Question

【題目】 Young sunflowers turn and swing every day. New findings add to evidence that the plants are animal-like.

Harmer, a professor in the University of California at Davis, Department of Plant Biology, carried out a series of experiments on sunflowers in the field, in pots outdoors and in indoor growth chambers.

By staking plants so that they could not move, Harmer showed that he could destroy their ability to track the sun. He also noticed that sunflowers prevented from moving were not as tough and leafy as those that were free to move. When plants were moved indoor with a settled overhead light, they continued to swing back and forth for a few days.

The indoor plants did start tracking the “sun” again when the apparent source of lighting was moved across the room. The plants could reliably tack the movement and return at night when the artificial day was close to a 24-hour cycle, but not when it was closer to 30 hours.

When sunflowers track the sun, the east sides of their stems grew more rapidly than the west sides. At night, the west sides grew faster as the stem swung the other way. The team identified a number of genes that were expressed at higher levels on the sunward side of the plant during the day or on the other side at night. A plant growth-regulating hormone (激素), called auxin, appears to be a key driver.

The “dance” to the sun cycle obviously slows when the sunflower matures (成熟) and its flowers open up. At that point, the plants stop moving during the day and settle down facing the sun in the east.

“Bees like warm flowers.” Harmer said, adding that the bees are cold-blooded, so landing on a warm flower saves them energy and perhaps feels really good.

“The morning warmth changes the flowers in a way to make them more appealing to insects, perhaps causing them to release more attractive scents earlier in the day.” he said “We’re currently testing this idea.”

【1】Why did Harmer do the experiment on sunflowers?

A.To see how sunflowers grow upB.To show what sunflowers’ genes are.

C.To study why sunflowers track the sun.D.To check if sunflowers swing in cloudy days.

【2】What does the underlined word “staking” probably mean in Paragraph 3?

A.breakingB.controllingC.growingD.searching

【3】What is the result of sunflowers being stopped from moving?

A.They will produce a number of new genes.B.They will grow faster than usual.

C.They won’t swing back though set free.D.They won’t grow well.

Answer 1

【答案】

【1】C

【2】B

【3】D

【解析】

每天向日葵會(huì)隨著太陽(yáng)的方向轉(zhuǎn)動(dòng)搖擺，加州大學(xué)的教授Harmer做了一系列研究發(fā)現(xiàn)向日葵向陽(yáng)會(huì)使它更好地成長(zhǎng)，吸引更多的昆蟲(chóng)授粉。

【1】推理判斷題。根據(jù)文章前兩段可知，加州大學(xué)的教授Harmer做了一系列研究為什么向日葵追隨太陽(yáng)的方向而轉(zhuǎn)動(dòng)方向，故選C。

【2】詞句猜測(cè)題。breaking破壞；controlling控制；growing生長(zhǎng)，產(chǎn)生；searching搜尋。根據(jù)文中“so that they could not move”和“sunflowers prevented from moving”可知，此處表示“讓向日葵不動(dòng)”，所以此處劃線詞是“定樁，使……不動(dòng)”的含義，故選B。

【3】細(xì)節(jié)理解題。根據(jù)文中第三段中“Harmer showed that he could destroy their ability to track the sun. He also noticed that sunflowers prevented from moving were not as tough and leafy as those that were free to move.”可知，向日葵被固定后它們長(zhǎng)得柔弱，葉子少，所以被固定住使其生長(zhǎng)得不好，故選D。