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Plants that are homosporous produce spores of the same size and type. Heterosporous plants, such as seed plants , spikemosses , quillworts , and ferns of the order Salviniales produce spores of two different sizes: the larger spore (megaspore) in effect functioning as a "female" spore and the smaller (microspore) functioning as a "male".
All spores the same size (homospory or isospory). Horsetails (species of Equisetum) have spores which are all of the same size. [28] Spores of two distinct sizes (heterospory or anisospory): larger megaspores and smaller microspores. When the two kinds of spore are produced in different kinds of sporangia, these are called megasporangia and ...
Plant spores are most obvious in the reproduction of ferns and mosses. However, they also exist in flowering plants where they develop hidden inside the flower. For example, the pollen grains of flowering plants develop out of microspores produced in the anthers. Reproductive spores grow into multicellular haploid individuals or sporelings.
Flowering plants contain microsporangia in the anthers of stamens (typically four microsporangia per anther) and megasporangia inside ovules inside ovaries. In all seed plants, spores are produced by meiosis and develop into gametophytes while still inside the sporangium. The microspores become microgametophytes (pollen).
One of the outcomes of plant reproduction is the generation of seeds, spores, and fruits [13] that allow plants to move to new locations or new habitats. [14] Plants do not have nervous systems or any will for their actions. Even so, scientists are able to observe mechanisms that help their offspring thrive as they grow.
Early land plants had sporophytes that produced identical spores (isosporous or homosporous) but the ancestors of the gymnosperms evolved complex heterosporous life cycles in which the spores producing male and female gametophytes were of different sizes, the female megaspores tending to be larger, and fewer in number, than the male microspores ...
Heterosporous plants that produced microspores in microsporangia and megaspores in separate megasporangia evolved independently in several plant groups during the Devonian period. [ 1 ] Fossils of these plants show that they produced endosporic gametophytes, meaning that their gametophytes were not free-living as in bryophytes but developed ...
Seed plants, which first appeared in the fossil record towards the end of the Paleozoic era, reproduce using desiccation-resistant capsules called seeds. Starting from a plant which disperses by spores, highly complex changes are needed to produce seeds. The sporophyte has two kinds of spore-forming organs or sporangia.