Salicylic Acid Application Mitigates Oxidative Damage and Improves the Growth Performance of Barley under Drought Stress

Drought is a severe environmental constraint,causing a significant reduction in crop productivity across the world.Salicylic acid(SA)is an important plant growth regulator that helps plants cope with the adverse effects induced by various abiotic stresses.The current study investigated the potential effects of SA on drought tolerance efficacy in two barley(Hordeum vulgare)genotypes,namely BARI barley 5 and BARI barley 7.Ten-day-old barley seedlings were exposed to drought stress by maintaining 7.5%soil moisture content in the absence or presence of 0.5,1.0 and 1.5 mM SA.Drought exposure led to severe damage to both genotypes,as indicated by phenotypic aberrations and reduction of dry biomass.On the other hand,the application of SA to drought-stressed plants protected both barley genotypes from the adverse effects of drought,which was reflected in the improvement of phenotypes and biomass production.SA supplementation improved relative water content and proline levels in drought-stressed barley genotypes,indicating the osmotic adjustment functions of SA under water-deficit conditions.Drought stress induced the accumulation of reactive oxygen species(ROS),such as hydrogen peroxide(H2O2)and superoxide(O_(2)•^(−)),and the lipid peroxidation product malondialdehyde(MDA)in the leaves of barley plants.Exogenous supply of SA reduced oxidative damage by restricting the accumulation of ROS through the stimulation of the activities of key antioxidant enzymes,including superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),ascorbate peroxidase(APX)and glutathione peroxidase(GPX).Among the three-applied concentrations of SA,0.5 mM SA exhibited better mitigating effects against drought stress considering the phenotypic performance and biochemical data.Furthermore,BARI barley 5 showed better performance under drought stress than BARI barley 7 in the presence of SA application.Collectively,our results suggest that SA played a crucial role in improving water status and antioxidant defense strategy to protect barley plants from the deleterious effects of water deficiency.

Insight into 5-aminolevulinic acid-induced modulation of cellular antioxidant metabolism to confer salinity and drought tolerance in maize

The current study investigated the comparative oxidative damage in twomaize seedlings induced by saline,drought,and combined stress and the ameliorative role of two different doses(20 and 80μM)of 5-aminolevulinic acid(ALA)against the above-mentioned stresses.Hydroponically grown 10-day-old maize(Zea mays,var.BARI Hybrid Maize-7(BHM-7)and BARI Hybrid Maize-9(BHM-9))seedlings were exposed to 12 dS/m of saline solution,200 mM mannitol-induced drought stress alone and their combined stress for 7 days.Result revealed that individual stresses retard the plant growth to some degrees,however,their combined stress has more detrimental effects,which might be correlated with lipid peroxidation(MDA)-induced oxidative stress in seedlings,enhanced Na+/K+ratio,and augmented generation of superoxide(O_(2)•^(−))and hydrogen peroxide(H_(2)O_(2)).In contrast,exogenous ALA supplementation at 20μM concentration markedly recovered from chlorosis and growth inhibition,substantially scavenged reactive oxygen species(ROS)and MDA by preserving ionhomeostasis and relaxing oxidative stress,also,by boosting catalase(CAT)and glutathione S-transferase(GST),and exclusively via depressing the activity of lipoxygenase(LOX)antioxidant enzyme.On the contrary,80μM ALA made things worse,nevertheless,higher activities shown by other antioxidant enzymes,like,superoxide dismutase(SOD),ascorbate peroxidase(APX),peroxidase(POD),and glutathione peroxidase(GPX),which were related to lessen the oxidative damage by highly produced O_(2)•^(−)and H_(2)O_(2) under combined stress.Non-denaturing gel electrophoresis was done for further confirmation.However,ALA importantly increased the photosynthetic pigment contents in both genotypes irrespective of doses.Nevertheless,GST might have assisted the plants to escape from the herbicidal effect by detoxification.However,in the combined stress condition,high ALA concentration may have some positive role to play.Our findings also showed that BHM-9 performed better than BHM-7.Therefore,ALA at lower concentration was effective for single stress of saline and drought,while higher concentration can improve plant survival under combined stress.

Screening and Assessment of Selected Chilli (Capsicum annuum L.) Genotypes for Drought Tolerance at Seedling Stage

This study was undertaken to investigate oxidative stress tolerant mechanisms in chilli(Capsicum annuum L.)under drought genotypes through evaluating morphological,physiological,biochemical and stomatal parameters.Twenty genotypes were evaluated for their genetic potential to drought stress tolerant at seedling stage.Thirty days old seedlings were exposed to drought stress induced by stop watering for the following 10 days and rewatering for the following one week as recovery.Based on their survival performance,two tolerant genotypes viz.BD-10906 and BD-109012 and two susceptible genotypes viz.BD-10902 and RT-20 were selected for studying the oxidative stress tolerance mechanism.Drought reduced root and shoot length,dry weight,ratio,petiole weight and leaf area in both tolerant and susceptible genotypes,and a higher reduction was observed in susceptible genotypes.Lower reduction of leaf area and photosynthetic pigments were also found in tolerant genotypes.Moreover,tolerant genotypes showed higher recovery than susceptible genotypes after the removal of stress.A higher reduction of relative water content(RWC)may cause an imbalance between absorbed and transpirated water in susceptible genotypes.Higher accumulation of proline in tolerant genotypes might be helpful to for better osmotic maintenance than that in susceptible genotypes.Tolerant genotypes showed higher antioxidant activity as they showed DPPH radical scavenging percentage than the susceptible genotypes.Moreover,closer stomata in tolerant genotypes than susceptible ones helped to avoid dehydration in tolerant genotypes.Thus,the above morphological,physiological,biochemical and stomatal parameters helped to show better tolerance in chilli under drought stress.

Salt-Induced Changes in Physio-Biochemical and Antioxidant Defense System in Mustard Genotypes

Salinity stress is a major factor limiting plant growth and productivity of many crops including oilseed.The present study investigated the identification of salt tolerant mustard genotypes and better understanding the mechanism of salinity tolerance.Salt stresses significantly reduced relative water content(RWC),chlorophyll(Chl)content,K^(+) and K^(+)/Na^(+) ratio,photosynthetic rate(P N),tran-spiration rate(Tr),stomatal conductance(gs),intercellular CO_(2) concentration(Ci)and increased the levels of proline(Pro)and lipid peroxidation(MDA)contents,Na+,superoxide(O_(2)^(•−))and hydrogen peroxide(H_(2)O_(2))in both tolerant and sensitive mustard genotypes.The tolerant genotypes maintained higher Pro and lower MDA content than the salt sensitive genotypes under stress condition.The activities of superoxide dismutase(SOD),catalase(CAT),peroxidase(POD),glutathione peroxidase(GPX),monodehydroascorbate reductase(MDHAR)and dehydroascorbate reductase(DHAR)were increased with increasing salinity in salt tolerant genotypes,BJ-1603,BARI Sarisha-11 and BARI Sarisha-16,but the activities were unchanged in salt sensitive genotype,BARI Sarisha-14.Besides,the increment of ascorbate peroxidase(APX)activity was higher in salt sensitive genotype as compared to tolerant ones.However,the activ-ities of glutathione reductase(GR)and glutathione S-transferase(GST)were increased sharply at stress conditions in tolerant genotypes as compared to sensi-tive genotype.Higher accumulation of Pro along with improved physiological and biochemical parameters as well as reduced oxidative damage by up-regulation of antioxidant defense system are the mechanisms of salt tolerance in selected mustard genotypes,BJ-1603 and BARI Sarisha-16.

Oxidative Stress Tolerance Mechanism in Rice under Salinity

The research was conducted to investigate comparative oxidative damage including probable protective roles of antioxidant and glyoxalase systems in rice(Oryza sativa L.)seedlings under salinity stress.Seedlings of two rice genotypes:Pokkali(tolerant)and BRRI dhan28(sensitive)were subjected to 8 dSm^(−1) salinity stress for seven days in a hydroponic system.We observed significant variation between Pokkali and BRRI dhan28 in phenotypic,biochemical and mole-cular level under salinity stress.Carotenoid content,ion homeostasis,antioxidant enzymes,ascorbate and glutathione redox system and proline accumulation may help Pokkali to develop defense system during salinity stress.However,the activity antioxidant enzymes particularly superoxide dismutase(SOD),catalase(CAT)and non-chloroplastic peroxidase(POD)were observed significantly higher in Pokkali compared to salt-sensitive BRRI dhan28.Higher glyoxalase(Gly-I)and glyoxalase(Gly-II)activity might have also accompanied Pokkali genotype to reduce potential cytotoxic MG through non-toxic hydroxy acids conversion.However,the efficient antioxidants and glyoxalase system together increased adaptability in Pokkali during salinity stress.