BRAINCAKEFactors Affecting Transpiration
The rate of transpiration depends on how quickly water vapour can evaporate inside the leaf and diffuse out through the stomata. Four main environmental factors affect it.
Light intensity. Stomata open in the light so that carbon dioxide can enter for photosynthesis. As light intensity increases, more stomata open and the rate of transpiration increases. In the dark, most stomata close and transpiration is very low.
Temperature. A higher temperature gives water molecules more kinetic energy, so they evaporate and diffuse faster. Warm air can also hold more water vapour, so the air outside the leaf stays drier and the diffusion gradient is steeper. The rate of transpiration increases.
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Key terms in this lesson
- turgor
- The pressure exerted by the contents of a plant cell against its cell wall when the cell is full of water, keeping it rigid.
More in Transport in Plants
- Cohesion-Tension Theory
- Adhesion and Capillarity
- Modelling Transpiration
- Measuring the Rate of Water Uptake
- Root Pressure
- Translocation in the Phloem
- Phloem Loading
- The Symplast Pathway
All 21 lessons in Transport in Plants · All Edexcel AS-level Biology topics