AskDefine | Define sorus

Dictionary Definition



1 a spore-producing structure in certain lichens and fungi
2 cluster of sporangia usually on underside of a fern frond [also: sori (pl)]

User Contributed Dictionary



  1. Any reproductive structure, in some lichens and fungi that produces spores
  2. A cluster of sporangia on the edge or underside of a fern frond

Extensive Definition

Sori redirects here. For the commune in Italy, see Sori, Italy.
In ferns, a sorus (pl. sori'') is a yellowish or brownish cluster of sporangia on the edge or underside of a fertile frond. In some species, they are protected during development by a scale or film of tissue called the indusium, which forms an umbrella-like cover.
Sori occur on the sporophyte generation, the sporangia within producing haploid meiospores. As the sporongia mature, the indusium shrivels so that spore release is unimpeded. The sporangia then burst and release the spores.
The shape, arrangement, and location of the sori are often valuable clues in the identification of fern taxa. Sori may be circular or linear. They may be arranged in rows, either parallel or oblique to the costa, or randomly. Their location may be marginal or set away from the margin on the frond lamina. The presence or absence of indusium is also used to identify fern taxa.
In fungi and lichens, a sorus is a cluster of sporangia surrounded by an external layer.


References and external links

sorus in German: Sorus
sorus in Spanish: Soro
sorus in Persian: هاگینه
sorus in French: Sore (botanique)
sorus in Dutch: Sporenhoopje
sorus in Polish: Sori (botanika)
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