Ultrastructure of the Placental Epithelium inTillandsiaand its Modification in Connection to Anthesis

Abstract

SUMMARYThe epithelium cells lining the placental lobes of three species of Tillandsia are investigated under both light and electron microscope.The fine structure of the cells, fixed before anthesis, shows that an intense metabolic activity is in progress anticipating the phase of secretory activity. The secretion process starts after anthesis, and is mediated by the Golgi apparatus; it releases polysaccharides whose nature is at least partly acid which determine a development of the wall-membrane apparatus similar to that observed in transfer cells. Further the abundance of polysomes, associated with a well developed endoplasmic reticulum, reveals that synthesis of proteins is involved. These proteins may enter partly into the composition of the Golgi secretion product and partly be of enzymatic nature. Such proteins may be secreted to the outside by eccrine process, as suggested by breaking up of the vacuoles and by the morphology of the wall-membrane apparatus. The increase both in extension and thickness of the wall-membrane apparatus in Tillandsia facilitates the transport of the secretion products to the outside and also functions as a store of nutrients. Enzymes, which are synthesised by the cells themselves may mediate the degradation of this substrate for the nutritions of both male and female reproductive structures during their development.