Algal model systems and the elucidation of photosynthetic metabolism

The main impact of algal investigations on a wider understanding of photosynthesis in O-2 evolvers has come about through studies on microalgae. Experiments with flashing light led to the concepts of photosynthetic units and reaction centers. Work on photon yields and the Emerson enhancement effect with fluorescence and spectroscopy, as well as investigations with mutants, were crucial in elaborating and then testing the validity of the Z scheme for light reactions. The carbon reduction (or Calvin) cycle was discovered using C-14, chromatography, and Chlorella (plus Scenedesmus). The availability of complete gene sequences for several cyanobacteria and the flowering plant Arabidopsis and very soon for the eukaryotic alga Chlamydomonas pen-nit important advances in our understanding of photosynthesis in all these organisms. Eukaryotic microalgae and cyanobacteria remain advantageous in fundamental photosynthetic studies.