Photorespiration in the context of Rubisco biochemistry, CO2 diffusion and metabolism

Summary Photorespiratory metabolism is essential for plants to maintain functional photosynthesis in an oxygen‐containing environment. Because the oxygenation reaction of Rubisco is followed by the loss of previously fixed carbon, photorespiration is often considered a wasteful process and considerable efforts are aimed at minimizing the negative impact of photorespiration on the plant’s carbon uptake. However, the photorespiratory pathway has also many positive aspects, as it is well integrated within other metabolic processes, such as nitrogen assimilation and C1 metabolism, and it is important for maintaining the redox balance of the plant. The overall effect of photorespiratory carbon loss on the net CO2 fixation of the plant is also strongly influenced by the physiology of the leaf related to CO2 diffusion. This review outlines the distinction between Rubisco oxygenation and photorespiratory CO2 release as a basis to evaluate the costs and benefits of photorespiration. Significance Statement The overall effect of photorespiratory carbon loss on the net CO2 fixation of the plant is strongly influenced by the physiology of the leaf related to Rubisco kinetics and CO2 diffusion. This review outlines the distinction between Rubisco oxygenation and photorespiratory CO2 release as a basis to evaluate the costs and benefits of photorespiration.