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
2017-02-01
53
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).
A growing plant needs water for all of the following except _____.
选项
A、forming sugars
B、sustaining woody stems
C、keeping green
D、producing carbon dioxide
答案
D
解析
文章谈到的二氧化碳都是空气中的二氧化碳,不是植物“产生的二氧化碳”,故可知D项符合题意。A、B、C项都是植物的生长发育过程。尽管C项并没有在文中明言,但它也是植物内水分的作用之一。
转载请注明原文地址:https://kaotiyun.com/show/POF7777K
0
大学英语六级
相关试题推荐
InternationalWomen’sDay(8March)isanoccasionmarkedbywomen’sgroupsaroundtheworld.Thisdateisalsocommemoratedatth
A、Itcanhardlybeheard.B、Itcanhardlybenoticed.C、Itisusedeverywhere.D、Itchangespeople’sideas.B
AslongastheAmericanlandwasnotcompletelysettledandtheelementsof【B1】______orderwerenotyetimposedonthefrontier,
AslongastheAmericanlandwasnotcompletelysettledandtheelementsof【B1】______orderwerenotyetimposedonthefrontier,
A、Afitnessprogramofferedtothegeneralpublic.B、Aphysicalexercisetobuildupmuscles.C、Aprogramthatmakespeoplekeep
Aroundtheworldmoreandmorepeoplearetakingpartindangeroussportsandactivities.Ofcourse,therehavealwaysbeenpeop
A、Puttinguppostersforherworks.B、Attendinganartclass.C、Decoratingherdormroom.D、Organizingaglobaltour.C对话中男士说:“我
A、Ithastobelongandindetail.B、Itwillbegiveninaformalstyle.C、Itwillincludehisviewonthecompany.D、Itwillbe
WhySustainableBuildingsNeedtoFocusonCommunityAndCollaboration?[A]Accordingtothegovernment,buildingsintheUKacco
A、Hewantedtherailroadtobedeveloped.B、Hewantedtohaveamorepowerfulsteamengine.C、Hewantedtoownthelandnearthe
随机试题
对教师语言表达能力的要求有()。
考核者不加批判地接受别人的语言、行为、表现或其他事物,而迅速改变自己对被考核者的评价意见或看法,从而引起的考核误差被称为()
掌骨骨折的常规摄影位置为
下列不属于根据五行相生规律确立的治法是
A.甲氰咪胍B.消炎痛C.吗丁啉D.硫糖铝E.胶体次枸橼酸铋增加胃动力
甲乙为仇敌。某日甲教唆丙、丁去教训一下乙。丙、丁便各自拿了木棒一起去教训乙,乙被打倒在地。正在这时,丁的好友戊刚从工地回来,看到此情此景,便将自己手中的铁锨递给了丙,丙接过后继续打乙,戊站在旁边观看。后乙住院治疗了一个月。假如丙、丁二人都是年仅13岁的
下列关于类比分析法的表述,错误的是()。
“士为知己者死”这一古训反映了有效的领导始于()。
某体检记录表中有日期/时间型数据“体检日期”,若规定在体检30天后复检,需在本表中建立新字段“复检日期”,并给出预计的复检日期。在下列设计视力中,设置“复检日期”为计算字段,在表达式栏中,正确的表达式是()。
A、Inafast-foodrestaurant.B、Atashoppingcenter.C、Atacountyfair.D、Inabakery.C短文开头提到,县集市是新英格兰镇的一个传统,娱乐性非常强,其中一个受欢迎的项目
最新回复
(
0
)