首页
登录
职称英语
Plants are subject to attach and infection by a remarkable variety of symbio
Plants are subject to attach and infection by a remarkable variety of symbio
游客
2025-03-27
26
管理
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. [br] Why does the author mention "glycoproteins" in Line 16?
选项
A、To compare plant defense mechanisms to the immune system of animals.
B、To introduce the discussion of active defense mechanisms in plants.
C、To illustrate how chemicals function in plant defense.
D、To show the advantages of plant defense mechanisms.
答案
C
解析
文中第二段阐明了植物如何通过化学物质抵御外来入侵,举例后使意思更具体。选项C是正确的。
转载请注明原文地址:https://tihaiku.com/zcyy/4015126.html
相关试题推荐
ThegreatAmericanscientistEdisonhadaremarkable______forinventingnewth
Itissuggestedbytheauthorsofthepaperthattheirsubjectsaremorepronet
Botany,thestudyofplants,occupiesapeculiarpositioninthehistoryof
Botany,thestudyofplants,occupiesapeculiarpositioninthehistoryof
Botany,thestudyofplants,occupiesapeculiarpositioninthehistoryof
Plantsaresubjecttoattachandinfectionbyaremarkablevarietyofsymbio
Plantsaresubjecttoattachandinfectionbyaremarkablevarietyofsymbio
Plantsaresubjecttoattachandinfectionbyaremarkablevarietyofsymbio
Alloftheplantsnowraisedonfarmshavebeendevelopedfromplants______in
Ihavenodoubtthatifthestudents’interestinthesubjectisaroused,theyw
随机试题
PersonalDetailsFamilyname:PetersAddress:7【L4】____
BesidesFrenchwords,Englishalsoabsorbedasmanyas2,500wordsof_____inthe
RudolphValentinoboughtabeautifulring.Thejewelersaidthatithada【D6
给水排水系统试验中不包括的是()。A.承压管道压力试验 B.排水支管通
近年来,我国流动人口一直维持在2亿人以上,且持续增长,城乡间人口流动是主要的流动
图4显示了新中国成立后农业集体化的进程,其中的X应是()。 A.合作小组
()不属于意外现金储备的支付范围。A:重大疾病 B:意外灾难 C:犯罪事件
2003年至2011年,我国第一产业年增长4.6%,第二产业年均增长11.9%,
下列刑事案件应由中级人民法院管辖的是()。A.危害国家安全的案件 B.恐怖活动
祺航公司向法院申请破产,法院受理并指定甲为管理人。债权人会议决定设立债权人委员会
最新回复
(
0
)