Transpiration is the evaporation of water from plant tissues into the atmosphere. There are several factors that affect the rate of transpiration, temperature, humidity, wind speed, and atmospheric CO 2 levels. Temperature is the measure of hotness or coolness of air. If the temperature is high, transpiration rates will increase as the surrounding air is drying the leaf surfaces. In kind, if temperatures are low, transpiration rates will decrease.
Humidity is the amount of water vapor in the atmosphere.
When the atmosphere has a high humidity, the air is more saturated with water. Water diffuses from areas of high concentration to areas of lower concentration, so when humidity is high, transpiration rates will slow. When wind speeds are high, leaf surfaces become dry and transpiration rates will increase. When wind speeds are low, transpiration rates will decrease. Stomata are the openings in leaf surfaces where gas exchange takes place.