Question

What are guard cells? Explain their role in regulating transpiration.

Answer 1

Guard cells are the kidney shaped cells that surround the stomata and are responsible for opening and closing of the stomatal pore. When potassium ions accumulate in the guard cells, they absorb water and become swollen or turgid. Due to their turgidity the stomatal pore opens up completely and transpiration occurs. When they lose water due to external influences like sunlight, temperature,etc, they become flaccid and close the stomatal opening and hence stop the transpiration.