Most of the water that enters a plant will exit the leaf into the atmosphere.
This provides a continuous stream of water which is known as the transpiration stream.
The transpiration stream is important because:
If water availability is limited, plants will need to reduce transpiration.
In order to do this, the stomata (mainly found on the underside of the leaf) close.
|Factor||Effect on transpiration||How to change this factor experimentally|
|Surface area (not an environmental factor)||Smaller leaves will contain less stomata causing a decrease in transpiration.||Remove leaves.|
|Wind speed||A higher wind speed will increase the rate of evaporation causing an increase in transpiration.||Use a fan.|
|Temperature||A higher temperature will increase the rate of evaporation causing an increase in transpiration.||Use a heater.|
|Humidity||A higher humidity level will reduce the rate of evaporation causing a decrease in transpiration.||Place a clear, plastic bag over the plant shoot.|
|Light intensity||Darkness will cause the stomata to close causing a decrease in transpiration.||Use a lamp.|
If less water is being lost through transpiration the plant will absorb less water at the roots.