Abstract
Heat stress during reproductive and grain filling phases adversely affects the growth of cereals through reduction in grain's number and size. However, exogenous application of antioxidants, plant growth regulators and osmoprotectants may be helpful to minimize these heat induced yield losses in cereals. This two year study was conducted to evaluate the role of exogenous application of ascorbic acid (AsA), salicylic acid (SA) and hydrogen peroxide (H2O2) applied through seed priming or foliar spray on biochemical, physiological, morphological and yield related traits, grain yield and quality of late spring sown hybrid maize. The experiment was conducted in the spring season of 2007 and 2008. We observed that application of AsA, SA and H2O2, applied through seed priming or foliar spray improved the physiological, biochemical, morphological and yield related traits, grain yield and grain quality of late spring sown maize in both years. In both years, we observed higher superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activity in the plants where AsA, SA and H2O2,were applied through seed priming or foliar spray than control. Membrane stability index (MSI), relative water contents (RWC), chlorophyll contents, grain yield and grain oil contents were also improved by exogenous application of AsA, SA and H2O2, in both years. Seed printing of AsA. SA and H2O2 was equally effective as the foliar application. In conclusion, seed priming with AsA, SA and H2O2, may be opted to lessen the heat induced yield losses in late sown spring hybrid maize. Heat tolerance induced by ASA. SA and H2O2, may be attributed to increase in antioxidant activities and MSI which maintained RWC and chlorophyll contents in maize resulting in better grain yield in heat stress conditions.