A sorus (: sori) is a cluster of

sporangia A sporangium (from Late Latin, ; : sporangia) is an enclosure in which spores are formed. It can be composed of a unicellular organism, single cell or can be multicellular organism, multicellular. Virtually all plants, fungus, fungi, and many ot ...

(structures producing and containing

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

s) in

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

s and

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

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

Etymology

This

Neo-Latin Neo-LatinSidwell, Keith ''Classical Latin-Medieval Latin-Neo Latin'' in ; others, throughout. (also known as New Latin and Modern Latin) is the style of written Latin used in original literary, scholarly, and scientific works, first in Italy d ...

word is from

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

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

Structure

lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...

s 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 Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...

. 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 (: indusia), which forms an umbrella-like cover.

Life cycle significance

Sori occur on the

sporophyte A sporophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the biological life cycle, life cycles of plants and algae. It is a diploid multicellular organism which produces asexual Spo ...

generation, the sporangia within producing

haploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Here ''sets of chromosomes'' refers to the num ...

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''; : 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 name and ...

. 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'' 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. 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