单选题 A few milliamps of electricity can cause plants to increase synthesis of chemicals. These compounds often also have a pharmacological (related to medicine) or commercial value, so the trick could be used to help increase yields of commercially useful biologicals. Artemisinic acid, from sweet wormwood, for example, is used in malarial medications, and shikonin (紫草素), from the purple gromwell plant, is used against skin infections.
Researchers have long known that stressing plants can force them to take defensive action, often ramping up the production of protective chemicals that, for example, make them more resistant to insect attack. It has become common practice to stress such plants into increasing their yields. This is usually clone using physical stress elicitors (诱导子), including bits of the micro-organisms that normally attack the plants, or irritants made from metallic compounds such as copper chloride. These are effective, but they come at a cost. Most elicitors are toxic to plants and can build up in tissues, making it necessary to occasionally "clean" a plant of the chemicals so they keep having the same effect.
Recently, research groups at the University of Arizona in Tucson found that the application of an electric current to the hairy roots of the poisonous herb Hyoscyamus muticus stimulated the production of the herb's toxin hyoscyamine (天仙子胺). This unpublished finding inspired Hans Van Etten, also of the University of Arizona, and his colleagues to test sub-lethal levels of electrical currents on other plants, to assess electricity's potential to elevate chemical production.
The researchers exposed eight different plant species (ranging from Japanese pagoda tree seedlings to pea plants) to weak electrical currents of 30 milliamps. Seven of the plants increased their production o defensive chemicals. The average boost of chemical production was 20 times, they report in Biotechnology Progress. One plant, a type of alfalfa, increased its chemical yield by 168 times. These values are very similar to those achieved using chemical elicitors, and seem to have no lethal effects-just a negative effect on growth. The treatment can be used over and over again without the build-up of any unwanted material.
The useful compounds would be very easy to harvest: they simply pour out into solution if the plants are grown hydroponically. "The fact that we can use electricity instead of toxic materials to elicit chemical production is very exciting because it means we get to look at how these chemicals form without having to constantly add and remove toxins from the system," says Van Etten. "This is a really novel and creative approach that I've never seen before," says plant metabolic engineer Fabricio Medina Bolivar from Arkansas State University in Jonesboro. "The possibilities for using electricity with plants in this way are absolutely tremendous. /

单选题 Electricity acting on plants can be used to ______.
[A] take precautions against skin infections [B] increase production of useful biologicals
[C] increase pharmacological and commercial value [D] make plants more resistant to attack
【正确答案】 B
【答案解析】[解题思路] 文章开头便提到“几毫安的电流就能够使植物增加化学合成物”，然后接着阐述“这个诀窍可以被用来帮助增加对商业有用的生物制品的生产”，[B]是对本句的同义转述，符合题意。第一段末句提到is used against skin infections，但此处是举例说明紫草素的作用，并不是所有的电流都可以用来治疗皮肤病，故[A]不正确。题干的关键词是Electricity acting on plants，[C]和[D]表述皆不是作用于植物的电流的作用，[C]是compound(化合物)的作用，[D]是文中第二段提到的protective chemicals的作用。
单选题 The traditional ways of increasing the yields of chemical do NOT include ______.
[A] being attacked by micro-organisms [B] using physical stress elicitors
[C] applying copper chloride [D] employing electrical currents on plants
【正确答案】 D
【答案解析】[解题思路] 文章第二段第二句指出，对这些植物施压来增加化学品的产量已经是很普遍的做法，接下来介绍的就是传统施压的办法，文中第三句提到using physical stress elicitors(使用物理性应力诱导子)，bits of the micro-organisms that normally attack the plants(通常攻击植物的少量微生物)和irritants…such as copper chloride(刺激物……如氯化铜)，分别对应[A]、[B]和[C]。[D]是本文所讨论的新发现，不属于traditional ways，符合题意。
单选题 Which one of the followings is NOT the advantage of using electricity?
[A] It can achieve the same values as using chemical elicitors.
[B] It can be used time and again.
[C] It can boost chemical production.
[D] It has no adverse impacts on the growth of plants.
【正确答案】 D
【答案解析】[解题思路] 文章第四段谈到了使用电能的优缺点。倒数第二句提到have no lethal effects-just a negative effect on growth(没有致命的影响，只是对生长有副作用)，[D]表示对植物生长没有副作用，与原文冲突，故[D]符合题目要求。本句还提到这个值和那些使用化学诱导子达到的值非常接近，即[A]所表述内容。[B]与最后一句The treatment can be used over and over again表述一致。第四段的数字说明电刺激能够促进化学品的生产，故[C]正确。
单选题 The views of Fabricio and Van Etten towards the way of using electricity to elicit chemical production are ______.
[A] different [B] opposite [C] similar [D] complementary
【正确答案】 C
【答案解析】[解题思路] 通过分析题干可知，本题需要了解Fabricio和Van Etten的观点，然后进行比较。最后一段分别阐述了两人的观点，第二句指出Van Etten说“我们使用电力而不是有毒的材料来诱发化合物生产的事实很振奋人心。”第三句指出Fabricio Medina Bolivar的观点是“这真是一种既新奇又有创意的方法”，可见两人对使用电力来诱导化学物的产生都持正面观点，因此两人的态度是相似的，故[C]正确。
单选题 What is the main idea of the passage?
[A] Reactions to the electric stress lead to more chemical yields.
[B] Yields of commercially useful biologicals are increased.
[C] Using electricity to elicit chemical production is very exciting.
[D] Using electricity has a negative effect on plant growth.
【正确答案】 A
【答案解析】[解题思路] 主旨大意题需要把握全文框架结构。通览全文可知，通篇讲了一个问题，即开头所提到的“几毫安的电流就能够使植物增加化学合成物”，所以[A]正确。[B]只是其中一个方面，不够全面。[C]在最后一段提到，并不是本文的主体部分。文章通篇在介绍这种新的方法的积极意义，副作用只是一个方面．并不是通篇主旨，故[D]不正确。