问题 解答题

把一段带叶的茎放在盛有水的锥形瓶内(图一所示),并向锥形瓶内滴加几滴红墨水,将该装置放在阳光下3-4小时后,取其茎进行横切(图二所示),观察并回答下列问题:

(1)图一中变红的结构是______,图二中变红的结构是______.这一实验说明了植物根吸收的水分是通过______输送到植物的各个器官的.

(2)图二中的______是______,从植物体的结构层次看,属于______组织,该组织细胞经过分裂向外可形成______.

(3)该实验中,将带叶的茎放在阳光下照射,其目的是叶片上的气孔______,以利于水分的散失,从而提高植物的______作用,缩短实验时间.

答案

(1)茎中输导组织根据其构造和功能的不同,分为两类:导管和筛管,导管的主要功能是自下而上运输水和无机盐.筛管的主要功能是自上而下运输有机物质.将一根枝条插入滴有红墨水的瓶中,放在太阳下(促进蒸腾作用),过一段时间,将枝条纵切开来,可以看到染成红色的部分是木质部,正是因为木质部中含有导管是自下而上输送水分和无机盐的管道.叶片变红也是由此.

(2)在树皮以内有一层分生组织,叫形成层.形成层的细胞不断的侧向分裂增生,其中,大部分细胞向内形成木质部,少量细胞向外形成韧皮部,从而使得树干不断地生长加粗.

(3)气孔是由保卫细胞之间形成的凸透镜状的小孔.我们知道保卫细胞为半月形,因外侧较薄而内侧较厚,保卫细胞吸水时,细胞膨胀,细胞厚度增加,两细胞分离,气孔张开;保卫细胞失水时,细胞收缩,细胞厚度减小,两细胞并合,气孔闭合.所以明显可将知带叶的茎放在阳光下照射,其目的是叶片上的气孔开张,其通过量是由保卫细胞的开闭作用来调节,在生理上具有重要的意义.气孔被称为植物蒸腾失水的“门户”,也是气体交换的“窗口”.

故答案为:

(1)叶片(或叶子);[2]导管(或[5]木质部);[2]导管

(2)3;形成层;分生;[4]韧皮部;

(3)张开;蒸腾

阅读理解

Londoners are great readers. They buy vast numbers of newspapers and magazines and of books --- especially paperbacks, which are still comparatively cheap in spite of ever-increasing rises in the costs of printing. They still continue to buy “proper” books, too, printed on good paper and bound (装订) between hard covers.

There are many streets in London containing shops which specialize in book-selling. Perhaps the best known of these is Charring Cross Road in the very heart of London. Here bookshops of all sorts and sizes are to be found, from the celebrated one which boasts of being “the biggest bookshop in the world” to the tiny, dusty little places which seem to have been left over from Dickens’ time. Some of these shops stock, or will obtain, any kind of book, but many of them specialize in second-hand books, in art books, in foreign books, in books on philosophy, politics or any other of the countless subjects about which books may be written. One shop in this area specializes only in books about ballet!

Although it may be the most convenient place for Londoners to buy books, Charring Cross Road is not the cheapest. For the really cheap second-hand books, the collector must venture off the beaten track, to Farringdon Road, for example, in the East Central district of London. Here there is nothing so impressive as bookshops. The booksellers come along each morning and pour out their sacks of books onto small hand carts. And the collectors, some professionals and some amateurs, have been waiting for them. In places like this they can still, occasionally, pick up for a few pence an old one that may be worth many pounds.

小题1:”Londoners are great readers” means that ___________.

A.Londoners are great because they read a lot.

B.There are a great number of readers in London.

C.Londoners read a lot.

D.Londoners are readers who read only great books.小题2:According to this passage, Charring Cross Road __________.

A.is in the suburbs of London

B.is the busiest street in London

C.contains various kinds of shops

D.is famous for its bookshops小题3:In this passage, what does the underlined part “venture off the beaten track” mean?

A.move away from a busy street

B.buy books in a most busy street

C.waste time looking for books

D.take a risk of losing one’s life小题4:On Farringdon Road, _______________.

A.you can find fine bookshops for the latest books

B.there are only small bookshops for the second-hand books

C.you can see book sellers selling books on hand-carts

D.the same books as the ones in the bookshops of Charring Cross Road are sold

单项选择题