Journal
JOURNAL OF EXPERIMENTAL BOTANY
Volume 65, Issue 20, Pages 6049-6056Publisher
OXFORD UNIV PRESS
DOI: 10.1093/jxb/eru344
Keywords
Elevated CO2; panicle; photosynthetic capacity; rice; sink; source
Categories
Funding
- National Basic Research Program (973 Program) [2014CB954500]
- National Natural Science Foundation of China [31370457, 41301209, 31261140364, 31201126]
- Natural Science Foundation of Jiangsu province in China [BK20131051, BK20140063]
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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,V-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,V-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.
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