Question

The loss of water in the form of water vapour through stomata on leaves is known as
A. Distillation
B. Diffusion
C. Osmosis
D. Transpiration

Answer 1

Hint: Water is an important ingredient for plant growth but water is lost through the evaporation and guttation process. The stomata are small porous openings present on leaves and also on green stems. These structures allow water to be evaporated through water vapour exchange along with gaseous exchange.

Complete answer: The stomata are the porous cells present on the epidermis of the plant parts, especially leaves. These are guarded by specialized parenchyma cells called guard cells that regulate their functioning. The main function of stomata is to respire. The gases are exchanged through the opening and closing of the stomata. Also, when stomata open the water inside the plant gets evaporated. This process of loss of water from stomata is called transpiration.

The roots of the plants suck up water from the soil and transport it to the whole plant. Water is a basic necessity for plants to grow but they need a very less amount of water. A major portion of water is evaporated into the atmosphere. Plants require carbon dioxide for photosynthesis and in this, they open the stomata through which transpiration occurs simultaneously. When the guard cells swell up through osmosis the stomata pore opens and the opposite happens when guard cells are plasmolyzed. Various chemicals and plant hormones like abscisic acid play a major role in regulating the opening and closing of stomata pores. All of these events sum up to be named as the process of transpiration.
Distillation refers to the process through which different components of a solution are separated. Diffusion means the passive movement of molecules through a concentration gradient. Osmosis is defined as the movement of water molecules through a concentration gradient.
Therefore, the correct answer is option D.

Note: Transpiration is not only about water loss. It has various other impacts on plant development and functioning. Transpiration helps the plant to cool down. It helps in changing the osmotic pressure of cells that further assists in gaseous exchange. It enables the mass flow of mineral nutrients through roots to shoots. It also influences the rate of flow of water from roots.