Scientists used to think of plants as generally defenseless against herbivores. Research now shows that plants use a complex variety of chemical defenses. When a tomato, potato, or alfalfa leaf is wounded by a chewing insect or by other mechanical means, a chemical message travels rapidly throughout the plant. In response to this message, the plant produces and accumulates substances that inhibit digestion in the alimentary canal of the animal that eats the leaf. These wound-induced molecules function as inhibitors of trypsin, one type of enzyme involved in protein digestion.
In laboratory experiments, these wound-induced inhibitors had serious effects on animals. Because they could not break down ingested protein, chicks fed the inhibitors died, and rats and mice became malnourished. The growth period of insect larvae was prolonged, allowing diseases and predators to kill a greater number of the larvae.
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2007-11-29
13:31:44
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katiekcat5
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