Abstract: Root exudates of plants, such as organic acids and ions, play a role in regulating plant growth and development. The purpose of this study was to investigate how nitrogen (N) and phosphorous (P) nutrients affect the production of root exudates and rice quality. Two rice cultivars, Yangdao 6 (indica) and Yangjing 9538 (japonica), were used, with five treatments, 0 N (without N), 1/2 N (1/2 N in the standard Espino nutrition solution), 0 P (without P), 1/2 P (1/2 P in the standard Espino nutrition solution) and CK (standard Espino nutrition solution), during the grain filling period. The compositions in root exudates and their relations with grain appearance quality, cooking and eating quality, and protein components were analyzed. The result showed that nitrogen stress (0 N) during grain-filling significantly reduced root activity, concentrations of organic acids, amino acids, and ions in the root exudates, accelerated the root senescence. However, phosphorus stress (0 P) significantly increased the concentrations of organic acids, amino acids, and ions. Correlation analysis showed that the concentrations of tartaric acid, citric acid, and amino acid in root exudates were negatively correlated with chalkiness, amylose content, and breakdown values, and significantly and positively correlated with the setback values at early and mid filling stage (10 and 20 d after anthesis). The malic acid exuded from roots was significantly and positively correlated with chalkiness, amylose content, and breakdown values, and significantly and negatively correlated with the setback value. The [Ca²⁺], [K⁺], [Na⁺], [NO₃^-], [NH₄⁺], and [PO₄^3-] in root exudates were significantly correlated with chalkiness, amylose content, protein compositions. The results suggest that N and P nutrients play a role in regulating the production of root exudates, which influence the grain quality further.

Key words: Rice, Nitrogen, Phosphorus, Root exudation, Grain quality, Protein composition