Impact of high temperature stress on rice photosynthesis and biomass production during heading stage

Abstract

The dry matter of rice grain mainly originates from photosynthetic outcome. The relationships between 
photosynthetic characteristic and dry matter accumulation were measured based on room experiments with two rice 
varieties (Yangdao6 and Nanjing43) under different high temperature stress of heading stage in 2007 and 2008. The 
results showed that grain yield, chlorophyll content, net photosynthetic rate (NPn), superoxide dismutase activity 
(SOD) and leaf area index (LAI) suffered a sharply decline. On the other hand, relative conductivity and 
malondialdehyde content (MDA) increased gradually with the elevation of stress temperature and extension of stress 
time. The increasing rate (reducing rate) of some physiological and biochemical indexes in Yangdao6 were lower than 
that in Nanjing43 compared with the CK under the same temperature stress. It was shown that response of Nanjing43 
to high temperature was bigger than that of Yangdao6. According to the correlation analysis, grain yield showed a 
positive correlation with NPn and LAI at 0.01 level, the correlation coefficients of them were 0.94 and 0.88 respectively. 
The correlation between grain yield and DW after initial at mature stage, the export percentage of the matter in stem
sheath (EPMSS) and the transformation percentage of the matter in stem-sheath (TPMSS) were not significant. It was 
showed that grain yield under high temperature stress originated mostly from the photosynthesis and LAI of leaves 
after heading stage.