Correct Option
The correct option is A is true but R is false
Explanation
Stomata are minute pores found primarily on the epidermis of leaves. They facilitate gaseous exchange for photosynthesis and respiration, as well as transpiration. The opening and closing of these pores are regulated by specialized kidney-shaped or dumbbell-shaped cells known as guard cells.
Statement-wise Analysis
- Assertion (A): Correct
The primary function of the guard cells is to regulate the opening and closing of the stomatal pore. By changing their shape, guard cells control the size of the aperture, thereby managing gas exchange and water loss. - Reason (R): Incorrect
The mechanism of stomatal opening relies on turgor pressure. When water flows into the guard cells (endosmosis), they swell and become turgid. Due to the specific orientation of microfibrils and the thicker inner walls, this swelling causes the guard cells to bow outward, pulling the stomatal pore open. Conversely, when water flows out of the guard cells (exosmosis), they lose turgidity, become flaccid, and the pore closes. The reason statement incorrectly suggests that guard cells swell when water flows out.
Key Takeaway
Stomatal opening occurs when guard cells become turgid due to the entry of water. Stomatal closing occurs when guard cells become flaccid due to the loss of water.