Sporangium

Source: Wikipedia, the free encyclopedia.
For bacteria-related information, see endospore.
Photomicrograph of a mature sporangium of an Absidia
mold
diploid asexual sporophyte generation)[1]
Sporangia (clustered in sori) on a fern leaf
Scanning electron micrograph
of fern leptosporangia
Equisetum arvense strobilus cut open to reveal sporangia
Clusters of sporangia on a fern

A sporangium (from

haploid spores by meiosis
.

Fungi

In some phyla of fungi, the sporangium plays a role in

Spores are formed in the sporangiophore 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.[5]

Although sexual reproduction in fungi varies between phyla, for some fungi the sporangium plays an indirect role in sexual reproduction. For

zygosporangium in response to unfavorable conditions. The haploid nuclei within the zygosporangium then fuse into diploid nuclei.[6]
When conditions improve, the zygosporangium germinates, undergoes meiosis and produces a sporangium, which releases spores.

Land plants

In mosses, liverworts and hornworts, an unbranched

microsporangia
and megasporangia.

Sporangia can be terminal (on the tips) or lateral (placed along the side) of stems or associated with leaves. In

strobili
or flowers.

Cycads 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). Conifers 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 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). The megaspores become megagametophytes (embryo sacs).

Eusporangia and leptosporangia

Categorized based on developmental sequence, eusporangia and leptosporangia are differentiated in the vascular plants.

  • In a leptosporangium, found only in leptosporangiate ferns, development involves a single initial cell that becomes the stalk, wall, and spores within the sporangium. There are around 64 spores in a leptosporangium.
  • In a eusporangium, characteristic of all other vascular plants and some primitive ferns, the initials are in a layer (i.e., more than one). A eusporangium is larger (hence contain more spores), and its wall is multi-layered. Although the wall may be stretched and damaged, resulting in only one cell-layer remaining.

Synangium

A cluster of sporangia that have become fused in development is called a synangium. This structure is most prominent in Psilotum and Marattiaceae such as Christensenia, Danaea and Marattia.

Internal structures

A columella (pl. columellae) is a sterile (non-reproductive) structure that extends into and supports the sporangium of some species. In fungi, the columella, which may be branched or unbranched, may be of fungal or host origin. Secotium species have a simple, unbranched columella, while in Gymnoglossum species, the columella is branched. In some Geastrum species, the columella appears as an extension of the stalk into the spore mass (gleba).[9]

See also

References

  1. ^ "Life Cycle of a Moss - Infographic". STEM Lounge. 2018-09-13. Retrieved 2021-02-25.
  2. ^ "sporangium". Lexico UK English Dictionary. Oxford University Press. Archived from the original on May 28, 2020.
  3. ISBN 9780495013938
    .
  4. ^ "Fungi". Leaving Certificate Biology. 4 October 2018.
  5. ^ "Life History and Ecology of the Fungi". University of California Museum of Paleontology.
  6. ^ Webster, John; Weber, Roland (2007). Introduction to Fungi (3 ed.). Cambridge University Press.
  7. ^
    ISBN 978-1-5272-2630-2
    .
  8. ISBN 978-0-521-38294-6
    .
  9. ISBN 978-0-85199-826-8
    .
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