Factors Affecting Transpiration

Affecting factors of transpiration are of two types; External and Internal.

(a) External Factors:

Light: Photosynthesis takes place in presence of light and as a result stoma opens. So light is the main factor, which influences transpiration

Temperature: With the increase of temperature water vapourises rapidly and increased the humidity in the atmosphere. So temperature controls the rate of transpiration.

Relative Humidity: If relative humidity is less the water vapour holding capacity of the air decreases, therefore rate or transpiration decreases.

  • Air Current: The air current disposes of the saturated air (as a result of transpiration), away from the plant and thus increases the rate of transpiration.
  • Atmospheric pressure: Under low-pressure water vapourise at low temperature. So if pressure decreases the rate of transpiration increases and if pressure increases the rate of transpiration will decrease.
  • Soil water: If availability of soil water is less the rate of transpiration will decrease.

(b) Internal Factors:

  • Root-Leaf Ratio: If the number and total surface area of leaves become much less in comparison with root region (absorption region) the rate of transpiration will reduce.
  • Leaf area: The greater the leaf area, greater will be the rate of transpiration, and lesser the leaf area the lesser the rate of transpiration.
  • The internal surface of leaf: Thin cuticle, thin cell walls, exposed stomata, and well-developed spongy parenchyma favour transpiration. On the other hand, leaves those possesses thick cuticle, thick cell walls, well-developed palisade parenchyma, Sunken stomata etc. will reduce the rate of transpiration.