Embryological studies inCyperus alopecuroides rottb

Abstract

Development of microsporangium, male gametophyte, megasporangium, megagametophyte, endosperm, embryo, pericarp and seed coat inCyperus alopecuroides has been investigated. The anther wall consists of the epidermis, fibrous endothecium, a middle layer and glandular tapetum whose cells remain uninucleate throughout. The four nuclei formed after meiosis take an excentric position near the inner end of the microspore mother cell. One of the four nuclei increases in size and moves towards the center of the microspore mother cell and functions further, while the other three remain small and degenerate later. A simultaneous type of cytokinesis results in the formation of a thin cell wall separating the functional nucleus from the non-functional nuclei and similar walls separate the latter from each other. The pollen grains are shed at the three-celled stage. The gynoecium is bicarpellary, syncarpous and the ovary is unilocular with a single, basal, anatropous, bitegminal and crassinucellar ovule. The micropyle is formed by the inner integument only. Some of the funicular cells near the micropyle elongate and function as an obturator. After fertilization, a well-developed hypostase becomes differentiated at the chalazal region of the ovule just above the funicular vascular strand. The development of the megagametophyte conforms to the Polygonum type. The endosperm is of the Nuclear type and the embryo development corresponds to the Juncus variation of the Onagrad type (Johansen, 1950). Pericarp is four-layered. All the four layers become thick-walled in the mature fruit. Seed coat is two-layered and is formed by both the inner and the outer integuments. Seed coat is free from pericarp.