Fall is full of colorful wonders of nature

By Sue Pike

We live in a colorful world. Leaves contain green and yellow pigments that capture light energy from the sun and turn it into food for the rest of us (photosynthesis).

Flowers use various colors to attract pollinating insects.

Some animals use colorful patterns as camouflage; other animals use color to attract mates or advertise their reproductive fitness, and other animals use vibrant colors to warn predators they are poisonous.

We have such varied, colorful displays of foliage in the fall because, as trees begin to shut down in preparation for our cold, dry and winter conditions, the green photosynthetic pigment, chlorophyll, is broken down, unmasking yellow, orange and red pigments. The yellow and orange pigments help leaves absorb more wavelengths of light than they would using only green pigments. The function of some of the red pigments is under debate; they might act as sunscreen or as bug repellents, or both.

Mushrooms, which are neither plants nor animals, also can be quite colorful — red, orange, yellow, violet, blue and brown. Unlike pigments used by plants and animals, the purpose of these colors is not often obvious or well understood. For example, it was suggested that the color of the poisonous fly agaric mushroom, bright red, might be a warning that it is toxic. One recent study addressed this by studying whether some toxic mushrooms deter fungivores (animals that eat fungi) with warning coloration. No correlation between mushroom color and toxicity was found. Some mushrooms use insects to disperse their spores, so an attractive color might attract insects just as colorful flowers attract pollinating insects. However, even this is unclear as there is debate as to whether mushrooms actually do use insects to disperse spores.

Many fungi contain the pigment melanin, the same pigment that your skin uses to give you a tan. A study of fungi in the area around Chernobyl (site of the 1984 nuclear power plant meltdown) has found that black fungi (melanin-containing fungi) gravitate toward the ionizing radiation in the contaminated soil; the darker fungi grow better in contaminated soil than melanin-free fungi. In fact, melanin-containing fungi are a common contaminant of the radioactive water in many commercial nuclear reactors.

How does this pigment help fungi in the natural world, one not contaminated with radioactive waste? Melanin is known to provide protection from the sun, melanin soaks up ultraviolet rays, acting as a sun block as it absorbs destructive ultraviolet light and turns it into heat. This is thought to be the most likely explanation for the presence of melanin in fungi. Another interesting, but much more highly debated theory, suggests that dark fungi use melanin to absorb radiation and somehow turn it into useful energy — just as plants use chlorophyll to capture energy from the sun. This theory is hotly contested by many scientists, but wouldn't it be neat if mushrooms can supplement the energy they get through decomposing organic matter with a little help from the sun?

For the time being, the chemistry of fungi is poorly understood. They are certainly one of our oddest relations (fungi are more closely related, biochemically, to humans than plants are).

As the recent spate of hurricanes bring warmish, wet weather our way, take a walk and look for these colorful mysteries of nature.

Sue Pike of York has worked as a researcher and a teacher in biology, marine biology and environmental science for years. She teaches at York County Community College and St. Thomas Aquinas High School. She may be reached at spike3@maine.rr.com.