VOA慢速英语 2007 0102a（在线收听）

This is the VOA Special English Agriculture Report.

These days, if we hear about two different plants being combined, the first thing we think of might is modern biotechnology. But the low-technology process of grafting remains an extremely important form of genetic engineering in agriculture.


Grafting still holds an important place even in an age of high-tech agriculture

Many kinds of plants are grown not from seeds but from pieces cut from existing plants. Farmers cut branches or buds, young growths, from one plant and place them on a related kind of plant.

The branch or bud that is grafted is called a scion [pronounced SY-uhn]. The plant that accepts the graft is called the root stock.

Over time, the parts from the two plants grow together. The grafted plant begins to produce the leaves and fruit of the scion, not the root stock.

A graft can be cut in several ways. A cleft graft, for example, requires a scion with several buds on it. The bottom of the scion is cut in the shape of the letter V. A place is cut in the root stock to accept the scion.

The scion is then securely placed into the cut on the root stock. Material called a growth medium is put on the joint to keep it wet and help the growth.

Grafting can join scions with desirable qualities to root stock that is strong and resists disease and insects. Smaller trees can be grafted with older scions.

The United States Environmental Protection Agency says producing stronger plants by grafting can reduce the need to use pesticides.

Agriculture could not exist as we know it without grafting. Many fruits and nuts have been improved through this method. Some common fruit trees such as sweet cherries and McIntosh apples have to be grafted.

Bing cherries, for example, are one of the most popular kinds of cherries. But a Bing cherry tree is not grown from seed. Branches that produce Bing cherries must be grafted onto root stock. All sweet cherries on the market are grown this way.

And then there are seedless fruits like navel oranges and seedless watermelons. Have you ever wondered how farmers grow them? Through grafting.

The grapefruit tree is another plant that depends on grafting to reproduce. Grapes, apples, pears and also flowers can be improved through grafting.

In an age of high-technology agriculture, grafting still holds an important place.

And that's the VOA Special English Agriculture Report, written by Mario Ritter. You can learn more about agriculture, and download MP3 files and transcripts of our reports, at www.unsv.com.
  原文地址：http://www.tingroom.com/voa/2007/1/39767.html