Why small fluxes matter: the case and approaches for improving measurements of photosynthesis and (photo) respiration

Since its inception, the Farquhar et al. (1980) model of photosynthesis has been a mainstay for relating biochemistry to environmental conditions from chloroplast to global levels in terrestrial plants. Many variables could be assigned from basic enzyme kinetics, but the model also required measurem...

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Bibliographic Details
Published in:Journal of experimental botany 2016-05, Vol.67 (10), p.3027-3039
Main Authors: Hanson, David T., Stutz, Samantha S., Boyer, John S.
Format: Article
Language:English
Subjects:
Carbon Dioxide - analysis
Carbon Dioxide - metabolism
Chloroplasts - chemistry
Chloroplasts - metabolism
Photosynthesis - physiology
Plant Leaves - chemistry
Plant Leaves - physiology
Plant Transpiration - physiology
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Summary:Since its inception, the Farquhar et al. (1980) model of photosynthesis has been a mainstay for relating biochemistry to environmental conditions from chloroplast to global levels in terrestrial plants. Many variables could be assigned from basic enzyme kinetics, but the model also required measurements of maximum rates of photosynthetic electron transport (Jmax ), carbon assimilation (V cmax ), conductance of CO₂ into (gs ) and through (gm ) the leaf, and the rate of respiration during the day (Rd ). This review focuses on improving the accuracy of these measurements, especially fluxes from photorespiratory CO₂, CO₂ in the transpiration stream, and through the leaf epidermis and cuticle. These fluxes, though small, affect the accuracy of all methods of estimating mesophyll conductance and several other photosynthetic parameters because they all require knowledge of CO₂ concentrations in the intercellular spaces. This review highlights modified methods that may help to reduce some of the uncertainties. The approaches are increasingly important when leaves are stressed or when fluxes are inferred at scales larger than the leaf.
ISSN:0022-0957
1460-2431
DOI:10.1093/jxb/erw139