How plants drink water

How does a tall tree drink from the ground?

Plants have no mouth, so they drink through their roots, buried in the soil.

Roots spread out wide, so they can reach lots of water in the soil. Look closely and you see tiny hairs on the root. These are called root hairs.

• Roots spread wide
• Root hairs soak up water

Root hairs are very thin, so there are thousands of them, giving the plant a huge surface to drink from.

Now the clever part. There is less salt inside the soil water than inside the root, so water moves in. This movement of water is called osmosis. Water flows toward the side with more stuff dissolved in it. Once inside, the water travels up through tiny tubes called xylem, like straws inside the stem.

• Osmosis = water moves in

But what pulls the water up so high? The leaves do, by letting water escape as vapor.

This is called transpiration. As water leaves the leaf, it pulls more water up behind it.

Think of drinking juice through a straw. When you suck at the top, the juice rises from the bottom.

Here is an example. A sunflower on a hot day loses lots of water through its leaves, so it drinks more.

• Hotter day = more drinking

Plants also need minerals from the soil, and these dissolve in the water and travel up together.

Quick check. What pulls water up from the roots to the top of a tall plant? In short, root hairs soak up water by osmosis, and leaves pull it up the stem like a straw.