Which of the following is indicator of air pollution ?

Lichens are widely recognized as effective bioindicators of air pollution, particularly for levels of sulfur dioxide (SO2). They are symbiotic organisms consisting of a fungus and an alga or cyanobacterium. Unlike vascular plants, lichens lack a protective cuticle and roots, meaning they absorb water and nutrients directly from the atmosphere.

This characteristic makes them extremely sensitive to atmospheric pollutants. When air is heavily polluted with SO2, many lichen species cannot survive. Therefore, the diversity and health of lichen populations in an area provide a reliable measure of air quality. While some mosses can also indicate pollution, lichens are the primary biological tool used for this purpose in environmental science. Puffballs (fungi) and most algae do not serve as specific indicators for general air pollution in the same capacity.