title: Seasonal changes in canopy photosynthesis and respiration, and partitioning of photosynthate, in rice (Oryza sativa L.) grown under free-air CO2 enrichment.
abstract: An increase in atmospheric CO(2) concentration ( [CO(2)]) is generally expected to enhance photosynthesis and biomass. Rice plants (Oryza sativa L.) were grown in ambient CO(2) (AMB) or free-air CO(2)-enrichment (FACE), in which the target [CO(2)] was 200 micromol mol(-1) above AMB. (13)CO(2) was fed to the plants at different stages so we could examine the partitioning of photosynthates. Furthermore, canopy photosynthesis and respiration were measured at those stages. The ratio of (13)C content in the whole plant to the amount of fixed (13)C under FACE was similar to that under AMB at the vegetative stage. However, the ratio under FACE was greater than the ratio under AMB at the grain-filling stage. At the vegetative stage, plants grown under FACE had a larger biomass than those grown under AMB owing to enhancement of canopy photosynthesis by the increased [CO(2)]. On the other hand, at the grain-filling stage, CO(2) enrichment promoted the partitioning of photosynthate to ears, and plants grown under FACE had a greater weight of ears. However, enhancement of ear weight by CO(2) enrichment was not as great as that of biomass at the vegetative stage. Plants grown under FACE did not necessarily show higher canopy photosynthetic rates at the grain-filling stage. Therefore, we concluded that the ear weight did not increase as much as biomass at the vegetative stage owing to a loss of the advantage in CO(2) gain during the grain-filling period.
authors.affiliation: Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Japan. asa3ki@mail.ecc.u-tokyo.ac.jp
authors.forename: Haruto
authors.initials: H
authors.lastname: Sasaki
authors.forename: Takahiro
authors.initials: T
authors.lastname: Hara
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ito
authors.forename: Shu
authors.initials: S
authors.lastname: Miura
authors.forename: Md Mozammel
authors.initials: MM
authors.lastname: Hoque
authors.forename: Mark
authors.initials: M
authors.lastname: Lieffering
authors.forename: Han-Yong
authors.initials: HY
authors.lastname: Kim
authors.forename: Masumi
authors.initials: M
authors.lastname: Okada
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Kobayashi
mesh_terms: D000388:Air; D002245:Carbon Dioxide; D012275:Oryza / Q000254:growth & development / Q000502:physiology*; D010788:Photosynthesis; D012621:Seasons
chemical_list: D002245:Carbon Dioxide