Sporangium


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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 ?
The sporophyte consists of a basal foot, setum or connective stalk supporting a single sporangium or capsule.
The last sporangium has spores significantly smaller than the other two, and, interestingly, a mixture of spores from the UAE specimen (not taken from individual sporangia) had a bimodal size distribution, with some spores larger (~63 um), darker, and more strongly and evenly tetragonal than the others (which were ~49 um in diameter, more transparent, and irregularly shaped).
Each sporangium contains up to 20 endospores that are released on rupture.
Sporangium wall whitish (unpigmented); megaspores with honeycomb-like ridges (reticulate); plant aquatic (submerged or emergent), usually not associated with rock outcrops I.
The PIBs are known to be coformed during sporulation within the sporangium or spore-mother cell, but exact details concerning molecular and cellular events in their formation and maturation have not been obtained.
The sporangium is usually covered by a hairy calyptra (caplike spore case covering) that is yellowish or light brown.
Therefore, to evaluate synchrony in spore release in Pterygophora, we measured weekly changes in sporangium density during the reproductive seasons of 1991 and 1993.
However, the application of criteria, morphological features such as sporangium formation in submerged liquid culture and chemical composition of certain cell constituents (such as cell wall) in the characterization of these a typical isolates is therefore not sufficient to identify these isolates as members of the genus Streptomyces.
In the tissues, the organism forms characteristic abundant, large thick walled sporangium like structures containing large number of endospores.
They are unique in that the partially dependent sporophyte has an intercalary meristem at the base of the sporangium (Fig.
1 [micro]M - Spor shape-circular - Wollen sporangium - Anaerob growth + Voges proskauer - 8/6: PH Growth at nutrient broth pH + 7/5: PH wth at nutrient broth pH + Strach hydrolysis - Gelatin hyarolysis + Nitrate reduction - Growth at 40 c + Growth at 50 c + Utilization of: Citrate + D(+)Glucose + L-Arabinose + D-Xylose + D-Mannitol + Table 8: Used tests to identifing Pseudomonas fluorescens (Shaad et al.