CHANGES IN ENDOGENOUS HORMONAL STATUS IN CORN (ZEA MAYS) HYBRIDS UNDER DROUGHT STRESS

Abstract

Corn has several mechanisms that allow it to perceive the incoming water deficit and rapidly regulate its growth and physiology to cope with this stress. Among these regulated physiological responses, phytohormones, such as abscisic acid (ABA), gibberellin (GA3), indole acetic acid (IAA), and zeatin (ZT) have important roles. To evaluate changes in hormonal status of corn hybrids under different drought stress levels, a greenhouse study was conducted at the College of Agriculture, Shiraz University, Iran, during summer 2010. Treatments consisted of drought stress in five levels: 100% field capacity (F.C.) as control, 80, 60, 40, and 20% F.C. and three corn hybrids, including single cross 704 (SC704), Maxima, and double cross 370 (DC370). Results showed that drought stress significantly affected phytohormones concentration, ABA concentration was increased and GA3, IAA and ZT concentrations were decreased. Indeed, there was an initial increase (about 13.5% more than control) in IAA concentration. In severe drought condition, ABA concentration was eventually decreased (37.8% less than the first drought level, i.e., 80% F.C.). The ratios of GA3, IAA and ZT to ABA concentration were also decreased. Among hybrids, SC704 showed the highest phytohormone concentrations and DC370 had the highest ratios of GA3, IAA, and ZT to ABA concentrations. Overall, the results of this study suggest that although mild drought stress was associated with greater ABA concentration, it had negative impact on GA3, IAA, and ZT concentrations. Furthermore, SC704 hybrid appeared to be more resistant to drought stress than the other hybrids.