Question

Have you ever wondered why stems(莖)grow upwards and roots downwards? Why do plants always seem to turn towards the light and climbing plants run up rather than down? The answer is simple: auxin(生長(zhǎng)素), a chemical substance that controls growth in plants.

    Auxin gives away its secrets

Auxin is a plant hormone(激素). Darwin was already interested in it in the 19th century. Only in recent years, however, has the hormone started to give away its secrets, thanks to intensive molecular research. Auxin is produced in the young, growing parts of plants and then transported throughout the plant—to a low­lying stem for example. The stem needs to straighten out as soon as possible to be able to absorb the topside, resulting in the underside growing faster and the stem straightening out. For the same reason, plants in front of windows will always turn to the light. This active regulation of auxin transport allows plants to take ideal advantage of local and changing conditions.

   A new means of transport for auxin

   The transport of auxin through the plant plays a vital role. And, from all appearances, it is not a simple matter. The researchers identified an important new link and means of transport for auxin: PILS proteins (蛋白質(zhì)). PILS proteins are vital for auxin­dependent plant growth and adjust the intracellular(細(xì)胞內(nèi)的)storage of the hormone. It is exactly this compartmentalizing (分類) of auxin that seems functionally important for the various developmental processes.

Growing crops more efficiently: the right amount of auxin in the right place

 Higher auxin levels at the right moment and in the right place result in better growth and greater harvest. Better adjustment of auxin levels would make plants grow more efficiently. The researchers hope to contribute to the development of more efficient growing processes by continuing to sort out auxin transport processes.

 66. Which of the following is TRUE of auxin according to the text?

A. It helps the plant to bend at the right places while growing.

B．It prevents the roots of plants from growing faster.

C．It is no use when the surroundings have changed.

D．It helps the underside of plants grow faster than the topside.

67. What would make plants grow more efficiently?

A. Straightening out the stem.

B．The right amount of auxin in the right place.

C．Allowing plants to turn to the light.

D．Enough PILS proteins.

68. From Paragraph 3 we know that ________.

A. the researchers are not so sure if the transport for auxin is a new one

B．the levels of auxin remain the same during the growing processes of plants

C．PILS proteins delay the growth of plants

D．PILS proteins play an important part in the transport of auxin

69．According to Paragraph 2, the researchers got their results mainly by ________.

A. referring to Darwin's theory

B．observing plants straightening

C．doing intensive molecular research

D．watching plants in different places

70．Which of the following can be the best title for this passage?

A. Why Plants Grow Towards the Light?

B．Darwin's Dream Has Come True

C．How Did Scientists Find Out the Secret?

D．A New Way of the Growing of Plants

Answer 1

【語篇解讀】本文講述了現(xiàn)代研究條件下對(duì)于植物生長(zhǎng)素(auxin)的研究成果。

66．D　細(xì)節(jié)理解題。植物生長(zhǎng)素的功能在第二段中體現(xiàn)的是resulting in the underside growing        faster。

67．B　細(xì)節(jié)理解題。由最后一段的標(biāo)題及前兩句可得出答案。

68．D　細(xì)節(jié)理解題。根據(jù)第三段The researchers identified an important new link and means of transport for auxin: PILS proteins.可知PILS蛋白質(zhì)在生長(zhǎng)素的傳播過程中起著至關(guān)重要的作用。

69．C　細(xì)節(jié)理解題。達(dá)爾文一開始只是對(duì)生長(zhǎng)現(xiàn)象感興趣但并沒有得出結(jié)論，只有現(xiàn)在的研究者經(jīng)過了“密集的分子生物學(xué)研究”之后才得出結(jié)論。

70．A　主旨大意題。文章一開始就以疑問的方式提出了主題，然后陸續(xù)揭示生長(zhǎng)素(auxin)的功能。