Tips cikgu Aida!!

STOMATA OPENING

1. During the day, photosynthesis is occur in guard cells and produce glucose.



2. K+ ions are actively pumped from the surrounding epidermal cells into the guard cells.



3. The accumulation of K+ ions and glucose increases the osmotic pressure of guard cells.



4. Cell sap of guard cell is hypertonic to the cell sap of epidermal cell.



5. Water molecules from the cell sap of epidermal cell will diffuse into the cell sap of guard cell by osmosis.



6. Water concentration in the cell sap of epidermal cell is higher than the water concentration in the cell sap of guard cell.



7. The guard cell will become turgid and curved outwards, stomata opened.



8. Hence, water vapour diffuses out from stomata air space into surrounding.

STOMATA CLOSING

1. In the dark, photosynthesis does not occur. Sugar and amino acids are translocated out of the guard cell. This process is known as translocation.



2. K+ ions will diffuse out of guard cell to the epidermal cell.



3. Therefore, osmotic pressure of the guard cell will decrease.



4. Cell sap of guard cell is hypotonic to the cell sap of epidermal cell.



5. Water molecules from cell sap of guard cell will diffuse into the cell sap of epidermal cell by osmosis.



6. Water concentration in the cell sap of guard cell is higher than the water concentration in the cell sap of the epidermal cell.



7. The guard cell become flaccid and curved inwards, stomata closed.



8. Hence, water vapour cannot diffuse out to the surrounding. Transpiration stops.