Question

The shape of guard cells changes due to change in the

• A. Protein composition of cells
• B. Temperature of cells
• C. Amount of water in cells
• D. Position of nucleus in the cells

Answer 1

Answer: (C)

Amount of water in cells

Guard cells are cells surrounding each stroma. They help to regulate the rate of transpiration by opening and closing the stomata. If the guard cells are turgid or swollen, the stomatal opening is large. This turgdity is caused by the accumulation of K+ ions in the guard cells. As K+ levels increase in the guard cells the water potential of the guard cells drops and water enters the guard cells. In the second case, the guard cells have lost water, which causes the cells to become flaccid and the stomatal opening to close. This may occur when the plant has lost an excessive amount of water.

Therefore, the correct answer is option C.