Megaspore
/ˈmɛɡəˌspɔr/
Definition
Megaspore refers to the larger of the two spore types produced by heterosporous plants and seed plants. It forms inside the ovule or megasporangium and develops into the female gametophyte, the tissue that produces egg cells. This distinguishes it from a microspore, which develops into the male gametophyte. In flowering plants, usually only one functional megaspore remains after meiosis.
Role in Plant Biology
- Female gametophyte development: In seed plants, one surviving megaspore usually develops into the female gametophyte, the tissue that produces the egg cell and supports early fertilization events.
- Part of heterospory: Its presence reflects heterospory, a reproductive pattern with separate large and small spores. This separation is a major step in the evolution of seeds and more specialized reproduction.
- Location in flowering plants: In flowering plants, the megaspore forms inside the ovule within the ovary. Because it stays enclosed, the developing female structures are protected and closely linked to seed formation.
- Botanical comparison point: Patterns of megaspore formation and survival differ among major plant groups. Botanists use these differences to study reproductive development and evolutionary relationships among land plants.
Related Terms
Megasporangium
Megasporangium is a plant structure in which megaspores are produced by meiosis. In seed plants, the megasporangium is…
Microspore
Microspore refers to the small spore produced in the male sporangia of seed plants and many other land plants. It is…
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…
Gametophyte
Gametophyte is the haploid stage in a plant’s life cycle, meaning its cells carry one set of chromosomes. It develops…
Sporophyte
Sporophyte refers to the diploid, spore-producing stage in a plant’s life cycle. It develops from the fertilized egg…