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(有絨毛的)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(緊緊抓住)the soil.
The hairs are guided by a clever chemical trick. A protein(蛋白質(zhì)) at the tip of the root hairs called RHD2 helps them to take calcium(鈣) 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(栽培變種) are developed.”
小題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(chǎn) growth control system of plants
小題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
小題3:We can infer from the last paragraph that ________.
A．hairy rooted crops can grow better in unfriendly environments
B．a(chǎn) new cultivar of wheat with long hair has been developed by scientists
C．a(chǎn) new cultivar of wheat with long hair is still on test
D．the roots of plants always know which way to grow

小題1:A
小題2:A
小題3:C

小題1:主旨大意題。結(jié)合文章的主題句第一段的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。
小題2:細(xì)節(jié)理解題。結(jié)合A protein(蛋白質(zhì)) at the tip of the root hairs called RHD2 helps them to take calcium(鈣) from the soil. Calcium makes the hairs grow, and produce more RHD2, and take more calcium. 可知答案。
小題3:推理判斷題。結(jié)合it will be some time before new cultivars(栽培變種) are developed. 可知答案。
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科目：高中英語(yǔ) 來(lái)源：不詳 題型：閱讀理解

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As I understand, if scientists produced a human clone, there would be a great risk of it having a disease. Nobody seems to understand the ageing process of a clone. It would be terrible if a baby was the age of its parent at     31   . Its cells would grow old fast and it would die young.    32    until the technique is perfectly safe, it should be     33   .
I'd love to have a clone of     34   . I often wish I had a twin sister, someone who    35   me in everything. So why not a clone? Well, the idea    36   be fun but I'm not sure if it would be     37   . I think we would be playing with fire if we let scientists go ahead with     38   cloning. There are so many     39   
involved that all research in this area should be strictly controlled.
There are so many arguments     40    cloning that it is difficult to get anyone to consider the possible benefits. I am     41    that it is a technique which could be beneficial. The most obvious use would be for childless     42   . They would be able to have babies with their own genetic material. I don't see what's wrong with that.
Imagine a child     43    up knowing that his or her mother is really a sister or a brother. The emotional     44    on the child would be     45   . Or a child who was cloned from a dead brother or sister. What kind of emotional pressure would they feel, knowing they were made as a replacement for another? The whole idea
    46    me!
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小題1:
A．home B．lab C．process D．birth
小題2:
A．Besides B．Therefore C．Although D．Unless
小題3:
A．banned B．a(chǎn)llowed C．encouraged D．forced
小題4:
A．itself B．herself C．myself D．yourself
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A．overlookedB．contradicted C．a(chǎn)ccumulatedD．resembled
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A．may B．must C．can D．shall
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A．messy B．safe C．swift D．a(chǎn)wkward
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A．human B．a(chǎn)nimal C．plant D．pet
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A．a(chǎn)gainst B．with C．for D．a(chǎn)mid
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A．vanished B．convinced C．violated D．teased
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One report published earlier this year said that 5 percent to 10 percent of the population likely will experience Internet addiction (上癮).
It said signs include a disregard for health or appearance, lack of sleep and reducing physical activities and social communications with others, as well as dry eyes and juries of hands and fingers.
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B．how surfing the net has caused a bad result to people
C．why to throw off the Internet addiction becomes a hot problem
D．why so many adults want to spend less time on the interact
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