Membrane Stability Index Research Articles

Foliar Application of Zinc Oxide Nanoparticles Promotes Drought Stress Tolerance in Eggplant (Solanum melongena L.).

Water shortage and salinity are major challenges for sustaining global food security. Using nutrients in the nano-scale formulation including zinc oxide nanoparticles (ZnO NP) is a novel fertilization strategy for crops. In this study, two field-based trials were conducted during 2018 and 2019 to examine the influence of three ZnO NP concentrations (0, 50, and 100 ppm) in eggplant grown under full irrigation (100 of crop evapotranspiration; ETc) and drought stress (60% of ETc). Plant growth, yield, water productivity (WP), physiology, biochemistry, and anatomy responses were evaluated. Drought stress significantly decreased membrane stability index (MSI), relative water content (RWC), and photosynthetic efficiency, thus hampered eggplant growth and yield. In contrast, exogenous ZnO NP to water-stressed eggplant resulted in increased RWC and MSI associated with improved stem and leaf anatomical structures and enhanced photosynthetic efficiency. Under drought stress, supplementation of 50 and 100 ppm ZnO NP improved growth characteristics and increased fruit yield by 12.2% and 22.6%, respectively, compared with fully irrigated plants and nonapplied ZnO NP. The highest water productivity (WP) was obtained when eggplant was irrigated with 60% ETc and foliarly treated with 50 or 100 ppm of ZnO NP, which led to 50.8–66.1% increases in WP when compared with nontreated fully irrigated plants. Collectively, these findings demonstrated that foliar spraying ZnO NP gives the utility for alleviating drought stress effects on eggplant cultivated in saline soil.

Karrikinolide alleviates BDE-28, heat and Cd stressors in Brassica alboglabra by correlating and modulating biochemical attributes, antioxidative machinery and osmoregulators

In this study, we have evaluated the role of karrikin (KAR1) against the absorption and translocation of a persistent organic pollutant (POP), 2,4,4’-Tribromodiphenyl ether (BDE-28) in plants, in the presence of two other stressors, cadmium (Cd) and high temperature. Furthermore, it correlates the physiological damages of Brassica alboglabra with the three stresssors separately. The results revealed that the post-germination application of KAR1 successfully augmented the growth (200%) and pertinent physiochemical parameters of B. alboglabra. KAR1 hindered air absorption of BDE-28 in plant tissues, and reduced its translocation coefficient (TF). Moreover, BDE-28 was the most negatively correlated (−0.9) stressor with chlorophyll contents, while the maximum mitigation by KAR1 was also achieved agaist BDE-28. The effect of temperature was more severe on soluble sugars (0.51), antioxidative machinery (−0.43), and osmoregulators (0.24). Cd exhibited a stronger inverse interrelation with the enzymatic antioxidant cascade. Application of KAR1 mitigated the deleterious effects of Cd and temperature stress on plant physiological parameters along with reduced aero-concentration factor, TF, and metal tolerance index. The phytohormone reduced lipid peroxidation by decreasing synthesis of ROS and persuading its breakdown. The stability of cellular membranes was perhaps due to the commotion of KAR1 as a growth-promoting phytohormone. In the same way, KAR1 supplementation augmented the membrane stability index, antioxidant defense factors, and removal efficiency of the pollutants. Consequently, the exogenously applied KAR1 can efficiently alleviate Cd stress, heat stress, and POP toxicity.

Variability in drought response among the plus tree accessions of Tectona grandis (Linn f.) from the provenances of Kerala, South India

Moisture stress is one of the major impediments in establishment of plantations since the seedlings are susceptible to moisture stress. Rapid recovery from the drought stress is as important as stress tolerance of tree seedlings. Present study evaluated the physiological and biochemical responses related with stress tolerance and recovery in plus trees of teak from different provenances. One-and-a-half-year-old ramets of eleven plus trees of teak from different provenance of Kerala were exposed to two consecutive drought treatments, till most of leaves exhibited symptoms of wilting with an intervening period of stress relief through rehydration for six days in green house nursery. During the second cycle of drought stress and recovery, physiological parameters like relative water content, canopy air temperature, photosynthesis, stomatal conductance, transpiration, chlorophyll content, chlorophyll stability index and cell membrane stability index were determined. The biochemical constituents like total soluble protein, nitrate reductase, free amino acid, proline, glycine betaine, soluble sugar, super oxide dismutase, peroxidase and malondialdehyde were also recorded in addition to leaf numbers before and after stress. The results showed that physiological and biochemical parameters are crucial to maintain seedling functions during drought and to rapidly recover after re-watering during early vegetative stage. During stress and after rehydration, accessions exhibited variation between full and partial recovery in which both genetic and epigenetic factors may play crucial role. Combinations of photo-protection, osmoregulants and antioxidants measures are employed by teak to combat drought stress. Our results also suggest considerable variation that both drought stress and recovery among the plus trees that were originally selected for growth and wood quality and the potential to use them for further breeding.

Exogenously Used 24-Epibrassinolide Promotes Drought Tolerance in Maize Hybrids by Improving Plant and Water Productivity in an Arid Environment.

The influence of 24-epibrassinolide (EBR24), applied to leaves at a concentration of 5 μM, on plant physio-biochemistry and its reflection on crop water productivity (CWP) and other agronomic traits of six maize hybrids was field-evaluated under semi-arid conditions. Two levels of irrigation water deficiency (IWD) (moderate and severe droughts; 6000 and 3000 m3 water ha−1, respectively) were applied versus a control (well-watering; 9000 m3 water ha−1). IWD reduced the relative water content, membrane stability index, photosynthetic efficiency, stomatal conductance, and rates of transpiration and net photosynthesis. Conversely, antioxidant enzyme activities and osmolyte contents were significantly increased as a result of the increased malondialdehyde content and electrolyte leakage compared to the control. These negative influences of IWD led to a reduction in CWP and grain yield-related traits. However, EBR24 detoxified the IWD stress effects and enhanced all the above-mentioned parameters. The evaluated hybrids varied in drought tolerance; Giza-168 was the best under moderate drought, while Fine-276 was the best under severe drought. Under IWD, certain physiological traits exhibited a highly positive association with yield and yield-contributing traits or CWP. Thus, exogenously using EBR24 for these hybrids could be an effective approach to improve plant and water productivity under reduced available water in semi-arid environments.

Titanium dioxide nanoparticles elicited agro-morphological and physicochemical modifications in wheat plants to control Bipolaris sorokiniana.

The current study involves the biogenesis of titanium dioxide nanoparticles (TiO2 NPs) by using Moringa oleifera Lam. aqueous leaf extract for the reduction of titanium dioxide salt into TiO2 nanoparticles. The biosynthesized TiO2 nanoparticles were observed by using the UV-visible spectrophotometry, SEM, EDX and XRD analytical methods. It was confirmed that the nanoparticles are crystalline and exist in the size range of 10–100 nm. The FTIR analysis confirmed the presence of O-H (hydrogen bonding), N-H (amide), C-C (alkanes) and C-I (Iodo-stretch) functional groups responsible for the stabilization of nanoparticles. Various concentrations (20, 40, 60 and 80 mg/L) of TiO2 NPs were applied exogenously on wheat plants infected with a fungus Bipolaris sorokiniana responsible to cause spot blotch disease at different time intervals. The measurement of disease incidence and percent disease index showed the time-dependent response and 40 mg/L was reported a stable concentration of TiO2 NPs to reduce the disease severity. The effects of biosynthesized TiO2 NPs were also evaluated for agro-morphological (leaf and root surface area, plant fresh and dry weight and yield parameters), physiological (relative water content, membrane stability index and chlorophyll content) and non-enzymatic metabolites (soluble sugar, protein, soluble phenol and flavonoid content) in wheat plants under biotic stress and 40 mg/L concentration of TiO2 NPs was found to be effective to elicit modifications to reduce biotic stress. The current study highlights the significant role of biosynthesized TiO2 NPs in controlling fungal diseases of wheat plants and thus ultimately improving the quality and yield of wheat plants.

Potassium-enriched clinoptilolite zeolite mitigates the adverse impacts of salinity stress in perennial ryegrass (Lolium perenne L.) by increasing silicon absorption and improving the K/Na ratio

Salinity is a major abiotic stress that adversely affects turfgrass growth. Clinoptilolite zeolite, a silicon (Si)-rich mineral, may allow these plants to cope with salinity. Therefore, in the present study, the effects of ordinary clinoptilolite zeolite (OZ) and potassium-enriched clinoptilolite zeolite (K-EZ) on the growth of perennial ryegrass (Lolium perenne L.) were assessed under salinity stress. Perennial ryegrass seeds were cultured in soil mixtures amended, or not, with OZ or K-EZ, then exposed to three salinity levels (0, 50 or 100 mM NaCl) for three months. Control plants were grown in the same soil mixture without zeolites, but not exposed to salinity. In salinity, the application of both types of zeolite significantly decreased Na content by 44.36% and 21.31%, but increased K content by 272.34% and 81.59%, as well as the K/Na ratio by 590.47% and 129.43%, in shoots and roots, respectively, compared to the no-zeolite treatment. Similarly, Si content in shoots increased by 28.33%. Amending the soil mixture with zeolite, especially K-EZ, enhanced relative water content, membrane stability index, total chlorophyll content, total soluble proteins, peroxidase and superoxide dismutase activities but reduced the contents of total soluble carbohydrates, hydrogen peroxide, and malondialdehyde in saline conditions. Shoot and root dry weight, root volume and root/shoot ratio also improved. Soil amendment with both forms of zeolite, as a Si-rich mineral, partially offset the negative impacts of salinity on perennial ryegrass, although K-EZ had more noticeable positive and beneficial effects. The amendment of growth media with zeolite may be an effective sustainable management practice for turfgrass used in landscaping and sports fields exposed to saline water.

Screening of Onion (Allium cepa L.) Genotypes for Drought Tolerance Using Physiological and Yield Based Indices Through Multivariate Analysis.

Drought is a leading abiotic constraints for onion production globally. Breeding by using unique genetic resources for drought tolerance is a vital mitigation strategy. With a total of 100 onion genotypes were screened for drought tolerance using multivariate analysis. The experiment was conducted in a controlled rainout shelter for 2 years 2017–2018 and 2018–2019 in a randomized block design with three replications and two treatments (control and drought stress). The plant was exposed to drought stress during the bulb development stage (i.e., 50–75 days after transplanting). The genotypes were screened on the basis of the drought tolerance efficiency (DTE), percent bulb yield reduction, and results of multivariate analysis viz. hierarchical cluster analysis by Ward’s method, discriminate analysis and principal component analysis. The analysis of variance indicated significant differences among the tested genotypes and treatments for all the parameters studied, viz. phenotypic, physiological, biochemical, and yield attributes. Bulb yield was strongly positively correlated with membrane stability index (MSI), relative water content (RWC), total chlorophyll content, antioxidant enzyme activity, and leaf area under drought stress. The genotypes were categorized into five groups namely, highly tolerant, tolerant, intermediate, sensitive, and highly sensitive based on genetic distance. Under drought conditions, clusters II and IV contained highly tolerant and highly sensitive genotypes, respectively. Tolerant genotypes, viz. Acc. 1656, Acc. 1658, W-009, and W-085, had higher DTE (>90%), fewer yield losses (<20%), and performed superiorly for different traits under drought stress. Acc. 1627 and Acc. 1639 were found to be highly drought-sensitive genotypes, with more than 70% yield loss. In biplot, the tolerant genotypes (Acc. 1656, Acc. 1658, W-085, W-009, W-397, W-396, W-414, and W-448) were positively associated with bulb yield, DTE, RWC, MSI, leaf area, and antioxidant enzyme activity under drought stress. The study thus identified tolerant genotypes with favorable adaptive traits that may be useful in onion breeding program for drought tolerance.

Lead Toxicity in Cereals: Mechanistic Insight Into Toxicity, Mode of Action, and Management.

Cereals are the major contributors to global food supply, accounting for more than half of the total human calorie requirements. Sustainable availability of quality cereal grains is an important step to address the high-priority issue of food security. High concentrations of heavy metals specifically lead (Pb) in the soil negatively affect biochemical and physiological processes regulating grain quality in cereals. The dietary intake of Pb more than desirable quantity via food chain is a major concern for humans, as it can predispose individuals to chronic health issues. In plant systems, high Pb concentrations can disrupt several key metabolic processes such as electron transport chain, cellular organelles integrity, membrane stability index, PSII connectivity, mineral metabolism, oxygen-evolving complex, and enzymatic activity. Plant growth-promoting rhizobacteria (PGPR) has been recommended as an inexpensive strategy for remediating Pb-contaminated soils. A diverse group of Ascomycetes fungi, i.e., dark septate endophytes is successfully used for this purpose. A symbiotic relationship between endophytes and host cereal induces Pb tolerance by immobilizing Pb ions. Molecular and cellular modifications in plants under Pb-stressed environments are explained by transcription factor families such as bZIP, ERF, and GARP as a regulator. The role of metal tolerance protein (MTP), natural resistance-associated macrophage protein (NRAMP), and heavy metal ATPase in decreasing Pb toxicity is well known. In the present review, we provided the contemporary synthesis of existing data regarding the effects of Pb toxicity on morpho-physiological and biochemical responses of major cereal crops. We also highlighted the mechanism/s of Pb uptake and translocation in plants, critically discussed the possible management strategies and way forward to overcome the menace of Pb toxicity in cereals.

Comparison of plant growth and remediation potential of pyrochar and thermal desorption for crude oil-contaminated soils

Crude oil contamination is a serious environmental threat for soil and plants growing in it. This study provides the first experimental evidence for comparison of the efficacy of pyrochar (slow pyrolysis biochar), thermal desorption and their combined application for degradation of crude oil contaminated soil (0%, 10%, and 20%), and growth of lettuce under glasshouse conditions. Pyrochar was produced by pyrolysis of sawdust at 350 °C, whereas thermal desorption was done by soil pyrolysis at 500 °C. Soil incubations were done for 120 days. The results of soil analysis showed that the crude oil degradation efficiency for the combined application was highest (40%), whereas pyrochar and thermal desorption was 25% and 19.6%, respectively. The maximum degradation products of crude oil were manifested by the detection of low molecular weight hydrocarbons (ranged between 173 and 422) in the soil with combined application treatment using Gas Chromatography-Mass Spectrometry (GC–MS) analysis. Crude oil contamination significantly reduced the germination and growth of the lettuce plants. Similarly, the combined application also improved plant growth by an increase of 24% in germination percentage, 35.5% in seedling vigor index, and 27% in promptness index under 20% crude oil contamination. Remediation caused a significant increase in fresh and dry biomass (40%), leaf area (30%), total chlorophyll (21%), water potential (23.6%), osmotic potential (27%), and membrane stability index (40%). Moreover, there was an increase in the contents of proline (32%), total amino acids (29%), soluble sugars (37%), proteins (27%), and antioxidant enzymes such as superoxide dismutase (19%), catalase (33%) and peroxidase (38%). This study confirmed the efficacy of pyrochar (slow pyrolysis biochar), thermal desorption, and their combined application for crude oil decontamination of soil at laboratory scale and also in improving soil usability by improved germination and growth of lettuce.

Nanosilver/hydrogel: Synthesis and application in delaying senescence of cut flower

The superabsorbent Aquasorb hydrogel enriched with silver ion solutions was exerted with sodium borohydride (NaBH4) and glucose/ sodium hydroxide (NaOH) in various concentrations as reducing agents. Scanning electron microscopy (SEM), and transmission electron microscopy (TEM) images confirmed the presence of silver nanoparticles (SN) in the amorphous structure of hydrogel. The results showed that the swelling of hydrogel increased by glucose (5 mM) / sodium hydroxide (10 mM) 298.5 g water/g hydrogel, while atomic absorption analysis showed that the amount of SN (0. 1054 mg/ mg hydrogel) was in the reduced sample by glucose (10 mM)/ sodium hydroxide (10 mM). The highest antibacterial activity on Escherichia coli and Bacillus cereus was observed in reduced samples by NaBH4. Then the efficacy of this sample containing SN 1–3 nm sized particles (50 mg L−1) was evaluated in the preservative solution of rose cut flower cv. ‘Red Alert’. The results indicated positive effects of hydrogel enriched with silver nanoparticles on relative fresh water, membrane stability index, and the vase life extended (14.26 days) in cut flowers, and did not result in any evident toxic effects, so that the highest chlorophyll content was observed in the hydrogel containing silver nanoparticles (86.4%). The results indicated that the expression level of two senescence-associated genes (RhAA and RhCG) were decreased in rose petals, and the RhCTR1 as a negative regulator in the ethylene signaling pathway was induced at higher levels in the hydrogel- containing SN treatment. As our findings showed, the nanocomposite hydrogel containing silver nanoparticles can be used to control the toxicity of SN in the preservative solution with higher efficiency, and the ability to use multiple times for senescence delay in the cut flowers industry.

Assessment of cadmium and lead tolerance potential of quinoa (Chenopodium quinoa Willd) and its implications for phytoremediation and human health.

Soil contamination with Cd and Pb is a worldwide problem which not only degrades the environment but also poses a serious threat for human and animal health. Phytoremediation of these contaminated soils using halophytic plants like quinoa presents an opportunity to clean the soils and use them for crop production. The current experiment was performed to evaluate the Cd and Pb tolerance potential of quinoa and subsequently its implications for human health. Three weeks old quinoa seedlings were exposed to Cd (30, 60 and 90mgkg-1) and Pb (50, 100 and 150mgkg-1) levels along with a control. The results revealed that plant height decreased at highest levels of soil Cd and Pb. Shoot, root and seed dry weight decreased with increasing levels of soil Cd and Pb. Tissue Cd and Pb concentrations increased with increasing levels of Cd and Pb in soil, the highest Cd was found in roots while the lowest in seeds. The highest Pb concentration was found in shoots at low Pb level, while in roots at high level of Pb. Increasing levels of Cd and Pb stimulated the activities of measured antioxidant enzymes and decreased membrane stability index. The health risk assessments of Cd and Pb revealed that hazard quotient was < 1 for both the metals. However, the results of total hazard quotient showed that value was < 1 for Pb and 1.19 for Cd showing potential carcinogenicity. This study demonstrates that quinoa has good phytoremediation potential for Cd and Pb however, the risk of Cd toxicity is challenging for human health.

Influence of silicon and chitosan on growth and physiological attributes of maize in a saline field.

Soil salinity is the main constraint for crop productivity in many parts of the world. Application of silicon (Si) and chitosan (Chi) can improve crop growth under saline soil conditions. The current study was aimed to examine the effects of Si and Chi on mitigation of salinity, morphological and physiological attributes as well as the antioxidant system of maize (Zea mays L.) under saline soil conditions. A field experiment was conducted that comprised of nine treatments as follows: (i) Control (no amendment), (ii) Silicon 40kgha-1 (Si1), (iii) Chitosan 15kgha-1 (Chi1), (iv) Si1 + Chi1, (v) Silicon 80kgha-1 (Si2), (vi) Chitosan 30kgha-1 (Chi2), (vii) Si2 + Chi2, (viii) Si1 + Chi2 and (ix) Si2 + Chi1. Application of Si and Chi substantially improved the morphological and physiological attributes as well as antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) of maize plants, and combined application of Si and Chi was more effective when compared with Si and Chitreatments separately. Membrane stability index was improved by 25%, relative water content by 26%, chlorophyll a by 69% and b by 56% with combined application of Si and chitosan (Si2 + Chi2) compared with control. The SOD, POD and CAT increased by 36%, 38% and 65% with Si2 + Chi2 compared with control. The results suggest that Si and Chi application is the possible option for alleviating salinity stress in maize plant. Further research is suggested to examine Si and Chi effects on various crop's growth.

Salicylic acid retards senescence and makes flowers last longer in Nicotiana plumbaginifolia (Viv)

Salicylic acid (SA) is known to be a plant signalling molecule that plays an important role in growth, development and defence response in plants. During the present study the effect of exogenous application of SA on the senescence of cut Nicotiana plumbaginifolia flowers was investigated. The buds were subjected to different concentrations (0.05, 0.1, 0.15, 0.20 and 0.25 mM) of SA. A separate set of flowers kept in distilled water designated the control. The flowers treated with various concentrations of SA resulted in improved flower longevity besides maintaining higher membrane stability index, soluble proteins and sugar fractions. SA treatment decreased the α-amino acid, total phenol content, lipid peroxidase and lipoxygenase activity. The flowers treated with SA showed a significant increase in activity of antioxidant enzymes like superoxide dismutase, catalase and ascorbate peroxidase. Among various concentrations used, 0.05 mM SA was found to be most effective in enhancing the flower longevity. Thus, exogenous SA could maintain membrane integrity by increasing antioxidant system activity, thereby retarding the senescence of cut N. plumbaginifolia flowers.

Mitigating Drought Stress in Sunflower (Helianthus annuus L.) Through Exogenous Application of β-Aminobutyric Acid

Drought stress is a serious threat for sustainable crop production throughout the world especially in arid and semi-arid regions and one of the main constraints to sunflower (Helianthus annuus L.) production. Different mitigation strategies, including foliar spray of osmolytes such as β-aminobutyric acid (BABA), help the crop to combat drought conditions. A 2-year field study was conducted to evaluate the effect of exogenous application of BABA on the growth, productivity, and net return of sunflower under drought conditions. The experimental treatments comprised drought levels, viz., control (well watered (WW)); drought stress at vegetative stage (DVS); and drought stress at reproductive stage (DRS). Drought-mitigating treatments comprised foliar application of BABA, viz., 0 mM (control), 25 mM, 50 mM, and 75 mM with three replications. Foliar application of BABA under drought condition had significant effect on physiological traits, yield, and yield-related traits. Foliar application of 75-mM BABA solution improved SPAD–chlorophyll value and membrane stability index and maintained higher relative water contents. It also improved 1000-achene weight and achene yield, and produced about 41% and 44% more achene yield during 2018 and 2019 respectively compared with other treatments. Significant and positive correlations were also observed between yield and yield-contributing traits of sunflower under different water stress conditions. This finding suggests that foliar application of 75-mM BABA may be used as a viable option for sunflower growers to enhance achene yield and net benefit under drought conditions in arid and semi-arid regions.

Biological silicon nanoparticles improve Phaseolus vulgaris L. yield and minimize its contaminant contents on a heavy metals-contaminated saline soil

The synthesis of biological silicon nano-particles (Bio-Si-NPs) is an eco-friendly and low-cost method. There is no study focusing on the effect of Bio-Si-NPs on the plants grown on saline soil contaminated with heavy metals. In this study, an attempt was made to synthesis Bio-Si-NPs using potassium silica florid substrate, and the identified Aspergillus tubingensis AM11 isolate that separated from distribution systems of the potable water. A two-year field trial was conducted to compare the protective effects of Bio-Si-NPs (2.5 and 5.0 mmol/L) and potassium silicate (10 mmol/L) as a foliar spray on the antioxidant defense system, physio-biochemical components, and the contaminants contents of Phaseolus vulgaris L. grown on saline soil contaminated with heavy metals. Our findings showed that all treatments of Bio-Si-NPs and potassium silicate significantly improved plant growth and production, chlorophylls, carotenoids, transpiration rate, net photosynthetic rate, stomatal conductance, membrane stability index, relative water content, free proline, total soluble sugars, N, P, K, Ca2+, K+/Na+, and the activities of peroxidase, catalase, ascorbic peroxidase and superoxide oxide dismutase. Application of Bio-Si-NPs and potassium silicate significantly decreased electrolyte leakage, malondialdehyde, H2O2, O2•−, Na+, Pb, Cd, and Ni in leaves and pods of Phaseolus vulgaris L. compared to control. Bio-Si-NPs were more effective compared to potassium silicate. Application of Bio-Si-NPs at the rate of 5 mmol/L was the recommended treatment to enhance the performance and reduce heavy metals content on plants grown on contaminated saline soils.

Growth, leaf gas exchange and physiological parameters of two Glycyrrhiza glabra L. populations subjected to salt stress condition

Salinity is the major environmental stress affecting growth and physiological processes in plants. Glycyrrhiza glabra (licorice) is a perennial medicinal plant having many secondary metabolites. The effects of 0, 100, 200, 400, 600, and 800 mM NaCl on growth parameters, leaf relative water content, chlorophyll index, gas exchange parameters, membrane stability index, antioxidant activity, phenolic compounds, flavonoid, and soluble carbohydrate contents of licorice populations (Fars and Khorasan) cultivated with different rhizomes diameters were evaluated. The soil and rhizomes elements were also studied. The results indicated that the salinity significantly decreased the growth parameters, relative water content, and membrane stability index, compared to the controls. The thicker rhizomes can grow more than thinner ones in saline soil. Chlorophyll index and leaf gas exchange were declined under salt stress. Besides, the soluble carbohydrate content was decreased. Salinity caused oxidative stress in licorice rhizomes, so that by decreasing the membrane stability index, antioxidant capacity, phenolic compounds, and flavonoid contents of rhizomes have increased in line with NaCl treatments. Na+, Cl−, and Ca2+ levels increased, but K+ concentration was reduced. The PCA-biplot analysis revealed that Fars and Khorasan populations had different responses to salinity. The length of rhizomes, flavonoids, phenolic compounds, and soluble carbohydrates of two licorice populations and salinity stress had the largest amount of difference of traits. Thus, the elevation of osmolytes, the nutrient balance, and the antioxidant capacity lead to protect of licorice under osmotic, ionic, and oxidative stress, which is caused by the salinity stress. Accordingly, G. glabra can withstand salinity up to 600 mM NaCl and be introduced as a halophyte plant.

Identifying drought-tolerant genotypes of faba bean and their agro-physiological responses to different water regimes in an arid Mediterranean environment

Faba bean (Vicia faba L.), a major legume crop, helps in maintaining soil health by fixing atmospheric nitrogen (N2) and thus mostly used as a rotational crop. However, faba bean is sensitive to water stress, which limits its yield potential in water-limited environments. The objectives of the present study were to (i) characterize the agro-physiological performance of 14 faba bean genotypes with different genetic backgrounds to various levels of water stress in an arid environment and (ii) identify the most drought-tolerant genotypes that maximize the marginal use of unit water without significant yield loss. Field experiments were conducted for two consecutive growing seasons in an arid Mediterranean climate, and several agronomic and physiological measurements of different faba bean genotypes in response to water stress were recorded. A great variation among the tested genotypes, according to several drought-response indices, was observed as a result of water stress on the basis of which they were classified into five groups (A–E) ranging from drought-tolerant to highly sensitive genotypes. Yield and water productivity results indicated that drought-tolerant genotypes produced more yield with less water compared with drought-sensitive genotypes and thus are highly recommended for faba bean production in water-limited environments. Certain physiological parameters, such as photosynthetic pigment, net photosynthetic rate, transpiration rate, leaf nutrient status (N, P and K content), relative water content and membrane stability index, exhibited highly positive association with seed yield and yield contributing traits. It is valid to use these parameters as rapid indicators of drought tolerance in breeding programs aiming to screen and improve faba bean genotypes for drought tolerance in arid environments.

Transgenic chickpea (Cicer arietinum L.) harbouring AtDREB1a are physiologically better adapted to water deficit

BackgroundChickpea (Cicer arietinum L.) is the second most widely grown pulse and drought (limiting water) is one of the major constraints leading to about 40–50% yield losses annually. Dehydration responsive element binding proteins (DREBs) are important plant transcription factors that regulate the expression of many stress-inducible genes and play a critical role in improving the abiotic stress tolerance. Transgenic chickpea lines harbouring transcription factor, Dehydration Responsive Element-Binding protein 1A from Arabidopsis thaliana (AtDREB1a gene) driven by stress inducible promoter rd29a were developed, with the intent of enhancing drought tolerance in chickpea. Performance of the progenies of one transgenic event and control were assessed based on key physiological traits imparting drought tolerance such as plant water relation characteristics, chlorophyll retention, photosynthesis, membrane stability and water use efficiency under water stressed conditions.ResultsFour transgenic chickpea lines harbouring stress inducible AtDREB1a were generated with transformation efficiency of 0.1%. The integration, transmission and regulated expression were confirmed by Polymerase Chain Reaction (PCR), Southern Blot hybridization and Reverse Transcriptase polymerase chain reaction (RT-PCR), respectively. Transgenic chickpea lines exhibited higher relative water content, longer chlorophyll retention capacity and higher osmotic adjustment under severe drought stress (stress level 4), as compared to control. The enhanced drought tolerance in transgenic chickpea lines were also manifested by undeterred photosynthesis involving enhanced quantum yield of PSII, electron transport rate at saturated irradiance levels and maintaining higher relative water content in leaves under relatively severe soil water deficit. Further, lower values of carbon isotope discrimination in some transgenic chickpea lines indicated higher water use efficiency. Transgenic chickpea lines exhibiting better OA resulted in higher seed yield, with progressive increase in water stress, as compared to control.ConclusionsBased on precise phenotyping, involving non-invasive chlorophyll fluorescence imaging, carbon isotope discrimination, osmotic adjustment, higher chlorophyll retention and membrane stability index, it can be concluded that AtDREB1a transgenic chickpea lines were better adapted to water deficit by modifying important physiological traits. The selected transgenic chickpea event would be a valuable resource that can be used in pre-breeding or directly in varietal development programs for enhanced drought tolerance under parched conditions.

Physiological Basis of Combined Stress Tolerance to Low Phosphorus and Drought in a Diverse Set of Mungbean Germplasm

To understand the physiological basis of tolerance to combined stresses to low phosphorus (P) and drought in mungbean (Vignaradiata (L.) R. Wilczek), a diverse set of 100 accessions were evaluated in hydroponics at sufficient (250 μM) and low (3 μM) P and exposed to drought (dehydration) stress. The principal component analysis and ranking of accessions based on relative values revealed that IC280489, EC397142, IC76415, IC333090, IC507340, and IC121316 performed superior while IC119005, IC73401, IC488526, and IC325853 performed poorly in all treatments. Selected accessions were evaluated in soil under control (sufficient P, irrigated), low P (without P, irrigated), drought (sufficient P, withholding irrigation), and combined stress (low P, withholding irrigation). Under combined stress, a significant reduction in gas exchange traits (photosynthesis, stomatal conductance, transpiration, instantaneous water use efficiency) and P uptake in seed and shoot was observed under combined stress as compared to individual stresses. Among accessions, IC488526 was most sensitive while IC333090 and IC507340 exhibited tolerance to individual or combined stress. The water balance and low P adaptation traits like membrane stability index, relative water content, specific leaf weight, organic acid exudation, biomass, grain yield, and P uptake can be used as physiological markers to evaluate for agronomic performance. Accessions with considerable tolerance to low P and drought stress can be either used as ‘donors’ in Vigna breeding program or cultivated in areas with limited P and water availability or both.

Exogenous Zinc Induced NaCl Tolerance in Okra (Abelmoschus Esculentus) by Ameliorating Osmotic Stress and Oxidative Metabolism

ABSTRACT Zinc appeared to be an important modulator with specific functions in plant physiology and increase resistance against different abiotic stresses. Many advances regarding role of zinc under abiotic stress in plants have been made since its revelation, therefore, present study was intended to understand the ameliorating role of zinc on morpho-physiological and biochemical responses of the okra varieties (Anmol and Haseena) when exposed to salt stress. A solution culture experiment was conducted to understand the protective role of zinc in relation to growth, physiological, ionic and antioxidant attributes in two okra varieties under saline condition. The growth medium was salinized with three salinity (Control, 80 mM L−1 and 160 mM L−1 NaCl) and one zinc level (30 µM L−1) applied exogenously in combine and sole form. Salt stress significantly reduces plant dry matter accumulation, chlorophyll contents, relative water contents (RWC), membrane stability index (MSI), K+/Na+ ratio and activities of antioxidant enzymes (POD, SOD, APX, CAT) and these effects are more prominent at high salt level (160 mM). Addition of zinc-alleviated salt toxicity is more conspicuous in okra variety Anmol as compared to variety Haseena as demonstrated by increasing RWC, MSI, K/Na ratio and activities of antioxidant enzymes. Our results suggested that zinc induced salt tolerance in Okra which can serve as a potential source to get sustainable production from salt-affected lands.