Water Deficit Stress In Plants Research Articles

Simple and universal function of acetic acid to overcome the drought crisis

Acetic acid is a simple and universal compound found in various organisms. Recently, acetic acid was found to play an essential role in conferring tolerance to water deficit stress in plants. This novel mechanism of drought stress tolerance mediated by acetic acid via networks involving phytohormones, genes, and chromatin regulation has great potential for solving the global food crisis and preventing desertification caused by global warming. We highlight the functions of acetic acid in conferring tolerance to water deficit stress.

Overexpression of Chickpea Defensin Gene Confers Tolerance to Water-Deficit Stress in Arabidopsis thaliana.

Plant defensins are mainly known for their antifungal activity. However, limited information is available regarding their function in abiotic stresses. In this study, a defensin gene, Ca-AFP, from Cicer arietinum, commonly known as chickpea, was cloned and transformed in Arabidopsis thaliana for its functional characterization under simulated water-deficit conditions. Under simulated water-deficit conditions (mannitol and polyethylene glycol-6000 induced), the transgenic A. thaliana plants had higher accumulation of the Ca-AFP transcript compared to that under non-stress condition and showed higher germination rate, root length, and biomass than the wild-type (WT) plants. To get further insights into the role of Ca-AFP in conferring tolerance to water-deficit stress, we determined various physiological parameters and found significant reduction in the transpiration rate and stomatal conductance whereas the net photosynthesis and water use efficiency was increased in the transgenic plants compared to that in the WT plants under water deficit conditions. The transgenic plants showed enhanced superoxide dismutase, ascorbate peroxidase, and catalase activities, had higher proline, chlorophyll, and relative water content, and exhibited reduced ion leakage and malondialdehyde content under water-deficit conditions. Overall, our results indicate that overexpression of Ca-AFP could be an efficient approach for conferring tolerance to water-deficit stress in plants.

Novel Miscanthus genotypes selected for different drought tolerance phenotypes show enhanced tolerance across combinations of salinity and drought treatments.

Background and AimsWater deficit and salinity stresses are often experienced by plants concurrently; however, knowledge is limited about the effects of combined salinity and water deficit stress in plants, and especially in C4 bioenergy crops. Here we aim to understand how diverse drought tolerance traits may deliver tolerance to combinations of drought and salinity in C4 crops, and identify key traits that influence the productivity and biomass composition of novel Miscanthus genotypes under such conditions.MethodsNovel genotypes used included M. sinensis and M. floridulus species, pre-screened for different drought responses, plus the commercial accession Miscanthus × giganteus (M×g.). Plants were grown under control treatments, single stress or combinations of water deficit and moderate salinity stress. Morphophysiological responses, including growth, yield, gas exchange and leaf water relations and contents of proline, soluble sugars, ash and lignin were tested for significant genotypic and treatment effects.Key ResultsThe results indicated that plants subjected to combined stresses showed more severe responses compared with single stresses. All novel drought-tolerant genotypes and M×g. were tolerant to moderate salinity stress. Biomass production in M. sinensis genotypes was more resilient to co-occurring stresses than that in M×g. and M. floridulus, which, despite the yield penalty produced more biomass overall. A stay-green M. sinensis genotype adopted a conservative growth strategy with few significant treatment effects. Proline biosynthesis was species-specific and was triggered by salinity and co-occurring stress treatments, mainly in M. floridulus. The ash content was compartmentalized differently in leaves and stems in the novel genotypes, indicating different mechanisms of ion accumulation.ConclusionsThis study highlights the potential to select novel drought-tolerant Miscanthus genotypes that are resilient to combinations of stress and is expected to contribute to a deeper fundamental knowledge of different mechanistic responses identified for further exploitation in developing resilient Miscanthus crops.

Differential response of single and co-inoculation of Rhizobium leguminosarum and Mesorhizobium ciceri for inducing water deficit stress tolerance in wheat

Limited soil water availability is a major threat to agricultural productivity because it inhibits plant growth and yields. Various strategies have been adopted to mitigate water deficit stress in plants; however, using extremophilic microbes with plant growth promoting traits could be an environmentally friendly and cost-effective approach to improve crop stress resilience. Rhizobia are well known for their symbiotic association with legumes, but they can also improve the fitness of non-legumes under stressed conditions. Thus, different rhizobial strains were isolated from nodules of two legumes (lentil and chickpea) and tested for osmoadaptation at four different polyethylene glycol (PEG-6000) levels, i.e., − 0.05, − 0.65, − 1.57, and − 2.17 MPa. Two stress-tolerant rhizobial strains, SRL5 and SRC8, were selected to evaluate their potential to induce tolerance against water deficits in wheat grown at four different percentages of field capacity (FC; 40, 60, 80, and 100%). Rhizobial inoculation improved physiological parameters and growth of wheat under water deficit; however, co-inoculation of selected rhizobia was better than sole application. Grain yield was most limited at the highest level of water deficit but sole inoculation with SRC8 and SRL5 improved yield by 24% and 19%, respectively. Combined inoculation increased grain yield by up to 48% compared to the uninoculated control. Thus, rhizobia from different legumes possess enormous potential for improving the resilience of cereals (non-legumes) to water deficit stress. Moreover, co-inoculation of rhizobia could be more beneficial than their sole application.

Endogenous reduced ascorbate: an indicator of plant water deficit stress in wheat

Ascorbic acid plays an important role in scavenging the reactive oxygen species under abiotic stress. In this study, the association of endogenous reduced ascorbate with drought stress tolerance has been investigated in wheat genotypes at reproductive stage. Endogenous reduced ascorbate content of twenty-nine wheat genotypes under irrigated and water deficit condition showed a wide genotypic variability and a decreasing trend under drought. Our study indicated that endogenous level of reduced ascorbate content under irrigated condition is responsible for drought stress tolerance. Genotypes with higher level of reduced ascorbate under irrigated condition also showed higher level of membrane stability, chlorophyll content under drought condition as compared to the genotypes having low reduced ascorbate. The genotypes with higher reduced ascorbate under irrigated condition also had a low drought susceptibility index compared to the genotypes having low endogenous reduced ascorbate.

Mechanisms for tolerance to water-deficit stress in plants inoculated with arbuscular mycorrhizal fungi. A review

The expansion of areas affected by drought worldwide has a negative effect on yield and crops production, making water deficits the most significant abiotic stress that limits the growth and development of plants. The use of arbuscular mycorrhizal fungi (AMF) is a strategy that mitigates the effects of this stress in a sustainable way, given the increase in the tolerance to water deficit stress in plants inoculated with these fungi; however, the exact mechanism is unknown because the response depends on the water-deficit stress type and is specific to the AMF and the plant. This review describes the mechanisms that explain how the AMF colonization of roots can modify the response of plants during a water deficit, as well as its relationship with physiological processes that determine yield, photosynthesis and photoassimilate partitioning. These mechanisms may include modifications in the content of plant hormones, such as strigolactones, jasmonic acid (JA) and absicic acid (ABA). The JA appears to be involved in the stress signal in mycorrhizal plants through an increase of ABA concentrations and, at the same time, ABA has a regulating effect on strigolactone concentrations. Also, there is improvement of plant water status, stomatal conductance, nutritional status and plant responses to cope with a water deficit, such as osmotic adjustment, and antioxidant activity. These modifications cause an increase in CO2 assimilation and photoassimilate production, improving plant growth during a drought.

Physiological response of selected eragrostis species to water-deficit stress

Plant water-deficit stress is considered to be one of the greatest threats to world agriculture. In an effort to identify a better performing crop variety of Eragrostis tef under this stress, the responses of two varieties, white (W) and brown (B) seeded, were compared with those of the resurrection grass Eragrostis nindensis during a dehydration/rehydration cycle. After 6 days of dehydration, relative water content (RWC) dropped to 33%, 43% and 39% in En, Et(B) and Et(W) plants, respectively. This water loss was accompanied by a decline in transpiration and increased electrolyte leakage in the Et varieties. Et(W) did not recover from this level of drying when watered. Et(B) on the other hand recovered fully from 43% RWC, but lost viability after 9 days dehydration, RWC < 30%. En showed full metabolic recovery from drying to 10% RWC. Loss of viability in the Et varieties was accompanied by an increase in electrolyte leakage and irreversible decline in photosynthesis and transpiration. Ultrastructural study also indicated a drying-induced damage to membranes and organelles of Et tissues dehydrated for 6 days which was reversed in Et(B), 43% RWC, on rehydration. However, after 9 days of dehydration, (< 30% RWC), severe irreversible damage occurred to the entire subcellular organization of both Et varieties and was accompanied by loss of viability. This study shows that En is a true resurrection plant and both Et varieties are desiccation sensitive but drought tolerant to varying degrees. Et(B) is more drought tolerant and hence a better choice crop in drought prone areas. Comparative study of closely related plant species might be a better approach in finding adaptive characters in crop plants with respect to environmental stresses. Key words: Eragrostis tef, eragrostis nindensis, dehydration, desiccation, gas exchange, leakage, ultrastructure.

Relations of remote sensing leaf water indices to leaf water thickness in cowpea, bean, and sugarbeet plants

Remote sensing leaf water indices depend on two variables: the relative water content (RWC) of leaf cells, which may serve as an indicator for water deficit stress in plants, and leaf thickness. The measurement of leaf water thickness (LWT) appears to be an experimental method that can be well correlated with leaf water indices. We studied how leaf water indices relate to the LWT in cowpea, bean, and sugarbeet. In all three species, the LWT increased linearly with increasing leaf thickness. The T 1300/ T 1450 leaf water index, based on light transmitted through leaves, showed a strong exponential correlation with the LWT as expected from theoretical analysis. However, the R 1300/ R 1450 leaf water index, based on light reflected from leaves, exhibited a characteristic logarithmic correlation with the LWT. For both leaf water indices we found only minor differences between the three species examined.

Nondestructive Detection of Water Stress in Tomato Plants by NIR Spectroscopy.

The objective of this research was to experimentally determine whether signs of water deficit stress in plants can be detected from changes in the absorbance spectra based on the relationships between absorbance spectra and physiological parameters. Absorbance of tomato leaves in the near-infrared (NIR) wavelengths (1100 nm to 2500 nm) was measured simultaneously with photosynthesis and stomatal conductance during water stress. To observe small changes in absorbance which arise from water stress, a leaf in non-stressed conditions was used as a reference for the absorbance measurements. In general, under the effects of water stress, peaks formed in the absorbance spectra at water absorbance bands near 1 440 nm and 1 940 nm, and absorbance decreased near 1 600 nm forming a valley. Although the relationship between the changes in absorbance and physiological parameters varied depending on the individual plants tested, consistent overall trends were observed, demonstrating there is potential to nondestructively detect changes in plant condition resulting from water stress by measuring NIR absorbance.

Physiological responses of two soybean [ Glycine max (L.) Merr] cultivars to short-term flooding

Flooding of soybean plants [ Glycine max (L.) Merr] significantly reduces crop growth and yield, but the underlying physiological responses are poorly documented. The short-term physiological effects of flooding on soybean were studied in the field on a relatively impermeable soil classified as Typic Albaqualf. Flooding treatments were imposed on two soybean cultivars, Essex and Forrest, at a vegetative (V4) and a reproductive (R2) growth stage. Diurnal measurements of net photosynthesis ( P n), stomatal conductance ( g s), and components of leaf water potential were recorded on 4 consecutive days following flood application, and again at 14 days after the flood was removed. Photosynthesis of Essex was reduced significantly within 48 h of flooding by 33 and 32% for the V4 and R2 growth stages, respectively, while reductions of 16 and 22% in P n of Forrest were evident. Reductions in g s of 46 and 24% occurred within 48 h for Essex and Forrest in the V4 stage, although in the R2 growth stage, both cultivars experienced an approximate 48% reduction in g s. However, the decline in P n with flooding was only partially explained by changes in g s. Photosynthesis was correlated with stomatal closure at low g s (< 0.5 mol m −2 sec −1), but a higher values of g s an approximate 20% reduction in P n was observed presumably due to non-stomatal limitations. Flooding did not affect components of leaf water potential indicating that the decreases in P n and g s were not associated with plant water-deficit stress. Flooding of Essex and Forrest at either the V4 or R2 growth stage significantly reduced the dry matter accumulation during the flooding treatment and the subsequent growth. Final seed yields were reduced significantly by a mean of 52 and 40% for Essex and Forrest, respectively. Overall, Forrest appeared more tolerant to excess water than Essex.