Abstract: Nitrogen (N) and phosphorus (P) play important roles in regulating plant growth and development. The purpose of this study was to investigate how N and P nutrients affect amino acids in the root exudates and grains of rice using two rice cultivars, Yangdao 6 (indica) and Yangjing 9538 (japonica), with five treatments, 0N (without N), 1/2N (1/2 N of the standard Espino nutrition solution), 0P (without P), 1/2P (1/2 P of the standard Espino nutrition solution), and CK (standard Espino nutrition solution) during the grain filling period. The concentrations and components of amino acids in root exudates and grains were measured, and their relations were analyzed. The results showed that the concentration of each amino acid in root exudates decreased gradually with the process in grain-filling. Nitrogen stress (0N) during grain filling significantly reduced concentrations of the each amino acid in root exudates and grains. Phosphorus stress (0P) significantly increased concentrations of acidic and neutral amino acids in root exudates, whereas significantly reduced the contents of total amino acids, essential amino acids, and other amino acids in grains. The concentrations of amino acids in root exudates were significantly and negatively correlated with the relative content of amino acids in grains, and the concentration of alkali amino acids in root exudates was significantly and negatively correlated with 1 000-grain weight. The results suggest that the concentration and components of amino acids in root exudates are closely associ-ated with those in grains and with grain weight. N and P nutrients play a role in regulating the concentrations/contents and com-ponents of amino acids in roots and grains, and by which influence grain yield and nutrient quality of rice.

Key words: Rice, Nitrogen, Phosphorus, Root exudation, Amino acids, Grain filling period