Lichen morphology

Add links
Source: Wikipedia, the free encyclopedia.
Further information: Lichen growth forms and Lichen anatomy and physiology
Caperat lichen Flavoparmelia caperata (Parmelia caperata) on a branch of a tree
Xanthoria parietina Common orange lichen
Crustose lichens on a wall

Lichen morphology describes the external appearance and structures of a lichen. These can vary considerably from species to species. Lichen growth forms are used to group lichens by "vegetative" thallus types, and forms of "non-vegetative" reproductive parts. Some lichen thalli have the aspect of leaves (foliose lichens); others cover the substrate like a crust (crustose lichens) (illustration, right), others such as the genus Ramalina adopt shrubby forms (fruticose lichens), and there are gelatinous lichens such as the genus Collema.[1]

Although the form of a lichen is determined by the genetic material of the fungal partner, association with a photobiont is required for the development of that form. When grown in the laboratory in the absence of its photobiont, a lichen fungus develops as an undifferentiated mass of hyphae. If combined with its photobiont under appropriate conditions, its characteristic form emerges, in the process called morphogenesis.[2] In a few remarkable cases, a single lichen fungus can develop into two very different lichen forms when associating with either a green algal or a cyanobacterial symbiont. Quite naturally, these alternative forms were at first considered to be different species, until they were found growing in a conjoined manner.

Under magnification, a section through a typical foliose lichen

rhizines, which serve to attach the thallus to the substrate on which it grows. Lichens also sometimes contain structures made from fungal metabolites, for example crustose lichens sometimes have a polysaccharide
layer in the cortex. Although each lichen thallus generally appears homogeneous, some evidence seems to suggest that the fungal component may consist of more than one genetic individual of that species. This seems to also be true of the photobiont species involved.

Reproductive structures

A

apothecia
or both.

References

  1. ISBN 0-916422-33-X
    .
  2. ^ Brodo, Sharnoff & Sharnoff, 2001
  3. ^ a b Büdel, B.; Scheidegger, C. (1996). "Thallus morphology and anatomy". Lichen Biology: 37–64.
  4. ^ a b Alan Silverside's Lichen Glossary (p-z), Alan Silverside
Retrieved from "https://en.wikipedia.org/w/index.php?title=Lichen_morphology&oldid=1165954431"