This evaporation, called transpiration, creates negative pressure in the xylem, pulling watery xylem sap up the tree.

这种发，，在木质中产生一种负压，把液体的木质树液往树上方拉。

To understand this, first, you need to know about a process called transpiration, sometimes called the evapotranspiration.

要理解这一点，首先，你需要了解一个做的过程，有时也散。

To accomplish this herculean task, the xylem relies on three forces: transpiration, capillary action, and root pressure.

要完成这样艰巨的任务，木质要依赖于三种力：，毛细和根压。

Take away trees, and there's less transpiration.

树木变少了，就会减少。

After absorbing rain through their roots, they release water vapor into the air through their leaves in a process called transpiration.

在根部吸收雨水后，它们会在一个的过程中通过树叶把水气释放进空气中。

Look, here's a picture of part of the Amazon rainforest, you'll notice you can barely see anything through the layer of numerous small clouds created by transpiration.

看，这是一张亚马逊雨林一角的照片，你会注意到透过由产生的无数小云层，你几乎看不到任何东西。