04 January 2009

Plants Can Send Warning Signals

Scientists have discovered that some plants can send signals to warn their defense system about attacking insects. The scientists studied what happens when an insect eats leaf on a tomato plant. They found that the lead sends electrical signals to other leaves. Undamaged leaves begin producing defensive chemicals. The insect eats these chemicals when it attacks another leaf on the same plant. These chemicals harm the insect’s digestive enzymes which makes difficult for the insect to get the food it needs.

A team of scientists from Britain and New Zealand say the study shows that plants are like animals in some ways. However, the scientists say that the newly discovered signals are not exactly the same as the signals that an animal sends to warn it of danger. Animals send signals very quickly through their nerves. This permits an animal to flee when threatened by another animal. Plants send warning signals much more slowly.

The new study showed that leaves produce defense molecules when an electrical signal passes from a damaged leaf. Leaves do not produce defense molecules when the electrical signal is blocked. Scientists know that some unusual plants use electrical signal to move their leaves. For example, the Venus flytrap plant catches insects by closing its leaves around them.

Scientists, however, do not know which cells in a plant produce the electrical signals. And they do not know exactly how an insect feeding on a leave causes the electrical signals. They think a leaf’s cells lose water and tension when they are crushed by an insect. This seems to cause chemical changes in the leaf. The changes produced electrically charged particles that move from cell to cell to warn other leaves of the attack.

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