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.

Biochar potentially enhances maize tolerance to arsenic toxicity by improving physiological and biochemical responses to excessive arsenate

Metalloid pollution,including arsenic poisoning,is a serious environmental issue,plaguing plant productivity and quality of life worldwide.Biochar,a carbon-rich material,has been known to alleviate the negative effects of environmental pollutants on plants.However,the specific role of biochar in mitigating arsenic stress in maize remains relatively unexplored.Here,we elucidated the functions of biochar in improving maize growth under the elevated level of sodium arsenate(Na_(2)AsO_(4),AsV).Maize plants were grown in pot-soils amended with two doses of biochar(2.5%(B1)and 5.0%(B2)biochar Kg^(−1) of soil)for 5 days,followed by exposure to Na_(2)AsO_(4)(’B1+AsV’and’B2+AsV’)for 9 days.Maize plants exposed to AsV only accumulated substantial amount of arsenic in both roots and leaves,triggering severe phytotoxic effects,including stunted growth,leaf-yellowing,chlorosis,reduced photosynthesis,and nutritional imbalance,when compared with control plants.Contrariwise,biochar addition improved the phenotype and growth of AsV-stressed maize plants by reducing root-to-leaf AsV translocation(by 46.56 and 57.46%in‘B1+AsV’and‘B2+AsV’plants),improving gas-exchange attributes,and elevating chlorophylls and mineral levels beyond AsV-stressed plants.Biochar pretreatment also substantially counteracted AsV-induced oxidative stress by lowering reactive oxygen species accumulation,lipoxygenase activity,malondialdehyde level,and electrolyte leakage.Less oxidative stress in‘B1+AsV’and‘B2+AsV’plants likely supported by a strong antioxidant system powered by biochar-mediated increased activities of superoxide dismutase(by 25.12 and 46.55%),catalase(51.78 and 82.82%),and glutathione S-transferase(61.48 and 153.83%),and improved flavonoid levels(41.48 and 75.37%,respectively).Furthermore,increased levels of soluble sugars and free amino acids also correlated with improved leaf relative water content,suggesting a better osmotic acclimatization mechanism in biochar-pretreated AsV-exposed plants.Overall,our findings provided mechanistic insight into how biochar facilitates maize’s active recovery from AsV-stress,implying that biochar application may be a viable technique for mitigating negative effects of arsenic in maize,and perhaps,in other important cereal crops.