Healthy trees are important to us all. Trees provide shade, beauty, and homes for wildlife. Trees give us products like paper and wood. Trees can give us all these only if they are healthy. They must be well cared for to remain healthy.
Your trees’ trouble may be you yourself. People spend much time and money to plant and maintain trees. Trees improve the looks of homes, parks, business, and public buildings. Yet, people who love trees the most may be the ones who cause them injury. Of course, they do not do this on purpose. They are most likely not aware of the kinds of things that injure trees. There are many people-caused tree injuries. You should become aware of them and avoid them. Learn the things that can help to keep your trees healthy.
Healthy trees are beautiful. They make our world a pleasant place to live ill. Unhealthy trees are not as beautiful. They make our world less pleasant. Healthy trees help to cool and clean the air. They can even deade
A. beautiful
B. old
C. healthy
D. young
| Trees should only be pruned (修剪) when
there is a good reason for doing so. Many gardeners believe that more damage
results from doing it unnecessarily than from leaving the tree to grow in its
own way. First, pruning may be done to make sure that trees have a desired shape. The object may be to get a tree of the right height, and to help the growth of small side branches which will thicken its appearance or give it a special shape. Secondly, pruning may be done to make the tree healthier. You may cut out diseased or dead wood, or branches that are rubbing against each other and thus causing wounds. A tree may grow healthier by removing the branches that are locking up the centre and so preventing the free movement of air. One result of pruning is that an open wound is left on the tree and this provides an easy entry (进入) f A. Pruning is necessary when there are unwanted branches. B. Damage is done to a tree if it is left to grow in its own way. C. Diseased or dead branches should be cut away if they are found to rub against each other. D. Growing side branches often prevent air from moving freely. [单项选择]
THE CIRCULATORY SYSTEM OF TREES 1 Inside the tree’s protective outer bark is the circulatory system, consisting of two cellular pipelines that transport water, mineral nutrients, and other organic substances to all living tissues of the tree. One pipeline, called the xylem--or sapwood--transports water and nutrients up from the roots to the leaves. The other, the phloem--or inner bark---carries the downward flow of foodstuffs from the leaves to the branches, trunk, and roots. Between these two pipelines is the vascular cambium, a single--cell layer too thin to be seen by the naked eye. This is the tree’s major growth organ, responsible for the outward widening of the trunk, branches, twigs, and roots. During each growing season, the vascular cambium produces new phloem cells on its outer surface and new xylem cells on its inner surface. 2 Xylem cells in the roots draw water molecules into the tree, taking in hyd A. It is composed mainly of water. B. It causes water loss by transpiration. C. It gives leaves their green color. D. It is manufactured in the leaves. 我来回答: 提交
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