首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Plants are subject to attach and infection by a remarkable variety of symbiotically species and have evolved a diverse array of
Plants are subject to attach and infection by a remarkable variety of symbiotically species and have evolved a diverse array of
admin
2013-05-29
53
问题
Plants are subject to attach and infection by a remarkable variety of symbiotically species and have evolved a diverse array of mechanisms designed to frustrate the potential colonists. These can be divided into preformed or passive defense mechanisms and inducible or active systems. Passive plant defense comprises physical and chemical barriers that prevent entry of pathogens(病原体), such as bacteria, or render tissues unpalatable or toxic to the invader. The external surfaces of plants, in addition to being covered by an epidermis(表皮层) and a waxy cuticle, often carry spiky hairs known as trichomes(毛状物), which either prevent feeding by insects or may even puncture and kill insect larvae. Other trichomes are sticky and glandular and effectively trap and immobilize insects.
If the physical barriers of the plant are breached, then preformed chemicals may inhibit or kill the intrude, and plant tissues contain a diverse array of toxic or potentially toxic substances, such as resins, tannins, glycosides, and alkaloids, many of which are highly effective deterrents to insects that feed on plants. The success of the Colorado beetle in infesting potatoes, for example, seems to be correlated with its high tolerance to alkaloids that normally repel potential pests. Other possible chemical defenses, while not directly toxic to the parasite, may inhibit some essential step in the establishment of a parasitic relationship. For example, glycoproteins(糖蛋白) in plant cell walls may inactivate enzymes that degrade cell walls. These enzymes are often produced by bacteria and fungi.
Active plant defense mechanisms are comparable to the immune system of vertebrate animals, although the cellular and molecular bases are fundamentally different. Both, however, are triggered in reaction to intrusion, implying that the host has some means of recognizing the presence of a foreign organism. The most dramatic example of an inducible plant defense reaction is the hypersensitive response. In the hypersensitive response, cells undergo rapid necrosis—that is, they become diseased and die—after being penetrated by a parasite; the parasite itself subsequently ceases to grow and is therefore restricted to one or a few cells around the entry site. Several theories have been put forward to explain the basis of hypersensitive resistance.
What does the passage mainly discuss?
选项
A、The success of parasites in resisting plant defense mechanisms.
B、Theories on active plant defense mechanisms.
C、How plant defense mechanisms function.
D、How the immune system of animals and the defense mechanisms of plants differ.
答案
C
解析
从全文来看,主要讲述了植物的防御系统怎样发挥作用,并拥有两个方面,即physical和chemical barriers。显然答案是C。
转载请注明原文地址:https://www.kaotiyun.com/show/jKTO777K
0
研究生英语学位课统考(GET)
相关试题推荐
Theexchangeofgoodwillmissiongreatly______abetterunderstandingbetweenthetwocountries.
Theimageofthevolunteersontelevisionadvertisingprovides______intopeople’sattitudestowardvolunteering.
Discoveredintheearly1800sandnamed’nicotianine’,theoilyessencenowcallednicotineisthemainactiveingredientoft
Fewerandfeweroftoday’sworkersexpecttospendtheirworkinglivesinthesamefield,______thesamecompany.
Writeacompositionofatleast250wordsbasedonthetopic"Trust".Yourwritingshouldincludethefollowinginformation.1.当
Thesearchforlatentprintsisdoneinasystematicandintelligentmanner.Investigatorsdeveloptechniquestolocatetraceso
Thefactisthattheenergycrisis,whichhassuddenlybeenofficiallyannounced,hasbeenwithusforalongtimenow,andwill
We’veallheardaboutendangeredanimals.Creatureslikethecriticallyendangeredblackrhinocerosarefamous.Butwhatarethe
Forsometimepastithasbeenwidelyacceptedthatbabies—andothercreatures—learntodothingsbecausecertainactsleadto
随机试题
“噫,连在静默地忆想上帝之时,你们也要合一。不过在你们合一之中,要有间隙。让天风在你们中间舞荡。”这段关于在婚姻关系中要保持相对独立性的看法,出自()
国家公务员复核处理决定的形式有
下列各项,采用复制法的炮制品是
属于井冈山旅游区的有()。
已知直线l1:y—2x—=0和直线l2:3y—x—3=0,它们之间的夹角为________.
就下列下划线部分的知识点进行解释英国打败荷兰,取得“新阿姆斯特丹”的领土,命名为“纽约”(NewYork)017世纪下半叶,纽约人口愈来愈多并成为商业中心,丰富的农产品得以出口;工业制品的进口,带动当地经济的发展;在缺乏劳力的情况下,纽约成为黑奴市场
斯地驳尔是一种经常毁坏北美谷类庄稼的有害昆虫。在其他一些大陆上,斯地驳尔对庄稼的毁坏可以被某种蜂所控制。因为这种蜂只以斯地驳尔为食,将其引进北美可使庄稼免遭斯地驳尔的毁坏且不危害其他北美的昆虫。下面哪一个是上面论述所基于的假设?
中国特色社会主义理论体系包括()
Itisnotunusualforchiefexecutivestocollectmillionsofdollarsayearinpay,stockoptions,andbonuses.Inthelastfif
假设你正负责一个网络改造项目,决定为这件工作设计工作流程图表。在线槽完工前必须购买到网络设备。在这个例子里,这种关系属于()。
最新回复
(
0
)