Photosynthesis and Chloroplast Development in Primary Leaves of Phaseolus vulgaris Illuminated with Continuous Far-Red Light

Abstract

Summary A comparative study of photosynthetic properties of bean primary leaves illuminated with continuous far-red or white light during an 8-day period revealed the following. Leaf size in far-red developed plants is about half that in white light developed plants. However, the rates of CO2 fixation on an area basis in far-red developed leaves are comparable to those in white light developed tissue, although the far-red developed leaves have 20 times less chlorophyll per unit leaf area. The ethanol soluble photosynthetic products, and the developmental patterns of ribulosebisphosphate carboxylase and of NADP-dependent glyceraldehyde-3-phosphate dehydrogenase in the two leaf types are similar. However, chloroplast ultrastructure, after prolonged far-red illumination, remains curtailed at a simple stage characterized by unappressed thylakoids. Gel electrophoresis indicates that chloroplasts from far-red illuminated leaves are deficient in a polypeptide corresponding in molecular weight to the protein moiety of the light harvesting chlorophyll protein (Complex II). In addition it appears that far-red illumination, while significantly affecting chlorophyll synthesis and chloroplast structure, has little effect on the development of the enzymes and activities associated with the dark reactions of photosynthesis.