Response of Soluble Substances Content in Flag Leaves during Late Growth Stage and Plant Productivity of Rice to Elevated CO 2 in North China

Abstract

The responses of high yield and good quality japonica varieties Songjing 9 and Daohuaxiang 2 to elevated CO2 concentration in North China were studied by using FACE experimental system. The soluble sugar content, soluble protein content and total chlorophyll content in flag leaves of rice were measured at late growth stage, rice yield per plot and yield components were measured at harvest stage. The results showed that elevated CO2 concentration increased soluble sugar content in flag leaf for Songjing 9 and Daohuaxiang 2 obviously during heading stage, milky stage and ripening stage, with the peak value of 11.7% and 47.5%, respectively. Elevated CO2 concentration obviously reduced soluble protein content in flag leaf during heading stage and ripening stage for Songjing 9 and Daohuaxiang 2, which was 16.2% and 10.5% in the largest reduction, respectively. Elevated CO2 concentration obviously increased total chlorophyll content in flag leaf for Songjing 9 and Daohuaxiang 2 from heading stage to milky stage, with the largest increase of 18.9% and 22.5%, and then decreased after milk stage. Elevated CO2 concentration increased seed yield of individual plant, total biomass and economic coefficient with an average of 6.82%, 1.50%, 12.64% for Songjing 9, and 2.56%, 2.13%, 26.05% for Daohuaxiang 2. The results indicated that elevated atmospheric CO2 concentration increases rice plant productivity, but with diffrence effects on soluble sugar, soluble protein and chlorophyll in flag leaf of different rice varieties at different growth stages. The reason is likely that elevated atmospheric CO2 concentration promotes rice growth and development, leading to a early maturity, then senescent leaf promotes soluble sugar's decomposition, and speeds up transportation of soluble protein from function leaf to seeds.