Question

What will be the effects on stomata, if relative humidity is 100% in the atmosphere?
A.Completely open
B.Partially open
C.No effects
D.Closed

Answer 1

Hint: Stomata are the apertures present in plant leaves that are responsible for exchange of carbon dioxide i.e gaseous exchange and water. They are present in epidermis of leaves. Stems and various other parts of plants.

Complete answer:
Stomata consists of a minute pore known as stoma and is surrounded by bean shaped cells called guard cells. They contain chloroplast. The opening and closing of the stomata is regulated by these guard cells only. The turgidity of guard cells leads to opening and closing of stomata. This change in turgidity of guard cells is determined by the potassium flow hypothesis. When the potassium ions enter the guard cells water potential of them decreases which leads to turgidity of guard cells hence stomata open. And when there is outflow of the potassium ions it leads to reverse of process i.e. water potential increases and guard cells lose turgidity leading to closing of it. Rate of transpiration occurring is directly proportional to the vapor pressure. Since the humidity is very high, the rate of transpiration will be less occurring even though the guard cells will remain completely open.
Hence, the correct option for this is option A i.e. completely open.

Note:Relative humidity can be described as amount of vapor present in the atmosphere i.e ratio of present amount of water vapour to the highest possible amount of water vapours that can be present. So if the water content in the atmosphere is less i.e atmosphere is warm then transpiration will also be less as the it will close it stomata to reduce water loss. It is also referred to as a cooling mechanism.