Effects of Rice Bacterial Blight on Photosynthesis in Naturally Infected Rice

Daily dynamics of photosynthetic characteristics in rice leaves infected by Xanthomonas oryzae pv. oryzae were analyzed by using the LI-6400 portable photosynthesis system. The results showed that diurnal changes of photosynthesis (Pn) in rice flag leaves had one peak, and there was no obvious midday depression in daytime. The phenomenon was possibly related to rice growth period and geographical environment conditions. Although no significant difference was observed in Pn and Tr between infected plants and the control, they were very different in the curves of diurnal variation. Correlation analysis showed that the main factors affecting Pn of infected plants were Gs and PAR. Compared with the control, stomatal characteristics changed more significantly in the infected plants. Length and width of the stoma increased, whereas the density decreased. Stoma distribution in flag leaves was not homogeneous in diseased plants. There were significant differences between infected plants and the control in chlorophyll and carotenoid. Chl a and carotenoid were higher in the control but Chl b was higher in infected plants by significance analysis. Rice showed strong adaptability and resistant ability when it was influenced by the pathogen. Rice growed under the stress of plant disease by changing structure, performance and metabolicway.