问题 填空题

当根毛的细胞液浓度______(填“大于”或“小于”)土壤溶液浓度时,根毛就吸水;当根毛的细胞液浓度______(填“大于”或“小于”)土壤溶液的浓度时,根毛就失水,这就是给植物施肥过多会出现“______”现象的原因.

答案

植物细胞吸水和失水的原理是细胞外部溶液的浓度大于细胞内部浓度时失水,细胞外部溶液的浓度小于细胞内部浓度时吸水.一次施肥过多,会使土壤溶液浓度过高,大于植物细胞溶液的浓度,植物细胞失水,导致植物因失水而萎蔫.当情势比较严重时,会造成烧苗.施肥后浇水可以降低土壤溶液的浓度,使土壤溶液浓度小于作物细胞的浓度,使作物细胞正常吸水.因此施肥后必须及时浇水.

故答案为:大于;小于;烧苗.

解答题
阅读理解

阅读理解。

     1970 was the World Conservation (保护) Year. The United Nations wanted everyone to know that the

world is in danger. They hoped that governments (政府) would act quickly in order to conserve nature. Here

is one example of the problems. At one time there were 1 300 different plants, trees and flowers in Holland,

but now only 860 remain (留下). The others have been destroyed (毁灭) by modern man and his technology

(技术). We are changing the earth, the air, the water, and everything that grows and lives. We can't live

without these things. If we go on like this, we shall destroy ourselves.

     What will happen in the future? Perhaps it is more important to ask "What must we do now?" The people

who will be living in the world of tomorrow are the young people today. A lot of them know that conservation

is necessary. Many are helping save our world. They plant trees, protect wild animals, and so on. In a small

town in the United States a large group of girls cleaned the 11 kilometer-long banks of the river. Young people

may hear about conservation through a record called "NO ONE'S GOING TO CHANGE OUR WORLD".  It

was made by the Beatles, Cliff Richard and other singers. The money from it will help to conserve wild

animals.

1. From the passage we know that there are ______ in Holland now.

A. more trees

B. more flowers

C. fewer plants

D. fewer animals

2. This passage is mainly about conserving ______.

A. man

B. nature

C. wild animals

D. wild plants

3. What's the meaning of the sentence "If we go on like this, we shall destroy ourselves"?

A. We can't live on the earth someday.

B. We can't see plants.

C. We can't see animals.

D. Our life will be hard.

4. We can guess from the passage that "NO ONE'S GOING TO CHANGE OUR WORLD" was ______.

A. a book about saving the earth

B. a song loved by young people

C. a film about protecting wild animals

D. a tape of songs calling on people to conserve nature

5. Which is not mentioned (提到) in the passage?

A. Plant trees.

B. Protect wild animals.

C. Clean the banks.

D. Collect waste paper for recycling.