Question

Lichens indicate SO2 pollution because they
(1) Show association between algae and fungi
(2) Grow faster than others
(3) Are sensitive to SO2
(4) Flourish in SO2 rich environment

Answer 1

Are sensitive to SO2

Answer 2

Lichens indicate SO₂ pollution because they (3) Are sensitive to SO₂

Lichens are used as SO₂ pollution indicators because Lichens are sensitive to sulfur dioxide(SO₂) as their efficient absorption systems result in rapid accumulation of sulfur when exposed to high levels of sulfur dioxide pollution. The algal partner seems to be most affected by the sulfur dioxide; chlorophyll is destroyed and photosynthesis is inhibited.