The ultrastructure of proplastids in the leaves of five species of Orchids. II. Intraplastid inclusions and DNA-containing areas

Abstract

In the stroma of leaves proplastids of all investigated species of orchids: Paphiopedilum, Stanhopea, Cymbium, Coleogyne and Orchis occur starch grains of different shape, size and electron density. The number of starch grains vary from one to several. The proplasitids from cells of the vascular bundle sheath are completely filled with numerous starch grains and the stroma is strongly reduced. The formation of protein crystaloids was observed only in the proplastids of Paphiopedilum. In the stroma of proplastids in investigated species the DNA-containing areas are present. A tendency of their peripheral situation and of the formation of contacts between DNA fibirils and the inner surrounding membrane or with rare thylakoid's membranes was observed. In these areas in priopastids of Stanhopea, Cymbidium, Coelogyne and Orchis starch grains of different size, shape and electron density occur.