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.
68.The passage suggests that the place of hypotha-
lamic hormones in the hormonal hierarchies of
animals is similara to the place of
which of the followeing in plants?
(A) Plant cell walls
(B)The complement of genes in each plant cell
(C)A subsetof a plant cell'sgene complement
(D)The five major hormones
(E)The oligosaccharins
The best answer is D.Acording to the passage ,"The pleiotropy ofthe five well-studied plant hormones is somewhat analogous to that ofcertain hormones in animals"(lines 24-26).The example given involves certain hypothalamic hormones that "stimulate the anterir love of the pituitary gland to synthesize and release many different hormones from the adrenal cortex"(lines27-30)……
请教：题目问的是 hypothalamic hormones 的place,为什么回答是D,难道是hormones 在The five major hormones里，请大虾们解释一下
在动植物不同的激素体系中，hypothalamic hormones所处的级别和The five
major hormones所处的级别相当。这是文章后两段的重点内容。
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. (这句话确定了动植物的比较对象是five hormones 和动物的hormones)For example, （说明后面的内容都是基于前一句话而言的）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.
68.The passage suggests that the place of hypotha-
lamic hormones in the hormonal hierarchies of
animals is similara to the place of
which of the followeing in plants?题目问的是动物与植物的一个类比，你定位在L24那里就可以了，至于place， 如果不能理解，你可以忽略，因为这个题目问的是动物的什么与植物的什么较为相似，然后动物那边出现了一个place， 植物那边也出现一个place， 所以不用比较，这个等价；而place后面的东西，动物那边出现了hyothamic hormones， 相应的你要在植物这边找个对应的。在读文章的时候你应该注意到在L24那里出现了两者的对应，同时，作者还用了例子说明，然后你回去定位找到与hyothamic hormones对应的东西就可以。
（罗嗦了半天，不知道有没有表达清楚？？呵呵）
(A) Plant cell walls
(B)The complement of genes in each plant cell
(C)A subsetof a plant cell'sgene complement
(D)The five major hormones
(E)The oligosaccharins
The best answer is D.Acording to the passage ,"The pleiotropy ofthe five well-studied plant hormones is somewhat analogous to that ofcertain hormones in animals"(lines 24-26).The example given involves certain hypothalamic hormones that "stimulate the anterir love of the pituitary gland to synthesize and release many different hormones from the adrenal cortex"(lines27-30)……
请教：题目问的是 hypothalamic hormones 的place,为什么回答是D,难道是hormones 在The five major hormones里，请大虾们解释一下
还是没搞懂，难道这里的place时表示级别吗？
能不能麻烦你将题干翻译一下，谢谢！
The passage suggests that the place of hypothaamic hormones in the hormonal hierarchies of animals is similara to the place of which of the followeing in plants?
本文表明，在动物荷尔蒙层级中，H荷尔蒙所处的地位，类似于植物层级的那种物质的地位？
place是指地位，等级，这一类的意思，这个题目里面你可以把它理解成作用。我上面的分析就是基于如果考试时候不知道place的意思，也没有关系，就按照这个方向去推就可以，至于其确切的意思，无需知道。
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