Factors Affecting Stomatal Movement
There are a number of factors which influence stomatal movements. These include light, temperature, potassium chloride, organic acid, carbondioxide concentration, water and abscissic acid.
Light greatly influences the opening and closing of stomata as it stimulates production of malic acid due to conversion of starch to sugar. Stomata do not open in U-V light and green light but remain opened in the blue and red regions of the spectrum.
Stomata open with rise in temperature and close at lower temperature as light and temperature are directly related. But higher temperatures also cause stomatal closure.
Accumulation of potassium chloride causes opening of stomata.
The increase of organic acid content in the guard cells causes the stomata to open.
Stomatal movement is influenced by the concentration of carbondioxide. At low concentrations of CO2, the stomata open. With increase in the concentration of CO2, the stomata begin to close and when CO2 concentration of cells is higher than its concentration in the air, the stomata completely close.
Stomatal movement is always influenced by the CO2 concentration of the intercellular spaces of the leaf and not the concentration of the air.
Water is responsible for causing changes in the turgor of the guard cells. Guard cells become flaccid on losing water and so the stomata close. Similarly the guardcells become fully turgid on gaining water and the stomata open. Under conditions of water scarcity also, the stomata close.
Abscissic acid accumulates in the leaves when the plants experience water stress or water deficit. It has been observed, that ABA (Abscissic acid) stimulates closure of stomata under these conditions.