title: The influence of light quality on C4 photosynthesis under steady-state conditions in Zea mays and Miscanthus×giganteus: changes in rates of photosynthesis but not the efficiency of the CO2 concentrating mechanism.
abstract: Differences in light quality penetration within a leaf and absorption by the photosystems alter rates of CO(2)  assimilation in C(3)  plants. It is also expected that light quality will have a profound impact on C(4)  photosynthesis due to disrupted coordination of the C(4)  and C(3)  cycles. To test this hypothesis, we measured leaf gas exchange, (13) CO(2)  discrimination (Δ(13) C), photosynthetic metabolite pools and Rubisco activation state in Zea mays and Miscanthus × giganteus under steady-state red, green, blue and white light. Photosynthetic rates, quantum yield of CO(2)  assimilation, and maximum phosphoenolpyruvate carboxylase activity were significantly lower under blue light than white, red and green light in both species. However, similar leakiness under all light treatments suggests the C(4)  and C(3)  cycles were coordinated to maintain the photosynthetic efficiency. Measurements of photosynthetic metabolite pools also suggest coordination of C(4)  and C(3)  cycles across light treatments. The energy limitation under blue light affected both C(4)  and C(3)  cycles, as we observed a reduction in C(4)  pumping of CO(2)  into bundle-sheath cells and a limitation in the conversion of C(3)  metabolite phosphoglycerate to triose phosphate. Overall, light quality affects rates of CO(2)  assimilation, but not the efficiency of CO(2)  concentrating mechanism.
authors.affiliation: School of Biological Sciences, Molecular Plant Sciences, Washington State University, Pullman, WA 99164, USA. sunwei8868@gmail.com
authors.forename: Wei
authors.initials: W
authors.lastname: Sun
authors.forename: Nerea
authors.initials: N
authors.lastname: Ubierna
authors.forename: Jian-Ying
authors.initials: JY
authors.lastname: Ma
authors.forename: Asaph B
authors.initials: AB
authors.lastname: Cousins
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis; D002734:Chlorophyll / Q000378:metabolism; D008027:Light; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism; D010788:Photosynthesis / Q000528:radiation effects*; D018515:Plant Leaves / Q000502:physiology / Q000528:radiation effects; D018526:Plant Transpiration / Q000528:radiation effects; D006109:Poaceae / Q000201:enzymology / Q000502:physiology / Q000528:radiation effects*; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D003313:Zea mays / Q000201:enzymology / Q000502:physiology / Q000528:radiation effects*
chemical_list: D002247:Carbon Isotopes; D002734:Chlorophyll; D002245:Carbon Dioxide; D010730:Phosphoenolpyruvate Carboxylase; D012273:Ribulose-Bisphosphate Carboxylase