ULTRASTRUCTURE, DEVELOPMENT AND SECRETION IN THE NECTARY OF BANANA FLOWERS

The nectaries of Musa paradisiaca L. var. sapientum Kuntze were found to secrete in addition to the sugar solution, a polysaccharide mucilage and a very electron dense, homogenous material which was apparently protein. The polysaccharide had already started to appear outside the epithelial cells of the nectary at very early stages of nectary development. At somewhat later developmental stages the very dense homogenous material appeared in the form of droplets between the plasmalemma and cell wall in masses in the nectary lumen. Nectar secretion started in flowers when the bract in the axil of which they occurred had just recoiled. The ER elements were dilated and formed vesicles and the Golgi bodies were very active, at the stage of the nectar secretion and at stages preceding it, except at the stage just before secretion. In all stages of nectary development the dilated ER elements and most large Golgi vesicles contained fibrillar material. It is suggested that both ER and the Golgi apparatus are involved in the secretion of the sugar solution and of the polysaccharides. There was not enough evidence as to where in the cell the very dense homogenous material is synthesized.A few developmental stages of the nectaries of the male flowers of the Dwarf Cavendish banana, which do not secrete nectar, were also studied. It was seen that at early stages of development, the ultra-structure of the nectary of this banana variety was similar to that of M. paradisiaca var. sapientum. However, the epithelial nectary cells of the Dwarf Cavendish banana disintegrated before maturation of the nectary. © 1979, Annals of Botany Company.