Pathways of Carbon Metabolism Related to Net Carbon Dioxide Assimilation by Monocotyledons

Abstract

Three pathways of net carbon assimilation and reduction have been detected in certain higher plant. The three recognized pathways are: the reductive pentose phosphate, the C4-dicarboxylic, and crassulacean acid metabolism. Leaves of a given plant may exhibit at least one of these pathways. A plant exhibiting a particular one of these carbon pathways also will possess a distinctive leaf morphology. Plants with crassulacean acid metabolism will have fleshy leaves. In a light or electron microscope, the vascular bundle sheath cells of neither crassulacean nor pentose types of leaves will exhibit extensive development of organelles such as chloroplasts, mitochondria, ro peroxisomes. Plants using the C4-dicarboxylic pathway will exhibit, in light and electron microscopy, a dense concentration of these organelles in leaf bundle sheath cells. Thus leaf cell morphology, plus organelle distribution and biochemistry, are intimately related in a very specific manner such that photosynthesis in a given plant proceeds...