[Effect of nitrogen nutrition on endogenous hormone content of maize under soil drought conditions]

It is realized in recent years that roots play an important role in the control of shoot growth and development, not only because they can continuously provide the shoot with water and nutrients, but also because some chemical messengers are produced in roots to response soil drought stress and transported through transpiration stream to shoot where physiological processes are regulated. Extensive studies showed that the decrease of leaf conductance was closely related to the increase of xylem ABA concentration, suggesting that ABA can act as a water stress signal to regulate the physiological response of shoot. Fertilizer plays an important role in increasing crop yield and water use efficiency (WUE) on dry-land farming. It is not clear, however, whether the application of N fertilizer can affect the root's signal intensity in drought stress and thus regulate its stomatal responses. Experiment with 3 water levels (35%, 55% [symbol: see text] 75% +/- 5% of field capacity) and 2 N fertilizer levels (high N and low N) was designed to investigate the effect of soil drought and N nutrition on endogenous hormone concentration (ABA and ZRs) and stomatal conductivity of maize under potted conditions. The results showed that the application of N significantly increased the stomatal conductivity of maize leaf under both drought and watered conditions. Meanwhile, it markedly decreased the ABA concentration in root xylem sap, but increased ABA concentration in leaf of maize under soil drought conditions. The application of N decreased ZRs concentration in root xylem sap as well, which means that ZRs did not play a role in counteractive to ABA under soil drought conditions. The lower ABA concentration in root xylem sap of high N maize rather than the higher ABA concentration in maize leaf accounted for the higher stomatal conductivity of high N maize leaf under soil drought conditions.