Physiological and Biochemical Effects of 24-Epibrassinolide on Heat-Stress Adaptation in Maize ( Zea mays L.)

Abstract

Brassinosteroids (BRs) are a family of about 70 structurally related polyhydroxy steroidal phyto-hormones that regulate a number of physiological processes in plants. Among these, brassinolide (BL), 28-homobrassinolide (28-homoBL) and 24-epibrassinolide (24-EpiBL) are more common. The present study aims at studying the usefulness of 24-epiBL in ameliorating the impacts of heat-stress in maize along with its role in regulating cellular antioxidant defense system. Maize hybrid PMH 3 was grown in pots in a green house maintained at 14 hours day (2 C)/10hours night (1 C). A solution of 24-epiBL (1 μM) was applied externally at V 4 stage. Leaf tissues were sampled from both treated and control plants. Subsequently, both the groups of pots were placed in plant growth chamber maintained at high temperature (48˚C; RH 50%). Plants were sampled for biochemical analysis after 3, 6, 9, 24 and 48 hours of high temperature exposure. Exogenous application of 24-EpiBL arrested protein degradation and enhanced cell membrane stability, as compared to the control. The biochemical activities of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD) and peroxidase (POX) were found to be dynamically and va-riably modulated post 24-epiBL treatment. Thus, the study supports the role of BRs as anti-stress agents.