Question

Describe briefly the mechanism of stomatal movement. [4 MARKS]

Answer 1

Mechanism: 4 Marks

In 1967, Leviff explained the mechanism of stomatal action. Starch produced during photosynthesis is converted into organic acids which causes low concentration of potassium ions. The increase in the concentration of organic acids in guard cells, increases the concentration of cell sap followed by subsequent absorption of water.
In the dark, photosynthesis stops accompanied by increased concentration of C$O_2$. The organic acids are converted into starch decreasing the concentration of cell sap. This results in movement of water out of hard cells, a decrease in their turgor leads to closure of stomata. Thus, stomata open during day time and close during night.