Question

Choose the correct answers from the alternatives given.
Which of the following changes in the cell sap of the guard cells is responsible for keeping stomata open during day time?

• A. Decrease in osmotic pressure but increase in turgor pressure
• B. Increase in osmotic pressure but decrease in turgor pressure
• C. Increase in both osmotic and turgor pressures
• D. Decrease in both osmotic and turgor pressures

Answer 1

The correct option is C Increase in both osmotic and turgor pressures

The increased concentrations of potassium ions are balanced by malate ions that form potassium malate. This is stored in the vacuoles of the guard cells, increasing the osmotic concentration. Hence, the water enters the guard cells by endosmosis. The turgor pressure of the guard cells also increases due to this endosmosis causing the stomata to open.

Hence, the correct answer is 'Increase in both osmotic and turgor pressures'.