Effect of free-air CO 2 enrichment on the storage of carbohydrate fixed at different stages in rice ( Oryza sativa L.)

Abstract

Increasing global atmospheric CO 2 concentrations are expected to influence crop production. To investigate the effect on rice ( Oryza sativa L.), plants were grown under ambient CO 2 (AMB) or free-air CO 2-enrichment (FACE) at CO 2 concentrations ranged from 275 to 365 μmol mol −1 above AMB. We supplied 13CO 2 to the plants at different growth stages so we could examine the contribution of carbohydrate stored during the vegetative stage or newly fixed carbohydrate produced during the grain-filling stage to ear weight at grain maturity. In plants supplied with 13C at the panicle-initiation or pre-heading stages, plants grown under FACE had more starch in the stems at heading, but there was no difference in stem 13C content. Furthermore, there were no differences between treatments in whole-plant 13C contents at heading and grain maturity. In contrast, plants supplied with 13C at the grain-filling stage had more 13C in the whole plant and the ears at grain maturity under FACE than under AMB, indicating that the increased amount of photosynthate produced at the grain-filling stage under CO 2 enrichment might be effectively stored in the grains. Furthermore, regardless of when the 13C was supplied, plants had more 13C in starch in the ears at grain maturity under FACE than under AMB. Therefore, CO 2 enrichment appears to promote partitioning of photosynthate produced during both vegetative and grain-filling stages to the grains.