When we get hot, our bodies perspire: we lose moisture through tiny pores in our skin. If the atmosphere is dry, and especially if it is windy, the sweat evaporates from our skin into the air. This helps to keep us cool.  Plants also lose water in the form of water vapour through pores in their leaves called stomata. We call this process transpiration.

Leaves have tiny pores called stomata, usually on their undersides. The plant loses water through these pores. Guard cells open and close the pore to regulate the amount of water vapour that escapes from the leaf.

During the hot, dry, windy months of summer, water evaporates very quickly. For plants to survive, they must be able to avoid losing too much water.

In this section we will find out about some of the ways in which Cape plants reduce transpiration from their leaves. How do plants avoid losing too much water? Look at each of the science concepts below (click arrow) and think about how it relates to the process of plants losing or conserving water. To find out how this concept relates to the process of transpiration in plants click on the word "transpiration".

Small, hard leaves

• So many Fynbos plants have small leaves that people think these fine-leafed bushes gave “Fyn-bos” its name.

• Most Fynbos shrubs have woody stems and hard leaves. The cell walls of these plants contain substances that make them very strong. Even if the cells lose water during summer, the cell walls don’t collapse and the stems and leaves keep their shape.

• In addition to being small, the leaf edges of plants like Ericas and Blombos are rolled under. Only a tiny slit remains through which water vapour can evaporate. Leaves that look like this are called ericoid leaves.

• Look for plants with small leaves on the poster, e.g. Blombos, Cape May, Erica, Tortoise Berry and Renosterbos.

Because plants lose most water through the pores in their leaves, some plants reduce water loss by having no leaves at all. The Medusa’s Head and Restios (Cape Reeds) have no leaves; the stems of these plants are green in order to photosynthesise.

Some plants are deciduous. You may be familiar with oak trees and grape vines that lose their leaves in winter. These plants come from Europe where they lose their leaves in winter to survive freezing temperatures.

Some Cape plants are deciduous but most of them lose their leaves during the dry summer months to avoid losing water. Most of these plants are not trees but geophytes.

• To avoid losing water, some plants have adaptations to keep their leaves cool. Colours like grey and silver reflect more light and heat than dark colours, so many plants that grow in dry areas have a woolly, hairy or waxy coating on the green leaves that makes them look grey.

• Leaves of Wild Rosemary and young Bietou leaves have woolly hairs that reflect light. These hairs also reduce water loss by covering the stomata and trapping a layer of moist air around the leaf.

• Some plants keep cool by exposing only a small area of the leaf to the sun. Sometimes the leaves grow upright rather than flat, so that only the tips of the leaves are exposed to the sun at midday. In other plants, older leaves shade younger leaves on the stem. Still other plants grow in the shade of larger plants.