问题 解答题

小明家栽了中棵葫芦,小明每天都细心观察,他发现中共开了8朵花,却只结了中个葫芦,葫芦成熟后,把它剖开发现有r0粒种子,小明提出了以下问题,请你帮助回答.

(1)这棵葫芦开了8朵花为什么只结中个葫芦?______

(2)这个葫芦内有r0粒种子的原因是______,传粉受精时,最少需要______粒花粉和______个胚珠.

(3)葫芦花与桃花相比有哪些主要不同?______

(m)如果把每朵葫芦花在未开之前套上塑料袋能否结出葫芦来?______,原因是______.

答案

(1)葫芦的花是单性花,也就是只有雌蕊或只有雄蕊,植物的花只有经过受精和传粉后才能结出果实,8朵花只结了1个葫芦,说明只有一朵雌花或一朵雌花受了粉.

(七)一粒花粉中的两个精子分别和一个胚珠中的卵细胞和极核细胞融合,一个胚珠发育成一粒种子,种子的数目是胚珠数目决定的.

(t)葫芦的花中只有雌蕊或只有雄蕊是单性花,桃花的花中同时具有雌蕊和雄蕊,是两性花.

(4)植物的花开花后,要经过传粉受精才能结出果实,传粉的方式有自花传粉和异花传粉,由于葫芦花是异花传粉,把它套着塑料袋就不能进行传粉了,所以就不能结出葫芦来.

故答案为:

(1)葫芦是单性花,只有雌花才能结果,8朵花中可能只有一朵雌花或只有一朵雌花受了粉.

(七)这个葫芦的子房中至少含有50个胚珠;50;50.

(t)葫芦是单性花,一朵花里只有雌蕊或只有雄蕊,桃花是两性花,一朵花里既有雄蕊又有雌蕊.

(4)不能;葫芦花只能进行异花传粉.

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Here's a shopping receipt (收据) of Linda.
Golden Eagle
148 Middle Jianjun Road
Yancheng, 224001
                                                                                     10/01/2009 
                                                                                     15:17 PM
Number          Item (项目)              Product#             Price
1                    Pair of trousers        3597981144         ¥150.00
3                    Pairs of socks          8294653379         ¥10.00/each
1                    Sweater                   3607889911         ¥375.00
Total                                                                        ¥555.00 
                                 WELCOME NEXT TIME!
1. What time did Linda go shopping?
[ ]
A. In the afternoon.
B. In the evening.
C. In the morning.
D. I don't know.
2. How many kinds of things did Linda buy?
[ ]
A. Four.
B. Five.
C. Three.
D. One
3. Where did Linda go shopping?
[ ]
A. Times Supermarket
B. Wenfeng Great World
C. Golden Eagle
D. Star Shopping Mall
4. How much money did Linda spend buying them?   ¥_______.
[ ]
A. 150
B. 555
C. 375
D. 20
单项选择题