Measurements of photosynthesis and respiration in plants

Methods for measuring the rates of photosynthesis and respiration in plants are reviewed. Closed systems that involve manometric techniques, (CO2)-C-14 fixation, O-2 electrodes and other methods for measuring dissolved and gas phase O-2 are described. These methods typically provide time-integrated rate measurements, and limitations to their use are discussed. Open gas exchange systems that use infra-red CO2 gas analysers and differential O-2 analysers for measuring instantaneous rates of CO2 and O-2 exchange are described. Important features of the analysers, design features of gas exchange systems, and sources of potential error are considered. The analysis of chlorophyll fluorescence parameters for estimating the quantum yield for O-2 evolution and CO2 fixation is described in relation to new fluorescence imaging systems for large scale screening of photosynthetic phenotypes, and the microimaging of individual chloroplasts.