Where does the plant grow?

admin2010-07-06  21

问题 Where does the plant grow?  
  
This morning I want to tell you about a recent scientific discovery dealing with the relation between plants and animals. This is about a desert shrub whose leaves can shoot up a stream of poisonous rosin for a distance of six feet. Do you think it would be safe from all attacks by insects? But a recant study has found one insect, a beetle, which can chew its way past the plant’s defense system by cutting the main vein that delivers the poison to the leaves. This vein cutting is jut one method the beetles used to prepare a safe meal. Then they simply eat between the veins of poison. In the past, scientists who studied insect adaptation to plant defenses have focused on chemical responses. It is only after a beetle has survived several encounters with the plant’s resin that it learns how to avoid the poison by chewing through the resin transporting veins on the next leaf it eats and thus gives itself a meal. However, it can take a beetle an hour and a half of careful vein cutting to prepare a small leaf that takes it only a few minutes to eat. So, though the method is effective, it’s not very efficient.

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答案Six feet.

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