|ZHU, CHUNWU - Chinese Academy Of Sciences|
|ZHU, JIANGUO - Chinese Academy Of Sciences|
|CAO, JING - Jiangsu Academy Agricultural Sciences|
|JIANG, QIAN - Chinese Academy Of Sciences|
|LIU, GANG - Chinese Academy Of Agricultural Sciences|
Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2014
Publication Date: 11/1/2014
Citation: Zhu, C., Zhu, J., Cao, J., Jiang, Q., Liu, G., Ziska, L.H. 2014. Biochemical and molecular characteristics of leaf photosynthesis and relative seed yield of two contrasting rice cultivars in response to elevated [CO2]. Journal of Experimental Botany. 65:6049-6056.
Interpretive Summary: In addition to being a greenhouse gas, carbon dioxide (CO2) is also a resource necessary for plant growth. Consequently, its increase in the atmosphere can result in potentially greater yield among crop plants. However, different varieties of the same crop can result in different yield responses when grown at future elevated CO2 levels, and the basis for these different responses is poorly understood. Understanding why some varieties can convert more CO2 into additional seed yield may be a strategy to both adapt crop lines to yield more and to reduce the accumulation of CO2 in the atmosphere. To that end, we examined two rice varieties, S63 and W14, which differed consistently in their enhancement of seed yield when grown at elevated carbon dioxide in multiple field trials. We examined various photosynthetic characteristics, including genetics, biochemistry, and rate during grain filling. Overall data from the study indicated that for the S63 variety, photosynthetic capacity was enhanced consistently with more carbon dioxide, possibly because of genetic differences in how that additional CO2 was partitioned between reproduction (seed) and vegetative (leaves) structures. This information may be of use for agronomists, rice breeders, farmers and policy makers interested in the links between climate change and food security.
Technical 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, we examined two rice lines, S63 and W14, which differed consistently in their enhancement of seed yield when grown at elevated [CO2] in multiple field trials. To determine if the different cultivar responses were linked to changes in photosynthetic characteristics at elevated [CO2], we quantified spatial and temporal changes in photosynthetic stimulation and the occurrence of down-regulation, or acclimation, in relation to panicle sink development for the uppermost canopy leaves. Changes in photosynthetic capacity were determined by quantifying changes in sink:source ratio, leaf nitrogen (N) content, the concentration and mRNA expression of the large Rubisco subunit, and changes in Vcmax, the maximum 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 Vcmax. 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 until 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.