I have always been fascinated by lichen‚ the colorful symbiotic organisms that attach themselves to rocks. Lichen is considered a composite life form, comprised of both green algae and fungi.
The algae utilizes photosynthesis to produce food for the fungus which in turn provides water and protects the algae. This elaborate interdependence creates a structure that is more durable than either organism in isolation. Interestingly, fungus is thought to control the relationship, which is why some describe lichen as a “fungi that discovered agriculture.”
There are over 14,000 species of lichen that exist globally and, along with bacteria, they are considered to be among the oldest forms of life on the planet. Lichen thrives in wet environments; however, it is found throughout the desert southwest and can continue to produce food at any temperature above freezing.
Lichen absorbs water directly into its cells from the air—the moisture does not have to pass through roots or stems like most plants. By gathering all it needs from the atmosphere, scientists use lichen as a reliable indicator of clean air.
In the desert, lichen seeks out shade and produces much needed nitrogen for surrounding plants—creating productive microclimates. While most species are green, the colors produced by lichen are astonishing. The pigments in these organisms vary due to light exposure, genetics and age. Colors range from grey, blue and green to bright yellow, orange and red. The explosive displays of color, form and texture are surprising and inspiring—rivaling any trip to a museum.