Megasporangium
/ˌmɛɡəspəˈrændʒiəm/
Definition
Megasporangium is a plant structure in which megaspores are produced by meiosis. In seed plants, the megasporangium is the nucellus within an ovule and gives rise to the megaspore that develops into the female gametophyte. In other vascular plants, such as ferns and lycophytes, it is contained within a megasporangium-bearing structure and produces megaspores that develop into female gametophytes.
Function in Plants
- Megaspore production: Meiosis within the tissue produces megaspores, typically yielding four haploid products from one megaspore mother cell. In many seed plants, only one of these remains functional.
- Female gametophyte development: The surviving megaspore undergoes mitotic divisions to form the female gametophyte, which contains the egg cell and other cells involved in sexual reproduction.
- Ovule relationship: In seed plants, the megasporangium forms the central tissue of the ovule and is surrounded by integuments. This arrangement connects megaspore formation with the later development of the seed.
- Evolutionary distinction: Megasporangia occur across vascular plants, but their organization differs between groups. In heterosporous ferns and lycophytes, they produce relatively large megaspores that develop into separate female gametophytes.
Related Terms
Megaspore
Megaspore refers to the larger of the two spore types produced by heterosporous plants and seed plants. It forms inside…
Ovule
Ovule is the seed-producing structure inside a flower’s ovary, or on the scales of cones in gymnosperms. It contains…
Integument
Integument refers to one or two protective layers of tissue that surround a plant ovule, the structure that contains…
Micropyle
Micropyle refers to a tiny opening in the ovule, and later in the seed coat, where the integuments do not fully close…
Microsporangium
Microsporangium refers to the pollen-producing spore case in seed plants and other vascular plants. It is a plant…
Sporophyte
Sporophyte refers to the diploid, spore-producing stage in a plant’s life cycle. It develops from the fertilized egg…
Sporangium
Sporangium is a spore-producing structure found in plants, algae, fungi, and some plant-like organisms. In land plants…