Plant Physiol. Journal of Pharmacology and Experimental Therapeutics
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Plant Physiology 61:62-67 (1978)
© 1978 American Society of Plant Biologists

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Articles

Oxygen Inhibition of Photosynthesis and Stimulation of Photorespiration in Soybean Leaf Cells

Jerome C. Servaites1

William L. Ogren

Department of Agronomy, University of Illinois, Urbana, Illinois 61801, United States Department of Agriculture, Agricultural Research Service, Urbana, Illinois 61801

The occurrence of photorespiration in soybean (Glycine max [L.] Merr.) leaf cells was demonstrated by the presence of an O2-dependent CO2 compensation concentration, a nonlinear time course for photosynthetic 14CO2 uptake at low CO2 and high O2 concentrations, and an O2 stimulation of glycine and serine synthesis which was reversed by high CO2 concentration. The compensation concentration was a linear function of O2 concentration and increased as temperature increased. At atmospheric CO2 concentration, 21% O2 inhibited photosynthesis at 25 C by 27%. Oxygen inhibition of photosynthesis was competitive with respect to CO2 and increased with increasing temperature. The Km (CO2) of photosynthesis was also temperature-dependent, increasing from 12 µM CO2 at 15 C to 38 µM at 35 C. In contrast, the Ki (O2) was similar at all temperatures. Oxygen inhibition of photosynthesis was independent of irradiance except at 10 mM bicarbonate and 100% O2, where inhibition decreased with increasing irradiance up to the point of light saturation of photosynthesis. Concomitant with increasing O2 inhibition of photosynthesis was an increased incorporation of carbon into glycine and serine, intermediates of the photorespiratory pathway, and a decreased incorporation into starch. The effects of CO2 and O2 concentration and temperature on soybean cell photosynthesis and photorespiration provide further evidence that these processes are regulated by the kinetic properties of ribulose-1,5-diphosphate carboxylase with respect to CO2 and O2.

1 Present address: Department of Agronomy, University of Wisconsin, Madison, Wisconsin 53706.






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Copyright © 1978 by the American Society of Plant Biologists