It’s a sound you will probably never hear, a sickened tree sending out a distress signal. But a group of scientists has heard the cries, and they think some insects also hear the trees and are drawn to them like vulture to a dying animal. Researchers with the US Department of Agriculture’s Forest Service fastened sensors to the bark of drought-stricken trees clearly heard distress calls. According to one of the scientists, most parched trees transmit their plight in the 50-hertz to 50-kilohertz range. (The unaided human ear can detect no more than 20 kilohertz). Red oak, maple, white pine, and birch all make slightly different sounds in the form of vibrations at the surface of the wood.

The scientists think that the vibrations are created when the water columns inside tubes that run along the length of the tree break, a result of too little water following through them. These fractured columns send out distinctive vibration pattems. Because some insects communicate at ultrasonic frequencies, they may pick up the trees' vibration and attack the weakened trees. Researchers are now running tests with potted trees that have been deprived of water to see if the sound is what attracts the insects. “Water-stressed trees also smell differently from other trees, and they experience thermal changes, so insects could be responding to something other than sound”, one scientist said.

It can be inferred from the passage that the sounds produced by the trees ...............

Câu hỏi liên quan

• The man mentioned in the passage, who used his cell phone too often, ...........

• The word “metamorphosis” in paragraph 2 is closest in meaning to_________.

• The word formulaic is closest in meaning to___________.

ZUNIA12

• The word “they” in paragraph 3 refer to ...........

• What is the meaning of “waterproof” in the second paragraph?

• The underlined word “they” in paragraph 2 refers to ..........

• The word "tragedy" in the third paragraph mostly means ........

• What is the main topic of the passage?

• What is the main idea of this passage?

• According to the passage, an exuberant tone of voice may be an indication of a person’s ............

• When does television encourage people to read?

• The word “tolls” in paragraph 4 is closest in meaning to which of the following?

• According to the passage, writing ...............

• Why does the author of the passage mention the report of the President’s Science Advisory Committee (lines 14-15) ?

• The word "they" in the last paragraph refers to ...............

• What is the Pareto principle?

• This article is about ________.

• The word “advantage” in the last paragraph most closely means ...........

• The word "frustrating" in paragraph 7 is closest in meaning to ______.

• It can be inferred from the passage that a soil sample with little or no clay in it ______.