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请听一段生物学课上的讲座内容。

Narrator: Listen to part of a lecture in a biology class.

我们通常认为植物会尽可能多地获取阳光。在大多数情况下，确实如此。

Professor: We usually think of plants trying to get as much sunlight as possible. In most cases, it's true.

植物向光生长。但有趣的是，在某些情况下，植物会做出相反的行为。

Plants grow toward light. But what's interesting is, in some cases, plants do the opposite.

有时植物实际上会背光生长或避开光线。下面我们来讨论几个中原因。

Sometimes plants actually grow away from or avoid light. Let's talk about a couple of reasons why.

有些植物需要寻找树木等其他物体来攀附生长以获取支撑。这些植物会被高大物体在地面投下的阴影所吸引。

Some plants need to find other objects like trees to cling to grow on for support. These plants are attracted to the dark shadows that tall objects cast on the ground.

通过在阴影中沿着地面生长，这些植物最终会到达高大物体旁，然后沿着它向上生长，获得支撑。

By growing along the ground in a dark shadow, these plants eventually reach the tall object and then grow upward along it, being supported by it.

例如，一些藤蔓植物就是这样。藤蔓在阴影中生长，直到遇到树木或建筑物，然后会攀爬或沿着该物体向上生长。

For example, some vines do this. Vines grow in shadows until they reach a tree or building, then the vine will climb or grow up that object.

其他植物避开光线是为了保存水分。通常植物的叶子朝上，因此整个表面都会暴露在阳光下。

Other plants avoid light in order to conserve moisture. Usually a plant's leaves face upward, so their whole surface is exposed to the sun's rays.

然而，由于强烈的阳光会使植物失水，一些植物因暴露过多而面临干枯的危险。

However, since intense sunlight makes plants lose water, some plants are in danger of drying out from too much exposure.

白天，当光线变得非常强烈时，这些植物会改变叶子的位置，以减少对阳光的暴露，从而保留水分。

During the day, when the light gets really intense, these plants change the position of their leaves to decrease their exposure to the sun and therefore retain moisture.

例如，一种豆科植物就是这样。当豆科植物感知到正午阳光太强时，会将叶子侧转。

For example, a species of bean plant does this. When the bean plant senses that the sunlight is too strong in the middle of the day, it turns its leaves sideways.

阳光只会照射到叶子的侧面，即薄边。这样一来，豆科植物就避免了干枯。

The sun only hits the sides of the leaves, the thin edge. This way, the bean plant avoids drying out.

<img src="/upload/ti/sardine/2658000-2659000/2658750/a9da610c0afe4a1a9b13a16dca228fae.png">
 Using the examples of the vine and the bean plant, discuss two reasons that some plants avoid light.