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Pulvinus in Mimosa Pudica
In Mimosa pudica, the internal biological clock mediates the closing of leaflets at night and opening during day. Seismonastic or rapid movement of leaves is triggered in response touch and temperature.

The pulvinus is located at the base of each leaflet of the plant. Mechanical stimulation via touch is perceived and is translated to electrical stimulation causing the flow of ions out of the pulvinus cells. An upregulation of aquaporin and H+ - ATPase allows for the rapid flux of water out of these motor cells. Water flux out of the cells results in a decrease in turgor pressure, and the characteristic closing of the leaves of Mimosa pudica. However, the drop in turgor pressure is reversible but slow. Leaves slowly open to their initial position after 20 minutes of lack of stimulation. It has been demonstrated that seismonastic movement can be inhibited with the use of anesthetics.

Using nuclear magnetic resonance, upward movement of water within the pulvinus joint in response to electrical stimulation was observed in the pulvinus at the base of the petiole. Movement of water to the upper or lower part of the pulvinus causes asymmetric swelling therefore causing the petiole to either droop or rise and contributing to the characteristic displacement of the petioles. The transmittance of internal electrical and chemical signals cause changes in the pulvinus which allows the M. pudica to respond accordingly to touch stimuli.