一篇阅读理解题.Have you ever wondered why stems(茎)gro一篇阅读理解题.Have you ever wondered why stems(茎)grow upwards and roots downwards?Why do plants always seem to turn towards the light and climbing plants run up rather than down?

一篇阅读理解题.Have you ever wondered why stems(茎)gro一篇阅读理解题.Have you ever wondered why stems(茎)grow upwards and roots downwards?Why do plants always seem to turn towards the light and climbing plants run up rather than down?
一篇阅读理解题.Have you ever wondered why stems(茎)gro
一篇阅读理解题.
Have you ever wondered why stems(茎)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(生长素),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 (蛋白质).PILS proteins are vital for auxin­dependent plant growth and adjust the intracellular(细胞内的)storage of the hormone.It is exactly this compartmentalizing (分类) of auxin that seems functionally important for the various developmental processes.
Growing crops mor

一篇阅读理解题.Have you ever wondered why stems(茎)gro一篇阅读理解题.Have you ever wondered why stems(茎)grow upwards and roots downwards?Why do plants always seem to turn towards the light and climbing plants run up rather than down?
Have you ever wondered why stems(茎)grow upwards and roots downwards?Why do plants always seem to turntowards the light and climbing plants run up rather than down?The answer issimple:auxin(生长素),a chemical substance that controlsgrowth in plants.
Auxingives away its secrets
Auxinis a plant hormone(激素).Darwin was already interested in it inthe 19th century.Only in recent years,however,has the hormone started togive away its secrets,thanks to intensive molecular research.Auxin isproduced in the young,growing parts of plants and then transported throughoutthe plant—to a low­lying stem for example.The stem needs to straighten out assoon as possible to be able to absorb the topside,resulting in the undersidegrowing faster and the stem straightening out.For the same reason,plants infront of windows will always turn to the light.This active regulation of auxintransport allows plants to take ideal advantage of local and changingconditions.
A new means of transport for auxin
The transport of auxin through the plantplays a vital role.And,from all appearances,it is not a simple matter.Theresearchers identified an important new link and means of transport for auxin:PILS proteins (蛋白质).PILS proteins are vital forauxin­dependent plant growth and adjust the intracellular(细胞内的)storage of the hormone.It is exactly this compartmentalizing (分类) of auxin that seems functionally important for the variousdevelopmental processes.
Growingcrops more efficiently:the right amount of auxin in the right place
Higher auxin levels at the right momentand in the right place result in better growth and greater harvest.Betteradjustment of auxin levels would make plants grow more efficiently.Theresearchers hope to contribute to the development of more efficient growingprocesses by continuing to sort out auxin transport processes.
1.Which of the following is TRUE of auxinaccording 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.
2.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.
3.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 ofplants
C．PILS proteins delay the growth of plants
D．PILS proteins play an important part in the transport of auxin
4．According to Paragraph 2,the researchers got their results mainlyby ________.
A.referring to Darwin's theory
B．observing plants straightening
C．doing intensive molecular research
D．watching plants in different places
5．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 ScientistsFind Out the Secret?
D．A New Way of the Growing of Plants
【解题导语】本文讲述了现代研究条件下对于植物生长素(auxin)的研究成果.
1．D　细节判断题.植物生长素的功能在第二段中体现的是resulting in the underside growing faster.
2．D　细节判断题.由Theresearchers identified an important new link and means of transport for auxin:PILSproteins.可知PILS蛋白质在生长素的传播过程中起着至关重要的作用.
3．C　细节理解题.达尔文一开始只是对生长现象感兴趣但并没有得出结论,只有现在的研究者经过了“密集的分子生物学研究”之后才得出结论.
4．A　主旨大意题.文章一开始就以疑问的方式提出了主题,然后陆续揭示auxin的功能.