Question

Lichens are ecologically important, because:
1. They are associated with mycorrhizal roots
2. They are association of algae and fungi
3. They are pioneers (earliest settlers on barren rocks) and pass xeric conditions successfully
4. They can grow in greatly polluted area

Answer 1

Correct Answer - Option 3 : They are pioneers (earliest settlers on barren rocks) and pass xeric conditions successfully

Concept:

• The sequential, gradual, and predictable changes in the species composition in an area are called succession or ecological succession.
• The entire sequence of communities that successively changes in a given area is called sere(s).
• The individual transitional communities are termed as seral stages or seral communities.
• The community that is in near equilibrium with the environment is called a climax community.
• The species that invade a bare area are called pioneer species.​

Explanation:

• Lichen is the symbiotic association of fungi and algae
• Lichens are ecologically very important as they are the pioneer species on a bare area or Xerarch condition.
• The lichen secretes some acids to dissolve rock and help in weathering and soil formation.
• Later, some small bryophytes invade and hold a small amount of soil.
• The bryophytes are succeded by herbs, shrubs, and ultimately big trees.
• At last, a stable climax forest is formed.
• The xerophytic habitat gets converted into a mesophytic one

 

• Lichens are good indicators of air pollution. 
• Lichens are sensitive to SO2 (sulphur dioxide). They die in more concentration of SO2. Therefore they are not found in those areas (polluted areas) where the concentration of SO2 is high

• Mycorrhizae is a symbiotic association between a fungus and roots of higher plants. The term mycorrhiza refers to the role of the fungus in the plant’s rhizosphere, its root system.
• Mycorrhizal fungi allow plants to draw more nutrients and water from the soil. They also increase plant tolerance to different environmental stresses. They play a major role in the soil aggregation process and stimulate microbial activity.