TY - JOUR
AU - Edwards, Gerald E.
AB - Abstract The response of whole leaf photosynthesis of wheat (Triticum aestivum L.) in relation to soluble CO2 available to the mesophyll cells, under low (1.5%) O2 at 25, 30, and 35 C, followed Michaelis-Menten kinetics up to saturating CO2 but deviated at high CO2 levels where the experimental V max is considerably less than the calculated V max. The affinity of the leaves for CO2 during photosynthesis was similar from 25 to 35 C with Km (CO2) values of approximately 3.5 to 5 μM. In considering the effect of O2 on photosynthesis at 25, 30, and 35 C where O2 and CO2 are expressed on a solubility basis: (a) the effect of O2 on carboxylation efficiency was similar at the three temperature; (b) increasing temperature caused only a slight increase in kinetic constants Ki(O2) and Km(CO2), while the ratio of Ki(O2)/Km(CO2) was similar at the three temperatures; and (c) the reciprocal plots of apparent rate of photosynthesis versus (CO2 - Γ) at various O2 levels showed O2 to be a competitive inhibitor of photosynthesis. A model for separating O2 inhibition of photosynthesis into two components, direct competitive inhibition and inhibition due to photorespiration, was presented from both simulated and experimental data of photosynthetic response curves to varying CO2 concentrations at low O2 versus 21% O2. The photorespiratory part of O2 inhibition is considered as a major component at Γ and increases with increasing temperature and with increase in O2/CO2 solubility ratio. The competitive component of O2 inhibition is considered as a major component of O2 inhibition under atmospheric CO2 levels and is relatively independent of temperature at a given O2/CO2 ratio. 1 This research was supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison. This content is only available as a PDF. © 1977 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
TI - Oxygen Inhibition of PhotosynthesisII. Kinetic Characteristics as Affected by Temperature 
JF - Plant Physiology
DO - 10.1104/pp.59.5.991
DA - 1977-05-01
UR - https://www.deepdyve.com/lp/oxford-university-press/oxygen-inhibition-of-photosynthesisii-kinetic-characteristics-as-7rSxJSWFpe
SP - 991
EP - 999
VL - 59
IS - 5
DP - DeepDyve
ER -