We all enjoy the beautiful show of colours as leaves change each autumn. But did you ever wonder how and why this happens?
Leaves are nature’s food factories. Plants take water from the ground through their roots and take carbon dioxide (二氧化碳) from the air. Plants use sunlight to turn water and carbon dioxide into glucose (葡萄糖). Glucose is a kind of sugar, which plants use as food for energy and growing.
The way plants turn water and carbon dioxide into sugar is called photosynthesis that means “ putting together with light”. A chemical called chlorophyll helps photosynthesis. It gives plants their green colour. As summer ends and autumn es, the days get shorter and shorter, and trees “know” to begin getting ready for winter.
During winter, there is not enough light or water for photosynthesis. Trees rest during this time and live on the food they store during the summer. They begin to shut down their food-making factories.
As the green chlorophyll disappears from the leaves, we begin to see yellow and orange leaves. Small amounts of these colours have been in the leaves all along. We just can’t see them in the summer, because they are covered up by the green chlorophyll.
The bright reds and purples we see in leaves are made mostly in autumn. In some trees, like maples (枫树), glucose is caught in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn turn this glucose into a red colour. The brown colour of trees like oaks (橡树) is made from waste left in the leaves.
It is the mixture of all these things that makes the beautiful colours we enjoy during autumn.
【小题1】The word “chlorophyll” in the third paragraph means in Chinese. A．叶绿素B．氧气C．胡萝卜素D．蛋白质【小题2】The leaves of the trees in autumn turn yellow because of the short of . A．water and carbon dioxideB．glucose and energyC．sunlight and waterD．sunlight and carbon dioxide【小题3】The way that is called Photosynthesis . A．plants change water and carbon dioxide into sugarB．plants turn water and carbon dioxide into sugar with the help of sunlightC．plants use glucose as food for energy and growingD．chlorophyll is a great help【小题4】Which of the following is NOT true?A．When autumn and winter e, the days get shorter and shorter. B．During winter trees rest and live on the food they store during the summer. C．During winter small amounts of yellow and orange colours are kept in the leaves all the time. D．Trees begin to stop making food in summer.【小题5】This passage tells us . A．all the plants can grow well with the strong sunlightB．there are all kinds of plants on the earthC．all the colours of the leaves aren’t made from chlorophyllD．maples and oaks have the same reason as other trees for the change of coloursA
网友回答
(答案→)A
解析：这篇短文主要介绍了树叶颜色变化的原理，以及树叶在植物生长发育中的作用。
【小题1】联系下文It gives plants their green colour它给指物提供了绿色。可知这个单词与绿色有关，故选A。
【小题2】根据短文第四五段描述，可知树叶在秋天变黄主要是因为缺少光照和水分，故选C。
【小题3】根据第三段The way plants turn water and carbon dioxide into sugar is called photosynthesis 描述，可知选B。
【小题4】根据短文第四段描述，可知植物在秋天停止制造食物，故选D。
【小题5】根据最后一段It is the mixture of all these things that makes the beautiful colours we enjoy during autumn. 及上文描述，可知并不是植物所有的颜色都是来自于叶绿素，故选C。