A Transient Burst of CO2 from Geranium Leaves during Illumination at Various Light Intensities as a Measure of Photorespiration

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Abstract
A transient CO2 burst is exhibited by irradiated leaves of the C3 plant geranium (Pelargonium X hortorum, Bailey) after the irradiance is quickly lowered. The light CO2 burst appears to be related to photorespiration because of its irradiance dependency and its sensitivity to other environmental components such as CO2 and O2 concentration. The term post-lower-irradiance CO2 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 C3 plants but not with C4 leaves. Therefore, it is proposed that, after maximizing intact leaf photosynthetic rates and leaf chamber gas measuring conditions, photorespiration can be measured with intact C3 leaves such as geranium as a transient post-lower-irradiance CO2 burst.