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What is Lichen?

By S. Mithra
Updated Mar 05, 2024
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When an alga and fungus physically intertwine in a very close symbiotic relationship, they actually form an entirely new growth called lichen. Lichen is a kind of primitive plant species that's nothing more than strands of alga linked with roots and branches of a fungus that together absorb minerals from the ground and conduct photosynthesis. They can grow almost anywhere, from moist bark to recently cooled lava to frozen rocks.

Unlike most parasitic or symbiotic relationships, when a fungus and alga grow together so tightly they can't be separated, they qualify as a different kind of material. Biologists have agreed that lichen straddles the monera and fungi kingdoms of living things since it is part one and part another. Its body, called a thallus, can be made of different types of fungi and blue-green algae, which will determine how much water it needs or to what it can attach.

The alga, called the physobiont, contains chlorophyll, so it can photosynthesize energy that it passes onto the fungus. The mycobiant, the fungus, has roots that leech minerals and water from rocks or plants that it, in turn, passes onto the alga. This allows the new growth to thrive in a greater diversity of climates than either algae or fungi do alone. It can even dry out during drought and reconstitute itself when the rains come.

Three major types of lichen grow into different shapes on various substrates. Crustose grows into unique flat plates that look like mushrooms. Foliose looks leafier, with small, green lobes, and grows in wetter climates beside moss. Lichen that resembles viney clumps hanging from branches is usually fruticose. It can be found in rainforests on partially rotting logs, in arctic regions on rocks, or cliffsides near salty ocean spray.

Lichen is not just a peculiar, uncategorizable kind of living matter; people use it for practical purposes, too. Since it's very sensitive to pollution, especially sulfur dioxide, environmentalists use it's presence as a gauge of the cleanliness of the air. Dyes and medicine can be extracted from them as well, and virtually every plant and animal relies on their slow erosion of wood and rock to replenish the topsoil with nutrients.

Frequently Asked Questions

What exactly is lichen?

Lichen is a complex life form that is a symbiotic partnership between a fungus and an alga or a cyanobacterium. The fungus provides structure and protection, while the photosynthetic partner produces nutrients through photosynthesis. This unique combination allows lichens to thrive in diverse and extreme environments, from arctic tundras to arid deserts.

How does lichen reproduce?

Lichens can reproduce both sexually and asexually. Sexually, the fungal partner produces spores that must encounter compatible algal cells to form new lichens. Asexually, lichens can propagate through fragmentation or by producing structures called soredia or isidia, which are small clusters of algal cells surrounded by fungal filaments, ready to grow as new lichens when dispersed.

Where can lichen be found?

Lichens are incredibly adaptable and can be found in almost every ecosystem on Earth. They grow on a variety of surfaces, including rocks, soil, tree bark, and even man-made structures. According to research, there are over 20,000 known species of lichens, each adapted to specific environmental conditions, from tropical rainforests to polar ice caps.

Is lichen important to the environment?

Yes, lichens play several crucial roles in the environment. They are pioneer species that initiate soil formation by breaking down rocks. Lichens also serve as indicators of air quality since they are sensitive to air pollution. Furthermore, they provide food and habitat for various organisms, contributing to biodiversity in many ecosystems.

Can lichens be used by humans?

Historically, humans have used lichens for various purposes. Some species are used in traditional medicine, while others have been utilized as natural dyes. Lichens are also important in the perfume industry for their fixative properties. Additionally, they are studied for potential antibiotic compounds and are used in ecological research as bioindicators.

How do lichens contribute to scientific research?

Lichens are valuable to scientific research in many ways. They are used as bioindicators to monitor environmental changes, including air quality and climate change. Their resilience to extreme conditions also makes them subjects for studying adaptation and survival strategies. Moreover, lichens are being investigated for their unique chemical compounds, which may have pharmaceutical applications.

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Discussion Comments

By anon218048 — On Sep 27, 2011

How do you get rid of this Lichen?

By kmcteer — On Feb 07, 2010

The azaleas have not changed much. Still scrawny. I am glad I have good air, I only wish my roadside hedge were taller! I have not tried to remove the lichen.

By anon63941 — On Feb 04, 2010

Kmcteer: That is a good question. Well, what is the answer?

By kmcteer — On Jul 14, 2008

I have some azaleas with branches covered with lichen. Is it hurting the plants? It is unsightly, and the plants do not seem to be thriving. (This may not be due to the lichen, but if it is, what can I do to remove it from the plant without damaging the plant?

By heather2571 — On May 19, 2008

Why would Lichen be an ingredient in a deodorant? What benefit does it have?

By jonas032972 — On Oct 05, 2007

How can you distinguish the fungus from the algae when observing the lichen?

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