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A sporangium (from Late Latin, ; : sporangia) is an enclosure in which are formed. (2025). 9780495013938, Thompson Brooks/Cole. ISBN 9780495013938 It can be composed of a single cell or can be multicellular. Virtually all , fungus, and many other groups form sporangia at some point in their life cycle. Sporangia can produce spores by mitosis, but in land plants and many fungi, sporangia produce genetically distinct haploid spores by meiosis.
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 haploid nuclei within the zygosporangium then fuse into Ploidy nuclei. When conditions improve, the zygosporangium germinates, undergoes meiosis and produces a sporangium, which releases spores.
Sporangia can be terminal (on the tips) or lateral (placed along the side) of stems or associated with leaves. In , sporangia are typically found on the surface (underside) of the leaf and are densely aggregated into clusters called Sorus. Sori may be covered by a structure called an indusium. Some ferns have their sporangia scattered along reduced leaf segments or along (or just in from) the margin of the leaf. Lycophytes, in contrast, bear their sporangia on the surface (the upper side) of leaves or laterally on stems. Leaves that bear sporangia are called . If the plant is heterosporous, the sporangia-bearing leaves are distinguished as either microsporophylls or megasporophylls. In seed plants, sporangia are typically located within strobili or flowers.
form their microsporangia on microsporophylls which are aggregated into strobili. Megasporangia are formed into ovules, which are borne on megasporophylls, which are aggregated into strobili on separate plants (all cycads are dioecious). typically bear their microsporangia on microsporophylls aggregated into papery pollen strobili, and the ovules, are located on modified stem axes forming compound ovuliferous cone scales. Flowering plants contain microsporangia in the anthers of (typically four microsporangia per anther) and megasporangia inside 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). The megaspores become megagametophytes (embryo sacs).
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