title: Soil and water warming accelerates phenology and down-regulation of leaf photosynthesis of rice plants grown under free-air CO2 enrichment (FACE).
abstract: To enable prediction of future rice production in a changing climate, we need to understand the interactive effects of temperature and elevated [CO2] (E[CO2]). We therefore examined if the effect of E[CO2] on the light-saturated leaf photosynthetic rate (Asat) was affected by soil and water temperature (NT, normal; ET, elevated) under open-field conditions at the rice free-air CO2 enrichment (FACE) facility in Shizukuishi, Japan, in 2007 and 2008. Season-long E[CO2] (+200 µmol mol(-1)) increased Asat by 26%, when averaged over two years, temperature regimes and growth stages. The effect of ET (+2°C) on Asat was not significant at active tillering and heading, but became negative and significant at mid-grain filling; Asat in E[CO2]-ET was higher than in ambient [CO2] (A[CO2])-NT by only 4%. Photosynthetic down-regulation at E[CO2] also became apparent at mid-grain filling; Asat compared at the same [CO2] in the leaf cuvette was significantly lower in plants grown in E[CO2] than in those grown in A[CO2]. The additive effects of E[CO2] and ET decreased Asat by 23% compared with that of A[CO2]-NT plants. Although total crop nitrogen (N) uptake was increased by ET, N allocation to the leaves and to Rubisco was reduced under ET and E[CO2] at mid-grain filling, which resulted in a significant decrease (32%) in the maximum rate of ribulose-1,5-bisphosphate carboxylation on a leaf area basis. Because the change in N allocation was associated with the accelerated phenology in E[CO2]-ET plants, we conclude that soil and water warming accelerates photosynthetic down-regulation at E[CO2].
authors.affiliation: Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba, 305-8506 Japan.
authors.forename: Minaco
authors.initials: M
authors.lastname: Adachi
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fukayama
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tokida
authors.forename: Hidemitsu
authors.initials: H
authors.lastname: Sakai
authors.forename: Toshinori
authors.initials: T
authors.lastname: Matsunami
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Nakamura
authors.forename: Ryoji
authors.initials: R
authors.lastname: Sameshima
authors.forename: Masumi
authors.initials: M
authors.lastname: Okada
mesh_terms: D018533:Biomass; D002245:Carbon Dioxide / Q000378:metabolism / Q000494:pharmacology*; D002734:Chlorophyll / Q000378:metabolism; D018556:Crops, Agricultural; D002523:Edible Grain / Q000254:growth & development / Q000502:physiology / Q000528:radiation effects; D007564:Japan; D008027:Light; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D012275:Oryza / Q000187:drug effects / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects; D010788:Photosynthesis; D018515:Plant Leaves / Q000254:growth & development / Q000502:physiology / Q000528:radiation effects; D054046:Plant Stomata / Q000254:growth & development / Q000502:physiology / Q000528:radiation effects; D018526:Plant Transpiration; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism*; D012274:Ribulosephosphates / Q000378:metabolism; D012621:Seasons; D012987:Soil; D013696:Temperature; D014867:Water / Q000502:physiology
chemical_list: D012274:Ribulosephosphates; D012987:Soil; D014867:Water; D002734:Chlorophyll; D002245:Carbon Dioxide; C001933:ribulose-1,5 diphosphate; D012273:Ribulose-Bisphosphate Carboxylase; D009584:Nitrogen
keywords: Ecosystem warming; FACE (free-air CO2 enrichment); Oryza sativa; Photosynthetic down-regulation