1. Temperature : Rate of transpiration is directly proportional to the temperature. Transpiration rate increases with increase in temperature.
2. Light : More light closes the stomata.
3. Relative humidity : Rate of transpiration is inversely proportional to the relative humidity.
4. Velocity of the wind : The rate of transpiration is directly proportional to the velocity of wind. However, the wind of 40-50 km/hr brings closing of stomata and thus decreases the rate of transpiration.
5. Atmospheric pressure : Rate of transpiration is inversely proportional to the atmospheric pressure.