A sorus (pl. sori) is a cluster of

sporangia A sporangium (; from Late Latin, ) 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 lineages form sporangia at some point in their life cyc ...

(structures producing and containing

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

s) in

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...

s and

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

. A coenosorus (plural coenosori) is a compound sorus composed of multiple, fused sori.

Etymology

This

New Latin New Latin (also called Neo-Latin or Modern Latin) is the revival of Literary Latin used in original, scholarly, and scientific works since about 1500. Modern scholarly and technical nomenclature, such as in zoological and botanical taxonomy ...

word is from

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

σωρός (''sōrós'' 'stack, pile, heap').

Structure

In lichens and other fungi, the sorus is surrounded by an external layer. In some red algae, it may take the form of depression into the thallus. In ferns, the sori form a yellowish or brownish mass on the edge or underside of a fertile

frond A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...

. In some species, they are protected during development by a scale or film of tissue called the indusium, which forms an umbrella-like cover.

Lifecycle significance

Sori occur on the

sporophyte A sporophyte () is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase. Life cycle The sporophyte develops from the zygote pr ...

generation, the sporangia within producing haploid meio

s. As the sporangia mature, the indusium shrivels so that spore release is unimpeded. The sporangia then burst and release the spores.

As an aid to identification

The shape, arrangement, and location of the sori are often valuable clues in the identification of fern

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

. 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.

Gallery

Image:Сорус папоротника Polypodium aureum.jpg, Sorus of ''

Phlebodium aureum ''Phlebodium aureum'' (golden polypody, golden serpent fern, cabbage palm fern, gold-foot fern, blue-star fern, hare-foot fern; syn. ''Polypodium aureum'', ''Polypodium leucotomos'') is an epiphytic fern native to tropical and subtropical regio ...

'' Image:Scattered-sori.jpg, Scattered sori Image:Linear sori.jpg, Linear sori Image:Dense sori.jpg, Sori covering a frond's entire underside ( acrostichoid) Image:Immature sorus.jpg, Fern sorus with immature sporangia Image:Round sori.jpg, Circular sori with mature sporangia Image:Rumohra adiantiformis sori 01.jpg, Sori with indusia at different stages of development. File:Triphragmium ulmariae, Meadowsweet Rust.jpg, Fungal sori of the

Meadowsweet Rust gall ''Triphragmium ulmariae'' is a species of rust fungus in the family Sphaerophragmiaceae. It causes meadowsweet rust gall, which develops as a chemically induced swelling, arising from the lower surface of the meadowsweet (''Filipendula ulmaria' ...

. File:Large Sori (fern).JPG, Large sori File:Polypodium vulgare, sores (Matthieu Gauvain).JPG, ''Polypodium vulgare'' File:Sword fern sori, scale bar 1 mm.tif, Sword fern. The indusia have opened, revealing the sporangia. Scale bar, 1 mm

References and external links