Question

Movement of Mimosa pudica (sensitive plant) leaves is due to

• A. Nerve impulse
• B. Delicate leafs
• C. Loss of tissue
• D. Turgor change in leaf base

Answer 1

The correct option is D Turgor change in leaf base

Paratonic or induced turgor movements are turgor movements induced by stimuli, such as light, temperature and contact. These movements are also called as nastic movements and may be of various types, such as
(i) Siesmonasty
(ii) Nyctinasty
Siesmonasty means a response to shaking. The best example is Mimosa pudica ("Touch - me - not" plant) which is the sensitive plant. Such plants respond to stimuli, such as touch, blow or mechanical shock by folding their leaflets and lowering their leaves. This effect is caused by a change in the turgidity of the leaflets brought about by the movement of water into and out of the parenchymatous cells of the pulvinus or swollen leaf base.
Nyctinasty or sleep movements are caused by relative changes in cell size on the opposite sides of the leaf base called pulvinus. The movements are attributed to the amount of auxin, $K^{+}$ ions and therefore the movement of water. Entry of water to the lower side of the pulvinus causes the leaves to stand erect and the exit of water causes them to droop.