Influence of water stress on endogenous hormone contents and cell damage of maize seedlings.

Phytohormones play critical roles in regulating plant responses to stress. We investigated the effects of water stress induced by adding 12% (w/v) polyethylene glycol to the root medium on the levels of abscisic acid (ABA), indole-3-acid (IAA), zeatin (ZT), and gibberellin(3) (GA(3)) in maize leaves. The results suggested that water stress had significant effects on the four hormone levels. There was a transient increase in the IAA content during the initial stage of adaptation to water stress in maize leaves, but it dropped sharply thereafter in response to water stress. ABA content increased dramatically in maize leaves after 24 h of exposure to water stress, and then the high levels of ABA were maintained to the end. The contents of ZT and GA(3) rapidly declined in maize leaves subjected to water stress. The effects of water stress on chlorophyll content, electrolyte leakage and malondialdehyde levels in maize leaves were also studied. The variation of cell damage was negatively correlated with ZT and GA(3) levels in maize leaves under water stress. Thus, we explored the roles of ZT and GA(3) on the growth of maize seedlings under water stress by exogenous application. It is possible that both ZT and GA(3) were effective in protecting maize seedlings from water stress, which would be of great importance for the improvement of drought tolerance in maize by genetic manipulation.