Lichen: The Organism That Looks Like a Plant, But Isn’t

By Deb Drain

When you are out and about, and you see rocks that have orange, grey, black, or green stuff on them that looks like a plant, but not quite like a plant, do you wonder what it is?  If so, the answer is lichen, a truly amazing organism.  Although it may resemble a plant, it is actually an organism composed of algae or cyanobacteria, fungi, and yeast that co-exist in a mutually beneficial relationship.  Like a plant, algae or cyanobacteria can photosynthesize.  The algae or cyanobacteria provide nutrients from photosynthesis to the fungus.  The fungus provides minerals and water that it accesses from the atmosphere or its substrate to the cyanobacteria/algae.  This relationship allows each lichen partner to survive in extreme habitats, like a rock surface.

Lichen on a rock
Lichen attached to a rock

There are approximately 20,000 species of lichen worldwide and they come in all shapes, colors, and sizes.  Lichens occur in almost every habitat and geographic area and are some of the oldest organisms on the planet.  They reproduce either asexually, a piece breaks off and establishes itself on a substrate, or sexually through spores.  They have a very slow growth rate, up to 0.08 inches in diameter/year.  The lichen photo was taken in Island Park and shows several lichen species sharing the same rock.  

Lichens may look fragile, but they are tough organisms.  Lichens survive severe drought; they completely dehydrate and return to normal when water becomes available.  They also withstand direct exposure to the extreme temperatures and cosmic radiation of space (European Space Agency studies).  What they cannot survive are air pollutants.  Because lichens don’t have roots, the air is the primary source of elements lichen need for growth.  Air pollutant accumulation can stress or kill lichen.  Consequently, they have been used to monitor air quality since 1859.  

Next time you see these amazing little organisms, give them a shout-out!  

Deb resides in Island Park and never tires of nature. For further information on Lichens, she recommends Merlin Sheldrake’s book Entangled Life: How Fungi Make Our Worlds, Change Our Minds, and Shape Our Futures.