Explaining the Effects of Temperature, Wind Speed & Humidity (Cambridge (CIE) IGCSE Biology): Revision Note
Exam code: 0610 & 0970
Explaining the effects of temperature, wind speed & humidity: Extended
Extended Tier Only
Wind speed, humidity and temperature all have an effect on the rate at which transpiration occurs
The table below explains how these factors affect the rate of transpiration when they are all high; the opposite effect would be observed if they were low
Transpiration rate factors table
Factor | Condition | Effect on the rate of transpiration (more/less) |
|---|---|---|
Wind speed | High | More — air movement removes water vapour from around the leaf, maintaining a steep concentration gradient between the leaf's air spaces and the surrounding air, which increases the rate of diffusion of water vapour out of the stomata |
Humidity | High | Less — high humidity means the air already contains a lot of water vapour, reducing the concentration gradient between the leaf's air spaces and the surrounding air, so less water diffuses out |
Temperature | High | More — higher temperatures give water molecules more kinetic energy, increasing the rate of evaporation from the mesophyll cells into the leaf's air spaces, and increasing the rate of diffusion of water vapour out through the stomata |
A potometer can be used to investigate the effect of environmental factors on the rate of transpiration
Wilting: Extended
Extended Tier Only
If more water evaporates from the leaves of a plant than is available in the soil to move into the root by osmosis, then wilting will occur
This is when all the cells of the plant are not full of water, so the strength of the cell walls cannot support the plant and it starts to collapse
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