Microsporogenesis, Megasporogenesis, and the Development of Male and Female Gametophytes in Eustoma grandiflorum

Abstract

Embryological characters during microsporogenesis, megasporogenesis, and the development of male and female gametophytes in Eustoma grandiflorum were observed by microscopy. The results are as follows. 1. The formation of anther walls was of the dicotyledonous type. The tapetum was of the heteromorphic and glandular type. Tapetal cells on the connective side elongated radially. 2. Cytokinesis in microsporocyte meiosis was of the simultaneous type and microspore tetrads were tetrahedral. 3. Mature pollen grains were 2-celled and had 3 germ furrows. 4. The ovary was bicarpellary syncarpous and unilocular, having parietal placentas. Ovules were numerous and anatropous. 5. The archespore under the nucellar epidermis directly developed a megaspore mother cell, which in turn underwent meiotic division to form 4 megaspores arranged in a line or T-shape. The chalazal megaspore was observed to be functional. 6. The formation of the embryo sac was of the polygonum type. Before fertilization, the 2 polar nuclei fused into a secondary nucleus. The mature embryo sac was made up of 7 cells. 7. It was found at a very low rate that there were 2 megasporocytes or 2 embryo sacs in an ovule.