Effect of Nitrogen on Water Content, Sap Flow of Rice Plants in Association with Tolerance to Brown Planthopper, Nilaparvata lugens

Water content (WC), sap flow and changes in relative water content (RWC) of rice plants damaged by brown planthopper (BPH), were determined in laboratory, and the tolerance of rice plants with different nitrogen regimes to BPH was evaluated in greenhouse at International Rice Research Institute (IRRI). Results indicated that both WC and RWC were increased significantly, while the sap amount flowed from rice plants were reduced statistically, with the increase of nitrogen content in rice plants. RWC in rice plants applied with high nitrogen fertilizer decreased strongly by the injury of BPH nymphs. Those may be considered to be one of the key factors to increase the susceptibility to BPH damage on rice plants applied with nitrogen fertilizer.