Synopsis The present title "Photosynthesis in Plants" is a classical branch in plant physiology. Biochemists purify photosynthetic enzymes and study their characteristics in the test tube; biophysicists isolate photosynthetic membranes and determine their spectroscopic properties in cuvettes; molecular biologists clone the genes that encode photosynthetic proteins and study their regulation during development. In contrast, plant physiologists study photosynthesis in action at different levels of organisation, including the chloroplast, the cell, the leaf and the whole plant, stated differently, biochemists, biophysicists and molecular biologists study cellular components more or less in isolation, whereas plant physiologists investigate the way in which the components interact with each other to carry out biological processes and functions.