Which of the following groups of plants can be used as indicators of S02 pollution of air?

Lichens are widely recognized as effective bio-indicators for air quality monitoring [1]. They are particularly sensitive to sulfur dioxide (SO2) because they lack a protective cuticle and obtain their nutrients and water directly from the atmosphere [2]. When SO2 levels increase, the chlorophyll in lichens can be damaged, leading to their decline or disappearance in polluted areas [2]. This sensitivity makes them reliable early warning systems for detecting atmospheric pollution [2]. While some bryophytes like mosses can also be used as biomonitors for sulfur and metal uptake [1], lichens are the most classic and frequently cited example of SO2 indicators in ecological studies [2]. Other options like Mentha or ferns do not exhibit the same specific and extreme sensitivity to sulfur dioxide concentrations as lichens do.

Sources

1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > lndicators > p. 103
2. [2] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 8: Biodiversity > ki'4" ENV|RONMENT > p. 150