Evaporation and Transpiration | Plant Physiology

The upcoming discussion will update you about the differences between Evaporation and Transpiration.

Difference # Evaporation:

1. Water vapours are formed at the free surface of water.

2. It takes place at the surface of non-living objects.

3. It is a physical process which is controlled by the environmental conditions like relative humidity and air current.

4. Evaporation stops when the air is fully saturated.

5. It varies directly according to the velocity of wind.

6. Light does not directly influence the rate of evaporation.

7. Evaporation is comparatively faster.

8. It is not much influenced by the structure of the evaporating surface.

9. It continues as long as water is available on the surface.

10. CO₂ pH and hormones have no effect on evaporation.

Difference # Transpiration:

1. Water vapours are formed mostly in internal tissues of the plant.

2. It occurs at the exposed surface of plants.

3. It is both a physical and physiological process. Besides being controlled by the environmental conditions, it is influenced by the rate of water absorption, osmotic pressure of cells, thickness of cuticle and number, position and opening of stomata.

4. Formation of vapours continues for some time even after the saturation of outside air. This is due to the fact that the temperature of the leaf is slightly higher than the outside air, and therefore, the saturation point of the internal air is slightly higher.

5. The rate of transpiration is slightly lower than evaporation under the influence of wind velocity because it lowers the leaf temperature.

6. Light influences transpiration to a great extent. Stomata usually open in the presence of sunlight resulting in full-scale trans­piration. They close during darkness, thus lowering the rate of transpiration to a great extent.

7. It is a comparatively slow process.

8. Transpiration is controlled by anatomy of the transpiring organ.

9. It is largely dependent upon absorption of water from the soil.

10. Transpiration is influenced by pH. CO₂ and hormones.