首页
登录
职称英语
Most growing plants contain much more water than all other materials combine
Most growing plants contain much more water than all other materials combine
游客
2024-05-14
16
管理
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). [br] The crucial function of photosynthesis in terms of plant needs is______.
选项
A、to form sugars
B、to preserve water
C、to combine carbon dioxide with water
D、to derive energy from light
答案
A
解析
仔细阅读第二段一开始对光合作用的叙述:"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."
转载请注明原文地址:https://tihaiku.com/zcyy/3598490.html
相关试题推荐
Mostgrowingplantscontainmuchmorewaterthanallothermaterialscombine
[originaltext]Aftertwodecadesofgrowingstudentenrollmentsandeconomic
[originaltext]Aftertwodecadesofgrowingstudentenrollmentsandeconomic
Nowadays,wehearalotaboutthegrowingthreatofglobalisation,accompani
Nowadays,wehearalotaboutthegrowingthreatofglobalisation,accompani
Nowadays,wehearalotaboutthegrowingthreatofglobalisation,accompani
Nowadays,wehearalotaboutthegrowingthreatofglobalisation,accompani
Nowadays,wehearalotaboutthegrowingthreatofglobalisation,accompani
Nowadays,wehearalotaboutthegrowingthreatofglobalisation,accompani
Nowadays,wehearalotaboutthegrowingthreatofglobalisation,accompani
随机试题
Whereisthehomeoftigers?[br]Whatisthemostdangerouswaytohuntatiger
[originaltext]W:Tellmefrankly,whatareyouafraidof?M:I’mnotsure.Ius
Anewanalysisoffederalmoneythatpublicschoolsreceiveforlow-incomes
在远距离运输时,运送速度最快的是()。A.飞机 B.火车 C.汽车 D.
A.任何一种疾病都可找到形态的或化学的改变 B.不仅关心患者的躯体,而且关心病
治疗产后发热感染邪毒证,应首选( )。A.小柴胡汤 B.大柴胡汤 C.桃红
AB0亚型主要特征是( )。A.抗体弱 B.抗原性弱 C.与A细胞和B细胞
下列各项中,属于固定资产内部控制测评程序的有( )。A.审查计提折旧的范围 B
TheThamesTunnelprojectwasmorediffi
苍术主治的病证有A.湿阻中焦 B.夜盲眼目昏涩 C.风湿痹证 D.表证夹湿
最新回复
(
0
)