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
Most growing plants contain much more water than all other materials combined. C. R. Barnes has suggested that it is as proper t
Most growing plants contain much more water than all other materials combined. C. R. Barnes has suggested that it is as proper t
admin
2019-06-23
56
问题
Most growing plants contain much more water than all other materials combined. C. R. Barnes has suggested that it is as proper to term the plant a water structure as to call a house composed mainly of brick a brick building. Certain it is that all essential processes of plant growth and development occur in water. The mineral elements from the soil that are usable by the plant must be dissolved in the soil solution before they can be taken into the root. They are carried to all parts of the growing plant and are built into essential plant materials while in a dissolved state. The carbon dioxide(CO
2
)from the air may enter the leaf as a gas but is dissolved in water in the leaf before it is combined with a part of the water to form simple sugars—the base material from which the plant body is mainly built. Actively growing plant parts are generally 75 to 90 percent water. Structural parts of plants, such as woody stems no longer actively growing, may have much less water than growing tissues.
The actual amount of water in the plant at any one time, however, is only a very small part of what passes through it during its development. The processes of photosynthesis, by which carbon dioxide and water are combined—in the presence of chlorophyll(叶绿素)and with energy derived from light—to form sugars, require that carbon dioxide from the air enter the plant. This occurs mainly in the leaves. The leaf surface is not solid but contains great numbers of minute openings, through which the carbon dioxide enters. The same structure that permits the one gas to enter the leaf, however, permits another gas—water vapor—to be lost from it. Since carbon dioxide is present in the air only in trace quantities(3 to 4 parts in 10,000 parts of air)and water vapor is near saturation in the air spaces within the leaf(at 80°F, saturated air would contain about 186 parts of water vapor in 10,000 parts of air), the total amount of water vapor lost is many times the carbon dioxide intake. Actually, because of wind and other factors, the loss of water in proportion to carbon dioxide intake may be even greater than the relative concentrations of the two gases. Also, not all of the carbon dioxide that enters the leaf is synthesized into carbohydrates(碳水化合物).
From the passage, we learn that _____.
选项
A、the mineral elements will not be absorbed by the plant unless they are dissolved in its root
B、the woody stems contain more water than the leaves
C、air existing around the leaf is found to be saturated
D、only part of the carbon dioxide in the plants is synthesized
答案
D
解析
第2段最后一句话明确指出,并非所有进入植物叶片的二氧化碳都与水化合成为碳水化合物。故D正确。A与第1段第4句不符,即矿物质需溶解在土壤溶液(soil solution)中而非植物的根部(root);C在倒数第3句可以找到反证,即水蒸气在叶片空隙中接近饱和状态,而非如C项所说“在叶片周围呈饱和状态”;B在文中未提及。
转载请注明原文地址:https://kaotiyun.com/show/f3X7777K
0
大学英语六级
相关试题推荐
Utopiaisaperfectplace.Itisaplacewithoutwar,hunger,poverty,orcrime.Itisaplacewherethepeopleworktogetheran
A、Theirfavoriteplayers.B、Theircareers.C、Theirfamily.D、Theirrecentlife.A男士提到男女在谈话方面的差异时,举了例子——在球赛中,他们的谈话内容会围绕运动员和比赛进程,别
A、WhenthePresidentandtheFirstLadydancedintheWhiteHouse.B、WhenanoldslavewasinterviewedaboutAmericanBlackHist
A、Createimagesmakingpeoplestopthinking.B、Runaftermanyfunthingsinlife.C、Trythingsthatdoctorsthinkimpossible.D、
VideogameshavebecomeincreasinglypopularinbotharcadesandtheaverageAmericanhome.Peopleofallagesandfromallwalk
EatingOurYoung[A]AtFeltonvilleSchoolofArtsandSciences,amiddleschoolinapoorneighborhoodofPhiladelphia,thesch
Since2007,theAmericanPsychologicalAssociation(APA)hasconductedasurveyofdifferentaspectsofstressinAmerica.This
A、Byinformingpeoplethatit’sanincurabledisease.B、Byprovidingeffectivemedicinetostopitstransmission.C、Bydisciplin
A、Salesincreasesinglobalmarkets.B、Consumersincreaseinglobalmarkets.C、Morefamousbrandsmakemoreprofits.D、Peoplebo
Everyotherweekitseemsanewstudycomesoutthataddstoouralready-formidablestoreofparentalworries.Butevenbythose
随机试题
关于动脉血压形成的机制,以下哪一项是错误的?
关于重症多形红斑,下列正确的是
根据《标准施工招标文件》,下列事件中,既可索赔工期又可索赔费用的是()。【2010年真题】
会计的两项基本职能是相辅相成、辩证统一的关系,下列说法正确的有()。
零售商业物业的分类,主要依据()等方面。
以下对遗忘的理解正确的是()。
下列图中左图为北半球山地垂直自然带与水平自然带关联示意图,右图为某自然带景观图片,回答问题。左图中的数字序号表示自然带,则右图景观所处的自然带是()。
对儿童应该受到保障的生命权、生存权和发展权等做了具体规定的国际条约是()
Intheworldofmanagement,employeesarenonexemptorexempt,dependingonwhethertheygetpaidforovertimeornot.【21】acrea
Whatdodietingandenergypolicyhaveincommon?TheSnackWelleffect.Thenamecomesfromthosetastylittlecookiesthatare【
最新回复
(
0
)