A sporangium (from Late Latin, ; : sporangia) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, 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.

Fungi

alt=refer to caption|thumb|200px|[[Photomicrograph of a mature sporangium of an Absidia mold]]

In some phyla of fungi, the sporangium plays a role in asexual reproduction, and may play an indirect role in sexual reproduction. The sporangium forms on the sporangiophore and contains haploid nuclei and cytoplasm. Spores are formed in the sporangium by encasing each haploid nucleus and cytoplasm in a tough outer membrane. During asexual reproduction, these spores are dispersed via wind and germinate into haploid hyphae.

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 diploid nuclei. When conditions improve, the zygosporangium germinates, undergoes meiosis and produces a sporangium, which releases spores.

Land plants

thumb|200px|alt=refer to caption|Moss sporangia (the capsule and the stalk/seta make up the [[diploid asexual sporophyte generation)]]

In mosses, liverworts and hornworts, an unbranched sporophyte produces a single sporangium, which may be quite complex morphologically. Most non-vascular plants, as well as many lycophytes and most ferns, are homosporous (only one kind of spore is produced). Some lycophytes, such as the Selaginellaceae and Isoetaceae, the extinct Lepidodendrales, and ferns, such as the Marsileaceae and Salviniaceae are heterosporous (two kinds of spores are produced).

See also

  • Archegonium
  • Antheridium
  • Spore formation

References