Ontogenetic changes in the photosynthetic apparatus and effect of cytokinins

Data on structural and functional changes in the photosynthetic apparatus of agricultural plants are presented. Results of studies on the regulatory effects of cytokinin-like phytohormones on photosynthesis are discussed. Cytokinins were found to be involved in the structural formation and maintenance of the photosynthetic apparatus, conditions of the stomata and the supply of CO2 to carboxylation sites through the leaf mesophyll, the syntheses of pigments and enzyme systems, and the regulation of photoreduction and carbon metabolism. Possible mechanisms mediating the regulatory effects of cytokinins are discussed.