Environmental Responses of the Post-lower Illumination CO(2) Burst as Related to Leaf Photorespiration

As leaf irradiance is decreased in increments, a single transient CO₂ burst is exhibited by C₃ plant leaves. This post-lower illumination CO₂ burst (PLIB) is sensitive to changes in irradiance, to changes in the concentrations of O₂ and CO₂, and to temperature. Increasing O₂ concentrations above ambient produces a progressively larger PLIB while increasing CO₂ 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 C₃ 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 C₃ leaves in air.