Microsporangium

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microsporangium

[¦mī·krō·spə′ran·jē·əm]
(botany)
A sporangium bearing microspores.

Microsporangium

 

the multicellular organ of heterosporous Pteridophyta and seed plants in which the microspores develop. In Selaginella and Sigillaria the microsporangia are located singly in the axils of microsporophylls or on the upper-sides of the leaves (in Lepidodendron, Pleuromeia, and Isoetes). In Pleuromeia and Isoetes they are submerged in a special cavity. In some extinct ferns the microsporangia are on the underside of the sporophylls. In water ferns they are formed in sporocarps: 64 microspores develop in the microsporangium of Sahinia, and 32 or 64 in the microsporangium of Marsilea. In gymnosperms the microsporangia develop singly on microsporophylls (in some joint firs); more often several develop on a microsporophyll, arranged singly (conifers), in sori (many sago palms, ginkgoes) or in synangia (Caytoniales, many Bennettitales, Ephedra, Welwitschia). In angiosperms the pollen sac of the anther is homologous to the microsporangium.

References in periodicals archive ?
[0.2-1.5] cm long, 8-64 abaxial microsporangia (rarely a few adaxially)
Generally in cycads, pollen-bearing microsporangia are found only
microsporangia only on the abaxial surface, and wine-red to dark
microsporangia on both the adaxial and abaxial surfaces, and tan to
The latter may be particularly important for grains in newly opened anthers and microsporangia.
Because of boundary-layer effects, mean wind speeds corresponding to u[prime] for a particular pollen type are typically insufficient to liberate pollen grains from anthers, microsporangia, or vegetative surfaces.
Surprisingly little is known about the aerodynamics of pollen liberation from anthers and microsporangia, in contrast to fungal-spore liberation (e.g., Aylor, 1978) and pollen interception by ovulate organs (e.g., Niklas, 1985).
The compound pollen strobili of Austrotaxus have a unique arrangement whereby the stalks of the microsporophylls are vestigial, the microsporangia of each microsporophyll are fused to each other and partially adnate to the microsporophyll itself (Saxton, 1934; Wilde, 1975).
10; microsporophylls 6-14, perisporangiate, radially symmetrical, peltate, each bearing 4-9 microsporangia.
The microsporangia of Taxus, as with Pseudotaxus, are distinctive among conifers in that they are radial (as opposed to being positioned only abaxially on the sporangiophore), which has led Wilde (1975) to suggest that the pollen strobilus is a reduced lateral one.