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Tab will move on to the next part of the site rather than go through menu items. Is this a lichen or a moss growing on a tree trunk? Photo by Chad Merda. Most of us assume the fuzzy green stuff we see growing on tree trunks or rocks on the forest floor is moss. And while moss is a likely suspect, it could also be a lichen. So what's the difference between a moss and a lichen? Telling them apart can be difficult. It certainly doesn't help that some lichens have common names that include the word "moss," like reindeer moss, which is actually a lichen, according to 21st Century Parks.
Making it even more difficult: Lichens and mosses frequently grow in close proximity to one another, often even on the same object, said Angela Rafac, an interpretive naturalist at the Forest Preserve District's Four Rivers Environmental Education Center in Channahon. It's common to see both on the same tree trunk or rock. Both mosses and lichens are considered non-vascular plants, but only mosses are truly plants, according to the U.
Forest Service. Lichens aren't plants at all. Figure 1. This cross-section of a lichen thallus shows its various components. The upper cortex of fungal hyphae provides protection. Photosynthesis occurs in the algal zone. The medulla consists of fungal hyphae. The lower cortex also provides protection. The rhizines anchor the thallus to the substrate. In some ways, the symbiotic relationship between lichens and algae seems like a mutualism a relationship in which both organisms benefit.
The fungus can obtain photosynthates from the algae or cyanobacterium and the algae or cyanobacterium can grow in a drier environment than it could otherwise tolerate. However, most scientists consider this symbiotic relationship to be a controlled parasitism a relationship in which one organism benefits and the other is harmed because the photosynthetic organism grows less well than it would without the fungus.
It is important to note that such symbiotic interactions fall along a continuum between conflict and cooperation. Lichens are slow growing and can live for centuries. They have been used in foods and to extract chemicals as dyes or antimicrobial substances. Some are very sensitive to pollution and have been used as environmental indicators.
Lichens have a body called a thallus, an outer, tightly packed fungal layer called a cortex , and an inner, loosely packed fungal layer called a medulla Figure 1. Lichens use hyphal bundles called rhizines to attach to the substrate. Lichens are classified as fungi and the fungal partners belong to the Ascomycota and Basidiomycota. Lichens can also be grouped into types based on their morphology.
There are three major types of lichens, although other types exist as well. They can survive in salt water and in freshwater on their own, and in any environment when part of a lichen relationship. Although cyanobacteria are called blue-green algae, they are actually bacteria, and are part of the bacteria kingdom, Monera. The "blue" in the common name refers to the fact that they need to live in water, and "green algae" refers to their photosynthetic abilities, like green algae.
Peltigera britannica , dog-pelt lichen. Notice the bright green surface that is green algae showing through. Look closely and you will see dark spots.
Those spots are pockets of cyanobacteria. Photo by Karen Dillman, U. Isn't lichen that mossy stuff on rocks and trees? When people think of lichens, many of them think of them as a kind of moss. That could not be further from the truth.
Although moss and lichens are both called non-vascular plants, only mosses are plants. Mosses are included in a group of non-vascular plants called bryophytes. Mosses are believed to be the ancestors of the plants we see today, like trees, flowers, and ferns.
Lichens, on the other hand, are not similar in any way to mosses or other members of the plant kingdom. Cladina arbuscula , a lichen, is also known as reindeer moss.
In this picture, it is surrounded by real moss. This species is rare in Colorado. Photo by Gay Austin, U. Look closely at this moss. Notice how leaf-like it is.
The structures on top produce spores. They are the main mode of moss reproduction. Photo by Charles Peirce, Michigan Wildflowers. Although mosses are very primitive, they still have plant-like structures that look like and function like leaves, stems and roots. They have chloroplasts throughout their entire bodies and can photosynthesize from all sides of their structures.
Lichens, on the other hand, are completely different. They do not have any roots, stems or leaves and their chloroplasts are contained only in the algae on the top surface of the lichen.
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