Lichens

Pl P 421/521General Mycology

DefinitionsLichen

An association between a fungus and a photosynthetic partnerMycobiont

The fungal partner in a lichenPhotobiont

The photosynthetic partner in a lichen; either a green alga or cyanobacterium

Mycobionts >13,500 species of

lichens recognized Make up 20% of all

known fungal taxa

Most mycobionts are either zygomycetes or ascomucetes Relatively few

basidiomycetes

http://www.kki.pl/zenit/grzyby_spyt

Photobionts Only approx. 10% of

lichens have a cyanobacterium photobiont The other 90% are

algae Photobiont/mycobiont

interface is wall-to-wall (abut each other) or intracellular (fungus invades cell wall of algae)

Lichen thalli (body) Unique form that bears no resemblance to non-

lichenized alga or fungus Slow-growing

most grow <1mm/year, maximum of 4 cm/year Growth favored by high humidity, cool temps and low

light Long-lived

Reach maturity at 4-8 years Alpine-arctic lichens may be 1000-4500 years old Longevity attributable to ability to withstand drought

periods of several months Able to absorb up 300% of its weight in water when

available

Types of lichens Non-stratified

Photobiont cells evenly distributed throughout thallus

Leptogium

Collema

Types of lichens Stratified

Differentiated into cortex (upper only, or upper and lower) and medulla

Cortex is made up of individual fungal cells

Medulla is a dense fungal mycellium

Photobiont cells form a discrete layer just under upper cortex

Foliose lichens - Flattened, leaf-like thallus with an upper and lower cortex

Peltigera elizabethae

Leprose lichens – aka dust lichens - Lack both upper and lower cortex, medulla attached directly to substrate

Lobaria pulmonaria--Lungwort

http://www.mcelroy.ca/bushlog/images/10a-4329.jpg

Crustose lichens - Lacking a lower cortex, attached to soil, rock or bark by hyphae of the medulla

XanthoparmeliaUmbilicaria

How are lichens used? Nesting/bedding, food

source for animals Source of dyes

litmus paper Woolens such as Harris

tweed Essential oils for

perfumes, soaps Oakmoss (Evernia)

Medicines—antiviral and antibacterial Up to 50% of all lichens

believed to have antibiotic properties

Distribution Worldwide, in some of the most extreme

environments, from the Arctic to Antarctic, deserts to tropics

Occur on soil, plants, animals, on or in rock, and on man-made structures

Mainly in rural areas rather than cities Lichens are intolerant of atmospheric pollution,

particularly sulphur dioxide

Lichens as pioneers Typically one of first vegetation to inhabit

a new environment Occurs if there is new land due to volcanic

eruption or large scale fire damage Begins on rock formation or loose soil

The basic nature of lichens allows them to easily attach to rocks and soil

Able to break down rocks to obtain some nutrients As more rocks are broken down by lichens, more

dominant plant species are able to take over the environment

Lichens as components of soil crusts

Images from www.soilcrust.org