Estimating the rate of photorespiration in leaves

Photorespiration is the light‐dependent evolution of CO 2 , which accompanies photosynthesis in C 3 plants. The four best known methods of measuring the rate of photorespiration have theoretical or technical problems, which make the results unreliable. However, the rate of photorespiration can be calculated from the rate of net CO 2 assimilation and the partial pressures of CO 2 and O 2 . Estimates of rates of photorespiration in the past and future can be made. The rate of photorespiration as a proportion of the rate of photosynthesis will fall to one half the current rate when the CO 2 level in the atmosphere doubles.