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  3. We often think of agriculture as planting seeds and harvesting crops. But many crops do not come from seeds. Many kinds of trees

We often think of agriculture as planting seeds and harvesting crops. But many crops do not come from seeds. Many kinds of trees

admin2012-09-19  49
问题 We often think of agriculture as planting seeds and harvesting crops. But many crops do not come from seeds. Many kinds of trees and plants are grown from【S1】______cut from existing trees and plants. This is called grafting(嫁接) .
    Farmers cut branches or young growths, called【S2】______, from one plant and place them on a related kind of plant. The branch or bud that is grafted is called a scion(接穗) . The plant that【S3】______the graft is called the root stock. Over time, the【S4】______from the two plants grow together, the grafted plant begins to【S5】______the leaves and fruit of the scion, not the root stock.
    A graft can be cut in several ways. A cleft graft(割接，劈接) , for example, requires a scion with several buds on it. The bottom of the scion is cut in the【S6】______of the letter V. A place is cut in the root stock to accept the scion. The scion is then【S7】______placed into the cut on the root stock. Growth medium is put on the【S8】______to keep it wet and help the growth.
    Grafting can join scions with【S9】______qualities to root stock that is strong and resists disease and insects. Some common fruit trees such as sweet cherries have to be grafted.
    In an age of hightechnology agriculture, grafting is a lowtechnology method that remains【S10】______important.

A blossoms              B pieces                C composes                  D parts  
E securely              F extremely             G buds                      H agreeable
I accepts               J firmly                K grow                      L desirable                              M produce               N shape                 O join
【S7】
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