Grades: K – 8

We know that all plants have basic needs. To remember plant needs we use the word: L.A.W.N.S. (light, air, water, nutrition and space). Let’s look at how water moves in and out of plants in a process called transpiration.

Transpiration is the movement of water through a plant’s system. The water journey starts in the roots which draws water from the soil. From there water moves up through the stems and into the leaves and flowers. Finally, water exits the plant through tiny pores on the leaves called stomata. Transpiration helps to cool the plant and the Earth; works together with respiration; and keeps plants upright.

One reason that plants transpire water is to stay cool. When water is inside the plant, it is a liquid. Once it leaves the plant through the stomata it quickly evaporates. It’s a lot like when we humans sweat on a hot day. Our skin feels damp but as the sweat evaporates (turns into a vapour) and we start to feel cooler – the same thing happens to a plant. Plants also help to regulate temperature on Earth. Think of a really tall tree. It feels cooler when you sit underneath a big tree on a hot summer’s day, partly because of the shade but also because the water vapour has a cooling effect. The moisture released by plants eventually cycles into the environment and returns to the Earth as rain or snow.