title: Biochemical and molecular characteristics of leaf photosynthesis and relative seed yield of two contrasting rice cultivars in response to elevated [CO₂].
abstract: Understanding the basis for intraspecific yield variability may be important in elucidating biological mechanisms that are associated with superior yield performance in response to projected increases in carbon dioxide concentration, [CO₂]. Using a free-air CO₂ enrichment (FACE) facility, two rice lines, S63 and W14, which differed consistently in their enhancement of seed yield when grown at elevated [CO₂] in multiple field trials, were examined. To determine if the different cultivar responses were linked to changes in photosynthetic characteristics at elevated [CO₂], spatial and temporal changes in photosynthetic stimulation and the occurrence of down-regulation, or acclimation, in relation to panicle sink development were quantified for the uppermost canopy leaves. Changes in photosynthetic capacity were determined by quantifying changes in the sink:source ratio, leaf nitrogen (N) content, the concentration and mRNA expression of the large Rubisco subunit, and changes in V c,max, the maximum ribulose bisphosphate (RuBP)-saturated rate of carboxylation. For the W14 cultivar, significant reductions in photosynthesis at the elevated, relative to ambient [CO₂], signalling photosynthetic acclimation, were observed following panicle initiation. The observance of photosynthetic acclimation was consistent with significant reductions in N, Rubisco content and expression, and V c,max. In contrast, for the cultivar S63, elevated [CO₂] resulted in increased spikelet number and grain weight, increased sink:source ratios, and continued stimulation of photosynthesis up to grain maturity. Overall, these data suggest that the greater response of the S63 line to elevated [CO₂] may be associated with enhanced carbon sinks relative to sources, and the ability to maintain photosynthetic capacity during grain development.
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu 210008, PR China.
authors.forename: Chunwu
authors.initials: C
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu 210008, PR China.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Zhu
authors.affiliation: Institute of Agricultural Economics and Information, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu 210008, PR China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu 210008, PR China.
authors.forename: Gang
authors.initials: G
authors.lastname: Liu
authors.affiliation: Crop Systems and Global Change Laboratory, USDA-ARS, 10300 Baltimore Avenue, Beltsville, MD 20705, USA l.ziska@ars.usda.gov.
authors.forename: Lewis H
authors.initials: LH
authors.lastname: Ziska
mesh_terms: D000064:Acclimatization; D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000494:pharmacology*; D057965:Carbon Sequestration; D009584:Nitrogen / Q000378:metabolism*; D009928:Organ Specificity; D012275:Oryza / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D010788:Photosynthesis / Q000187:drug effects*; D018515:Plant Leaves / Q000254:growth & development / Q000502:physiology; D012639:Seeds / Q000254:growth & development / Q000502:physiology; D013045:Species Specificity
chemical_list: D002245:Carbon Dioxide; D002244:Carbon; D009584:Nitrogen
keywords: Elevated CO2; panicle; photosynthetic capacity; rice; sink; source.