The hygroscopic nature of lichen also does not allow them to survive highly polluted environments. This is because they will also absorb the toxins from the atmosphere into their systems. The toxins will then affect their growth, negatively.
Explanation:
Lichen is one pioneer species in primary succession. They have undefined roots hence do not require soil and can grow on rocks and break them down slowly by chemical weathering (using excreted organic acids). More so lichen does not need to absorb nutrient via roots because the organism is a symbiotic relationship between fungi and algae. The algae can use photosynthesis to manufacture food while the fungi complex hyphae that surround the algae can absorb water & nutrients from the air due to their high hygroscopic nature.
