Abstract: In order to study the effects of different nitrogen forms and water stress on physiological characteristics and water absorption pathway of root system,hydroponic experiment was conducted in a greenhouse. Water stress was simulated by treatment with polyethylene glycol（PEG6000）. Four rice（Oryza sativa L.） genotypic varieties （Shanyou 63,Yangdao 6,86you 8 and Wuyunjing 7） were utilized in the experiments. The results showed that regardless of water conditions,rice biomass was higher in the plants supplied with ammonium nutrition than that in nitrate nutrition. Under water stress condition, root activity, absorption area and water uptake ability were higher in the plants supplied with ammonium nutrition than that in nitrate nutrition. Regardless of water status, water uptake and transport were mainly through cell-cell passway in the plants supplied with ammonium nutrition; as for the plants supplied with nitrate nutrition, they were mainly through cell-cell pathway under non-water stress condition and throught apoplastic pathway under water stress condition. Compared with non-water stress condition, water stress significantly stimulated root growth in both N forms, and the stimulation was higher in nitrate nutrition. As to indica rice,water stress had no negative effects on shoot biomass and tillers in the plants supplied with ammonium nutrition, while significantly decreased them in nitrate nutrition. As to japonica rice, water stress significantly decreased shoot biomass and tillers in both N forms.

Key words: water stress, nitrogen form, rice （Oryza sativa L.）, water uptake