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C 4 photosynthesis in a single C 3 cell is theoretically inefficient but may ameliorate internal CO 2 diffusion limitations of C 3 leaves
Author(s) -
VON CAEMMERER S.
Publication year - 2003
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.0016-8025.2003.01061.x
Subject(s) - photorespiration , photosynthesis , c4 photosynthesis , chloroplast , limiting , diffusion , transpiration , biology , botany , biophysics , chemistry , biological system , physics , biochemistry , thermodynamics , engineering , mechanical engineering , gene
Attempts are being made to introduce C 4 photosynthetic characteristics into C 3 crop plants by genetic manipulation. This research has focused on engineering single‐celled C 4 ‐type CO 2 concentrating mechanisms into C 3 plants such as rice. Herein the pros and cons of such approaches are discussed with a focus on CO 2 diffusion, utilizing a mathematical model of single‐cell C 4 photosynthesis. It is shown that a high bundle sheath resistance to CO 2 diffusion is an essential feature of energy‐efficient C 4 photosynthesis. The large chloroplast surface area appressed to the intercellular airspace in C 3 leaves generates low internal resistance to CO 2 diffusion, thereby limiting the energy efficiency of a single‐cell C 4 concentrating mechanism, which relies on concentrating CO 2 within chloroplasts of C 3 leaves. Nevertheless the model demonstrates that the drop in CO 2 partial pressure, p CO 2 , that exists between intercellular airspace and chloroplasts in C 3 leaves at high photosynthetic rates, can be reversed under high irradiance when energy is not limiting. The model shows that this is particularly effective at lower intercellular p CO 2 . Such a system may therefore be of benefit in water‐limited conditions when stomata are closed and low intercellular p CO 2 increases photorespiration.