期刊
JOURNAL OF EXPERIMENTAL BOTANY
卷 65, 期 13, 页码 3683-3693出版社
OXFORD UNIV PRESS
DOI: 10.1093/jxb/eru205
关键词
C-3-C-4 intermediates; C-3 photosynthesis; leaf gas exchange; photosynthetic model; stomatal conductance; water use efficiency
资金
- US Department of Agriculture, Agriculture and Food Research Initiative [2011-67003-30222]
- US Department of Energy, Terrestrial Ecosystem Sciences [11-DE-SC-0006967]
- US-Israeli Bi-national Science Foundation [2010320]
- Natural Sciences and Engineering Research Council of Canada
- Faculty of Natural Resources and Agricultural Sciences, Swedish University of Agricultural Sciences
- Faculty of Natural Resources and Agricultural Sciences
C-4 photosynthesis evolved independently numerous times, probably in response to declining atmospheric CO2 concentrations, but also to high temperatures and aridity, which enhance water losses through transpiration. Here, the environmental factors controlling stomatal behaviour of leaf-level carbon and water exchange were examined across the evolutionary continuum from C-3 to C-4 photosynthesis at current (400 mu mol mol(-1)) and low (280 mu mol mol(-1)) atmospheric CO2 conditions. To this aim, a stomatal optimization model was further developed to describe the evolutionary continuum from C-3 to C-4 species within a unified framework. Data on C-3, three categories of C-3-C-4 intermediates, and C-4 Flaveria species were used to parameterize the stomatal model, including parameters for the marginal water use efficiency and the efficiency of the CO2-concentrating mechanism (or C-4 pump); these two parameters are interpreted as traits reflecting the stomatal and photosynthetic adjustments during the C-3 to C-4 transformation. Neither the marginal water use efficiency nor the C-4 pump strength changed significantly from C-3 to early C-3-C-4 intermediate stages, but both traits significantly increased between early C-3-C-4 intermediates and the C-4-like intermediates with an operational C-4 cycle. At low CO2, net photosynthetic rates showed continuous increases from a C-3 state, across the intermediates and towards C-4 photosynthesis, but only C-4-like intermediates and C-4 species (with an operational C-4 cycle) had higher water use efficiencies than C-3 Flaveria. The results demonstrate that both the marginal water use efficiency and the C-4 pump strength increase in C-4 Flaveria to improve their photosynthesis and water use efficiency compared with C-3 species. These findings emphasize that the advantage of the early intermediate stages is predominantly carbon based, not water related.
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