Factors affecting water uptake

Plant structures and their functions · Leaves, water uptake and extreme environments · note 1 of 2

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Factors affecting water uptakeSpec 6.12

In short

The rate of water uptake by a plant depends on the rate of transpiration, which is increased by higher light intensity, more air movement and higher temperature. Light opens the stomata, moving air carries water vapour away to keep a steep concentration gradient, and warmth makes water evaporate and diffuse faster. A potometer measures the rate.

The rate at which a plant takes up water depends on the rate of transpiration. When more water is lost from the leaves, more is pulled up through the xylem. Three environmental factors affect it.

Effect of environmental factors on water uptake
Factor	Effect on water uptake	Explanation
Light intensity	Higher light intensity increases the rate	Stomata open in the light, so more water vapour can diffuse out of the leaf. Low light or darkness makes the stomata close.
Air movement	More air movement increases the rate	Moving air carries away water vapour from around the stomata. This keeps a steep concentration gradient, so water vapour diffuses out faster.
Temperature	Higher temperature increases the rate	Water evaporates from the cells faster, and water vapour particles move faster, so diffusion out of the leaf is faster.

A potometer is used to measure the rate of water uptake of a leafy shoot. As the shoot takes up water, an air bubble moves along a capillary tube. The distance moved in a set time is a measure of the rate. You can compare the rate in different conditions, for example with and without a fan, or in the light and in the shade.

A potometer: a leafy shoot sealed with an airtight seal into a water-filled tube, a water reservoir with a tap, and a capillary tube over a ruler with an air bubble that moves towards the shoot; the end of the capillary dips into a beaker of water. — A potometer: the **distance the bubble moves** in a set time measures the rate of water uptake.

Common mistake:

Say what happens and why. 'The rate goes up' is not enough. Add 'because the stomata are open' or 'because the water vapour is carried away, keeping a steep concentration gradient'.

Written and checked against the Edexcel GCSE Combined Science (1SC0) specification · Updated October 2026

Frequently asked questions

How does light intensity affect the rate of transpiration?

A higher light intensity increases the rate of transpiration. The stomata open in the light, so more water vapour can diffuse out of the leaf, and more water is pulled up through the xylem. In low light or darkness the stomata close, so less water vapour is lost and the rate of water uptake falls.

How does a potometer work?

A potometer measures the rate of water uptake of a leafy shoot. As the shoot takes up water, an air bubble moves along a capillary tube. The distance the bubble moves in a set time is a measure of the rate. You can compare conditions, for example with and without a fan, or in the light and in the shade.