megasporocyte

A megasporocyte, also known as the megaspore mother cell, is a diploid cell in the megasporangium of seed plants that undergoes meiosis to produce haploid megaspores. It resides in the nucellus of the ovule, within the megasporangium, and is surrounded by protective integuments.

During megasporogenesis, the megasporocyte undergoes meiosis I and II to yield four haploid megaspores arranged in a tetrad. In most seed plants, only one megaspore remains viable as the functional megaspore; the remaining three typically degenerate. The functional megaspore then divides by mitosis to form the female gametophyte, the embryo sac in angiosperms, or the equivalent female gametophyte in gymnosperms.

In flowering plants, the embryo sac develops within the ovule and contains the structures necessary for fertilization, including the egg cell. The megasporocyte thus provides the genetic material for the female lineage that will participate in fertilization after pollen delivers sperm. The megasporocyte is contrasted with the microsporocyte, the corresponding cell in the microsporangium that gives rise to male gametophytes (pollen grains). Patterns of megasporogenesis and subsequent development vary among plants, with many angiosperms exhibiting monosporic development where a single megaspore forms the embryo sac, while other species show alternative patterns.