日日人人_亚洲美女在线视频_av手机在线播放_国产大片aaa_欧美中文日韩_午夜理伦三级

Plants may not have eyes and ears，but they can recognize their siblings (兄弟姐妹)，and researchers at the University of Delaware have discovered how.The ID system lies in the roots and the chemical signals they secrete (分泌)．

Canadian researchers published that sea rocket，a common seashore plant，can recognize its siblings.Susan Dudley observed that when siblings are grown next to each other in the soil，they “play nice” and don’t send out more roots to compete.However，the moment one of the plants is thrown in with strangers，it begins competing with them by rapidly growing more roots to take up the water and mineral nutrients in the soil.

After reading Dudley’s study，Bais decided to find the method behind the sibling recognition.Working in his laboratory，Bais and his doctoral student Meredith Biedrzycki set up a study with wild populations of Arabidopsis thaliana.In a series of experiments，young seedlings were exposed to liquid media containing the root secretions from siblings，from strangers，or only their own secretions.The length of the longest lateral (側面的) root was measured.The exposure of plants to the root secretions of strangers induced (引誘) greater lateral root formation than exposure of plants to sibling secretions.Strangers planted next to each other are often shorter，because so much of their energy is directed at root growth.Because siblings aren’t competing against each other，their roots are often much shallower (淺的)．

Biedrzycki did the painstaking laboratory research，observing more than 3,000 plants involved in the study every day for seven continuous days and documenting the root patterns.“Arabidopsis roots are nearly translucent (半透明的) when they are young and were also twisted when I removed them from plates，”Biedrzycki notes.“This manuscript (手稿) is very important for my research since the focus of my thesis project is understanding the biochemical ways behind root secretions.”

The research also may have implications for the home gardener.“Often we’ll put plants in the ground next to each other and when they don’t do well，we blame the local garden center where we bought them or we attribute their failure to a germ，”Bais says.“But maybe there’s more to it than that.”

1.Which of the following would be the best title for this passage?

A．A Great Biology Researcher

B．Plants Recognize Their Siblings

C．Plants’ Roots and Secretions

D．A Research on Plants

2. What encouraged Bais to study the sibling recognition?

A．Sea rocket.

B．Plants’ sensing system.

C．Biedrzycki’s thesis project.

D．Dudley’s study.

3. What does the underlined word “painstaking” in Paragraph 4 probably mean?

A．Important.? B．Adventurous.

C．Careful.? D．Hard?working.

4.What can we infer from the last paragraph?

A．The local garden center should be blamed when plants can’t grow well.

B．The local garden center often sells low quality seeds to customers.

C．Plants in the home garden can’t grow well because of the germ and seeds.

D．Competing against strangers，plants in the home garden can’t grow well.

Be quick, _____ we’ll miss the beginning of the fireworks display in the park.

A．so               B．or               C．because          D．though

1) We must ___________ (限制) our spending.
2) I was very i___________ by one young man at my lectures; he’s a tall man with brown hair.
3) Jesus was the founder of the Christian ____________. (宗教)
4) The trees provide s__________ for the animals in the summer.
5) I don’t know much about the __________ (內容) of the letter.
6) If you b_________ from something, it helps you or improves your life.
7) As a child I was ____________(包圍，環繞) by love and kindness.
8) The chair was i___________ for the kid, but a young man took it away.  
9）We’ll e__________ the business to make it bigger and includes more people, goods, or activities.
10) For further information, please _________(參考，參看) to Chapter Ten.

If we sit near ________ front of the bus，we’ll have ________ better view.(2010·山東，22)

A．/；the? B．/；a

C．the；a? D．the；the

If we _________ now to protect the environment, we’ll live to regret it.

A．hadn’t acted      B．haven’t acted     C．don’t act         D．won’t act