Two reasons that some plants avoid light.

So, we usually think of plants trying to get as much sunlight as possible. And in most cases it’s true; plants grow toward light. But what’s interesting is in some cases plants do the opposite. Sometimes plants actually grow away from or avoid light. Let’s talk about a couple of reasons why.

Now, uh, some plants need to find other objects like trees to cling to, to grow on for support. These plants are attracted to the dark shadows that tall objects cast on the ground. By growing along the ground in the dark shadow, these plants eventually reach the tall object and then grow upward, along it, being supported by it. For example, some vines do this. Vines grow in shadow until they reach a tree or a building. Then the vine will climb or grow up that object.

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. However, since intense sunlight makes plants lose water, some plants are in danger of drying out from too much exposure. So 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. For example, a species of bean plant does this. When the bean plant senses that the sunlight’s too strong, in the middle of the day, it turns its leaves sideways so the Sun only hits the sides of the leaves, the thin edge. This way the bean plant avoids drying out.

部分植物避光的两个原因：

所以，我们通常认为植物试图获得尽可能多的阳光。在大多数情况下，这是真的;植物向着光生长。 但有趣的是，在某些情况下，植物会做相反的事情。 有时候植物实际上是远离阳光生长的。 让我们来谈谈其中的几个原因。  

现在，嗯，一些植物需要找到其他物体，比如树木，来依附、生长以获得支持。这些植物被高大物体投在地上的阴影所吸引。 通过在黑暗的阴影中沿着地面生长，这些植物最终到达这个高大的物体，然后沿着它向上生长，受到它的支撑。 例如，一些藤蔓就能做到这一点。 藤蔓生长在阴影中，直到它们到达一棵树或建筑物。 然后藤蔓就会爬到那个物体上。  

其他植物避光以保持水分。通常植物的叶子朝上，所以整个叶子表面都暴露在阳光下。 然而，由于强烈的阳光会使植物失去水分，一些植物由于过度暴露而面临干燥的危险。 所以在白天，当光线变得非常强烈的时候，这些植物会改变叶子的位置，以减少暴露在阳光下的时间，从而保持水分。 例如，一种豆类植物就能做到这一点。 中午的时候，当豆类植物感觉到阳光太强烈时，它就会把叶子转向一边，这样阳光就只能照到叶子的边缘，也就是薄薄的边缘。 这样豆类植物就不会变干。