GMAT考试 12月7日更新GMAT阅读机经（十八）.

　　GMAT考试已于12月1日更换题库，以下是2011年12月的GMAT阅读机经更新，更新日期从12月1日起至12月7日，目前共40题。澳际留学祝大家GMAT考试顺利!

　　第一篇【大意就差不多了】

　　Dodder is a wiry, orange vine that steals water and nutrients from other plants. Scientists have now found that this vine chooses its victim by smell, growing its shoots in the direction of a plant&aposs natural perfume. A seedling of a vine known as dodder attaches to a tomato plant.

　　When a dodder seed sprouts, it doesn&apost grow roots to seek its own food. Instead, it grows a shoot that reaches out to other plants, tapping them for food. The baby vine needs to find a host within a week to survive. It then grows into a spaghetti tangle that can even ensnare more than one plant.

　　Also known as strangleweed and witches&apos shoelaces, dodders are listed among the 10 worst weeds in the United States. They can cost farmers millions of dollars by stunting their crops.

　　To figure out how a type of dodder vine known to prer tomato plants finds a victim, scientists placed dodder sprouts near several possible targets. These targets included pots of moist soil, little jars of dyed water that created colored lights, young tomato plants, and even a cup of perfume made from chemicals that tomato plants give off.

　　Seedlings grew toward the tomato plant. They also reached out toward the cup of tomato perfume. They tended not to grow toward the moist soil or colored water.

　　The scientists then used a different setup, hiding the targets in chambers connected to dodder sprouts only by curving pipes, so the vine could find them only by smell. Dodder sprouts still grew toward their favored targets.

　　By placing dodder sprouts near different plants, the scientists found that the type of dodder that they were studying prers tomatoes and a flower called impatiens. And when given a choice between tomato and wheat, vine seedlings grow toward tomato.

　　The researchers then tested seven of the ingredients that make up tomato perfume separately. Dodder sprouts were attracted to three of them.

　　One of these ingredients turns up in wheat perfume, but the wheat perfume also contains a substance that repels dodder sprouts. This chemical could offer farmers one way to fight the vine and save their crops.—C. Gramling

　　第二篇【据说原文比这简单点，实验内容什么的描述的很简单】

　　One of the parasitic plants called dodders responds to volatile compounds wafting off nearby plants and shows prerences for certain species, says Consuelo De Moraes of Pennsylvania State University in University Park. They say that their new work marks the first time that anyone has shown that a plant will grow toward airborne chemicals from other plants.

　　The experiment finally identifies a cue—scent—that draws dodder to its victims, adds Mark C. Mescher, also of Penn State.

　　The U.S. Department of Agriculture lists dodder among the country&aposs 10 worst weeds. When a dodder seed sprouts, it doesn&apost grow roots. All its energy goes into a tendril that shoots out in search of plants to tap for water and nutrients. If it&aposs going to survive, it must latch on to a victim within about a week. The vine grows into a spaghetti tangle and can attack multiple plants, stunting their growth but not killing them.

　　Of the 150 species of dodder, the researchers selected Cuscuta pentagona, says coauthor Justin Runyon, also of Penn State. This species bedevils tomato growers in California, where it costs them an estimated $4 million a year in reduced yields.

　　De Moraes&apos team and other researchers have studied the volatile compounds released by plants that are mauled by caterpillars or other pests. In the new study, reported in the Sept. 29 Science, the team took a different point of view, looking at how an attacker, the dodder, takes advantage of volatiles to target its prey.

　　At first, the researchers set various possible targets several centimeters from dodder sprouts. A pot of moist soil alone didn&apost attract the seedlings, nor did vials of dyed water that created colored light. But a pot with a young tomato plant, and even a cup of perfume made of tomato volatiles, did attract the seedlings (see movie at www.aoji.cn

　　To minimize any confounding cues, such as shading or light, the researchers then set the possible attractants in chambers connected to the plant by curving pipes. Again, the seedlings grew toward the scent.

　　Testing various victim species, the researchers found that dodder grows toward impatiens and tomatoes. Wheat won&apost sustain dodder well, and given a choice, parasite seedlings shunned it and grew toward tomatoes.

　　When researchers tested seven ingredients in the tomato perfume individually, three of them proved attractive to the dodder. One of those attractants showed up in wheat, but the wheat perfume also contained a substance that repelled the seedlings. Such a repellent might offer a new route for fighting dodder, Mescher speculates.

　　An insect ecologist who has also studied plant volatiles, Rick Karban of the University of California, Davis comments, "The significance of this [study] to me is that it indicates that without a central nervous system, plants are capable of behaving in ways that appear fairly sophisticated."

　　以上就是12月7日更新的GMAT阅读机经，考生可以适当借鉴，并通过练习来掌握GMAT阅读的解题规律，从而在GMAT考试中发挥出更好的水平。 相关链接：

1.GMAT考试 12月7日更新GMAT阅读机经（十七）

2.GMAT考试 12月7日更新GMAT阅读机经（十六）

3.GMAT考试 12月7日更新GMAT阅读机经（十五）

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