Abstract
The sensitive plant, Mimosa pudica L. closes the leaves and hangs the petiole down when stimulated by touch or heat treatment. This bending of the petiole is caused by rapid shrinking of the lower side of motor organs called the pulvinus. MRI technique indicates that the water in the main pulvinus transfers from the flexor to the extensor during the rapid bending. The actin cytoskeleton in the motor cells plays in important role in the petiole bending. The actin molecules in Mimosa pudica L. is heavily tyrosine-phosphorylated. The bending of Mimosa pudica L. is correlated with reduced actin phosphorylation in the pulvinus.
