CONTROL OF METABOLISM AND DEVELOPMENT IN HIGHER-PLANT PLASTIDS

The most fundamental difference between plants and other eukaryotic organisms is the presence of a unique additional compartment called, plastid. This chapter summarizes some of the recent topical areas of higher plant plastid metabolism and the evolutionary origin and development of plastids. Plastids are the biosynthetic powerhouse of the plant cell, being responsible not only for the reductive biosynthesis of intermediary carbohydrates from CO2 but also for the synthesis of starch, fatty acids, amino acids, and the generation of precursors for secondary metabolism. Plastids are divided into two main groups—namely, photosynthetic and nonphotosynthetic. Nonphotosynthetic plastids include the plastid precursors proplastids/eoplasts, and etioplasts, and specialized plastids that may be considered functionally mature. These specialized nonphotosynthetic plastids include chromoplasts, amyloplasts, and elaioplasts. The chloroplast is the photosynthetic plastid of higher plant cells. It contains chlorophyll and is found in all photosynthetic parts of a plant, mainly in the leaves but also in stems, tendrils, cotyledons, and runners. The study of the metabolism of nonphotosynthetic plastids is receiving increasing attention because the major primary products of biosynthesis and yield for human consumption—lipids, amino acids, and starch—are all made within these organelles in storage organs and seeds. © 1993, Academic Press, Inc.