Automated measurement of leaf photosynthetic O2 evolution as a function of photon flux density

An automated procedure is described that allows the rate of photosynthesis, as a function of photon flux density (PFD), to be determined and plotted within 30 minutes. The method is based on polarographic measurement of O2 evolution from a piece of leaf enclosed in a chamber and illuminated from above by an array of light-emitting diodes. The light emitted from these diodes is altered by a computer which also facilitates analyses of the data so derived. Applications of the procedure to leaves of shade and sun plants, to studies of photoinhibition and to analysis of the Kok effect, are described.