Abstract: Two rice near-isogenic lines (NILs) with different resistance to blast, i.e. CO39 (susceptible) and C101LAC(Pi-1) (resistant), were used to investigate the impacts of silicon application on organic acid content of rice plants infected by Magnaporthe oryzae, the pathogen of rice blast. In infected leaves, Si application significantly increased oxalic acid and maleic acid contents and reduced fumaric acid and citric acid contents of both rice lines. Malic acid and oxalic acid contents in roots of infected plants for both lines were also increased by Si application. Tartaric acid content in the infected leaves was significantly reduced by Si application in CO39 on the third day after the pathogen infection, but it increased in C101LAC(Pi-1) on the seventh day after the infection. The distribution of organic acids in both lines of rice plants varied: Citric acid was mainly distributed in leaves, malic acid in roots, and maleic acid, fumaric acid, tartaric acid and oxalic acid in both leaves and roots. These results suggest that Si application influences plant metabolism and thus enhances the resistance to blast under M. oryzaeinfected conditions.

Key words: urban heat island, urban green space, field measurement, cooling effect