Question

State two disadvantages of transpiration to the plant.

Answer 1

Hint: Transpiration is considered as the excretory system of plants and although it has great importance in the plant body, it also has some drawbacks as well. Therefore, it is said to be the necessary evil of the plants.

Complete answer:
Transpiration is the process where extra water of the plant body gets out of the aerial parts like leaves, stems, and flowers by evaporation.
Two disadvantages of transpiration are:
-Transpiration during the mid-day time may cause wilting of the plant as, due to evaporation, water deficit occurs which sometimes can also be fatal to the plant.
-Energy is required to absorb water from the soil by the root and in the transportation of this water. As 90% of this water gets evaporated in the transpiration process, the energy burnt during the absorption and conduction gets wasted.

Additional Information: We can consider the transpiration as the excretory system of the plants, as it excretes out excessive water from the aerial parts of the plant. In fact, only 10% of the water absorbed by the root actually gets used by the plant in its life processes and the other 90% gets excreted by transpiration.
This process is of 3 types- Stomatal, Lenticular, and Cuticular. As the names state, the stomatal one occurs through the stomata i.e. the minute pores of the leaf and stem. It is the main transpiration that excretes most of the water. The lenticular one occurs through lenticels which are minute pores found in the bark and Cuticular transpiration occurs through the cuticles. In dry conditions, Cuticular transpiration is the most common one.
Several factors like light, humidity, temperature, atmospheric pressure, etc. as well as some cellular factors affect the rate of transpiration.

Note: Other than the disadvantages mentioned in the answer, transpiration can be harmful in some other ways as well. Along with mid-day wilting, it often causes water deficit in capillary water that causes injury to the plants as it may cause desiccation. In dry areas, where water is already a shortage, excessive transpiration can be a fatal case. Therefore, plants like xerophytes have to modify in order to reduce the rate. Excessive transpiration even causes stunted growth in plants.