Abstract:

Abstract: In order to investigate the regulation mechanisms of nitrogen form on water utilization of maize seedlings under fixed partial root-zone water stress conditions, a split-root system composed of two root compartments was used. Polyethylene glycol (PEG 6000) was added to one root compartment simulating fixed partial root-zone water stress. Physiological indices, such as xylem water transportation rate, physiological water use efficiency and abscisic acid concentration in different parts of plant were examined at different time after water stress treatments. Nitrogen was set as three forms (50%NO3--N+50%NH4+-N；NO3--N；NH4+-N), and added to two root compartments homogenously. It showed that, under fixed partial root-zone water stress conditions, plant supplied with mixed nitrogen could maintain relative higher water transportation rate as time of water stress prolonged comparing with NH4+-N and NO3--N supplement. Thickness of mesophyll and leaf, vessel number and diameter in plant supplied with mixed nitrogen was also high. These traits could adapt plants to water stress by improving water absorption and translocation. However, ammonium nutrition had a greater effect on the increment in xylem sap pH and ABA concentration in different parts of plant compared to other nitrogen sources. Xylem sap pH in plant supplied with ammonium increased evidently at late stage of the water stress treatment, which could enhance the regulation of plant transpiration. Ammonium nutrition improved water use efficiency of maize seedlings under fixed partial root-zone water stress.