Question

The shade of trees is often cooler than the exposed atmosphere because of
A. Photosynthesis
B. Respiration
C. Transpiration
D. Guttation

Answer 1

Transpiration is a process during which water is released in the environment from plants through stomata. This water is released in the form of vapor. This keeps the environment around trees cooler.
The temperature on the surface of leaves is also maintained at 10$^{\circ}$C less.

Complete answer: In plants the loss of water through stomatal openings, in form of vapor is called transpiration.
1. In this process, 95 % of the water from the plant is removed.
2. Transpiration is a very important process because it creates a negative pressure in xylem vessels. Due to this negative pressure water is pulled upside in plants.
3. The loss of water from stomata is caused due to the difference in the concentration of water molecules between the external environment and the sub-stomatal cavity of leaves.
So water molecules are diffused outside through stomatal openings.
4. At stomatal pores, guard cells are found. The change in osmotic concentration of guard cells causes the opening and closing of stomatal pores.
5. Stomata are opened during the daytime and closed during the night.

Additional information: Guttation is a process during which water loses in form of liquid not from the stomata but from any other part of the plant.
During photosynthesis and respiration gases are exchanged from the environment but not water molecules.

So the correct answer is C. Transpiration

Note: Transpiration is represented by cobalt chloride method.
Transpiration causes the uptake of water and minerals in plants.