanine ammonia lyase (PAL) and WRKY proteins are analysed by quantitative RT PCR after 1 mM SA treatment under short-term drought stress. It is observed that 1 mM SA pre-treatment is optimum to increase tolerance against short-term drought stress. [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]

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]

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]

Drought stress has a negative impact on crop growth and productivity worldwide. Plant symbionts such as arbuscular mycorrhizal fungi (AMF) can enhance plant growth and improve plant resistance to drought stress. AMF mixture inocula and plant responses to drought still require further study. The objective of this study was to investigate the effects of non-inoculation (NM) or inoculation with three commercial AMF inocula containing a single or mixtures comprising different numbers of AMF species: M1 (Rhizophagus intraradices), M2 (Rhizophagus clarus, R. intraradices, Septoglomus deserticola, Funneliformis mosseae), and M3 (Rhizophagus intraradices, R. aggregatum, Funneliformis mosseae, Olaroideoglomus etunicatum) on growth, nutritional, and physiological responses of soybean (Glycine max L. cv. Hutcheson) grown in a greenhouse under different water stress levels [WW = well watered (90% FC), MS = medium (60% FC) and SS = severe stressed (30% FC)]. The AMF-inoculated plants had significantly higher plant biomass, chlorophyll content, stomatal conductance, leaf water relations, and mineral contents in comparison to NM plants. Applied mycorrhizal inocula differed in their response to water-deficit conditions. M2 inoculant generally supported greater plant biomass, stomatal conductance, leaf water content, and leaf N, P, K, S, Mn, and Cu contents than M1 and M3 inocula, especially under MS and SS treatments. These results indicated that all mycorrhizal inocula supported plant growth both generally and with soil water deficit; however, M2-inoculated plants performed better than M1 and M3 under drought stress. Therefore, mycorrhizal inocula are effective for supporting soybean growth and offsetting the effects of drought and AMF technology that can support sustainable crop cultivation under soil water-deficit conditions. Different types of inocula have different effects, however, and thus require testing for individual crops. [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]

Drought stress hampers the yield of oilseed crops throughout the world. However, foliage application of plant growth regulators might be useful to reduce drought induced yield losses. In this study, the role of 5-aminolevulinic acid (5-ALA) in improving the performance of different sunflower hybrids under drought stress was evaluated. Five levels of 5-ALA viz., (i) control, (ii) 25, (iii) 50, (iv) 75 and (v) 100 mg L−1 were foliage applied on two sunflower hybrids (Parsun and Senji) under drought [40% water-holding capacity (WHC)] and well-watered (80% WHC) conditions. The results revealed that imposition of drought stress negatively impacted the performance of sunflower than well-watered conditions. However, foliage application of 5-ALA, at either rate, improved the performance of sunflower under drought stress by improving stay green and antioxidant enzyme activities which was translated to higher achene yield and better oil contents in both sunflower hybrids. Among the sunflower hybrids, the performance of sunflower hybrid 'Senji' was better in terms of morphological and yield related traits than 'Parsun'. Foliage application of 5-ALA at 75 mg L−1 was the most beneficial for improvement in sunflower performance which improved the achene yield, oil contents and stay green by 12.3, 9, 26%, respectively, than no 5-ALA application. Application of 5-ALA also enhanced the activities of catalase, ascorbate peroxidase and superoxide dismutase by 157.1, 90 and 80% under drought stress than no 5-ALA application. In conclusion, foliage application of 5-ALA at 75 mg L−1 in sunflower hybrid 'Senji' is useful to reduce drought induce yield losses and improve oil contents which is attributed to an improvement in stay green and activities of catalase, superoxide dismutase and ascorbate peroxidase. [ABSTRACT FROM AUTHOR]

Taro (Colocasia esculenta (L.) Schott) is a staple food and represents an important food security role in most tropical regions. It is, unfortunately, susceptible to prolonged drought conditions. Abscisic acid (ABA) is a well-documented stress-induced phytohormone that tolerant crops usually accumulate in leaves to induce stomatal closure, preventing water loss through inhibition of transpiration. Hitherto, exists very scarce information regarding the ABA role in taro response to drought. Here, we determined the ABA content in the shoots and corms of taro subjected to seven months of water scarcity and linked ABA to other drought resilience traits, including carbon isotopic discrimination (Δ13C), oxalic acid (OA), chlorophyll content index (CCI), water use efficiency (WUE), and biomass (B). The Δ13C-shoot content showed partially open stomata in all accessions, and significant correlation with Δ13C-corm, CCI, and WUE. The osmotically active OA-shoot decrease seemed not to interfere with the stomatal aperture. The tolerant accessions subjected to drought stress had higher B-corm, ABA-shoot, Δ13C-shoot, CCI, OA, and WUE. However, the observed under drought conditions increase of ABA in the shoots, and its decrease in the corms were not significantly correlated, nor with other traits, suggesting that ABA was not the main regulator of taro physiological processes under stress. The information gained should be considered in breeding programs to predict taro's response to climate change. [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]

Drought has significant effect on wheat production by decreasing grain yield. Phenotyping the populations is a useful tool for understanding the interactions between phenotype and genotype. 135 doubled haploid (DH) genotypes and their parental varieties Plainsman (Pl) and Cappelle Desprez (CD) were phenotyped in glasshouse under well-watered (WW) and drought-stress (DS) conditions. The response of plant height, heading time, aboveground biomass, grain yield, root dry mass harvest index (HI) under both conditions, and stress tolerance index (STI) and water consumption in WW conditions was studied. We found 20% decrease in the plant growth, 66% decrease in the aboveground biomass, and 77% decrease in the grain yield. Under WW conditions, high water consumption was not related to high yields, STI, and HI. The tolerant and the sensitive genotypes were selected. In the WW and water consumption treatment, the sensitive genotype group had better grain yield performance, but under DS, the tolerant group had higher grain yield. The average yield loss was 59% in the tolerant group compared to the WW treatment, and the sensitive yield loss was 68%. Correlation was found between the grain yield and root dry mass in the tolerant group. There was significant difference between the tolerant and sensitive groups on water consumption, as the sensitive genotypes had higher water need. We found strong positive correlation between the water consumption and the grain yield in the tolerant group. This study showed that the tolerant genotypes had improved water regulating efficiency. [ABSTRACT FROM AUTHOR]

Crested wheatgrass ( Agropyron cristatum L.) is a cool-season perennial grass, which has demonstrated its potential for use as turfgrass. However, limited information is available on its drought and salinity tolerance. The main purpose of this study was to investigate the changes in the antioxidant defence system and physiological traits of six Iranian crested wheatgrass genotypes under drought and salinity stresses. The experimental design comprised a split plot with water treatments (control well-watered, salinity stress and water stress) as main plots and genotypes as subplots. This study demonstrated the variations in drought and salinity tolerance among crested wheatgrass genotypes. 'ACSKI', 'ACAMI' and 'ACDTI' generally performed better than other genotypes under drought and salinity conditions, mainly by maintaining higher activities of antioxidant enzymes like superoxide dismutase, peroxidase, catalase, ascorbate peroxidase and non-enzyme antioxidants like glutathione, higher proline and total non-structural carbohydrates content. The increased, decreased, and unchanged activities of antioxidant enzymes in the crested wheatgrass genotypes indicates a different forms of metabolism of antioxidant enzymes in response to drought and salinity stress. In general, drought and salinity stress increases the malondialdehyde (MDA) content and hydrogen peroxide (HO) content; however, 'ACSKI', 'ACAMI' and 'ACDTI' genotypes could tolerate an increase in MDA content and HO content; therefore, lower levels of MDA content and HO content were observed. The results showed that increasing levels of diamine oxidase and polyamine oxidase have been associated with increasing drought and salinity tolerance. Based on the biochemical and physiological parameters that were evaluated, we concluded that the genotype 'ACSKI' was superior in terms of drought and salinity tolerance. This superiority was mainly a result of better enzymatic and non-enzymatic antioxidant defence system and better osmotic adjustment under stress conditions. [ABSTRACT FROM AUTHOR]

Drought stress inhibits rice growth and biomass accumulation. To identify novel regulators of drought-stress responses in rice, we conducted a proteome-level study of the stress-susceptible (SS) Oryza sativa L. cv. 'Leung Pratew 123' and its stress-resistant (SR) somaclonal mutant line. In response to osmotic-stress treatments, 117 proteins were differentially accumulated, with 62 and 49 of these proteins detected in the SS and SR rice lines, respectively. There were six proteins that accumulated in both lines. The proteins in the SS line were mainly related to metabolic processes, whereas the proteins identified in the SR line were primarily related to retrotransposons. These observations suggest that retrotransposons may influence the epigenetic regulation of gene expression in response to osmotic stress. To identify the biological processes associated with drought tolerance in rice, we conducted a co-expression network analysis of 55 proteins that were differentially accumulated in the SR line under osmotic-stress conditions. We identified a major hub gene; LOC_Os04g38600 (encoding a glyceraldehyde-3-phosphate dehydrogenase), suggesting that photosynthetic adaptation via NADP(H) homeostasis contributes to drought tolerance in rice. [ABSTRACT FROM AUTHOR]

Fitness traits that determine the reproductive ability of individuals and the persistence of populations are affected by drought stress. Medicago truncatula that commonly encounters drought stress in its natural area, and for which large natural diversity and genetic tools are available, is a suitable species to investigate genetic determinism of fitness traits under stress. In a common garden, three successive cycles of short drought stress were applied after flowering, during the reproductive stage that is the most susceptible to drought for that species. Ten genotypes derived from natural populations and a mapping population were used to investigate the genetic determinism of vegetative and reproductive traits as components of fitness. A large genetic variation was observed and transgressive genotypes (more resistant or more susceptible than the parental genotypes) were found in the mapping population. Fitness traits were reduced by 5-74% in drought condition compared to well-watered condition. The most affected characters were total pod number per plant and total pod weight per plant. A total of 49 QTL, explaining between 6 and 38% of phenotypic variation for vegetative and reproductive fitness traits, were detected on all chromosomes except chromosome 6. A major QTL for flowering date ( R of 19 and 38%) that co-located with QTL for reproductive fitness traits were found on chromosome 7. In this study, no major QTL specific to drought-stressed or well-watered conditions were detected. We, thus, showed that QTL explaining fitness traits were numerous with small effects, in accordance with the genetic determinism of a complex trait. [ABSTRACT FROM AUTHOR]

Peppermint ( Mentha piperita) is known as an important medicinal plant throughout the world. In the present study, after exposing peppermint plants under drought stress, the qRT-PCR was use to analyze the expression of genes involved in menthol biosynthesis pathway and encoding: limonene synthase ( lS), limon-3-hydroxylase ( l3oh), trans-isopiperitenol dehydrogenase ( ipd), isopiperitenone reductase ( ipr), pulegone reductase ( pr), menthol dehydrogenase ( mdeh), and menthofuran synthase ( mfs), which also evaluated the morphological and physiological traits. The results revealed that due to water stress, the gene expression levels of ipd, ipr, and mfs were increased, whereas the gene expression level of pr and mdeh was decreased under water stress conditions. The most of essential oil components (menthol, menthofuran, and plugene), which were analyzed by gas chromatography-mass spectrometry (GC-MS), was positively correlated with genes expression. Drought stress decreased morphological and induces increasing contents of pulegone and menthofuran and reduction in menthol percentages. Results from this study suggest that up-regulation of mfs might contribute to the altered of menthofuran as well as down-regulation of mdeh might cause the reduction of menthol. Furthermore, increasing ls gene expression levels might induce more essential oil yield, while reduction of mfs gene expression levels causes an improvement of essential oil quality. [ABSTRACT FROM AUTHOR]

The availability of sufficient irrigation water and the development of drought-tolerant species are challenging factors in the design and maintenance of green roofs in modern cities. Green roof plants of Petunia hybrid Headliner Red Star, Ageratum hybrid Artist blue, and Mentha spicata L. grown in a simulated green roof pot system under controlled greenhouse conditions. The plants were watered every 2 or 6 days (2DWI/6DWI) for 8 weeks accompanied by either a 6-day treatment of seaweed extracts of Ascophyllum nodosum as a soil drench or foliar spray, or two concentrations of trinexapac-ethyl (TE) biweekly sprays. Following treatments, leaf number, leaf area, dry weights, plant height, stomatal conductanse, photosynthetic and transpiration rates and leaf water potential and relative water content were determined in two seasons during 2016 and 2017. The prolonged irrigation intervals reduced plant growth as revealed by morphological and physiological parameters. The application of SWE as drench treatment improved Petunia and Ageratum plant vegetative growth, stomatal conductance, photosynthetic and transpiration rates and leaf water potential and relative water content during prolonged irrigation intervals. TE increased the vegetative growth as well as the physiological performance of Ageratum plants. However, neither SWE nor TE treatments improved the performance of Mentha plants under prolonged irrigation intervals. It was suggested that improved photosynthetic rates were stimulated by enhanced stomatal conductance leading to improved leaf water potential as well as increased relative water content during prolonged irrigation conditions. [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]

Metabolomics offers opportunities for studying the systematic response of an organism to a genetic and/or an environmental change. Here, the metabolic consequences of drought stress were characterized in the highly drought tolerant plant Caragana korshinskii. The time-of-flight mass spectrometry platform employed identified several hundred metabolites in extracts of the leaf, stem, root collar, and root of plants which had been either subjected to drought stress or were well-watered. Each of the four organs harbored a number of potential metabolite markers for the drought response. An increased abundance of various small carbohydrates and soluble amino acids in each of the four organs was induced by the stress; these compounds may act as compatible solutes or antioxidants. Across the whole plant, there was a fall in the content of several Krebs cycle and glycolysis intermediates, as well as in that of the amino acids glutamic acid and aspartic acid. Pathway analysis suggested that most of the potential metabolite markers were involved in energy metabolism and amino-acid metabolism. The implication was that energy metabolism and photosynthesis are compromised during the adaptation of C. korshinskii to drought stress. Given the different spectrum of metabolites associated with the drought response in the four organs, it was concluded that each organ employs a distinct strategy to cope with drought stress. [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]

Drought stress in plants often leads to reduced productivity and limited geographic distribution, which can affect human life and ecosystems. The responses of diploid and tetraploid Paulownia tomentosa × Paulownia fortunei to drought have been reported, but the effects of drought stress on the levels of microRNA (miRNA) expression have not been published so far. Here, we constructed four small RNA (sRNA) libraries and four corresponding degradome libraries of well-watered and severe drought-treated diploid and tetraploid plants to identify the miRNAs and their putative target genes in Paulownia 'yuza 1', a P. tomentosa × P. fortunei hybrid clone, by sRNA and degradome sequencing. The putative target genes of miRNAs were annotated with gene ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways. Three conserved and 21 novel miRNAs responsive to drought stress were found, in which 15 were identified as the main drought responsive miRNAs that conferred higher resistance in tetraploid than in diploid of Paulownia 'yuza 1'. Our results will lay the foundation for investigating the roles of miRNAs in Paulownia and other trees in response to drought. [ABSTRACT FROM AUTHOR]

Maize is an agro-economically important crop and its global scale cultivation dates back to ancient times. It is vital to find organic solutions for the agricultural sustainability of maize. Trichoderma spp. is a cheap bio-control candidate having favorable effects on plant growth and enhances resistance to abiotic stresses. Herein, the effect of the endophytic fungus Trichoderma atroviride, our local isolate named ID20G (TaID20G), was evaluated in maize ( Zea mays L.) seedlings under drought stress. The fungal strain was characterized based on the internal transcribed spacer (ITS) sequence of 5.8S rDNA. Relative water content, phenotypic characters of roots, antioxidant enzyme activity, hydrogen peroxide content, lipid peroxidation and chlorophyll fluorescence (Fv/Fm ratio) were recorded. Root colonization of TaID20G increased fresh and dry weight of maize roots under drought stress. Chlorophyll and carotenoid contents of seedlings were reduced by drought stress and membrane damage was high in uninoculated plants. Root colonization of TaID20G almost totally prevented increase in lipid peroxidation and reversed the changes caused by drought in pigment contents and photosystem efficiency. Antioxidant enzyme activity was induced and hydrogen peroxide (HO) content was less in response to drought stress in inoculated plants. Taken together, these data indicate that TaID20G inoculation could diminish the injurious effects of drought and might have a function in arranging resilience against stress by inducing antioxidant machinery. Low cost and effortless nature of Trichoderma-based formulas might be developed as crop protectors in drought-affected lands around the world, leading to an eco-friendly insight into the plant stress tolerance. [ABSTRACT FROM AUTHOR]

Ginkgo ( Ginkgo biloba) as a precious relict plant is cultivated around the world, and it is also a typical dioecious tree. Drought is a major environmental stress that limits the growth and development of ginkgo. Although many studies have examined the impact of drought on ginkgo, few have investigated gender-related under drought treatment in the species. In our research, we examined comparative morphology, physiology and the ultrastructure of mesophyll cell in male and female ginkgoes to determine which gender shows superior adaptability to drought stress. Two-year-old cutting-propagated male and female ginkgoes suffered to drought treatment. The experiments showed that drought significantly limited growth and development, disrupted photosynthesis, and destoried the antioxidant protection system in both male and female ginkgoes. When the gender differences in the species were compared, females showed better growth, activities of SOD and POD, concentrations of chl t, chl a/ b ratio and proline, P , C , g , qP and NPQ under drought, but lower concentrations of HO and O , and relative electrolyte leakage. In the aspect of cell ultrastructure, female plants showed a slower rate of cell breakdown and chloroplast decomposition under drought stress than males. The results indicate that female plants of ginkgo show superior growth performance and self-protective mechanisms and higher photosynthetic capacity than male plants under drought stress. Thus, we conclude that female individuals of ginkgo possess better adaptability to drought stress than male individuals. [ABSTRACT FROM AUTHOR]

The applicability of root electrical capacitance (EC) measurement for in situ investigation of root activity and drought tolerance was tested in soybean cultivars. Well-watered and drought-stressed plants were grown in pots with repeated EC measurements, followed terminally by harvest to determine root dry mass (RDM), shoot dry mass (SDM), root/shoot ratio (RSR) and leaf area (LA). EC measurement showed the cultivar differences in root growth and biomass production. EC increased till the beginning of flowering, then became nearly constant. Terminal EC was highly correlated with RDM for non-stressed ( R = 0.844) and stressed plants ( R = 0.936). Drought reduced the EC of cultivars by 28.8-50.5 %, consistently with the corresponding changes of SDM (25.5-49.1 %) and LA (23.6-51.5 %), but considerably exceeded the loss of RDM (12.6-47.3 %) in some cultivars. The reason is drought increased the RSR (by 3.9-21.9 %), leading to decreased water uptake, and thus EC per unit of RDM. This was confirmed by the significantly decreased slope of EC-RDM regression line from 0.437 to 0.317 nF g RDM calculated for well-watered and drought-stressed plants, respectively. As EC referred to root uptake activity, it was better indicator of the actual root status than RDM. EC measurement was adequate for monitoring the cultivar-specific differences in root growth and for estimation of biomass loss caused by drought. By supplementing the conventional methods, this in situ technique could be useful for various fields of agriculture, including cultivar selection or stress tolerance studies. [ABSTRACT FROM AUTHOR]

The supplemental foliar application of nutrients is a viable approach to mitigate the drastic effects of water stress on growth and productivity of crop plants. However, the choice of an effective combination of elements is necessary to achieve the desired results. We report the role of foliar applied nitrogen and potassium in improving the drought tolerance of two sunflower hybrids, i.e., Hysun-33 (drought tolerant) and LG-5551 (drought susceptible). The combined effect of NK was found to be effective in maintaining turgor, enhancing accumulation of osmoprotectants, increasing stomatal conductance and net photosynthesis and reducing the production of reactive oxygen species and resulted in higher yield under water deficit conditions. Foliar spray of NK also improved the concentration of N (7 %), P (27 %) and K (27 %) in achenes. The exposure to drought stress was observed to be more detrimental at vegetative than reproductive stage. Moreover, Hysun-33 performed better than LG-5551 under both normal and water deficit conditions. To the best of our knowledge, the study provides one of the first reports regarding combined nutrients application to regulate physiological and biochemical mechanisms responsible for improved drought tolerance in sunflower. [ABSTRACT FROM AUTHOR]

Trehalose, a natural disaccharide, has already been under the attempt of improving stress tolerance in a variety of crop plants. Keeping in view its role in stress tolerance, the effectiveness of seed presoaking with trehalose (25 mM) was tested in radish ( Raphanus sativus L.) plants grown under water stress and non-stress conditions. Two radish cultivars namely Manu and 40-day were grown under control (normal watering) and water-deficit (60 % field capacity) conditions. After 45 days of drought stress treatment, a significant suppression was observed in plant fresh and dry biomass, chlorophyll ( a and b), relative water content (RWC), rate of photosynthesis ( P), sub-stomatal CO concentration ( C), and shoot and root K, Ca and P, while a rise in water-use efficiency (WUE), total soluble sugars (TSS) leaf free proline and glycinebetaine (GB) contents, activities of superoxide dismutase (SOD) and peroxidase (POD) in both radish cultivars under water stress. However, trehalose application caused a significant increase in plant fresh and dry biomass, chlorophyll a content, TSS, P, WUE, free proline contents as well as the activity of SOD enzyme. Of both radish cultivars, cv. Manu was relatively better in chlorophyll b content, TSS and C, while cv. 40-day in shoot K and P contents. However, pattern of decrease or increase was same for all other tested attributes in both radish cultivars. Overall, seed pre-sowing treatment induced growth improvement of radish plants under water stress that was found to be associated with a significant increase in chlorophyll a content, P, WUE, TSS, free proline contents as well as the activity of SOD enzyme in both radish cultivars. [ABSTRACT FROM AUTHOR]

Choice of native woody species with higher drought tolerance is the basic work on afforestation in Qinghai-Tibet Plateau (QTP) region. However, no systemic evaluation has been made of the drought tolerance ability. In the present study, we compared the drought injury degree and ten physiological and biochemical indices from six native deciduous and broad-leaved woody plant species seedlings under continuous drought for 21 days. The ten indices included relative water content, net photosynthetic rate, transpiration, water use efficiency, superoxide dismutase, peroxidase, catalase and malondialdehyde, proline and soluble sugars contents of leaves. Under drought stress, six native species showed the different response. According to analysis of the mean membership function values, the drought tolerance of six native species could be ranked in the following order: Berberis hemsleyana > Sophora viciifolia > Betula platyphylla > Cotoneaster rotundifolius > Prunus mira > Hippophae rhamnoides. Species B. hemsleyana and S. viciifolia were relatively high drought-tolerant, while P. mira and H. rhamnoides were relatively low tolerant. The two high-tolerant native species resist to drought by different strategies after long-term adaptation, and these two species should be given prior consideration in deciduous woody plant species selection for afforestation in arid and semi-arid area of QTP in the future. [ABSTRACT FROM AUTHOR]

Drought and ultraviolet-B (UV-B) radiation are the most adverse factors for plant growth and productivity. The aim of this study was to compare the effects and interaction of drought and UV-B radiation in the seedlings of maize and soybean. The relative leaf water content was the main factor resulting in reduced growth in response to drought. The anthocyanin and phenol levels were increased under UV-B radiation. Drought and UV-B radiation caused great membrane damage, as assessed by lipid peroxidation and osmolyte leakage. Catalase, peroxidase, superoxide dismutase and hydrogen peroxide were observed under both stress conditions. Proline increased primarily in drought-stressed seedlings and may be the drought-induced factor with a protective role in response to UV-B. The total dry matter of both plant species was decreased due to the chlorophyll content and photosynthetic rate decreased under single and combined stress conditions. UV-B radiation had more adverse effects on growth of maize and soybean seedlings than drought by the physiological and biochemical parameters measured. [ABSTRACT FROM AUTHOR]