Question

Lichens indicate ${\mathrm{SO}}_2$ pollution because they

• A. grow faster than others
• B. flourish in ${\mathrm{SO}}_2$ rich environment
• C. show association between algae and fungi
• D. are sensitive to ${\mathrm{SO}}_2$

Answer 1

The correct option is D are sensitive to ${\mathrm{SO}}_2$

Lichens are formed by symbiotic relationship between algae or cyanobacteria and fungi. Lichens typically grow in harsh environments, but are sensitive to pollutants. Hence, they have been widely used as biological ${\mathrm{SO}}_2$ pollution indicator. Sulphur dioxide destroys the chlorophyll in the algal partner and photosynthesis is inhibited. Due to chlorophyll degradation, the colour of the lichen changes, also affecting its growth. This visual change in the lichen indicates pollution in the surrounding.