题目内容

【题目】植物生长素具有低浓度时促进生长、高浓度时抑制生长的特性。以下哪一现象或应用不能说明生长素调节具有“两重性”

A.在自然状况下,大型乔木的树冠多呈圆锥形

B.被大风刮倒的树木,其露出地面的根总是向地生长

C.置于窗台上的盆栽植物总是朝窗外生长

D.棉花的顶芽比侧芽生长快

【答案】C

【解析】在自然状况下,大型乔木的顶端产生较多的生长素,生长素高,由于顶端向下运输,导致侧芽处的生长素浓度升高,离顶端越近的芽生长素的浓度越高,这种高浓度的生长素抑制了侧芽的生长,而顶芽处则由于生长素向下运输,生长素的浓度较低,所以生长的较快,使树冠多呈圆锥形,A错误;由于重力作用,生长素横向运输,使刮倒的树木露出地面的根处近地侧生长素浓度高,远地侧浓度低;又根对生长素浓度最敏感,低浓度促进生长,高浓度抑制生长,所以根总是向地生长能说明生长素调节具有“两重性”,B错误;置于窗台上的盆栽植物,由于单侧光的影响,背光的一侧生长素浓度高,促进作用大,生长快,所以总是朝窗外生长,只体现了促进作用,C正确;顶端优势中,顶芽优先生长,侧芽的生长受抑制,说明生长素调节具有“两重性”,D正确。

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相关题目

【题目】 [1] Jean Paul Getty was born in 1892 in Minneapolis, Minnesota. He became a millionaire when he was only 24. His father was wealthy, but he did not help his son. Getty made his millions alone. He made his money from oil. He owned Getty Oil and over 100 other companies. The Fortune magazine once called Getty “the richest man in the world.”

[2]But money_________. He married five times and divorced five times. He had five children but spent little time with them. None of Getty’s children had very happy lives.

[3]Getty loved to make money and loved to save it. In spite of his great wealth, Getty was miser. Every evening, he wrote down every cent he spent that day. He even put pay telephone in the guest’s bedrooms in his house so he could save money on phone bills.

[4] In 1973, kidnappers took his 16-year-old grandson, and demanded a large amount of money for his safe return. Getty’s son asked his father for money to save his child. But Getty refused. The kidnappers were merciless and Getty’s son made repeated requests for help from his father. Finally, Getty agreed to lend the money, but at 4 percent interest.

[5] Getty started a museum at his home Malibu, California. He bought many important and beautiful pieces of art for the museum. When Getty died in 1976, the value of the collection in the museum was $1 billion. He left all his money to the museum. After his death, the museum grew in size. Today it is one of the most important museums in the United States. Getty made a large fortune in his life, but he gave his money to the art world because he wanted people to learn about and love art.

【1】 What is the main idea of Paragraph 1? (no more than 8 words)

_____________________________________________________________________

【2】 Fill in the blank in Paragraph 2 with proper words. (no more than 7 words)

_____________________________________________________________________

【3】 Explain the underlined sentence in Paragraph3.

_____________________________________________________________________

【4】 What did the kidnappers do to Getty’s family. (no more than 10 words)

_____________________________________________________________________

【5】What does the author want to tell us about Getty in the last paragraph? (no more than 10 words)

_____________________________________________________________________

【题目】A

Americans like to travel on their yearly holiday. Today, more and more travellers in the United States are spending nights at small houses or inns(客栈) instead of hotels. They get a room for the night and the breakfast the next morning.

Rooms for the night in private(私人的) homes with breakfast have been popular with travellers in Europe for many years.In the past five or ten years, these bed-and-breakfast places have become popular in the United States. Many of these Americas bed-and-breakfast inns are old historic buildings. Some bed-and-breakfast inns have only a few rooms, while others are much larger. Some inns do not provide telephones or televisions in the rooms; others do.

Staying at a bed-and-breakfast inn is much different from staying at a hotel. Usually the cost is much less. Staying at an inn is almost like visiting someones home. The owners are glad to tell about the areas and the interesting places to visit. Many vacationers say that they enjoy the chance to meet local families.

【】Americans take a holiday trip ___________.

A. all the year round B. for years

C. every year D. every other year

【】According to the passage, which of the following is NOT true?

A. Some Americans like to stay at bed-and-breakfast homes instead of at hotels.

B. The bed-and-breakfast inns are private homes opened to vacationers.

C. The bed-and-breakfast inns have been popular in America for a long time.

D. The bed-and-breakfast inn owners provide a morning meal for their visitors and a room for the night.

【】Staying at the bed-and-breakfast inns, ___________.

A. the travellers neednt pay anything

B. the travellers dont have to pay for the telephone or television

C. the travellers can meet and talk with the local people

D. the owners will show the travellers around the area

【】 Which is TRUE according to the passage?

A. European and American vacationers like staying at bed-and-breakfast inns.

B. All Americans enjoy travelling.

C. These bed-and-breakfast inns are all old historic buildings.

D. Staying at a bed-and-breakfast inn is just like at the travellers home.

【题目】七选五

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

Make home a happier place to be

Sometimes, kids don’t think their parents are fair to them. When you want to dress in a modern way, your mum doesn’t approve of what you’re wearing. When you are making phone calls to friends, they ask if you’re speaking to a boy or a girl. Sometimes, it seems that you’re not at close to your parents as you used to be. 1

Closing the Gap, by American author Jay McGraw, gives advice on how to have a better relationship with your parents. 2 When you think “my parents don’t want me to have any fun, that usually means your parents want you to be safe. 3 They need to feel they are important and loved. You should tell your parents your needs, and find out what their needs are. Then, you can think of a way to make all of you happy. The book gives you some ideas.

4 You could talk about your school life and your plans for the future.

Keep a diary. This is t help you understand more about yourself and your feelings.

Show your parents you are growing up. Wash your own clothes and help around the house. 5

If you follow these steps, slowly, you will be able to break down the walls between your parents and yourself.

A. Make time to talk.

B. Here are some suggestions.

C. How can you become close again?

D. Both parents and children have needs.

E. Your parents will feel thatyou are no longer a small child.

F. Show respect for your parents, relatives and all the guests.

G. He gives ways to help teens understand their parents.

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