Question

How do guard cells of a leaf help to maintain homeostasis in a plant?

Answer 1

Hint: Homeostasis is maintaining a stable internal environment within a plant or an animal cell despite external conditions or factors. Water is a universal solvent and thus helps in maintaining proper homeostasis in an individual.

Complete answer:
The opening and closing of stomata is mediated by the kidney bean-shaped cells called guard cells. The stomata are involved in a very important phenomenon namely ‘photosynthesis’.
It aids in exchange of gases and also uptakes sunlight in this process. It is also involved in maintaining proper moisture level by transpiration.
The guard cells are also involved in maintaining homeostasis by regulation of water loss by the leaves.
If there is excess water loss by transpiration the homeostasis will not be regulated properly and the plant can’t survive.
When there is high concentration of sodium, potassium or other ions the guard cells swell and gets opened up due to great influx of water (as water moves from low solute concentration to high solute concentration) and when there minimum amount of ions water tends to move out of cell by transpiration.
In case of extreme conditions like drought or high temperature the guard cells tend to close the stomata to minimize the water loss by the cell thereby maintaining homeostasis.

Note: Guard cells are kidney bean-shaped cells present at the periphery of the stomata on either side of it. They are involved in opening and closing of stomata for maintaining homeostasis and also exchange of gases during photosynthesis or respiration. It follows a simple process of osmosis wherein there is flow of water from regions of lower solute concentration to higher solute concentration.