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Microspores are land plant spores that develop into male gametophytes, whereas megaspores develop into female gametophytes. [1] The male gametophyte gives rise to sperm cells, which are used for fertilization of an egg cell to form a zygote .
Exosporic gametophytes can either be bisexual, capable of producing both sperm and eggs in the same thallus , or specialized into separate male and female organisms (dioicous). In heterosporous vascular plants (plants that produce both microspores and megaspores), the gametophytes develop endosporically (within the spore wall).
In exosporic species, the smaller spores germinate into free-living male gametophytes and the larger spores germinate into free-living female gametophytes. In endosporic species, the gametophytes of both sexes are very highly reduced and contained within the spore wall. The microspores of both exosporic and endosporic species are free-sporing ...
The pollen grains, which are the male gametophytes, are reduced to only a few cells (just three cells in many cases). Here the notion of two generations is less obvious; as Bateman & Dimichele say "sporophyte and gametophyte effectively function as a single organism". [8] The alternative term 'alternation of phases' may then be more appropriate ...
Microspores: Produced sexually through meiosis, and give rise to a male gametophyte: Pollen in seed plants In plants, microspores, and in some cases megaspores, are formed from all four products of meiosis. Megaspores (macrospores) Produced sexually through meiosis, and give rise to a female gametophyte: Ovule in seed plants
These plants have two spore types, megaspores and microspores. Generally speaking, the megaspore, or large spore, germinates into a female gametophyte , which produces egg cells . These are fertilized by sperm produced by the male gametophyte developing from the microspore.
A microsporangium (pl. microsporangia) is a sporangium that produces microspores that give rise to male gametophytes when they germinate. Microsporangia occur in all vascular plants that have heterosporic life cycles, such as seed plants, spike mosses and the aquatic fern genus Azolla.
An antheridium is a haploid structure or organ producing and containing male gametes (called antherozoids or sperm). The plural form is antheridia, and a structure containing one or more antheridia is called an androecium. [1] The androecium is also the collective term for the stamens of flowering plants.