如图为植物叶片纵切面图，请据图回答．（1）叶片蒸腾作用需要_爱下问搜题

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问题填空题

如图为植物叶片纵切面图，请据图回答．

（1）叶片蒸腾作用需要的水大部分是由____________运来的．

（2）对叶片内部起保护作用的是____________和____________．

（3）图中各结构的细胞内含有较多叶绿体的是____________，植物的光合作用主要在此进行．

（4）气体进出植物体的门户是____________，它的开闭受______的控制．

答案

（1）叶脉里有导管和筛管，导管的作用是运输水分和无机盐，筛管的作用是运输有机物；因此叶脉具有输导的作用．

（2）表皮包括上表皮和下表皮，表皮由一层排列紧密、无色透明的细胞构成，表皮细胞的外壁上有一层透明的、不易透水的角质层，表皮主要起保护作用；即图示中的①和⑤．

（3）叶肉细胞里含有较多的叶绿体：靠近上表皮的叶肉细胞呈圆柱形，排列整齐，是栅栏组织，细胞里含有的叶绿体多些；接近下表皮的叶肉细胞形状不规则，排列疏松，是海绵组织，细胞里含叶绿体少些．光合作用在叶绿体能进行．

（4）散布在表皮细胞中的由半月形的保卫细胞组成的气孔是叶片与外界进行气体交换的窗口，也是植物蒸腾失水的门户；气孔的张开和闭合由构成它的保卫细胞控制．

故答案为：

（1）③叶脉（2）①上表皮 ⑤下表皮（3）②栅栏组织（4）⑥气孔

完形填空

It was lunchtime and I walked into a small branch office on the West Side. I had come to   36  a checking account. The only officer on   37  was a fortyish black man, standing   38  a small counter from a young white boy who was wearing a V-necked sweater. I think I was especially   39  of the boy because he looked more like a kid from a prep school than a   40  in a West Side bank.
The boy continued to   41  my attention because of what happened next. He was holding an open savings-account book and   42  an expression of disappointment. “But I don’t understand. I opened the account myself, so why can’t I   43  any money?” the boy said, his voice breaking.
“I know it is, but those are the rules. I’ve already explained to you that a fourteen-year-old is not   44  to withdraw money without a letter from his parents,” the officer explained patiently.
Suddenly I noticed the account had a series of small deposits and withdraws. Then I questioned the officer, “How do you   45  that? Why did you let him withdraw money before, but not now?” He looked   46 . “Because the tellers were not aware of his age before and now they are. It’s really very   47 .” I turned to the boy with a shrug. “You’re really getting   48 ,” I said. “You ought to get your parents to come in here and   49 .” The boy looked destroyed.   50 , he put his savings book in a rear-pocket and walked out of the bank.
The officer turned to me. “You know,” he said, “you really shouldn’t have got   51 .” I couldn’t believe what this idiot was saying. “We were   52  this morning that some neighborhood bully has been shaking down (敲诈) this boy for more than a month. The other guy was   53  him to take money out every week and hand it over. The poor kid was   54  too scared to tell anyone. Anyway, the police are on the case and they’ll probably make a(n) 55  today."
“You mean there is no rule about being too young to withdraw money from a savings account?”
“Not that I ever heard of. Now, sir, what can we do for you?”

B．disappointed

B．interrupted

B．unwillingly

单项选择题

导轮V型槽槽底的半径必须（）钼丝半径，以保证钼丝不易晃动。

A、小于；

B、等于；

C、大于