Environmental Factors Affecting Transpiration

• Temperature: Increased temperature increases evaporation of water from mesophyll cell walls into air spaces, increases water potential gradient between air spaces and the atmosphere as warmer air holds more water vapour (these molecules have more kinetic energy so diffuse faster)
• Humidity: The water potential gradient between the leaf air spaces and the atmosphere is steeper
• Air Movement/Wind Speed: The water vapour around the stomata (the boundary layer of water vapour) is blown away more quickly from the leaf surface, this increases the water potential gradient
• Light Intensity: More stomata are open when the light intensity is higher to allow faster diffusion of carbon dioxide into the leaf for photosynthesis, but this inevitably increases the transpiration rate