The Measurement and Significance of CO₂-Gas Exchange Transients in Leaves

Abstract

While studies on plants at the organellar and molecular level are yielding a comprehensive understanding of the mechanism of photosynthesis, efforts at the whole plant and leaf levels strive to reveal which reactions limit photosynthesis and thus growth and dry matter accumulation. One of the tools available to the plant physiologist is the study of transient phenomena in gas exchange induced by an environmental perturbation of a preconditioned leaf. Sivak and Walker (1) have described the use of an array of gas exchange transients coupled to measurements of fluorescence to probe regulation of photosynthesis during induction of this process upon illumination of a previously darkened leaf. Studies of the effects of light flecks on photosynthesis are pertinent to photochemical efficiency in variable environments such as those found in dense leaf canopies and under-stories (2). The transient peak in the rate of release of CO₂ observed upon darkening (3–6) or shading (7, 8) a preilluminated leaf has long been a basis for estimation of photorespiration.