问题 问答题 简答题

病原物致病有哪些致病方式?

答案

参考答案:

病原物有以下致病方式:

(1)夺取寄主的营养物质和水份;

(2)分泌各种酶类,消解和破坏植物组织和细胞,侵入寄主并引起病害;

(3)分泌毒素,是植物细胞中毒;

(4)分泌植物生长调节物质,或干扰植物的正常激素代谢,引起生长畸形。

填空题
阅读理解

Beijing, Shanghai, Guangzhou and other big cities are exciting places to live. There are many interesting things to see and to do. You can go to different kinds of museums, plays and movies. You can also go to supermarkets to buy things from all over the world. But there are serious problems in big cities, too. The cost of living is high, and there are too many people in some big cities. Every year many people move to the cities because there are more chances to find jobs, to study at good schools, and to receive good medical care. But sometimes these people cannot find work or a good place to live. Also, too many people in a small space make it hard to keep the cities safe and clean.

Some people enjoy living in big cities. Others do not. Before people move to big cities, they should think about the problems of living there.

小题1:In big cities people can                                .

A.find jobs more easily

B.study at good schools

C.receive good medical care

D.A, B and C小题2:According to the passage, big cities                                  .

A.are not exciting places to live

B.have not many serious problems

C.are terrible

D.are not always clean and safe enough小题3:In this passage the writer tells us                            .

A.to move to a big city

B.not to move to a big city

C.not to move to a big city without thinking about the problems there

D.not to think too much about the problems before moving to a big city小题4:Which is NOT mentioned in the passage?

A.Beijing, Shanghai and Guangzhou are all big cities.

B.Some people enjoy living in big cities.

C.People have more chances to find jobs in big cities.

D.Big cities are not as good as small cities.小题5:Which is the best title for the passage?

A.Exciting Places to live

B.Serious Problems in Big Cities

C.Big Cities

D.Chances to Find Jobs