You may see in many neighborhoods, gardens, or forests, the bottom of the trees painted white. While painting the trunks of the trees white has been around for ages, people are still baffled by this strange yet interesting phenomenon. Why do people paint tree trunks white? Generally speaking, the purpose of whitewashing is to protect the tree from heat and insects.

You might sometimes notice that some chunks of a tree’s bark buckle (褶皱弯曲) and look as if they are about to fall. In gardening terms, that process is called Winter Sun Scald or Southwest Injury and usually occurs during the tree’s infancy. But what causes this phenomenon? Simply put, Sun Scald happens in areas such as New Mexico, where there is intense sun exposure, and the temperatures change wildly between day and night. Fortunately, once you whitewash your young trees, their trunks’ surfaces won’t get dry and crack easily anymore.

Painting the base of a young tree will also help it remain cool in the spring. Why? Because white paint acts as a protective screen that reflects the heat and allows the tree to spend more time on transpiration (蒸腾) and growing its fruits. Additionally, when trees are cooler, they have less stress, which makes their stomata (气孔) stay open a bit longer for the exchange of gases. That’s extremely important because the more carbon dioxide the trees take in, the more energy they create.

More often than not, a tree’s bark will crack, allowing insects to move inside. Once that happens, fungi and bacteria will feed on the tree’s innards, preventing its growth and eventually killing it. As a result, whitewashing mixtures contain three parts water and one part interior latex (内墙乳胶漆) paint. The paint itself prevents insects from moving up the tree and entering inside through the cracks. 

Therefore, if you have any young trees in your garden, you should consider whitewashing them regularly. Not only will you fend off insects, but you will give your trees enough protection for them to fully grow without the fear of Sun Scald. 

1.What does the underlined word “baffled” mean?

A Excited.

B Satisfied.

C Puzzled.

D Disappointed.

解析：选C。C 词义猜测题。根据后一句问句“Why do people paint tree trunks white?”可知，人们对于把树干漆成白色这一现象感到很困惑。故选C。

2.What can be known about Sun Scald?

A It often occurs when it’s freezing cold.

B It generally happens to young trees.

C It makes the trunks’ surfaces dry.

D It helps young trees grow healthily.

解析：选B。B 推理判断题。根据第二段的“and usually occurs during the tree’s infancy”以及最后一句“Fortunately, once you whitewash your young trees, their trunks’ surfaces won’t get dry and crack as easily anymore.”可知，日灼病主要发生在幼小的树苗身上。故选B。

3.How does whitewashing protect trees?

A By keeping them dry.

B By reducing their stress.

C By keeping away insects.

D By filling cracks with paint.

解析：选C。C 细节理解题。根据第四段的“The paint itself prevents insects from moving up the tree”可知，给树干刷白可以防止虫害。故选C。

4.Who could benefit most from this text?

A A designer.

B A painter.

C A farmer.

D A gardener.

解析：选D。D 推理判断题。本文主要描述了给树刷白带来的好处，并结合最后一段的“if you have any young trees in your garden”可知，一个园艺爱好者最有可能从本文学到有用的东西。故选D。