Introductory Crop Physiology (1+1)

Transpiration as a Necessary evil

• It is a vital and unavoidable phenomenon of plants.
The loss of water does not serve any good purpose in plant life. Besides, the transpiration also consumes energy and causes unnecessary absorption of excess water by roots. Nevertheless, the internal structure is basically meant for the exchange of gases during photosynthesis and respiration.
When the rate of transpiration is high and soil is deficient in water, internal water deficit is created in the plants which may affect metabolic processes.
Many xerophytes have developed structural modification and adaptation to check transpiration.
Deciduous trees have to shed their leaves during autumn to check loss of water.
But, in spite of the various disadvantages,

• The plants cannot avoid transpiration due to their peculiar internal structure, particularly those of leaves.
• Their internal structure although basically mean for gaseous exchange for respiration, photosynthesis etc., it cannot check the evaporation of water.
• Therefore, many workers like Curtis (1926) have called transpiration as necessary evil.