Ébauches intracytoplasmiques de grains protéiques dans des cotylédons de Raphanus en développement

Abstract

Protein bodies were characterized at an early stage of their maturation in thin green cotyledons of developing radish embryos. They appeared as granules in the cytoplasm of meristematic cells. Their diameter (0.5 to 1 μm) was in the range of that of mitochondria. They were distinguished from vacuoles by their morphology, size, and structure. Some appeared to be associated with cisternae of endoplasmic reticulum or dictyosomes (permanganic fixations). Their evolution was synchronous in the cell and also in the cotyledonary tissue. Compact in appearance, they were constituted of thin packed fibrillar structures, limited by a denser peripheral layer. It is difficult to know whether or not they had a limiting membrane. Some possessed thin dense crystals or globoids (aldehydic fixations). During this early phase, several types of organelles seemed to contribute to the development of protein bodies, including saccules of rough endoplasmic reticulum and dictyosomes. Polyribosomes constituted a network around their surface. They did not exhibit any acid phosphatase activity. In this respect, they differed from the vacuoles, saccules of endoplasmic reticulum, and several neighbouring vesicles.