首页
登录
职称英语
Most growing plants contain much more water than all other materials combined
Most growing plants contain much more water than all other materials combined
游客
2023-12-23
17
管理
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 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 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. [br] The essential function of photosynthesis in terms of plant needs is ______.
选项
A、to form sugars
B、to derive energy from light
C、to preserve water
D、to combine carbon dioxide with water
答案
A
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3299381.html
相关试题推荐
下面你将听到外国媒体就中国艾滋病问题的一段评论。HIV/AIDSisnowrecognizedclearlyasagrowing
下面你将听到外国媒体就中国艾滋病问题的一段评论。HIV/AIDSisnowrecognizedclearlyasagrowingthr
[originaltext]Moneyfrommigrantworkersnowexceedsthecombinedtotalofall
[originaltext]Moneyfrommigrantworkersnowexceedsthecombinedtotalofall
[originaltext]Moneyfrommigrantworkersnowexceedsthecombinedtotalofall
[originaltext]Moneyfrommigrantworkersnowexceedsthecombinedtotalofall
Whatdoesthepassagemainlytalkabout?[br][originaltext]Agrowingnumber
Whatdoesthepassagemainlytalkabout?[br][originaltext]Agrowingnumber
Thereisagrowingnumberofeconomistswhobelievetoday’sbrutallytoughl
Pollutioncontrolismanagementofwastematerialsinordertominimizethe
随机试题
Thepathtoprisonoftenstartsatayoungage.Onewaytokeepyoungoffend
戏曲艺术:《牡丹亭》
采用工作模型直接加钉制作可卸代型时,需对工作模型底部进行磨平,并使之保留一定厚度
请按所提供的教材设计1课时的教学简案(也可以是单元中的一课) 要求: (1)
下列各种瓣膜病,可闻及心尖部舒张中晚期隆隆样杂音的是A.二尖瓣关闭不全 B.二
M公司用甲材料生产A产品,甲材料标准价格是100元/千克,用量标准为5千克/件,
王某假冒公安人员,以“抓流氓”为名,对妇女李某进行胁迫奸淫。对王某应当( )。
A.氯喹 B.奎宁 C.伯氨喹 D.乙胺嘧啶 E.甲氟喹可根治间日疟和控
按照国家规定的业务范围、服务标准和资费标准,为中华人民共和国境内所有用户提供的邮
下列商品属于消费税征收范围的是()。A.高尔夫车 B.酒精 C.溶剂油原料
最新回复
(
0
)