Environmental Responses of the Post-lower Illumination CO₂ Burst as Related to Leaf Photorespiration

As leaf irradiance is decreased in increments, a single transient CO(2) burst is exhibited by C(3) plant leaves. This post-lower illumination CO(2) burst (PLIB) is sensitive to changes in irradiance, to changes in the concentrations of O(2) and CO(2), and to temperature. Increasing O(2) concentrations above ambient produces a progressively larger PLIB while increasing CO(2) concentrations above ambient produces a progressively smaller PLIB. The PLIB, which exhibits many responses to environment common with other methods for measuring photorespiration and photosynthesis, is proposed as a measure of photorespiration in illuminated leaves of C(3) plants. Although the PLIB cannot be used as a quantitative measurement of photorespiration, we propose that the PLIB is a rapid, easy, relatively inexpensive, nondestructive method for evaluating photorespiration in intact illuminated C(3) leaves in air.