OG12逻辑分析

liu977

大家觉得这篇文章在生物类里算什么难度的啊？读起来感觉比较吃力，主要是1.专有名词太多记不住。2.有些名词虽然字同但指代对象好像不大一样。

最主要的是三段与四段之间的逻辑关系不很清晰，第三段是在谈植物的5个hormones与动物的某些特定的hormones相似，但是为什么在L31提到这些hormones有specific effects呢？那不是与植物的Oligosaccharins了吗？

liu977

Up...Up...Up

蓝夕叶子

Passage 12

All of the cells in a particular plant start out with the

same complement of genes. How then can these cells

differentiate and form structures as different as roots,

stems, leaves, and fruits? The answer is that only a

(5) small subset of the genes in a particular kind of cell are

expressed, or turned on, at a given time. This is accom-

plished by a complex system of chemical messengers

that in plants include hormones and other regulatory

molecules. Five major hormones have been identified:

(10) auxin, abscisic acid, cytokinin, ethylene, and gibberel-

lin. Studies of plants have now identified a new class of

regulatory molecules called oligosaccharins.

Unlike the oligosaccharins, the five well-known plant

hormones are pleiotropic rather than specific, that is,

(15) each has more than one effect on the growth and devel-

opment of plants. The five has so many simultaneous

effects that they are not very useful in artificially

controlling the growth of crops. Auxin, for instance,

stimulates the rate of cell elongation, causes shoots to

(20) grow up and roots to grow down, and inhibits the

growth of lateral shoots. Auxin also causes the plant to

develop a vascular system, to form lateral roots, and to

produce ethylene.

The pleiotropy of the five well-studied plant

(25) hormones is somewhat analogous to that of certain

hormones in animal. For example, hormones from the

hypothalamus in the brain stimulate the anterior lobe

of the pituitary gland to synthesize and release many

different hormones, one of which stimulates the release

(30) of hormones from the adrenal cortex. These hormones

have specific effects on target organs all over the body.

One hormone stimulates the thyroid gland, for

example, another the ovarian follicle cells, and so forth.

In other words, there is a hierarchy of hormones.

(35) Such a hierarchy may also exist in plants. Oligosac-

charins are fragments of the cell wall released by

enzymes: different enzymes release different oligosac-

charins. There are indications that pleiotropic plant

hormones may actually function by activating the

(40) enzymes that release these other, more specific chemical

messengers from the cell wall.

蓝夕叶子

科学类的文章，我个人的感受是要记住几个很佶屈聱牙的词之间的联系。然后要靠记忆。

偶就是一个死记的人。

感觉这篇文章在og里面的科学类文章中不算最难的。

偶觉得og1最难。

wangyu73cn

For example, hormones from the

hypothalamus in the brain stimulate the anterior lobe

of the pituitary gland to synthesize and release many

different hormones, one of which stimulates the release

(30) of hormones from the adrenal cortex. These hormones

have specific effects on target organs all over the body.

One hormone stimulates the thyroid gland, for

example, another the ovarian follicle cells, and so forth.

In other words, there is a hierarchy of hormones.

对于specific问题，我觉得，关键是在意思上来说，these hormones代many different hormones

liu977

谢谢蓝MM帮我贴出原题

看了WangyuGG的解释，似乎明白了，是不是说these hormones＝many different hormones＝植物的Oligosaccharins ？

wangyu73cn

以下是引用liu977在2005-6-18 11:16:00的发言：

谢谢蓝MM帮我贴出原题

看了WangyuGG的解释，似乎明白了，是不是说these hormones＝many different hormones＝（类比于）植物的Oligosaccharins ？

我认为是的。

liu977

Got it!!