A new study finds that plants communicate with one another to warn of danger.
We often consider plants as the furniture of the natural world. They don’t move; they don’t make sounds, they don’t seem to act on anything. But as is often the case, plants talk to each other all the time. And the language is chemical.
Over the years, scientists have reported that different types of plants, from trees to tomatoes, give out chemicals into the air to help neighboring plants. These chemical warnings can spread information about one plant’s disease or infestation(虫害), so other plants can protect themselves. But how plants receive and act on many of the information exactly is still mysterious.
In this week’s Science Magazine, researchers in Japan offered some explanations. They have found out one chemical message and traced it all the way from beginning to end.
The scientists looked at tomato plants infested by a common pest(害虫). To start out, they grew plants in two separate plastic spaces connected by a tube(管子). One plant was infested and placed upwind and the other was uninfested and placed downwind. The downwind plants were later exposed(暴露) to the pest. The results showed that plants near sick neighbors before were able to protect themselves better against the pest.
They found one chemical appeared more often in the exposed plants. The chemical is called HexVic. The scientists discovered where HexVic come from, and put it over healthy plants. Those plants were then able to produce HexVic. Researchers made sure that uninfested plants could fight off bugs and diseases. How do they know when to protect themselves? They are warned first by their friendly plant neighbors.
It is not a simple story, and it may be happening in more plant species than tomatoes. It may also be happening with more chemical signals that are still unknown to us. In a word, we know that plants not only communicate, but also look out for one another.
The underlined “traced” in the fourth paragraph probably means _________ here.
| A．reported | B．followed |
| C．doubted | D．developed |
For scientists, which are the right steps to watch tomato plants infested by a pest?
① Place the infested plant upwind.
② Place the uninfested plant downwind.
③ Expose the downwind plants to the pest.
④ Grow plants in two separate plastic spaces connected by a tube.
| A．③①②④ | B．①④③② |
| C．④①②③ | D．④②①③ |
You can put the sentence “The researches also studied leaves from exposed plants and unexposed plants.” At the beginning of
| A．Paragraph 3 | B．Paragraph 4 |
| C．Paragraph 5 | D．Paragraph 6 |
Which of the following can be the best title of this passage?
| A．Communicating Plants and Terrible Diseases |
| B．Talking Plants and Friendly Warnings |
| C．Protecting Plants and Clear Information |
| D．Growing Plants and Mysterious Chemicals |
What do people do with their old, out-of-date but still useful computers? Most people don’t know what to do with them. Many old computers are put away in homes. Many more are simply thrown out with the rubbish.
Finally, some companies are thinking of ways to bring down the number of old computers. Sony has agreed to help recycle old Sony products（产品）. Dell, Hewlett-Packard and other companies now also take back some old computers.
In some countries, laws（法规）are being passed, too. Computer companies will have to pay for collecting and recycling their used products. And 70% of computer waste must be recycled. The idea behind the laws is that computer companies themselves should pay the cost. That will encourage them to make computers that are easier and cheaper to repair and upgrade（升级）.
Yet while many people are throwing away good computers, others cannot afford them at all. Hundreds of organizations（组织）are working to solve this problem. They collect and repair old computers. Some also teach others how to repair computers.
The computers then go to schools, charities（慈善团体）and people who need them. Giving a used computer to one of these organizations can turn one person’s rubbish into someone else’s useful things—and cut down on waste, too.What do many people do with old computers?
| A．They repair them. | B．They sell them. |
| C．They send them to others. | D．They stop using them. |
How many computer companies are mentioned in the second paragraph？
| A．One. | B．Two. | C．Three. | D．Four. |
According tothe laws in some countries, computer companies must .
| A．collect and recycle most of their products | B．collect all their used products |
| C．repair and upgrade old computers | D．make more cheaper computers |
What do the organizations do to solve the problem of old computers?
| A．Help the computer companies to collect them. |
| B．Repair and send them to those who need them. |
| C．Help people to learn to use them. |
| D．Turn rubbish into useful things. |
What is the main idea of this passage?
| A．Repairing old computers. | B．Encouraging to make cheap computers |
| C．Recycling old computers. | D．Helping those who need computers. |
粤公网安备 44130202000953号