Photosynthetic light response curves determined with the leaf oxygen electrode: minimisation of errors and significance of the convexity term.
From photosynthetic studies on a range of monocotyledonous (C-3 and C-4) and dicotyledonous (C-3) plants using a leaf oxygen electrode, we conclude the following. (i) A non-linear model [J.H.M. Thornley (1976) Mathematical models in plant physiology, Academic Press, London; B. Marshall and P.V. Biscoe (1980) J Exp Bot 31:29-39] significantly better describes the photosynthetic light response curve [rate of photosynthesis (P) versus incident photosynthetic photon flux density (I)] than the frequently used linear hyperbolic model [E.I. Rabinowich (1951) Photosynthesis and related processes, vol 2, Wiley, New York]. (ii) When used at the recommended CO2 partial pressures (Ca = 1-5 kPa), CO2 supply saturates the photosynthesis rate in the C-3 dicot Phaseolus coccineus L. but not in the C-3 monocot Hordeum vulgare L.. (iii) Fits using a linear hyperbolic model for P versus I produce relatively large and statistically significant errors (approximately 60%) in the estimation of Pmax and quantum efficiency (alpha) if Ca is not > 5 kPa. (iv) The convexity term, theta, incorporated into the non-linear models for P versus I appears to reflect the limitation placed on the carboxylation processes by the supply of CO2 to the chloroplast stroma. Therefore, the use of a non-linear model providing an estimate of theta should be encouraged, as it is likely to provide information on the physiological status of plants.
Akhkha
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Division of Environmental and Evolutionary Biology, Institute of Biomedical and Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK.
Reid
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Clarke
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Dominy
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D015982:Bias; D002245:Carbon Dioxide / Q000378:metabolism / Q000494:pharmacology; D018481:Convection; D007887:Fabaceae / Q000502:physiology; D001467:Hordeum / Q000502:physiology; D017736:Ion-Selective Electrodes; D008027:Light; D008954:Models, Biological; D010100:Oxygen / Q000032:analysis*; D010788:Photosynthesis / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D045322:Photosynthetic Reaction Center Complex Proteins / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D018515:Plant Leaves / Q000502:physiology*; D003313:Zea mays / Q000502:physiology
D045322:Photosynthetic Reaction Center Complex Proteins; D002245:Carbon Dioxide; D010100:Oxygen