Let's start by talking about phototropism.

们先来谈谈向光性。

Auxin will always move away from the light in positive phototropism.

在正向光性中，生长素总是会远离光线移动。

In other words, how did phototropism come to be?

换句话说，光趋性是如何形成的？

And two big things that you should understand about plants are phototropism.

关于植你应该理解的两概念之一是向光性。

Negative phototropism would be growing in the other direction.

负向光性就是朝相反方向生长。

And so immediately when you plant a seed, the roots are going to show negative phototropism.

所以当你种下一颗种子时，根部会立即表现出负向光性。

The two plant ones we'll talking about are phototropism and then photoperiodism.

们讨论的两种植行为是光趋性和光周期性。

And so let's start with phototropism.

们从光趋性开始讲起。