Study of Some Paradoxical Responses of Photorespiration and Photosynthesis to CO₂ and O₂

Abstract

In steady state of Photosynthesis, it has been shown that the magnitude of the O₂ uptake, measured by ¹⁸O₂, can be equal to the net photosynthesis, and four times the dark respiration in C₃ plants (Gerbaud, André 1979). Symmetrical changes of CO₂ and O₂ uptakes (mirror effect) were observed in microalgae during a transitory phase (Radmer, Kok 1976) and in steady state in higher C₃ plants (Gerbaud, André 1979, 1980, Canvin et al. 1980). This effect is in good accordance with the kinetic properties of the Rubisco. Previous works, since Laing et al. 1974, have used enzymatic properties to predict the responses of plants to CO₂, O₂ and temperature. The availability of O₂ uptake measurements gives the opportunity to quantitatively analyse the O₂ and CO₂ exchanges of a few lower plants in comparison with a typical C₃ higher plant (wheat).