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. Darnes has suggested that it is as proper t
Most growing plants contain much more water than all other materials combined. C. R. Darnes has suggested that it is as proper t
admin
2012-11-30
62
问题
Most growing plants contain much more water than all other materials combined. C. R. Darnes has suggested that it is as proper to term the plant a water structure as to call a house composed mainly of bricks 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 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 (细小的) 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).
According to the passage, which of the following statements is TRUE?
选项
A、The mineral elements will not be absorbed by the plant unless they are dissolved in its root.
B、The stems contain more water than the leaves.
C、Air around the leaf is found to be saturated.
D、Part of the carbon dioxide in the plants is synthesized.
答案
D
解析
仔细阅读第三段中作者所提供的数据和第二段中"Also, not all of the carbon dioxide that enters the leaf is synthesized into carbohydrates (碳水化合物) "的内容。
转载请注明原文地址:https://kaotiyun.com/show/Blb7777K
0
大学英语六级
相关试题推荐
Harryseemedtohavelearnednothingfromthefailuresofhis___________sohemetwithcreditcrisisinthecompany.
Mostauthoritiesbelievethaturbanstreetcrimefromacombinationofpoverty,pooreducationandalackofopportunity.______
Everyoneelsewillbewearingschooluniform.You’ll________likeasorethumbinthatreddress.
Themanagementcontrolprocessshould______tomeasurewhetherpredeterminedgoalsarebeingachieved.
Inclassifyingtheaimistosortobjectsbytheirselectedpropertiesinto_________categories.
Studentswhocheatontheexaminationwillbe______bytheirclassmates.
Somemushroomsareediblewhileothers,whichlookalmostidentical,contain______poisons.
Studentscanbeexpelledforrefusingto______toschoolrules.
SometimeagoafriendwhohadlosthisCityjobconfessedhehadconsideredkillinghimself.Iwasappalledbutnotsurprised:
Amidweakjobandhousingmarkets,consumersaresavingmoreandspendinglessthantheyhaveindecades,andindustryprofessio
随机试题
下列哪项不是放置宫内节育器的禁忌证()
对工人工作时间进行分类研究时将工人在工作班内消耗的工作时间分为必需消耗的时间和损失时间。其中损失时间中包括多余和偶然工作、停工、违背劳动纪律所引起的损失时间。由于工程技术人员和工人的差错而引起的时间消耗属于()。
根据税收征收法律制度的规定,下列情形中,税务机关有权核定纳税人应纳税额的有( )。
教师辅导学生从活动中自己学习的模式主要包括以下步骤()
从所所给的四个选项中,选择最合适的一个填入问号处,使之呈现一定的规律性。
一项工作交给甲做要2小时完成,交给乙做要1.5小时完成,交给丙做要3小时完成。现在三个人两两组队,每队都工作相同的时间,共需要()完成这项工作。
程序编制有三个层次,即编码、测试和【】。
Cultureshockmightbecalledan【C1】______diseaseofpeoplewhohavebeensuddenly【C2】______abroad.Likemostailments,ithasi
Weareenteringaperiodinwhichrapidpopulationgrowth,thepresenceofdeadlyweapons,anddwindlingresourceswillbringin
Inflationreferstoan________rapidincreaseinprice.
最新回复
(
0
)