Have you ever wondered why the roots of the plants always know which way to grow
题型：不详难度：来源：
Have you ever wondered why the roots of the plants always know which way to grow—into the soil but not above it? Some British scientists have recently solved this mystery.
It turns out that roots have special hairs that tie them into the soil and help them grow their way past obstacles, a team at the John Inners Center in Norwich reports in the February 29 issue of Journal Science.
“The key is in the fuzzy(有绒毛的)coat of hairs on the roots of plants,” says professor Liam Dolan. “We have found a growth control system that enables these hairs to find their way and to become longer when their path is clear.”
Root hairs explore the soil in much the same way a person would feel their way in the dark. If they come across an obstacle, they make their way around until they can continue growing in an opening. In the meantime, the plant is held in place as the hairs grip(紧紧抓住)the soil.
The hairs are guided by a clever chemical trick. A protein(蛋白质) at the tip of the root hairs called RHD2 helps them to take calcium(钙) from the soil. Calcium makes the hairs grow, and produce more RHD2, and take more calcium.
But when an obstacle blocks the hair’s path, or the hair reaches the surface of the soil, the cycle is broken and growth starts in another direction.
This system gives plants the flexibility to explore a complex environment and to live in even the most unpromising soils, says Dolan.
In poor soils such as in parts of Australia and Africa, native plants have adapted by producing enormous numbers of root hairs. A better understanding of this adaptation will allow scientists to develop hairy rooted crops that can grow in unfriendly environments.
According to Dolan, “Research in the John Inners Center is taking a breeding approach to increase hair length in wheat but it will be some time before new cultivars(栽培变种) are developed.”
小题1:The passage is mainly about _______.| A．why the roots of plants grow into the soil but not above it | | B．how the roots of plants grow into the soil but not above it | | C．the process of plants growth | | D．a growth control system of plants |
小题2:How does the circle work?| A．RHD2 takes calcium from the soil, which makes hairs grow, and produce RHD2 and take more calcium | | B．Roots take RHD2 and calcium from the soil and produce RHD2 | | C．Roots make hairs grow, and produce RHD2, and take more calcium | | D．RHD2 takes protein, which makes hairs grow, and produce RHD2, and take more calcium |
小题3:We can infer from the last paragraph that ________.| A．hairy rooted crops can grow better in unfriendly environments | | B．a new cultivar of wheat with long hair has been developed by scientists | | C．a new cultivar of wheat with long hair is still on test | | D．the roots of plants always know which way to grow |
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答案
小题1:A
小题2:A
小题3:C |
解析
小题1:主旨大意题。结合文章的主题句第一段的why the roots of the plants always know which way to grow—into the soil but not above it? Some British scientists have recently solved this mystery可知答案。
小题2:细节理解题。结合A protein(蛋白质) at the tip of the root hairs called RHD2 helps them to take calcium(钙) from the soil. Calcium makes the hairs grow, and produce more RHD2, and take more calcium. 可知答案。
小题3:推理判断题。结合it will be some time before new cultivars(栽培变种) are developed. 可知答案。 |
举一反三
Even at school there had been an unhealthy competition between George and Richard.
“I’ll be the first millionaire in Coleford!” Richard used to boast.
“And you’ll be sorry that you knew me,” George would reply “because I’ll surely be the best lawyer in our town!”
After graduation, George never became a lawyer and Richard was anybody but a millionaire …. Instead, it happened that both men opened bookshops on opposite sides of Coleford High Street, while it was hard to make much money from books then, which made the competition between them worse. Eventually, Richard closed down his, dreaming of making a fortune elsewhere.
Now, with only one bookshop in the town, business was better for George. But sometimes he sat in his narrow old kitchen and gazed out of the dirty window, thinking about his former rival (竞争对手)。Perhaps he missed him?
George was very interested in old dictionaries, and he had recently found a collector in Australia who was selling a rare first edition. When the parcel arrived, the book was in perfect condition and George was quite delighted. But while he was having lunch, George glanced at the photo in the newspaper that the book had been wrapped in. He was astonished — the smiling face was older than he remembered but unmistakable! Trembling, George started reading: “Bookends Company has bought ten bookstores from its competitors. The company, owned by multi-millionaire Richard Pike, is now the largest bookseller in this country.”
小题1:George and Richard were at school. | A．roommates | B．good friends | C．competitors | D．booksellers |
小题2:How did George feel about Richard after his disappearance? | A．He envied Richard’s good fortune very much. | | B．He thought about Richard from time to time. | | C．He felt unlucky with no more rival in the town. | | D．He was unhappy of Richard’s disappearance. |
小题3:George got information about Richard from . | A．a dictionary collector in Australia | | B．one of Richard’s competitors | | C．some rare edition of a dictionary | | D．the wrapping paper of a book |
小题4:What happened to George and Richard in the end? | A．Both George and Richard became millionaires by selling books. | | B．Both of them realized their original ambitions, which were the same. | | C．George established a successful business while Richard was missing. | | D．Richard became a millionaire while George had no great success. |
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Plants can’t communicate by moving or making sounds, as most animals do. Instead, plants produce volatile compounds (挥发性化合物) —— chemicals that easily change from a liquid to a gas. A flower’s sweet smell, for example, comes from such volatile compounds to attract insects such as bugs and bees.
Plants can also discover volatile compounds produced by other plants. A tree under attack by hungry insets, for instance, may give off these chemicals in order to let other trees know about the attack. In response, the other trees may send off their chemicals to keep the bugs away —— or even chemicals that will attract the bugs’ natural enemies.
Now scientists have created a quick way to understand what plants are saying: a chemical sensor (传感器) called an “electronic nose”. The “e-nose” can tell such compounds as plants make. When plants are attacked, scientists say, the e-nose could help quickly decide whether plants are being eaten by insects. But today, the only way to spot such insects is to inspect individual plants by observing them. This is a challenging task for managers of greenhouses, including those that can house thousands of plants. The research team is working with an e-nose that can recognize volatile compounds. Inside the device, 13 sensors chemically react with volatile compounds based on the interactions (相互作用), and then the e-nose will give off electronic signals that the scientists can analyze by using computer software.
To test the e-nose, the team presented it with healthy leaves from cucumber, pepper and tomato plants, all being common greenhouse crops. Then scientists collected samples of the air around damaged leaves from each type of crop. These plants had been damaged either by insects or by scientists who made holes in the leaves with a hole punch (打孔器).
The e-nose, it turns out, can identify healthy cucumber, pepper and tomato plants based on the volatile compounds they produce. It could also identify tomato leaves that had been damaged. But even more impressive, the device could tell which type of damage —— by insects or with a hole punch —— had been done to the tomato leaves.
With some fine-tuning (微调), a device like the e-nose can one day be used in greenhouses to quickly spot harmful bugs, the researchers say. A device like this can also be used to identify fruits that are perfectly ripe and ready to pick and eat, says Natalia Dudareva, a biochemist at Purdue University in West Lafayette, India, who studies smells of flowers and plants. Hopefully, scientists believe, the device can bring large benefits to greenhouse managers in the near future.
小题1:We learn from the text that plants communicate with each other by ______.| A．making some sounds | | B．waving their leaves | | C．producing some chemicals | | D．sending out electronic signals |
小题2:What did the scientists do to find out if the e-nose worked?| A．They fixed 13 sensors inside the device. | | B．They presented it with all common crops. | | C．They collected different damaged leaves. | | D．They do tests on damaged and healthy leaves. |
小题3:According to the writer, the most amazing thing about the e-nose is that it can ______.| A．pick out ripe fruits quite expertly | | B．spot the insects in a very quick way | | C．tell different damages to leaves | | D．recognize unhealthy tomato leaves |
小题4:We can infer from the last paragraph that the e-nose ______.| A．is unable to tell the smell of flowers | | B．is not yet tested in greenhouses | | C．is designed by scientists at Purdue | | D．is helpful in killing harmful insects |
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Due to the increasing number of violence acts produced in schools all over the world，more and more parents prefer to have their children educated at home rather than at school. This way they can assure their safety and well-being，although teachers and school representatives are trying to improve the situation in schools by increasing the number of the persons in charge with the safety of the students．
The main reason for violence acts are the films and cartoons that fill the children’s time．They want to do everything．they watch on TV and never think at the consequences，and they may hurt a classmate or a teacher．
On the other hand, parents are not fully satisfied with the children’s results obtained in classes and they consider private classes would have better results．
When a teacher has to watch 30 students in class he can’t probably see what each of them is doing，how he is writing，or if he understands the explanations．At home the teacher can explain in details everything the child doesn’t understand as many times as he considers proper．
And many times．the child grows fond of the teacher at home，who becomes his best friend，and who helps him whenever he needs someone to talk to．
However, the best solution would be a mixture between the education received at school and that at home，because school makes children communicate and socialize．Keeping a child at home for fear there might happen something bad to him．only makes the child’s character weak and prevents him from knowing what real life is．Staying in a crystal ball only does harm to the child．
All in all．schools have been created to help children，not to harm them，so it’s best to keep children in these special places，where they learn，laugh，have fun and make new friends．
小题1:The writer’s purpose in writing the text is to ．| A．teach parents the ways to keep theft children safe | | B．show solutions to developing children’s character | | C．explain the main reason for violence acts in schools | | D．analyze an education problem and give opinions |
小题2:Parents prefer to have their children educated at home because the following EXCEPT that______.| A．More and more violence acts occur in schools | | B．Parents want to improve their Children"s grades | | C．Parents are concerned about their children’s safety | | D．The education system is far from satisfactory |
小题3:What does“a crystal ball”in the passage refer to?| A．A toy that can be used for entertainment． | | B．A safe and comfortable environment． | | C．An object that is made of crystal． | | D．A setback that is hard to overcome． |
小题4:We call infer from the passage that ．| A．violence TV programs have bad effects on children’s behavior | | B．The teacher at home is more patient than the teacher at school | | C．Children today are weak from lack of sense of right and wrong | | D．There are too many students in class for a teacher to teach |
小题5:Which of the following might be the best title of the passage?| A．Advantages and Disadvantages of Private Classes | | B．Who is to Blame, Parents or Schools? | | C．Which is Better, School Study or Home Study | | D．The Relationship between Teachers and Children |
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Let children learn to judge their own work. A child learning to talk does not learn by being corrected all the time; if corrected too much, he will stop talking. He notices a thousand times a day the difference between the language he uses and the language those around him use. Bit by bit, he makes the necessary changes to make his language like other people’s. In the same way, children learn to do all the other things without being taught to walk, run, climb, whistle, ride a bicycle…They compare their own performances with those of more skilled people, and slowly make the needed changes. But in school we never give a child a chance to find out his mistakes and correct them for himself. We do it all for him. We act as if we thought that he would never notice a mistake. If it is a matter in mathematics or science, give him the answer book. Let him correct his own papers. Why should we teachers waste time in such routine(日常的) work? Our job should be to help the child when he tells us that he can’t find the way to get the right answer. Let the children learn what all educated persons must some day learn, how to measure their own understanding, how to know what he does not know.
小题1:According to the passage, the best way for children to learn things is by_____.| A．listening to skilled people’s advice. | | B．asking older people many questions | | C．making mistakes and having them corrected | | D．doing what other people do |
小题2:Which of the following does the writer think teachers should NOT do?.| A．Give children correct answers | | B．Allow children to mark mistakes. | | C．Point out children’s mistakes to them. | | D．Let children mark their own work |
小题3:According to the writer, teachers in school should _____| A．allow children to learn from each other | | B．point out children’s mistakes whenever found | | C．correct children’s mistakes as soon as possible | | D．give children more book knowledge |
小题4:The passage suggests that learning to speak and learning to ride a bicycle are____| A．different from learning other skills | | B．the same as learning skills | | C．more important than other skills | | D．not really important skills |
小题5:The title of this passage could probably be_____| A．Let Us Teachers Stop Work | | B．Let Us Make Children Learn | | C．Let Children Correct Their Exercises | | D．Let Children Learn by Themselves |
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Does this sound familiar? It’s 3:00 am and you’re still awake and staring at the clock. You can’t sleep , and you’ve already tried all the familiar tricks – taken a warm bath , drunk a glass of heated milk ,tried counting sheep, and read a book –all with no success. If you are such a sufferer, remember you’re not alone. Experts said that one in every four Americans have trouble falling or staying asleep.
Lack of sleep can hurt your quality of life in so many ways. Short temper, impatience, poor decision-making, and mood swings are common among those with sleeping problems. Besides, relationships with family, friends, and co-workers may suffer as a result. Improper sleep can also put your safety at risk by reducing your awareness.
When you’re awake in the middle of the night, you can start to feel desperate for a way out . However, it makes sense to weigh the available treatments before choosing the one that’s right for you. Other sleep aids may seem like a quick fix, but it turns out that there are many disadvantages of these drugs. For one thing, they may require expensive, time-consuming trips to your physician. They may also be habit-forming or have unpleasant side effects like dizziness( 眩晕) dry mouth, and next-day sleepiness. Plus , they become less effective over time.
So what is the best sleep aid available on the market today? The answer is Somnapure , a product that represents nature and science coming together. This all-natural sleep aid which comes from Peak Life allows you to fall asleep quickly and remain asleep through the night . With Somnapure, you wake up feeling refreshed and energetic. Somnapure is currently giving away a 14-day trial here. Get your Somnapure trial for better, deeper sleep that you deserve.
小题1:From paragraph 1, we can know that sleep problems are_______.| A．easy to make a sufferer lonely | | B．common but hard to deal with | | C．severe throughout the world | | D．widespread only in the USA |
小题2:The underlined words“ a quick fix”(in paragraph3)most probably means____.| A．a waste of money | B．a quick repair | C．an easy way out | D．a cheap aid |
小题3:The purpose of the passage is to _______.| A．ask people with sleep problems to try and use Somnapure | | B．introduce a kind of medicine to help sleep better | | C．draw people’s attention to the bad effects of the lack of sleep | | D．talk about what the main causes of the sleep problems are |
小题4:We can infer that the passage is probably immediately followed by information about ______. | A．the instructions to take Somnapure | | B．the side effects of Somnapure | | C．the price of Somnapure | | D．the way to get Somnapure |
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