Movement of leaves of the sensitive plant
We all see the shrinking of leaves in touch me not plant (Chui-Mui) in response to touch or air.
Plant shrink its leaves and the stem droop in response to touch.
This happens due to changes in the turgor pressure.
Turgor pressure is the pressure exerted by water on the cell walls present in the sensitive plant. When turgor pressure is high leaves are open.
However, when we touch the plant or blow air to them efflux of sodium and potassium ion causes a decrease in the turgor pressure. As a result, leaves fold themselves and look like dry.
It saves themselves from grazing animals as grazing animal prefer green leaves than dry stems.
Movement of a shoot towards the light
As we have seen in Activity 7.2, shoot of a plant move in the direction of light.
This movement happens due to secretion of growth hormones in the plant.
Stem towards the light source produces Auxin hormone.
This hormone diffuses to the back part of the stem.
Here it promotes the growth of the shoot.
This disproportionate growth of shoot cause bending in the plant. As a result, plant appear bent toward the light
