Microspores are land plant spores that develop into male gametophytes, whereas megaspores develop into female gametophytes. The male gametophyte gives rise to sperm cells, which are used for fertilization of an egg cell to form a zygote. Megaspores are structures that are part of the alternation of generations in many seedless vascular cryptogams, all gymnosperms and all angiosperms. Plants with heterosporous life cycles using microspores and megaspores arose independently in several plant groups during the Devonian period. Microspores are haploid, and are produced from diploid microsporocytes by meiosis.
Microscopic photo of spores (in red) of Selaginella. The large three spores at the top are megaspores whereas the numerous smaller red spores at the bottom are microspores.
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, fungi and protozoa. They were thought to have appeared as early as the mid-late Ordovician period as an adaptation of early land plants.
Fresh snow partially covers rough-stalked feather-moss (Brachythecium rutabulum), growing on a thinned hybrid black poplar (Populus x canadensis). The last stage of the moss lifecycle is shown, where the sporophytes are visible before dispersion of their spores: the calyptra (1) is still attached to the capsule (3). The tops of the gametophytes (2) can be discerned as well. Inset shows the surrounding, black poplars growing on sandy loam on the bank of a
Sporangium of Fungi
Zygospores on Rhizopus
Aceium on foilage