Effect of CO₂ Enrichment on the Translocation and Partitioning of Carbon at the Early Grain-filling Stage in Rice (Oryza sativa L.)

Abstract

Rice plants (Oryza sativa L.) were grown under normal (350 μL L^-1 CO₂) and CO₂-enriched (660 μL L^-1 CO₂) conditions, and ¹³CO₂ was supplied to the rice plants after heading to examine the translocation and partitioning of photosynthate at the early grain-filling stage. At 2 days after supplying ¹³CO₂, no difference in the ¹³C content of the whole plant was observed between the plants grown under normal and CO₂-enriched conditions, but translocation of ¹³C from the leaf blade to other plant organs seemed to be accelerated by CO₂ enrichment. Up to 9 days after supplying, ¹³CO₂ fixed into sucrose was mainly used to synthesize starch in the stem rather than translocated to the ear in plants grown under normal conditions. In contrast, the supplied ¹³C was rapidly translocated to the ear, and ¹³C stored as starch in the stem was also translocated to the ear in plants grown under CO₂-enriched conditions. Therefore, we concluded that CO₂ enrichment accelerated the translocation of carbohydrates to the ear.