Analysis of carbon distribution in rice plants grown at elevated CO2

Abstract

Elevated CO2 increased the amount of photosynthate under high light condition. To examine the distribution of the photosynthate and its contribution to grain yield in rice plants grown at elevated CO2 condition (550ppm), we fed 13CO2 at some stages. In the plants fed 13CO2 at the vegetative stage, the distribution of 13C at 2 days after feeding, at the heading stage, and at harvesting time were not influenced by elevated CO2. On the other hand, in the plants fed 13CO2 at the heading stage, accumulation of 13C in the ear was accelerated, and 13C content in the whole plant and in the ear at harvest time were increased by elevated CO2. This tendency was also observed in the plants fed 13CO2 at the early and late grain filling stages. These results indicated that elevated CO2 increased not only photosynthesis but also transport of photosynthate to the sink. However, photosynthesis under low light condition and respiration in the plants grown at elevated CO2 were of no advantage to carbon storage. In conclusion, although the translocation to sink was increased by elevated CO2, total carbon assimilation per day might not be as high as was expected from photosynthesis under high light condition, so that grain yield might not be increased drastically.