问题 问答题 论述题

试述苗圃松土除草的意义和原则。

答案

参考答案:

意义:在苗木生长发育过程中,由于降雨和灌溉,土壤板结,通气不良,根系发育不好,而且杂草滋生,与苗木争光、夺肥,严重影响苗木生长。所以,应该及时松土除草。松土和除草是两个概念,但通常是结合进行。通过松土除草,切断了土壤毛细管,使土壤疏松、通气良好,保蓄水分,消灭杂草。苗木生长期松土,有利于促使苗木根发育。雨季松土,促进气体交换和气态水的蒸发,可以防止苗木沥涝在盐碱地松土有利于抑制土壤返碱。

原则:苗圃除草,应掌握“除旱、除小、除了“的原则,应在雨季以前,将杂草全部除净,做到圃地无杂草。松土除草最好在雨后或灌溉后进行,当土壤湿润时将草连根拔掉,松土效果好。随着苗木的生长松土应逐次加深。在苗木生长前期,一般2-6cm,生长后期8-12cm;为了不伤根,不压苗,苗根附松土宜浅,行间、带间宜深。

解答题
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NOT all memories are sweet. Some people spend all their lives trying to forget bad experiences. Violence and traffic accidents can leave people with terrible physical and emotional scars. Often they relive these experiences in nightmares.

Now American researchers think they are close to developing a pill, which will help people forget bad memories. The pill is designed to be taken immediately after a frightening experience. They hope it might reduce ,or possibly erase(抹去),the effect of painful memories.

In November, experts tested a drug on people in the US and France. The drug stops the body releasing chemicals that fix memories in the brain. So far the research has suggested that only the emotional effects of memories may be reduced, not that the memories are erased.

The research has caused a great deal of argument. Some think it is a bad idea, While others support it.

Supporters say it could lead to pills that prevent or treat soldiers' troubling memories after war. They say that there are many people who suffer from terrible memories.

"Some memories can ruin people's lives . They come back to you when you don't want to have them in a daydream or nightmare. They usually come with very painful emotions," said Roger Pitman, a professor of psychiatry at Harvard Medical School. "This could relieve a lot of that suffering."

But those who are against the research say that changing memories is very dangerous because memories give us our identity (特质). They also help us all avoid the mistakes of the past.

"All of us can think of bad events in our lives that were horrible at the time but make us who we are. I'm not sure we want to wipe those memories out, "said Rebecca Dresser, a medical ethicist.

1. The passage is mainly about_____________.

A. a new medical invention          B. a new research on the pill

C. a way of erasing painful memories  D. an argument about the research on the pill

2. The drug tested on people can_____________.

A. cause the brain to fix memories

B. stop people remembering bad experiences

C. prevent body producing certain chemicals

D. Wipe out the emotional effects of memories

3. We can infer from the passage that_____________.

A. people doubt the effects of the pills

B. the pill will stop people's bad experiences

C. taking the pill will do harm to people's health

D. the pill has probably been produced in America

4. Which of the following does Rebecca Dresser agree with?

A. Some memories can ruin people's lives.

B. People want to get rid of bad memories.

C. Experiencing bad events makes us different from others.

D. The pill will reduce people's sufferings from bad memories.