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实验一:将空白琼脂和含EDTA的琼脂做成帽状,分别套在甲、乙两组玉米胚根的根冠外(示意图如下)。提示:EDTA的作用是去除与其临接部位的 Ca2+。
将胚根水平放置培养一定时间后,观察到甲组胚根向重力(下)生长,乙组胚根水平生长。根据上述实验结果,得出实验结论: 。
实验二:水平放置的胚根弯曲向下生长,与根冠近地侧的Ca2+浓度明显高于远地侧有关。研究表明,根总是朝着Ca 2+浓度高的方向弯曲生长。为验证这一结论,有人设计了下列实验方案。请根据提供的实验材料和用具,写出第二步及以后的实验步骤和实验结果,并回答问题。
(1)实验材料和用具:胚根等长的萌发玉米种子,空白琼脂帽,含EDTA的琼脂帽,上面部分含Ca2+的琼脂帽(水平方向),培养皿等。
(2)实验步骤:
第一步:取若干个培养皿,在每个培养皿中放置适量的萌发玉米种子,按实验一中乙组的方法处理胚根一定时间后,移去根冠外的琼脂帽。然后将培养皿平均分成两组,编号为 A组、B 组。
第二步: 。
第三步: 。
(3)实验结果: 。
(4)科学家进一步证实,根冠中生长素的分布受Ca2+浓度影响,当胚根水平放置时,重力诱导Ca2+向根冠下侧移动,导致近地侧的生长素浓度比远地侧高。请分析胚根的生长素分布与向重力生长的关系: 。 查看习题详情和答案>>
A man got a new car and he was very proud 26 it. One day, when he 27 back home, he saw his three-year-old son 28 hitting the new car with a toy hammer. The man was 29 angry that he ran to his son, grabbed the hammer from 30 , and used the hammer to hit the little boy’s hands too hard. The 31 boy cried out but his father didn’t care.
When the father 32 , he took his son to the 33 as fast as he could. Although the doctor tried his best to save the 34 bones(骨头), he had to cut the fingers from both of the boy’s hands in the end.
When the boy 35 in the hospital and saw his hands, he innocently(天真) said, “Dady, I’m sorry about your car.” Then he asked, “but 36 are my fingers going to grow back?” The father 37 very sad.
Think about the story when 38 steps on your feet or when you wish to take revenge(报复). Think first before you lose your patience with someone. Cars can 39 , but broken bones and hurt feelings often can’t.
People often make mistakes. But we should remember that forgiveness is greater than revenge. 40 before act!
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短文填空 (共10分,每空1分)
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come, fall, sit, look, be, walk, jump, sell, hear, drop |
根据短文内容,用方框中所给词的正确形式填空,使短文完整、正确。(每个词只能用一次)(共10分,每小题1分)
Early in the morning, Mr. Black was carrying a big basket of cabbages to the market. She hoped 1.___them to the people from town.
The mountain road was narrow(狭窄的)and the old woman 2.___carefully. Suddenly she 3.___a loud bell. It passed her and very fast down the hill. The old woman had to 4.__to one side of the road so quickly that the basket of cabbages nearly 5.___into the valley.
She saw a young boy 6..___on the bicycle without even 7.___round to see if the old woman was all right.
The old woman shouted, 8.___back.”
“What 9.___it?” the boy asked impolitely, pushing his bike towards the old woman.
“What did I drop?”
“Little boy, you 10.___your manner.” The old woman answered.
查看习题详情和答案>>
短文填空 (共10分,每空1分)
| come, fall, sit, look, be, walk, jump, sell, hear, drop |
Early in the morning, Mr. Black was carrying a big basket of cabbages to the market. She hoped 【小题1】___them to the people from town.
The mountain road was narrow(狭窄的)and the old woman 【小题2】___carefully. Suddenly she 【小题3】___a loud bell. It passed her and very fast down the hill. The old woman had to 【小题4】__to one side of the road so quickly that the basket of cabbages nearly 【小题5】___into the valley.
She saw a young boy 【小题6】.___on the bicycle without even 【小题7】___round to see if the old woman was all right.
The old woman shouted, 【小题8】___back.”
“What 【小题9】___it?” the boy asked impolitely, pushing his bike towards the old woman.
“What did I drop?”
“Little boy, you 【小题10】___your manner.” The old woman answered. 查看习题详情和答案>>
When the father 32 , he took his son to the 33 as fast as he could. Although the doctor tried his best to save the 34 bones(骨头), he had to cut the fingers from both of the boy’s hands in the end.
When the boy 35 in the hospital and saw his hands, he innocently(天真) said, “Dady, I’m sorry about your car.” Then he asked, “but 36 are my fingers going to grow back?” The father 37 very sad.
Think about the story when 38 steps on your feet or when you wish to take revenge(报复). Think first before you lose your patience with someone. Cars can 39 , but broken bones and hurt feelings often can’t.
People often make mistakes. But we should remember that forgiveness is greater than revenge. 40 before act!
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