Q1.
Have you ever seen white-green patches on the tree trunk, damp walls or stones? What do you think about these patches? Visit a village and talk to an elderly person about these patches.
Answer
Those patches are lichens — and both the village elder and the researcher read them the same way: as a sign of clean air.
What a lichen actually is: not one organism but two, living in a symbiotic (mutual) association — one partner is an autotrophic alga, the other a heterotrophic fungus. The fungus provides protection and holds water; the alga photosynthesises and provides food. Neither could occupy a bare rock or a dry tree trunk alone.
Why they work as pollution meters: a lichen has no roots and no waxy cuticle. It takes everything it needs — water and minerals — straight out of the air across its whole surface. Whatever the air carries goes in with it, including sulphur dioxide and other pollutants, which the lichen cannot exclude or excrete. So it accumulates what the air contains. Lichens change their colour with air pollutants, and researchers use that colour to work out the concentration of pollutants in the air. This makes them natural bioindicators for the measurement of air quality.
What the elder is likely to tell you (this is the part of the activity you must actually do — the notes below are what such conversations usually contain):
- The patches mean the air here is clean; where there is smoke or a factory, they disappear.
- Some kinds, commonly called patthar ke phool, are collected as forest produce and used as a spice.
- Some are used as medicines.
- Since ancient times some have been used to make dyes giving maroon, violet or burgundy colour to woollen and silk fabrics.
Caution — and the reason classification matters: some lichens are poisonous. Identifying them properly is not an academic exercise; it decides whether a collected lichen goes into food or into a dye pot. That is precisely why the box ends by insisting they be classified and identified correctly for safe and proper utilisation.
Sample answer for your notebook: "I spoke to Shri Ram Singh of our village. He showed me grey-green crusts on the neem trunk near the well and said they grow only where the air is good; he remembers them vanishing from the trees along the road after the brick kiln started. His family collects a leafy kind called patthar ke phool from the hill for use in masala. He warned that not every patch on a rock is the same thing and that only some can be eaten."