(E)

British scientists are breeding a new generation of rice plants that will be able to grow. in soil con­taining salt water. Their work may enable abandoned farms to become productive farms once more.

Tim Flowers and Tony Yeo, from Sussex University’s School of Biological Sciences,. have spent several years researching how crops, such as rice, could be made to grow in water that has become salty. The pairs have recently begun a three-year programme, funded by the Biotechnology and Bio­logical Sciences Research Council, to establish which genes enable some plants to survive salty condi­tions. The aim is to breed this capability into crops, starting with rice.

It is estimated that each year more than 10 million hectares (公顷) of agricultural land are lost because salt gets into the soil and stunts(防碍生长) plants. The problem is caused by several factors. In the tropics, mangroves that create swamps (沼泽) and traditionally formed barriers to sea water have been cut down. In the Mediterranean, a series of droughts have caused the water table to drop, allowing sea water to seep (渗透) in. In Latin America, irrigation often causes problems when water is evaporated by the heat, leaving, salt deposits behind.

Excess salt then enters the plants and prevents them functioning normally. Heavy concentrations of minerals in the plants stop them drawing up the water they need to survive.

To overcome these problems. Flowers and Yeo decided to breed rice plants that take in very little salt and store what they do absorb in cells that do not affect the plants’ growth. They have started to breed these characteristics into a new rice crop, but it will take about eight harvests before the resul­ting seeds are ready to be considered for commercial use.

Once the characteristics for surviving salty soil are known, Flowers and Yeo will try to breed the appropriate genes into all manners of crops and plants. Land that has been abandoned to nature will then be able to bloom again, providing much needed food for the poorer countries of the world. (from www.nmet168.com)

72. Which of the following statements about Flowers and Yeo is true?

A. They are students at Sussex University.

B. They are rice breeders.

C. They are husband and wife.

D. They are colleagues at an institution of higher learning.

73. Which of the following is NOT mentioned as a cause of the problem discussed in the passage?

A. Natural barriers to sea water have been destroyed.

B. The water table has gone down after droughts.

C. Sea level has been continuously rising.

D. Evaporation of water leaves salt behind.

74. The word "affect" in Paragraph 5 could be best replaced by________.

A. influence                B. effect                 C. stop                     D. present

75. The attitude of the author towards the research project is________.

A. positive                   B. negative             C. suspicious             D. indifferent

上一页  [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]  ... 下一页  >>