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

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Abstract
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.