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Megasporogenesis, formation of the megaspores in the megasporangium (nucellus) by meiosis; Megagametogenesis; development of the megaspore(s) into the megagametophyte(s) which contains the gametes. [2] In gymnosperms and most flowering plants, only one of the four megaspores is functional at maturity, and the other three soon degenerate.
Location of ovules inside a Helleborus foetidus flower. In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the integument, forming its outer layer, the nucellus (or remnant of the megasporangium), and the female gametophyte (formed from a haploid megaspore) in its center.
Plant ovules with megasporocytes before meiosis: Gymnosperm ovule on left, angiosperm ovule (inside ovary) on right. After megasporogenesis, the megaspore develops into the female gametophyte (the embryo sac) in a process called megagametogenesis. The process of megagametogenesis varies depending on which pattern of megasporogenesis occurred.
Flowering plants contain microsporangia in the anthers of stamens (typically four microsporangia per anther) and megasporangia inside ovules inside ovaries. In all seed plants, spores are produced by meiosis and develop into gametophytes while still inside the sporangium. The microspores become microgametophytes (pollen).
Runcaria, small and radially symmetrical, is an integumented megasporangium surrounded by a cupule. The megasporangium bears an unopened distal extension protruding above the mutlilobed integument. It is suspected that the extension was involved in anemophilous (wind) pollination.
A superior ovary is an ovary attached to the receptacle above the attachment of other floral parts. A superior ovary is found in types of fleshy fruits such as true berries, drupes, etc. A flower with this arrangement is described as hypogynous. Examples of this ovary type include the legumes (beans and peas and their relatives).
The ovary changes structure and function beginning at puberty. [2] Since the ovaries are able to regulate hormones, they also play an important role in pregnancy and fertility . When egg cells (oocytes) are released from the fallopian tube, a variety of feedback mechanisms stimulate the endocrine system, which cause hormone levels to change. [ 10 ]
The ovary (from Latin ovum, meaning egg) is the enlarged basal portion which contains placentas, ridges of tissue bearing one or more ovules (integumented megasporangia). The placentas and/or ovule(s) may be born on the gynoecial appendages or less frequently on the floral apex.