The factors affecting transpiration can be classified into two groups:
- External factor:
a) Light : It is very important factor of transoiration because most of the stomata open during day time. If light intensity is increased, it increase the rate of transpiration.
b) Temperature : The increase in temperature increase the rate of transpiration by increasing the rate of evaporation of water from cell surface. It also cause opening of stomata.
c) Wind velocity : The increase in the wind velocity normally increase the rate of transpiration by removing the moist air surrounding the leaves. The transpiration is faster in mild wind but reduce in high velocity of wind due to rapture of stomata.
d)Humidity : The increase in the RH decrease the rate of transpiration because it influence the DPD gradient between the inter-cellular space and outside the atmosphere.
e) Soil water : The water in the soil directly effect the rate of transpiration. The water reduce in soil cause decrease in rate of transpiration because of minimized photosynthesis.
f) Atmospheric pressure : The low atmospheric pressure increase the rate of transpiration through a reaction of the density of the air.
g) Pollution , dust and chemicals: The pollution, dust particles and deposition of materials over a leaf surface decrease the rate of transpiration because of reduced atmospheric pressure and intensity of light.
- Internal factor :
a) Leaf surface : Some factors of leaf influence the rate of transpiration such as thick cuticle, less no. of stomata of leaves, sunken stomata , phyllode, phylloclade, etc. thus reduce the rate of transpiration.
b) Plant age: As the plant becomes mature , the rate of transpiration is increased.
c) Root and shoot ratio: High root and shoot ratio increase the rate of transpiration.
d) Leaf area : Leaf area directly affects the rate of transpiration because in large leaf area, there are more stomata.