Journal
JOURNAL OF EXPERIMENTAL BOTANY
Volume 68, Issue 11, Pages 2871-2883Publisher
OXFORD UNIV PRESS
DOI: 10.1093/jxb/erx148
Keywords
Antarctic plants; leaf traits; mesophyll conductance; photosynthesis; Rubisco; temperature.
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Funding
- National Fund for Scientific and Technological Development [FONDECYT 11130332]
- Associative Research Program of CONICYT [CONICYT-PIA ART-1102]
- Chilean Antarctic Institute [INACH AN-02-12, FI_02-13]
- Spanish Ministry of Science and Innovation [AGL2009-07999, AGL2013-42364R]
- FICM - Institute of Ecology and Biodiversity (IEB) [P05-02, PFB-023]
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Particular physiological traits allow the vascular plants Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth) Bartl. to inhabit Antarctica. The photosynthetic performance of these species was evaluated in situ, focusing on diffusive and biochemical constraints to CO2 assimilation. Leaf gas exchange, Chl a fluorescence, leaf ultrastructure, and Rubisco catalytic properties were examined in plants growing on King George and Lagotellerie islands. In spite of the species- and population-specific effects of the measurement temperature on the main photosynthetic parameters, CO2 assimilation was highly limited by CO2 diffusion. In particular, the mesophyll conductance (g(m))-estimated from both gas exchange and leaf chlorophyll fluorescence and modeled from leaf anatomy-was remarkably low, restricting CO2 diffusion and imposing the strongest constraint to CO2 acquisition. Rubisco presented a high specificity for CO2 as determined in vitro, suggesting a tight co-ordination between CO2 diffusion and leaf biochemistry that may be critical ultimately to optimize carbon balance in these species. Interestingly, both anatomical and biochemical traits resembled those described in plants from arid environments, providing a new insight into plant functional acclimation to extreme conditions. Understanding what actually limits photosynthesis in these species is important to anticipate their responses to the ongoing and predicted rapid warming in the Antarctic Peninsula.
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