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
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