第4部分：阅读理解（第31～45题，每题3分，共45分）
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"Salty" Rice Plant Boosts Harvests
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 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 pair 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 10m hectares （公顷） of agricultural land are lost because salt gets into the soil and stunts （妨碍生长） plants. The problem is caused by several factors. In the tropics, mangroves （红树林） 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 （蒸发） 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 in the poorer countries of the world.
