Question

Under what environmental conditions does ABA level increase in plants? Why would light cause a change in stomatal aperture? What specific molecular events cause the opening of the stomatal aperture? What specific changes occurred in the guard cells? Why is there a difference in your result when you used mannitol instead of KCl?

Answer 1

ABA plays a regulatory role in many physiological processes in plants. Different stress conditions like cold, water, drought, light and temperature resultd in the increased level of the abscisic acid.

In the presence of light the guard cells (which control the opening and closing of stomata) take up water by osmosis and becomes turgid. As their inner walls are rigid, they are pulled apart and thus the pore opens.In darkness, water is lost and the inner walls move together and thus the pore closes.

Stomata will close with mannitol.

Day light stimulates the plasma membrane H+ pumping ATPase , causing a change in the membrane potential, leading to the influx of K+ ions. The increase in solute concentration causes water to follow. The turgor increase stretches the cells to one side only, thus opening the stomata.