title: Chloroplast downsizing under nitrate nutrition restrained mesophyll conductance and photosynthesis in rice (Oryza sativa L.) under drought conditions.
abstract: The phenomenon whereby ammonium enhances the tolerance of rice seedlings (Oryza sativa L., cv. 'Shanyou 63' hybrid indica China) to water stress has been reported in previous studies. To study the intrinsic mechanism of biomass synthesis related to photosynthesis, hydroponic experiments supplying different nitrogen (N) forms were conducted; water stress was simulated by the addition of polyethylene glycol. Water stress decreased leaf water potential (Ψ(leaf)) under nitrate nutrition, while it had no negative effect under ammonium nutrition. The decreased Ψ(leaf) under nitrate nutrition resulted in chloroplast downsizing and subsequently decreased mesophyll conductance to CO(2) (g(m)). The decreased g(m) and stomatal conductance (g(s)) under nitrate nutrition with water stress restrained the CO(2) supply to the chloroplast and Rubisco. The relatively higher distribution of leaf N to Rubisco under ammonium nutrition might also be of benefit for photosynthesis under water stress. In conclusion, chloroplast downsizing induced a decline in g(m), a relatively higher decrease in g(s) under nitrate nutrition with water stress, restrained the CO(2) supply to Rubisco and finally decreased the photosynthetic rate.
authors.affiliation: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Li
authors.forename: Binbin
authors.initials: B
authors.lastname: Ren
authors.forename: Xiuxia
authors.initials: X
authors.lastname: Yang
authors.forename: Guohua
authors.initials: G
authors.lastname: Xu
authors.forename: Qirong
authors.initials: Q
authors.lastname: Shen
authors.forename: Shiwei
authors.initials: S
authors.lastname: Guo
mesh_terms: D002245:Carbon Dioxide / Q000494:pharmacology; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000187:drug effects* / Q000648:ultrastructure; D004058:Diffusion / Q000187:drug effects; D055864:Droughts; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D058503:Mesophyll Cells / Q000187:drug effects / Q000502:physiology*; D009566:Nitrates / Q000494:pharmacology*; D053141:Organelle Size / Q000187:drug effects*; D012275:Oryza / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D010788:Photosynthesis / Q000187:drug effects*; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects; D014867:Water
chemical_list: D009566:Nitrates; D014867:Water; D002734:Chlorophyll; D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase