Rice is one of the main crops in China and needs a lot of nitrogen fertilizer to ensure high yields Thus,nitrogen take up and utilization efficiency by rice is an important issue in agricultural production Due to inhibited nitrificaton in the bulk soil of lowland rice field,researches on nitrogen nutrition of rice mainly focus much more on ammonium(NH₄⁺) than on nitrate(NO₃^-) Much evidence has shown that rice can take up not only NH₄⁺-N but also NO₃^--N,but is different in capacity which varies with its genotype The responses of rice to different nitrogen forms and their physiological effects are poorly understood Hydroponic culture experiments were carried out to study the response of rice to different nitrogen forms(NH₄⁺/NO₃^- ratios of 100:0,50:50,and 0:100) Best growth of rice plants of all genotypes tested was found in the mixed solution of NH₄⁺ and NO₃^- but crops different in genotypes responded differently Based on the rice growth in two nitrogen solutions,i.e.,NH₄⁺/NO₃^- ratios of 100:0 and 50:50,the 40 varieties of rice tested could be divided into three groups,such as high response to NO₃^-,intermediate response to NO₃^- and non-response to NO₃^-Rice with high response to NO₃^- had much higher root dry weight and nitrogen accumulation in the mixed solution of ammonium and nitrate than in the single ammonium solution Thus,the root dry weight and nitrogen accumulation could be used as physiological indices for screening rice of genotypes with different responses to nitrate.