Lichen and Moss: The Pioneers That Survive Without Soil

1.1 What is a lichen made of?

A lichen is made of a fungus and a photosynthetic partner living together. The partner is an alga or a cyanobacterium. Photosynthesis means making food from sunlight. Most of the lichen is fungal filaments, with the algal cells living among them. The two form one body, called a thallus.

1.2 Why do the two partners stay together?

They stay together because each gets something it lacks. Fungi need carbon as food, and the photosynthetic partner supplies it. The fungus builds the body that holds the partnership together. The partner also seems to get good living conditions inside it.

• About 90% of lichens have a green alga as the partner.
• About 98% of lichen fungi are cup fungi, called ascomycetes.
• In some lichens the fungus cannot survive without its partner.

1.3 Is a lichen one organism?

No, because a lichen is a partnership of at least two organisms. The fungus also looks quite different inside a lichen than it does alone. ESA even calls lichens very simple ecosystems.

Scientists still debate whether the deal is a true mutualism, where both gain, or a controlled parasitism.

2.1 What is a moss?

A moss is a small green plant with no true roots and no vascular tissue. Vascular tissue means the tubes that carry water in larger plants. Mosses belong to the bryophytes, which people commonly call non-vascular plants.

2.2 Why are rhizoids not true roots?

They are not true roots because they mainly hold the moss in place. They do not take in most of its water. Rhizoids are strands at the base. They grip soil, rock or even roof tiles. The moss absorbs water directly through its leaflike parts.

Without a true root system, moss mats are easy to rip from a tree trunk.

2.3 Why do mosses need damp places?

They need damp places because their sperm must swim to the egg. Moss sperm have flagella, tail-like threads. Fertilisation therefore depends on water. More than 25,000 bryophyte species live mostly in damp habitats, though some live in deserts.

Ferns also have flagellated sperm. So ferns, too, depend on water for fertilisation.

3.1 How can a lichen grow on bare rock?

It can grow there because it takes water and nutrients mainly from the air, not from soil. It also pulls minerals out of the rock itself. To do that, it releases organic acids.

3.2 How do lichens weather rock with chemistry?

They release organic acids that can dissolve the rock’s structure. The main acid is oxalic acid. Some lichens use simpler acids, such as citric acid.

3.3 How do lichens break rock by force?

They break it by pushing into it and by swelling. Fungal threads, called hyphae, enter between mineral grains. The lichen body also expands when wet and shrinks when dry. Over time that wedges the rock apart.

3.4 Why does this matter for soil?

It matters because weathered rock is one of the first steps in soil development. One review says that at least some lichens speed up mineral weathering. It describes both physical and chemical effects.

4.1 What is primary succession?

It is the way life first settles on bare ground where nothing grew before. Plant succession means the development of plant communities over time. At Glacier Bay in Alaska, a retreating glacier left the land bare, and plants returned step by step.

4.2 Why do lichens and moss come first?

They come first because they can live where there is no soil. Lichens attack the rock. Moss then colonises glacial till, the loose material a glacier leaves. That paves the way for the plants that follow.

4.3 How long has this been studied?

Since 1916. That year Dr. William Skinner Cooper set up study plots in Glacier Bay. It is now the longest running plant succession study in the world.

5.1 What are the three lichen shapes?

Lichens are grouped by growth form, which means body shape. There are three main forms.

• Crustose. It forms a crust, with the bottom firmly attached to the surface.
• Foliose. It is flat and leaf-like, with a different top and bottom.
• Fruticose. It is bush or hair-like. It has no clear upper or lower side. It stands up or hangs down.

5.2 Why is a crustose lichen hard to lift off?

It is hard to lift off because its bottom is firmly attached to the surface. It grows as a crust on the rock or bark. A foliose lichen has different top and bottom sides instead.

5.3 Which shape is most common in India?

Crustose is the most common in the Eastern Himalaya. A review there counted 1,047 species. Of these, 592 were crustose, 321 foliose, 125 fruticose and 9 squamulose.

India has about 2,540 known lichen species. The 1,047 in the Eastern Himalaya are about 41% of them.

Sources: North Carolina Division of Air Quality; Eastern Himalaya lichen review. A fourth form, squamulose, had 9 species.

6.1 Why can lichens date a rock?

They can date a rock because some crustose lichens grow very slowly and live almost everywhere. If a species’ growth rate is known, its size can estimate the surface’s age. This method is called lichenometry. It assumes lichens settled right after the rock was exposed.

6.2 How fast do they grow?

Growth is slow and differs from place to place. In southern Iceland the mean was 0.64 mm a year between 2001 and 2005. Growth was 66% greater at the maximum in north Wales.

Below 0.2 mm a year, as in parts of Greenland and Antarctica, the growth curve is almost flat.

6.3 Why is age from size not exact?

It is not exact because growth speed changes with size. It rises in lichens under 10 mm across, stays near 0.8 mm a year, and falls above 50 mm. Studies that assume constant growth over many decades are probably unreliable.

Some lichens are over 1,000 years old.

7.1 What did the LICHENS experiment test?

It tested whether lichens can survive in open space. The European Space Agency (ESA) ran it on the Foton-M2 mission, launched on 31 May 2005. The lichens were Rhizocarpon geographicum and Xanthoria elegans.

7.2 What did the lichens face?

They faced vacuum, wide temperature swings, the full spectrum of solar UV light and cosmic radiation. UV means ultraviolet. The exposure lasted a total of 14.6 days before the lichens returned to Earth.

7.3 What was the result?

The lichens survived. ESA reported a full rate of survival and an unchanged ability for photosynthesis. ESA also noted that a lichen is multicellular and a eukaryote, so it is much more modern on the evolutionary scale than bacteria.

8.1 Why are lichens good air monitors?

They are good monitors because they take water and nutrients mainly from the air. Pollutants in air and rain reach them directly. A bioindicator is a living thing that responds in a clear way to a change in the environment.

Lichens also bind toxic elements and radioactive metals in their fungal threads. They concentrate these over time.

8.2 Why does sulphur dioxide harm lichens?

It harms them because it forms acids in moisture. Sulphur dioxide comes from burning coal and diesel fuel. It combines with moisture to form sulphurous or sulphuric acid, and acid rain.

In 1975 Rose calculated that more than one-third of England and Wales had lost nearly all its epiphytic lichens. These are delicate shrubby lichens that live on plants. Coal-burning power plants were largely to blame.

8.3 Does the surface a lichen grows on matter?

Yes, because the surface changes how strongly acid hits the lichen. An alkaline surface, such as basic bark or limestone, counteracts the acidity of the pollution. The first loss of pH-sensitive lichens happens on birches and conifers. One growth form is often replaced by a more tolerant one.

8.4 How small a rise in pollution is enough?

Even a small rise can matter. A small rise in sulphur dioxide levels can cause a decline in lichen diversity.

9.1 What did the 2026 study find?

It found five new species of the genus Allographa in the Western Ghats. Allographa is a genus of script lichens, in the family Graphidaceae. It has more than 200 species. The team was from MACS Agharkar Research Institute, Pune, an autonomous institute of the Department of Science and Technology.

9.2 Why was the study new?

It was new because it was the first comprehensive molecular phylogenetic investigation of Allographa species from the Western Ghats. Molecular phylogenetics compares genetic material to work out family relationships.

9.3 Which species were named?

Five species were named.

• Allographa keralensis, named after the state of Kerala.
• Allographa nayakae, honouring lichenologist Dr. Sanjeeva Nayaka.
• Allographa paraconsanguinea.
• Allographa persistinspersa.
• Allographa semicarbonisata.

9.4 Why do such finds matter for forests?

They matter because lichen-forming fungi indicate forest health and environmental quality. They are sensitive to pollution and habitat change.

10.1 What did UPSC ask?

10.2 Why are lichen and moss the answer?

They are the answer because both can live on bare surfaces. A lichen takes water and nutrients mainly from the air and pulls minerals from rock. A moss absorbs water through its leaves. Its rhizoids only anchor it. The question says most likely, so pick the typical cases.

Ferns are vascular plants that mostly occupy moist habitats. A mushroom is a fungus’s fruiting body, not a whole organism. The official key marks only options 2 and 3.

10.3 Which mix-ups come up?

• Lichen as one organism. It is a fungus plus a photosynthetic partner.
• Rhizoids as roots. They mainly anchor the moss.
• No soil means no water. Moss still absorbs water and needs it to reproduce.
• Crustose lichen. Its bottom is firmly attached to the surface.