Chromoplasts--the last stages in plastid development.

The results of investigations on the development of chromoplast fine structures in various plants are reviewed. Emphasis is placed on the specific pigment-containing structures and their development during chromoplast formation. There is a large variety of these structures, although four fundamental types can be discerned. These are plastoglobules, membranes, crystals, and tubules. During chromoplast development, various types of structure follow one after the other, or they may even be present simultaneously in the same chromoplast. Depending on the structures present in chromoplasts their pigment content also varies. It is still not clear whether the type of structure defines the pigment content of the chromoplast or vice-versa. Various possible ways of chromoplast development and dedifferentiation are discussed.