问题 问答题 简答题

简述嫁接的生物学原理。

答案

参考答案:

嫁接是一种在生产上应用很广的繁殖措施,其生物学原理是,植物受伤后具有愈伤的机能。

当砧木和接穗削面的形成彼此接触时,由于接穗与砧各自增生新的细胞形成愈伤组织,填满砧穗之间的空隙,愈伤组织进一步分化形成维管组织,将接穗与砧木连接在一起,嫁接苗就活了。

砧没和嫁接的亲和力是嫁接成活的基本条件。

一般亲缘关系愈近,亲和力愈强,所以品种间嫁接较容易成功。

完形填空

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项,选项中有两项为多余选项.

小题1:Such as runny noses, sore throats, nothing quite like the common cold to make you feel miserable. But experts believe that there is no link between cold weather and catching colds. 小题2:

Internal Medicine expert, Dr Meenakshi Jain of Max Hospital says, “One reason could be that people are likely to stay indoors, so the virus can spread easily. 小题3: ”

The common cold is a viral infection that can be caused by any of up to 250 strains of virus, the most common group of which are the rhinovirus(鼻病毒) that hit the nose.

小题4:“They are transmitted through the nose respiratory(呼吸的) passages, by touch, and by contact with airborne particles that are created by sneezing or coughing,” says Dr Jain.

There is no cure for the common cold and antibiotics(抗生素) are of no help. However, there are some precautions which can help:

小题5:In this case, you can protect your hands from getting germs.

Don’t touch your eyes, nose and mouth, which can limit your chances of infection.

Don’t share drinking glasses or utensils with anyone as this will prevent the spread of the virus.

Make sure to eat enough fruits to boost your immune system.

A.Also the virus thrives (兴盛,繁荣) in wetness in the atmosphere.

B.Drink lots of fluids to avoid dehydration.

C.They are responsible for anywhere between a third and half of all common colds.

D.Get enough sleep and you’ll certainly feel better.E.So why are we particularly vulnerable (脆弱的) this season?

F.Wash your hands regularly.

G.It’s winter and you have probably noticed germs are everywhere.

单项选择题 案例分析题