The efficiency of C4 photosynthesis under low light conditions in Zea mays, Miscanthus x giganteus and Flaveria bidentis.
The efficiency of C(4) photosynthesis in Zea mays, Miscanthus x giganteus and Flaveria bidentis in response to light was determined using measurements of gas exchange, (13) CO(2) photosynthetic discrimination, metabolite pools and spectroscopic assays, with models of C(4) photosynthesis and leaf (13) CO(2) discrimination. Spectroscopic and metabolite assays suggested constant energy partitioning between the C(4) and C(3) cycles across photosynthetically active radiation (PAR). Leakiness (φ), modelled using C(4) light-limited photosynthesis equations (φ(mod)), matched values from the isotope method without simplifications (φ(is)) and increased slightly from high to low PAR in all species. However, simplifications of bundle-sheath [CO(2)] and respiratory fractionation lead to large overestimations of φ at low PAR with the isotope method. These species used different strategies to maintain similar φ. For example, Z. mays had large rates of the C(4) cycle and low bundle-sheath cells CO(2 ) conductance (g(bs)). While F. bidentis had larger g(bs) but lower respiration rates and M. giganteus had less C(4) cycle capacity but low g(bs), which resulted in similar φ. This demonstrates that low g(bs) is important for efficient C(4) photosynthesis but it is not the only factor determining φ. Additionally, these C(4) species are able to optimize photosynthesis and minimize φ over a range of PARs, including low light.
School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA 99164-4236, USA.
Nerea
N
Ubierna
Wei
W
Sun
David M
DM
Kramer
Asaph B
AB
Cousins
D000704:Analysis of Variance; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D003433:Crosses, Genetic; D037142:Flaveria / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D055442:Metabolome / Q000528:radiation effects; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000528:radiation effects*; D054046:Plant Stomata / Q000502:physiology / Q000528:radiation effects; D006109:Poaceae / Q000502:physiology* / Q000528:radiation effects; D013057:Spectrum Analysis; D013816:Thermodynamics; D003313:Zea mays / Q000502:physiology* / Q000528:radiation effects
D002245:Carbon Dioxide; D002244:Carbon; D010100:Oxygen