- Lichen
is a symbiotic association of a photosynthetic organism and a
saprophytic fungus.
- The
photosynthetic organisms may be cyanobacteria (cyanobiont) or green
algae (phycobiont) and the fungi (mycobiont) may include group
Ascomycetes or Basidiomycetes
- Thy
algae or cyanobacteria conduct photosynthesis and provides glucose,
the fungal component provides water and nutrients.
Types
include:
1.
Crustose: Crust like hard on surface of trees, rocks.
2.
Foliose: Leaf-like and loosely attached.
3.
Fruticose: Perpendicular, Three dimensional.
- Lichens
are often indicators of air pollution.
- They
are sensitive to toxic air pollutants especially sulfur, nitrogen,
mercury. They are inhibited in pollutive areas, like in case of
acid rains.
- If in
an area, all three lichens types are visible- indicates good air
quality.
- Crustose and Foliose
indicate average air quality.
- Only
crustose will indicate pollutants and poor air quality.
- No
lichens indicate a high level of air pollution and toxic air
condition.
- Thus,
the disappearance of lichens from the neighborhood indicates
increased air pollution and is a reason for concern.