Enhanced Activity of Anti-oxidant Enzymes by Foliar Spray of Nanoscale Zinc Oxide under Drought Stress Conditions in Peanut ( Arachis hypogaea L.)

Background: Zinc plays an important role in controlling both generations and also detoxifies free oxygen radicals that can damage membrane lipids and sulfhydryl groups. Zinc in particular has an action that prevents membrane damage induced by superoxide radicals that produce NADPH oxidase. The use of zinc oxide (ZnO) nanoparticles in agriculture had a significant impact on crop growth regulation, improved quality and improved stress tolerance. Hence, the current study aimed to study the foliar spray effect of nanoscale zinc oxide (25 nm mean particle size) at different concentrations and chelated bulk zinc suphate (ZnSO4) and comparable control (unsprayed) in peanut to investigate the oxidative stress induction and enhanced antioxidant enzyme activity (SOD, POD, CAT) under conditions of water stress. Methods: The experimental design was a randomized block design with two water regimes as main treatments viz., well watered (WW) and water stress (WS) conditions, eight foliar sprays along with unsprayed treatment (control) as sub treatments and 3 replications. The eight foliar spray treatments, includes nanoscale ZnO concentrations @ 10, 20, 40, 50, 100, 300, 1000 ppm, chelated bulk ZnSO4 (EDTA based) @ 0.1% (recommended dose). The antioxidant enzyme activity (SOD, POD, CAT) under conditions of both WW and WS was determined in the lab using UV spectrophotometer. Result: The results of pot culture experiment revealed that nanoscale ZnO at a concentration of 50 ppm increased biomass and pod yield and promoted antioxidant enzyme activity under water stress and well watered conditions compared to chelated bulk ZnSO4. Nanoscale ZnO showed increased activity under lower concentrations and inhibitory activity at higher concentrations that highlights the need for careful use of these particles in agriculture.