ECONNECTION
Lichen
by Karen Dusek

Two heads, as we all know, are often better than one. In the human world, we call working together for a common cause "teamwork," but in the plant world such special relationships fall under the heading of symbiosis.

One of the most common examples of a symbiotic relationship is lichen, a plant that most people who have ever seen a tree, rock, log or soil have likely encountered because lichen (pronounced "liken") is a tough little plant that can survive just about anywhere.

Various species have been found as high as the Himalayas, as far south as Antarctica, as far north as the Arctic tundra, in the desert and even under water in the ocean. It can take many forms, from long green hairy beards hanging from trees to stiff pale green spikes with bright red caps rising from the soil to bright orange wallpaper-like floweret's pressed against boulders.

Thought to have evolved about 400 million years ago when some algae was washed from the sea and ended up on the damp ground around on-shore lakes, lichen is composed of algal cells living within a fungus. The theory is that some fungi were already inhabiting the soil on earth, helping to decompose the remains of dead plants.

Algae, a green plant, can produce its own food from sunlight. Fungi cannot. But fungi do produce an acid that breaks down soil and rocks, releasing nutrients that they, and the plants around them, can use. Whether or not it was love at first sight, who knows, but somehow an alga and a fungus recognized their weaknesses and decided to join forces. The alga provided the food, the fungus offered structure that not only gave the alga shape but also prevented it from drying out, kept out detrimental ultra-violet sunlight, and stored their joint food and water supply. Today, there are more than 25,000 species that range from .04 inch to 6.5 feet in diameter.

Not only do the components of lichen get along well together, but they are also adventurous. Belonging to a segment of plant society known as pioneer species, they prefer to live where others have not ventured and where they do not have to compete for food and sunlight. Their ability to break down rocks and other substances helps pave the way for other organisms to grow, as do the nutrients left behind when they die, which may not happen for a long, l..o..n..g time since some species may live to be 4,500 years old.

Lichen can reproduce by several different means. If spores produced by the fungal partner meet up somewhere with the right type of algae, a new colony of lichen may spring up, but the likelihood of that happening are, botanists believe, fairly slim. To improve their chances of survival, they have developed more sure-fire ways of regenerating. In some, the wind helps to disperse small pieces or upper layers that break off, which will often grow where they are dropped. Other species form a powdery substance called soredia that is carried to new locations by the wind, rain, insects and small animals.

If you've ever walked a mile down the road you've probably seen all three of the different types of lichens: crustose (crusty), which grow flat against rocks and tree trunks; foliose (leaflike), which sometimes resemble a miniature head of pale lettuce; and fruticose (shrubby), which can look like landscaping material for a gnome home or like the hair of a goblin hanging from a tree. Even though a tree may be covered in lichen, it is probably not suffering because of it, since most lichens are not parasitic.

While reindeer and caribou in Lapland find reindeer lichen to their likin', most species are inedible by humans but lichens do contribute to human society in other ways. Scientists have discovered that more than 50 percent of the species that have been studied have "antibiotic properties," according to Kingsley R. Stern, author of Introductory Plant Biology (Wm. C. Brown Publishers, 1991). Kingsley noted that lichen antibiotics have been used in Europe to treat tuberculosis and skin problems. Lichens have also been used for centuries by cultures worldwide to make dyes and are used in the manufacture of litmus paper, soaps and perfumes.

One of the other important roles lichen plays is that of an indicator species. Because it is so sensitive to air pollution, it will often change color and even die when the air is unclean. According to Kingsley, they are so sensitive to sulphur dioxide that "it has been possible to calculate the amount of sulphur dioxide present in the air solely by mapping the occurrence or disappearance of certain lichens in a given area. Such studies have shown that some species of lichens have disappeared entirely from industrial areas and are now facing extinction due to air pollution." He adds that their sensitivity to nuclear radiation allowed them to be used to monitor radioactive contamination resulting when a satellite fell to earth.

So, humans, in their infinite wisdom, have once again figured out how to destroy a spunky little organism that has managed to survive for hundreds of millions of years. And just when you were beginning to like lichens! You, however, can become an air pollution detective, of sorts, by learning which species are most sensitive to different types of pollution and then keeping track of the lichen in your area. A great website shows you how; just go to mgd.nacse.org/hyperSQL/lichenland/html and then start exploring your neighborhood. You'll probably be amazed at what you find. Bring a friend - two heads are better than one.

You can email Karen at karen@lakeshoreguardian.com.