A few milliamps of electricity can cause plants to increase synthesis of chemicals. These compounds often also have a pharmacological (related to medicine) or commercial value, so the trick could be used to help increase yields of commercially useful biologicals. Artemisinic acid, from sweet wormwood, for example, is used in malarial medications, and shikonin (紫草素), from the purple gromwell plant, is used against skin infections.
Researchers have long known that stressing plants can force them to take defensive action, often ramping up the production of protective chemicals that, for example, make them more resistant to insect attack. It has become common practice to stress such plants into increasing their yields. This is usually clone using physical stress elicitors (诱导子), including bits of the micro-organisms that normally attack the plants, or irritants made from metallic compounds such as copper chloride. These are effective, but they come at a cost. Most elicitors a
A. take precautions against skin infections
B. increase production of useful biologicals
C. increase pharmacological and commercial value
D. make plants more resistant to attack
I have always (36) going to school. I enjoy learning new things and (37) new people. I try to think of my school work (38) a challenge instead of a(n) (39) duty. My parents have taught me the value (40) a good education and the importance of (41) doing my best.
My father said that school was "the cradle of education". I think (42) he said is true. A student (43) school is like a baby who is put into a (44) . There the student begins his education, (45) will continue (46) he lives.
My school is not very large, (47) I think it is good. This year I am studying maths, English, Chinese, science and history to (48) college. My teachers are very strict so we have to study very (49) in class and always have homework. I am learning more and more (50) . My best grades are in English (51) science. In (52) , my Englis
A. learning
B. going
C. beginning
D. enjoying
| A report published recently brings bad
news about air pollution. It suggests that it could be as damaging to our health
as exposure to the radiation from the 1986 Ukraine nuclear power disaster. The
report was published by the UK Royal Commission on Environmental Pollution.
But what can city people do to reduce exposure to air pollution Quite a
lot, it turns out. Avoid walking in busy streets. Choose side streets and parks instead. Pollution levels can fall a considerable amount just by moving a few meters away from the main pollution source—exhaust fumes (烟气). Also don’t walk behind smokers. Walk on the windward side of the street where exposure to pollutants can be 50 percent less than on the downwind side. Sitting on the driver’s side of a bus can increase your exposure by 10 percent, compared with sitting on the side n A. on the left side in the bus B. on the right side in the bus C. in the middle of the bus D. at the back of the bus [单选题]( )所有客舱乘务员每 日历月需进行一次危险物品运输训练。
A.6个 B.12 个 C.24 个 D.36 个 [单选题] 诸多运转设备基础底座采用铸铁材质，是利用了其（ ）。 "
A.熔点低 B.易切削 C.便宜 D.减振性" [判断题] 持用通勤乘车证准乘各种旅客列车。
A.正确 B.错误 我来回答: 提交
|
