Submicroscopic structure and development of the chloroplasts of Cibotium chamissoi

Abstract

Embryonic and mature leaves of Cibotium chamissoi were used for the study of the fine structure and the development of chloroplasts. The chloroplasts of Cibotium are spherical in cross-section, about from 0.5 to 0.8 μ in diameter, and more or less elliptical in outline, when cut obliquely. They are bounded by a well-defined outer membrane. The grana are distributed more or less uniformly throughout the chloroplast, except in those instances in which an irregular peripheral zone is devoid of grana. The grana are randomly oriented between the stroma lamellae. The thickness of the lamellae within the grana was measured about 95 å. At the boundary of the grana, an osmiophilic substance is present. In addition to this substance, relatively large osmiophilic globules also occur in the stroma. From various stages of developing leaves, the following stages of developing chloroplasts were found: 1. (a) The first ultrastructure to be seen within the proplastids are vesicles. In most cases they also contain osmiophilic globules. A dense margin indicates a membrane. 2. (b) The lamellae layers are formed locally by the fusion of the vesicles. 3. (c) The number of lamellae layers increased with size of the chloroplasts. 4. (d) Within the plastids, lamellae appear in bundles, which indicate the grana formation. Lamellated grana are connected by the stroma lamellae, which are less numerous.