问题 解答题

如图表示从一朵桃花发育成一个桃子的过程,请据图分析作答:

(1)春天桃花盛开,一朵美丽的桃花中最主要的结构是______.

(2)甲图中所示的是植物有性生殖过程中的______

(3)受精作用完成后,乙图所示的结构中的______继续发育成丙图中的③.

(4)水蜜桃味美多汁,生产上常采用嫁接的方法繁殖后代,其最主要目的是______

A.短时间内大批生产               B.保持水蜜桃的优良性状

C.提高后代的生活力               D.防止植物病毒的侵害.

答案

由图可知①胚珠、②子房、③种子.

(1)一朵花是有花托、萼片、花瓣、雌蕊和雄蕊等组成,雌蕊由柱头、花柱、子房三部分组成,雄蕊由花药和花丝两部分组成,绿色开花植物要形成果实和种子,必须经过传粉和受精.花粉成熟后散落出来落到雌蕊柱头上,在柱头黏液的刺激下萌发长出花粉管,花粉管穿过花柱,进入子房,一直到达胚珠,同时,花粉管中的两个精子随花粉管的伸长而向下移动,最终进入胚珠内部,花粉管顶端破裂,两个精子释放出来,一个精子与胚珠中的卵细胞相融合形成受精卵,另一个精子与胚珠中的两个极核相融合,形成受精极核,受精作用完成后,子房继续发育成果实,其中子房壁发育成果皮,胚珠发育成种子,受精卵发育成种子的胚,受精极核发育成胚乳.可见与果实和种子的形成有直接关系且是一朵花的最主要的部分是花蕊(或雄蕊和雌蕊). 

(2)雄蕊花药里的花粉散落出来,落到雌蕊柱头上的过程叫传粉.两性花的雄蕊花药里的花粉,落到同一朵花的雌蕊柱头上的过程,叫做自花传粉,也叫自交. 自花传粉的植物必然是两性花,而且一朵花中的雌蕊与雄蕊必须同时成熟.自然界中自花传粉的植物比较少,如大麦、小麦、大豆、豆角、稻子、豌豆、指甲花等.雄蕊花药里的花粉,经过风力,水力,昆虫或人的活动把花粉通过不同途径传播到雌蕊的花柱上的过程叫异花传粉. 依靠风力传粉的花叫风媒花,依靠昆虫等传粉的花叫虫媒花.因此,甲图中所示的是植物有性生殖过程中的传粉(或异花传粉).

(3)受精作用完成后,只有花的子房继续发育,发育结果如下:

所以乙图所示的结构中的①胚珠发育成丙图中的③种子.

(4)嫁接没有经过雌雄两性生殖细胞的而结合,遗传物质没有发生变异,能保证遗传物质的稳定遗传.嫁接既能保持接穗品种的优良性状,又能利用砧木(根系)的有利特性,达到早结果、增强抗寒性、抗旱性、抗病虫害的能力,还能经济利用繁殖材料、增加苗木数量.常用于果树、林木、花卉的繁殖上;也用于瓜类蔬菜育苗上.

故答案为:(1)花蕊(或雄蕊和雌蕊);

(2)传粉(或异花传粉);

(3)①;

(4)B.

问答题 简答题
阅读理解

I’ve loved my mother’s desk since I was just tall enough to see above the top of it as mother sat doing letters. Standing by her chair, looking at the ink bottle, pens,   and white paper, I decided that the act of writing must be the more wonderful thing in the world.

Years later, during her final illness, mother kept different things for my sister  and brother. “But the desk,” she’d said again, “it’s for Elizabeth. ”

I never saw her angry, never saw her cry. I knew she loved me; she showed it in action. But as a young girl, I wanted heart-to-heart talks between mother and    daughter.

They never happened. And a gulf opened between us. I was “too emotional(易动感情的)”. But she lived “on the surface(表面)”.

As years passed I had my own family. I loved my mother and thanked her for our happy family. I wrote to her in careful words and asked her to let me know in any way she chose that she did forgive(原谅) me.

I posted the letter and waited for her answer. None came.

My hope turned to disappointment(失望), then little interest and, finally, peace— it seemed that nothing happened. I couldn’t be sure that the letter had even got to mother. I only knew that I had written it, and I could stop trying to make her into someone she was not.

Now the present of her desk told, as she’d never been able to, that she was    pleased that writing was my chosen work. I cleaned the desk carefully and found    some papers inside —a photo of my father and a one-page letter, folded(折叠) and refolded many times.

Give me an answer, my letter asks, in any way you choose. Mother, you always chose the act that speaks louder than words.

小题1:The writer began to love her mother’s desk ______.

A.after Mother died

B.before she became a writer

C.when she was a child

D.when Mother gave it to her小题2:The passage shows that ______.

A.mother was cold on the surface but kind in her heart to her daughter

B.mother was too serious about everything her daughter had done

C.mother cared much about her daughter in words

D.mother wrote to her daughter in careful words小题3:The word “gulf” in the passage means ______.

A.deep understanding between the old and the young

B.different ideas between the mother and the daughter

C.free talks between mother and daughter

D.part of the sea going far in land小题4:What did mother do with her daughter’s letter asking forgiveness?

A.She had never received the letter.

B.For years, she often talked about the letter.

C.She didn’t forgive her daughter at all in all her life.

D.She read the letter again and again till she died.小题5:What’s the best title of the passage?

A.My letter to Mother

B.Mother and Children

C.My mother’s Desk

D.Talks between Mother and Me