In this article we will discuss about the advantages and disadvantages of transpiration.
Advantages of Transpiration:
1. Ascent of Sap:
Ascent of sap mostly occurs due to transpiration pull exerted by transpiration of water. This pull also helps in absorption of water.
2. Removal of Excess Water:
It has been held that plants absorb far more amount of water than is actually required by them. Transpiration, therefore, removes the excess of water.
3. Cooling Effect:
Radiant heat falling on the plants increases their temperature which may be dangerous to the plants. Transpiration, by evaporating water, lowers down their temperature by 10°—15°C.
4. Mechanical Tissue:
The development of mechanical tissue, which is essential for providing rigidity and strength to the plant, is favoured by the increase in transpiration.
5. Distribution of Mineral Salts:
Mineral salts are mostly distributed by rising column of sap.
6. Increasing Concentration of Mineral Salts:
The sap absorbed from the soil contains low concentration of mineral salts. The loss of water through transpiration increases the concentration of mineral salts in the plant.
7. Root System:
Transpiration helps in better development of root system which is required for support and absorption of mineral salts.
8. Quality of Fruits:
The ash and sugar content of the fruit increases with the increase in transpiration.
9. Resistance:
Excessive transpiration induces hardening and resistance to moderate drought.
10. Turgidity:
Transpiration maintains the shape and structure of plant parts by keeping cells turgid.
11. Photosynthesis:
Transpiration supplies water for photosynthesis. As water evaporates through the stomata, it results in pulling of water, molecule by molecule into the leaf from the xylem.
Disadvantages of Transpiration:
1. Wilting:
Wilting or loss of turgidity is quite common during noon due to transpiration being higher than the rate of water absorption. Wilting reduces photosynthesis and other metabolic activities.
2. Reduced Growth:
Transpiration reduces availability of water inside the plant. Water deficit decreases growth and hence the plant gives a stunted appearance.
3. Reduced Yield:
As reported by Tumarov (1925), a single wilting reduces growth by 50%. It is because decreased availability of water inside the plant checks meristematic activity and hence the formation of flowers, fruits and seeds.
4. Abscisic Acid:
Water stress produces abscisic acid. Abscisic acid prevents several plant processes and promotes abscission of leaves, flowers and fruits.
5. Wastage of Energy:
Since 98-99% of absorbed water is lost through transpiration, the energy used in absorption and conduction of water goes waste.
6. Modifications:
In order to reduce transpiration during critical periods, the plants produce several types of modifications— thick cuticle, hair, prickles, spines, thorns, sunken stomata, phylloclades, cladodes, etc. Nevertheless transpiration cannot be checked.
Stomatal transpiration will always occur whenever stomata are open for gaseous exchange (so essential for photosynthesis and respiration). Similarly cuticular and lenticular types of transpiration cannot be checked as there is no method of their control. Hence transpiration is regarded as a necessary evil or unavoidable evil.