1 . Hundreds of native North American plants, often dismissed as weeds, deserve a lot more respect, according to a new study. These plants, distant cousins of foods like sunflowers and lettuce (莴苣), actually represent a botanical treasure now facing increased threats from climate change and habitat loss. The crops that the human race now depends on, including grains like wheat and tree fruit like peaches, originally were selected or bred (培育) from plants that grew wild hundreds or thousands of years ago. In the U.S., there are wild ancestors of blueberries, sweet potatoes, onions, potatoes, and many other food crops. “Some of them are quite common,” says Colin Khoury, a research scientist at the International Center for Tropical Agriculture. “Wild lettuce plants grow along sidewalks, or in backyards, but go unrecognized.”
Other crop relatives are rare and threatened. One of Khoury’s favorites is the paradoxical sun flower.” It grows just in wetlands of the deserts of New Mexico and Texas. Little salty areas where there’s a little bit of water beneath the soil,” he says. So plant growers crossbred it with commercial sunflowers and created new varieties that can grow in places where the soil contains more salt. Other wild relatives may be hiding similarly remarkable gifts, Khoury says, such as genes that could help their domesticated relatives survive diseases, or deal with pests.
Khoury and some of his colleagues just finished a survey of about 600 wild crop relatives that grow in North America, and they found that most of these plants are threatened by things like fires, farming and development. The scientists argue that they deserve more protection. For one thing, “gene banks” should collect and preserve them. In addition, these plants need more protection in their natural habitat.
According to Khoury, that doesn’t necessarily mean setting aside land for them. In many cases, the plants already are growing on public land that’s managed by the U.S. Forest Service (USFS) or the Bureau of Land Management (BLM). “It’s more about just being aware that these plants actually exist,” he says.
1. What did the new study mainly focus on?| A．Endangered plant species. |
| B．Wild relatives of food crops. |
| C．The impacts of climate change. |
| D．The threats from plant habitat loss. |
| A．It needs much water to grow well. |
| B．It grows along sidewalks or in backyards. |
| C．It seems capable of surviving various diseases. |
| D．It helps commercial sunflowers adapt to salty soil. |
| A．Relieved. | B．Concerned. | C．Annoyed. | D．Critical. |
| A．Join hands with the USFS. |
| B．Set aside land for wild plants. |
| C．Collect genes of threatened crop species. |
| D．Learn about plants on its managed land. |
2 . Flying over a desert area in an airplane, two scientists looked down with trained eyes at trees and bushes. After an hour's flight one of the scientists wrote in his book, “Look here for probable metal.” Scientists in another airplane, flying over a mountain area, sent a message to other scientists on the ground, “Gold possible.” Walking across hilly ground, four scientists reported, “This ground should be searched for metal.” From an airplane over a hilly wasteland a scientist sent back by radio one word: “Uranium.”
None of the scientists had X-ray eyes: they had no magic power of looking down below the earth's surface. They were merely putting to use one of the newest methods of locating minerals in the ground... trees and plants as signs that certain minerals may lie beneath the ground on which the trees and plants are growing.
This newest method of searching for minerals is based on the fact that minerals deep in the earth may affect the kind of bushes and trees that grow in the surface.
At Watson Bar Greek, a brook (小溪) six thousand feet high in the mountains of British Columbia,Canada, a mineral search group gathered bags of tree seeds. Boxes were filled with small branches from the trees. Roots were dug and put into boxes. Each bag and box was carefully marked. In a scientific laboratory the parts of the forest trees were burned to ashes and tested. Each small part was examined to learn whether there were minerals in it.
Study of the roots, branches, and seeds showed no silver. But there were small amounts of gold in the roots and a little less gold in the branches and seeds. The seeds growing nearest to the tree trunks had more gold than those growing on the ends of the branches.
1. Scientists were flying over a desert or a hilly wasteland or a mountain area in order to search for_____ in the ground.| A．gold | B．silver | C．minerals | D．metals |
| A．X-ray | B．trained eyes |
| C．a special instrument | D．magic power |
| A．Branches. | B．Roots. | C．Leaves. | D．Seeds. |
| A．Scientists Searching for Metals with Special Power |
| B．New Methods of Searching for Minerals |
| C．Gold Could Be Found by Trees and Plants |
| D．A New Method of Searching for Minerals-Using Trees and Plants |
