A lichen is a living association, not a single plant
A lichen combines a fungus with a photosynthetic partner, usually an alga or a cyanobacterium. The partner supplies products of photosynthesis, while the fungus provides much of the structure and a protected setting. Lichens can also contain other microbes, making the familiar patch more complex than it first appears.
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Partners form a distinctive body
The main body of a lichen is largely organised by a fungus. Within it lives a photosynthetic partner that captures light energy and supplies carbon compounds.
This close association produces forms that differ from the partners growing separately. Lichens may appear crust-like, leafy or branching, but they are not mosses or ordinary plants.
The partnership helps define the organism's visible form. Its performance still depends on water, light, temperature and the abilities of the partners involved.
- The fungus builds much of the structure.
- The photosynthetic partner supplies fixed carbon.
- Additional microbes may also be present.
Many lichens tolerate drying and resume activity when water returns. Tolerance varies, so their presence on exposed surfaces does not mean every lichen can survive any harsh environment.