Sporangium

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Related to sporangial: Sporangiospore

sporangium

[spə′ran·jē·əm]
(botany)
A case in which asexual spores are formed and borne.

Sporangium

 

a plant organ in which spores are formed. A sporangium may be unicellular (in many lower plants) or multicellular (in higher plants). Certain unicellular green algae undergo complete transformation in the sporangium. In multicellular algae, such as Ulothrix and Ulva, cells indistinct from other cells may become sporangia; in Ectocarpus and Laminaría the sporangium is formed from cells that differ from all other cells and occupy a definite position on the thallus. In certain acellular plants sporangia are formed on the thallus by forming a septum. The sporangia of some oomycetes become conidia, fall off, and sprout. The names of sporangia in lower plants reflect the structural features of the spores that form in them (for example, zoo-sporangium), the number of spores (monosporangium, tetraspo-rangium), the external appearance of the sporangium (cysto-carp), or the method of spore formation (mitosporangium, meiosporangium). The succession of nuclear phases in plant cycles of development is associated with meiosporangia.

Higher plants form only meiosporangia. In bryophytes the sporangium is represented by the capsule of the sporogonium. The sporangia of ferns develop on sporophylls or in their axils. Sporangia may be solitary or in groups (sori) and may be free or con-cresced (synangia). Isosporous ferns form sporangia of a single type, which produce spores that germinate in bisexual prothallia. Heterosporous ferns produce sporangia of two types— microsporangia and megasporangia—which, in turn, form microspores and megaspores (from which male and female prothallia develop). All seed plants are heterosporous; the nucellus of their ovule is homologous to a megasporangium. The pollen cell in an-giosperms is homologous to a microsporangium.

REFERENCES

See references under .

A. N. SLADKOV

References in periodicals archive ?
Colony characteristics and growth rates were useful as a first step in identification of Phytophthora species by complementing sporangial characteristics in the differentiation of P.
These are: #5, growth form of stem/axis erect [right arrow] rhizomatous; #71, sporangial stalk absent [right arrow] broad; #73, sporangial capsule large with thick wall [right arrow] small with thin wall; #74, functional annulus absent [right arrow] present; #78, number of spores per meio/microsporangium [greater than]512 [right arrow] 128-512; #79, ontogenetic origin of sporangia from several cells [right arrow] from approximately two cells; and #99, first division of zygote more or less transverse [right arrow] more or less longitudinal.
This indicates that the sporangial annulus has evolved separately in zygopterid and filicalean ferns.
An unusual botryopterid sporangial aggregation from the Middle Pennsylvanian of North America.
Following the work of Good (1981), sporangial maturation within a sorus is interpreted as simultaneous rather than gradate, as interpreted earlier (Holmes, 1981).
This character recognizes the unique sporangial position found in Psilotum and Tmesipteris.
Pattern of sporangial maturation: 0 = simple; 1 = gradate; 2 = mixed.
Sporangial stalk: 0 = absent; 1 = broad; 2 = narrow.
Length of sporangial stalk: 0 = sessile-short; 1 = long.
Megalastrum indusiatum is characterized by small indusia (about the size of a single sporangial capsule), non-bullate scales on the axes, glabrous tissue adaxially between the veins, and non-glandular axes abaxially (Fig.