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实验1:将切除的胚芽鞘尖端放置于琼脂块上(图1),移去尖端后,将琼脂切成体积相等的若干个方块,将方块放在除去尖端的胚芽鞘上,实验进行一定时间后,每个胚芽鞘弯曲的角度以图2的方法测量,并计算平均值。每次放在等面积、等体积琼脂块上的胚芽鞘尖端数量不同,这样重复上述过程。
实验2:用含有不同浓度IAA的琼脂块代替胚芽鞘尖端进一步实验。上述两个实验的结果如图3和图4所示。
(1)绘图表示,如何将琼脂块放置于胚芽鞘上,才能得到图3的结果?
(2)解释实验2的结果:IAA从0μmol/L~1.3μmol/L过程中 ;1.3μmol/L~1.8μmol/L过程中 。
(3)①比较实验1和实验2的结果有什么不同? 。
②为什么会出现这种不同? 。
(4)从本实验可知促进胚芽鞘生长的最适生长素浓度约为_______
图4中曲线上b点对应生长素浓度时胚芽鞘弯曲角度为17度,把琼脂块去掉后,胚芽鞘最终会如何生长?________ 查看习题详情和答案>>
补全对话(每空一词)
A:Excuse me,11 is the way to the Children’s Hospital?
B:12 ,I don’t know.You’d 13 ask that policeman.
A:Excuse me,14 can I get to the Children’s Hospital?
C:Oh,go along Huanghe Street,and 15 the second turning on your left.Then 16 No.3 bus and 17 off 18 the third stop.You’ll see a white building 19 the post office and the police station.You 20 miss it.
A:Thank you very much.
C:You are welcome.
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When I was a little girl,my mom liked to make breakfast food for dinner every now and then.And I remember one__1__when my mom placed a plate of eggs,sausage and extremely__2__toast (土司面包) in front of my dad.I remember__3__to see if anyone noticed!__4__all my dad did was reach for his toast,__5___at my mom and ask me how my day was at school.
When I__6__from the table that evening,I remember hearing my mom__7__to my dad for burning the toast.And I’ll__8__forget what he said,“Baby,I love burnt toast.” Later that night,I went to__9__Dad good night and I asked him if he really__10__his toast burnt.He wrapped me up in his__11__and said,“Debbie,your mom had a__12__day at work today and she’s really tired.And besides,a little burnt toast never__13__anyone!” In bed that night,I thought about the scene at dinner and the__14__my dad showed to my mom.
To this day,it’s a cherished (珍贵的)__15__from my childhood that I’ll never forget.And it’s one that came to__16__just recently when Jack and I sat down to eat dinner.
As I__17__the plate in front of Jack,I waited for a(n)__18__about the burnt toast.But all I got was,“Thank you,dear!This is__19__.I know you had a hard day!” Just then,I thought about my parents,and was quietly thankful for having a__20__where burnt toast wasn’t a deal?breaker either!
1.A.noon B.afternoon
C.morning D.night
2.A.expected B.burnt
C.sweet D.delicious
3.A.being encouraged B.being allowed
C.waiting D.refusing
4.A.Yet B.Although
C.So D.Until
5.A.laugh B.smile
C.shout D.stare
6.A.got up B.got back
C.broke away D.put forward
7.A.report B.shout
C.apologize D.complain
8.A.almost B.never
C.often D.hardly
9.A.ask B.greet
C.tell D.kiss
10.A.liked B.got
C.cooked D.made
11.A.head B.heart
C.arms D.hands
12.A.boring B.hard
C.disappointing D.sad
13.A.hurts B.comforts
C.invites D.hates
14.A.interest B.surprise
C.kindness D.satisfaction
15.A.feeling B.story
C.choice D.memory
16.A.life B.mind
C.an end D.a conclusion
17.A.set down B.took away
C.finished up D.washed up
18.A.answer B.question
C.comment D.suggestion
19.A.possible B.true
C.terrible D.great
20.A.condition B.future
C.situation D.marriage
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Jeff Keith has only one leg. When he was only twelve years old, Jeff had cancer. Doctors had to 16 off most of his right leg.
17 Jeff puts on an artificial leg(假肢). The leg is plastic. With the plastic leg, Jeff can ski, ride a bicycle, swim, and play soccer. He can also run.
Jeff made a plan with his friends who had plastic legs, 18 . They decided to 19 across America. They all wore special T-shirts. 20 it was “Run, Jeff, Run, Jeff Keith’s Run Across America”.
Jeff Keith ran across the United States from the east to the west 21 he was twenty-two years old. He started running in Boston(波士顿). Seven 22 later, he stopped 23 in Los Angeles(洛杉矶). He ran 3,200 miles (1 mile = 1.6093km). Jeff wore out thirty-six pairs 24 running shoes and five plastic legs. Jeff 25 in cities on the way to Los Angeles. In every city people gave Jeff money. The money was not for Jeff, 26 for the American Cancer Society. The Society used the money to help people know 27 about cancer.
On the way to Los Angeles, Jeff talked to people about 28 . Jeff is disabled, but he can do many things. He finished college and is studying to be a lawyer(律师). Jeff says, “People can do 29 they want to do. I want people to know that. I ran 30 for disabled people. I ran for everybody.”
1.A. take B. cut C. put D. set
2. A. Every day B. One day C. Some day D. A day
3. A. also B. too C. either D. neither
4.A. walk B. fly C. swim D. run
5. A. On B. In C. With D. Above
6.A. while B. because C. when D. if
7. A. months B. days C. hours D. minutes
8.A. running B. to run C. walking D. to walk
9.A. at B. for C. in D. of
10.A. reached B. studied C. stopped D. started
11. A. and B. but C. or D. so
12.A. more B. less C. fewer D. little
13.A. cancer B. walk C. society D. America
14.A. any B. thing C. nothing D. anything
15. A. not only B. not C. only D. just
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