Tree communication is the ability that trees can actively defend themselves
against serious insect attacks by either producing unsavory chemicals or poisons
to fight back the insects or communicating a warning to other trees in the
vicinity. In other words, trees cannot only protect themselves from insects
attack, but also communicate with each another by sending off warning gases when
attacked by insects, in order to trigger the defenses of neighbors.
Now hear a talk on the same subject The professor gives
an example to explain how willow trees protect each other through tree
communication. Explain how this example is related to the reading passage.
【正确答案】topic (reading)
The lecture is mainly on the point that by sending airborne signals, trees can communicate and defend each other. The professor sets willow trees as an example to explain this phenomenon.
example
In 1979, in order to prove the above viewpoint, a researcher conducted an experiment in which caterpillars bit one group of trees while the other group was free from such danger.
Later, they found that the trees eaten by caterpillars released poisons which keep caterpillars away. But what surprised them more was that the uneaten group of trees also released the same poisons. So the researcher came to a conclusion that the second group released such poisons after receiving some airborne signals delivered by the first group.
【答案解析】[听力原文]
W: Much like any other living organism, survival for trees is very important. Believe it or not, trees are also able to communicate with each other, in order to defend themselves against insects like caterpillars, even though they make no sounds or have no noses or eyes. Let me show you an example to further prove the theory.
In the spring of 1979 a zoologist Rhoades in U. S. took two groups of willow trees, and he infested one with caterpillars, and left the other alone as a control. Two weeks later, he took some leaves from the trees which had been infested and bit by caterpillars. To his surprise, he found that these caterpillars grew quite slowly because of a kind of poisonous chemical released from the willow trees. Another surprising finding was that the leaves of another group without caterpillars also produced such posion. Both groups of trees had apparently flooded their leaves with an unfavorable chemical that discouraged the insects' growth. Rhoades concluded that the attacked trees had conveyed to the other group a danger signal, and this must have been done by releasing a chemical into the air.