2.57B: Understand How the Rate of Transpiration is Affected by Changes in Humidity, Wind Speed, Temperature and Light Intensity

TRANSPIRATION: Loss of Water vapour from stems and leaves of plants - inevitable consequence of gas exchange

FACTORS THAT AFFECT RATE OF TRANSPIRATION:

FACTOR	EXPLANATION
TEMPERATURE	As temperature increases, the rate of transpiration will increase This is because the increase in temperature will cause Water molecules to gain kinetic energy, increasing the rate in which they vaporise and transpire out of the Stomata
HUMIDITY	Humidity is the amount of Water vapour present in the air As ambient humidity increases, the rate of transpiration will decrease This is because when ambient humidity surrounding plant is greater than humidity in Spongy Mesophyll, there is greater concentration of Water vapour outside the plant than inside As a result, this prevents the transpiration of Water vapour out of the Stomata
WIND	As wind exposure increases, the rate of transpiration will increase This is because the increase in wind exposure removes Water vapours surrounding the plant, reducing the proximal humidity as there will be a greater concentration of Water vapour inside the Spongy Mesophyll than surrounding the plant As a result, a strong concentration gradient will be created, increasing the rate of transpiration
LIGHT INTENSITY	As light intensity increases, the rate of transpiration will increase This is because the increase in light intensity will stimulate more Stomata to open in order to facilitate photosynthetic gas exchange As a result, the rate of transpiration will increase