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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 .
In gymnosperms and flowering plants, the megaspore is produced inside the nucellus of the ovule.During megasporogenesis, a diploid precursor cell, the megasporocyte or megaspore mother cell, undergoes meiosis to produce initially four haploid cells (the megaspores). [1]
Although sexual reproduction in fungi varies between phyla, for some fungi the sporangium plays an indirect role in sexual reproduction. For Zygomycota , sexual reproduction occurs when the haploid hyphae from two individuals join to form a zygosporangium in response to unfavorable conditions.
The microspore has three different types of wall layers. The outer layer is called the perispore, the next is the exospore, and the inner layer is the endospore.The perispore is the thickest of the three layers while the exospore and endospore are relatively equal in width.
Microspores develop within the microsporangium by meiosis. In a willow (like all seed plants) the zygote first develops into an embryo microsporophyte within the ovule (a megasporangium enclosed in one or more protective layers of tissue known as integument). At maturity, these structures become the seed. Later the seed is shed, germinates and ...
Within the stamen, the microsporangium forms grains of pollen, surrounded by a protective microspore, which form the male gametophyte. Within the carpel the megasporangium form the ovules, with its protective layers in the megaspore, and the female gametophyte. Unlike the male gametophyte, which is transported in the pollen, the female ...
Signs and symptoms are also applied to physiological states outside the context of disease, as for example when referring to the signs and symptoms of pregnancy, or the symptoms of dehydration. Sometimes a disease may be present without showing any signs or symptoms when it is known as being asymptomatic . [ 13 ]
Microsporum gypseum. Microsporum is a genus of fungi that causes tinea capitis, tinea corporis, ringworm, and other dermatophytoses (fungal infections of the skin). Microsporum forms both macroconidia (large asexual reproductive structures) and microconidia (smaller asexual reproductive structures) on short conidiophores.