63篇之24第3题，没找到相关讨论，不知道是否有重合但用了别的编号的讨论，麻烦有知道的指点一下，谢谢

lydiar_020

PASSAGE 24
*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 planthormones 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.
3. The passage suggests that which of the following is afunction likely to be performed by an oligosaccharin?
(A) To stimulate a particular plant cell to become part ofa plant's root system
(B) To stimulate the walls of a particular cell to produceother oligosaccharins
(C) To activate enzymes that release specific chemicalmessengers from plant cell walls
(D) To duplicate the gene complement in a particularplant cell
(E) To produce multiple effects on a particularsubsystem of plant cells

答案是A

问，定位应该是在哪里？

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.

这句应该怎样翻译呀？

lydiar_020

ding