A podetium (plural: podetia) is the upright secondary

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 ''

Cladonia ''Cladonia'' is a genus of moss-like lichenized fungi in the family Cladoniaceae. They are the primary food source for reindeer/caribou. ''Cladonia'' species are of economic importance to reindeer-herders, such as the Sami in Scandinavia or th ...

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. It is a hollow stalk extending from the . Podetia can be pointed stalks, club like, cupped, or

branch A branch, also called a ramus in botany, is a stem that grows off from another stem, or when structures like veins in leaves are divided into smaller veins. History and etymology In Old English, there are numerous words for branch, includ ...

ed in shape and may or may not contain the

ascocarp An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. Ascoc ...

, the fruiting body, of the lichen. It is not considered part of the primary thallus as it is a fruiting structure for

reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. There are two forms of reproduction: Asexual reproduction, asexual and Sexual ...

. A lichen can be described as "podetiate" when it forms a podetium.

Structure and development

Podetia are unique expanded structures produced at the tips of the in ''Cladonia''. They are produced in three

sections Section, Sectioning, or Sectioned may refer to: Arts, entertainment and media * Section (music), a complete, but not independent, musical idea * Section (typography), a subdivision, especially of a chapter, in books and documents ** Section sig ...

of ''Cladonia'': true , podetia, and funnel-like structures. The development of podetia is highly variable, with growth rates depending on species and environmental conditions. Annual growth typically ranges from 1 to 15 mm. True scyphi are goblet-like structures that are closed or rarely secondarily perforated at the bottom. They usually produce numerous conidiomata along their margins and, later, apothecia or hymenial disks. Scyphi may also produce vegetative secondary branchlets from their margins or centers. Verticillate podetia feature centrally proliferating scyphi forming conspicuous configurations characteristic of many species in ''Cladonia'' sect. ''Cladonia''. Funnels, or open cups, are trumpet-like structures with a central opening at the tip or axis of the podetium.

Taxonomic significance

The configurations of podetia are highly variable, ranging from simple unbranched to complex, densely branched patterns, offering many useful taxonomic characters. Several branching patterns are recognized in ''Cladonia'': :*Dichotomous branching: One, two, three, or many branches produced from the same place :*Isotomous branching: Branches equal in length and thickness :*Anisotomous branching: Branches unequal in length and thickness In ''Cladonia'', "regular" branching patterns have been recognized, although in boreal species, regular branching correlates with seasonal climates. Species of ''Cladina'' normally ramify once a year, following a dominant pattern such as anisotomic trichotomy or isototomic tetrachotomy. The axis of the branching podetia is taxonomically useful. Open axils are perforated, either from the production of the first branches or in later development. Primary perforations differ from secondary ones that are mechanically produced by irregular growth.

References

{{reflist, refs= {{cite book , author-link=Teuvo Ahti , last=Ahti , first=Teuvo , year=2000 , title=Cladoniaceae , series=Flora Neotropic Monograph , volume=78 , location=Bronx, New York , publisher=New York Botanical Garden Press , isbn=978-0-89327-431-3 , pages=9–12 Fungal morphology and anatomy