Differences between Guard Cells in Light and Guard Cells in Dark

The upcoming discussion will update you about the differences between guard cells in light and guard cells in dark.

Guard Cells in Light:

1. CO₂ is consumed in photosynthesis

2. pH rises, i.e., guard cells show alkaline reaction.

3. An increase in pH favours hydrolysis of starch into sugars.

4. Sugars increase osmotic pressure of cell sap of guard cells.

5. Water enters in the guard cells due to rise of O.P. and turgor pressure and volume of cells increase.

6. Guard cells become turgid and change their shape.

7. As a result stomata opens.

Guard Cells in Dark:

1. CO₂ released from respiration accumulates in the intercellular spaces. There is no photosynthesis.

2. pH falls, i.e., guard cells show acidic reaction.

3. A decrease in pH favours formation of starch from soluble sugars present in cell.

4. Due to presence of starch O.P. of cell sap of guard cells falls.

5. Water moves out of guard cells to subsidiary cells and O.P., T.P. and volume of cells decrease.

6. Guard cells become flaccid due to loss of water and change their shape,

7. As a result stomata closes.