STUDIES ON THE EMBRYOLOGY OF CALAMUS PRASINUS (ARECACEAE) – AN ENDEMIC PLANT FROM THE WESTERN GHATS OF KARNATAKA

Abstract

The genus Calamus in the family Arecaceae is embryologically not well studied. The present work on the embryology of Calamus prasinus is the first investigation. A transverse section of young male staminate flower shows 6 tetrasporangiate anthers. The anther wall comprises an epidermis, an endothecium, a middle layer and a tapetum. The tapetum is of secretory type and its cells are 2–3 nucleated. The successive meiotic division in the pollen mother cells resulting in the formation of isobilateral and tetrahedral microspore tetrads. Occasionally, T-shaped and linear tetrads have been observed. The pollen grains are shed at 2-celled condition. The ovary is superior, tricarpellary, syncarpous and contains 3 ovules on an axile placenta. The ovule is anatropous, bitegmic and crassinucellate. The archesporial cell divides periclinally to form a primary parietal cell and a sporogenous cell. The sporogenous cell differentiates transformsin to megaspore mother cell, which undergoes meiotic division and subsequent cytokinesis forming a linear tetrad. The chalazal functional megaspore undergoes three successive mitotic divisions without cytokinesis that results in the formation of an 8‑nucleate embryo sac. The embryo sac contains two synergids, one an egg cell at the micropylar end, three antipodal cells at the chalazal end and a central cell with two polar nuclei. The development of female gametophyte conforms to the Polygonum type.