Shades of Green: Earth's Forests -- Plants

Thorns on the stems of a wild rose bush. Photo by Maya Walters.

The soft green leaves of most plants are an ideal food source for many vegetarian creatures. Most plants suffer at least some damage from leaf-eating animals, and occasionally extreme pest outbreaks can occur. To help prevent complete defoliation, plants have evolved defenses to protect themselves from hungry insects. Some plants discourage herbivores by growing sharp-edged, spiny leaves. The thistle is one example of a plant that will remain untouched in a field after a herd of grazing animals have passed through.

Though relatively low in energy, leaves are an important food source for many animals. Photo by Maya Walters.

But the majority of foliage damage is the responsibility of insects, which are small enough to walk around thorns and not be bothered by sharp-edged leaves. It is for this reason that plants have evolved chemical defenses. We avoid poison ivy because of the plant's chemical defense--it contains oils which are responsible for the skin irritation it causes. Stinging nettles "sting" because, when disturbed, the plant's tiny hairs give off an irritating acid.

Flowers can be found on all kinds of plants, even trees which have such inconspicuous blooms they often go un-noticed. While some plants depend on wind to move pollen from one flower to another, insects are much more reliable pollinators. Many insects depend on flowers for their nectar, just as the flowers depend on insects for pollination.
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plants -- page 4 of 5
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sub-topics
[bark, wood, roots, & leaves] [flowers & pollen] [seeds, nuts, & fruit]

related topics
[insects] [camouflage & chemical defenses]

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