Tree rings are made of tissue called xylem.

构成年轮的组织被称为部。

This capillary motion is in full effect in xylem filaments thinner than human hair.

纤维中毛细作用无处不，这些纤维比人的头还细。

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

这种蒸，叫作蒸腾作用，中产生一种负压，把液体的树液往树上方拉。

Right beside the phloem is the tree's other tissue type: the xylem.

就韧皮的旁边是树的另外一种组织叫。

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，要依赖于三种力量：蒸腾作用，毛细作用和根压。

This process, called osmotic movement, creates nutrient-rich xylem sap, which will then travel up the trunk to spread those nutrients through the tree.

这个过程，叫做渗透运动，会产生营养丰富的树液，这些树液会沿着树干向上把营养传送到整棵树。

And where these two forces pull the sap, the osmotic movement at the tree's base creates root pressure, pushing fresh xylem sap up the trunk.

这两种力量推动树液向上，树根部的渗透作用也产生树压，把新鲜的树液推上树干。

Here at the tree's base, there are more of these particles in one tissue than the other, so the water from the phloem sap is absorbed into the xylem to correct the balance.

树的根部，这些组织里的微粒分布不均匀，因此，韧皮树液中的水分被吸收到中，来调节平衡。