28 Transpiration

The absorption of water and minerals from the soil is only one part of a bigger process called transpiration.

Transpiration is the movement of water through a plant. Water is absorbed by the roots and passes through the plant. It is eventually lost by evaporation, mainly through the leaves. This is sometimes called a transpiration stream.

We are learning how to:

• explain the importance of transpiration to the movement of dissolved minerals through a plant

If the stem and leaves of a plant are sealed in a polythene bag and left for 24 hours, condensation forms inside the bag. The water is not coming from the soil, but from the leaves of the plant.

As a result of transpiration, water is continually being lost from the surface of the leaves and more water is drawn up through the xylem to replace it. In turn, soil water containing minerals is absorbed by the plant roots to replenish the water in the xylem. This is called transpiration pull.

Interesting fact

Although carnivorous plants, like the Venus flytrap, absorb water through their roots just like other plants, they do not rely on soil water for minerals.

Carnivorous plants obtain nutrients by trapping and digesting insects.