A Transient Burst of CO(2) from Geranium Leaves during Illumination at Various Light Intensities as a Measure of Photorespiration.

A transient CO(2) burst is exhibited by irradiated leaves of the C(3) plant geranium (Pelargonium X hortorum, Bailey) after the irradiance is quickly lowered. The light CO(2) burst appears to be related to photorespiration because of its irradiance dependency and its sensitivity to other environmental components such as CO(2) and O(2) concentration. The term post-lower-irradiance CO(2) burst or PLIB is used to describe the phenomenon. The PLIB appears to be a quantitative measurement of photorespiration with intact geranium leaves. The PLIB has been observed with intact leaves of other C(3) plants but not with C(4) leaves. Therefore, it is proposed that, after maximizing intact leaf photosynthetic rates and leaf chamber gas measuring conditions, photorespiration can be measured with intact C(3) leaves such as geranium as a transient post-lower-irradiance CO(2) burst.