Page 2 - 2.4-Lesson Notes-Coordination in Plants-(i)

Mechanism

• The sensitive plant has pulvini at the base of each leaf. This pulvini contains a
lot of water in their cells and due to internal pressure of water they are firm
and keep the leaf upright.

• As soon as we touch the leaves there is sudden loss of water from pad-like
swellings (pulvini). This is why pulvini lose its firmness and leaves droop.

• When we touch the sensitive place electric impulses travel through the cells of
the plant and act on plant hormone. The plant hormone migrate water from
the cells of the pulvinus to the intercellular spaces of the other half of pulvinus.
This loss of water makes pulvini lose firmness and thus its leaves droop.

• After 15 to 30 minutes water comes back to the cells and leaf gets back to its
original shape.

The leaves of sensitive plant fold due to the loss of water from pulvinus at
their base.