Effects of Light and Growth Substances on the Diurnal Movements of the Leaflets ofMimosa pudica

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Abstract
The leaflets of Mimosa pudica show diurnal opening and closing movements for some days when they are removed in pairs from the parent plant along with the pulvini and a small section of the rachis, and floated in water. The movements can be measured from changes in the angle of the blades. When the leaflets are kept in darkness they show a diurnal movement of opening in the morning at the same time as opening occurs in light. Light, however, is necessary to prevent the leaflets from closing during the day after an initial opening. Blue light was most effective in maintaining the open condition throughout the day. Low concentrations of indole-3-acetic acid (IAA) and gibberellic acid (GA) promoted opening of the leaflets while higher concentrations prevented their closure at night. IAA and GA acted synergistically in reducing dark-closure. Growth substances also prevented daylight closure of the leaflets in the dark. The results arre discussed in relation to the changes in the osmotic relations of pulvinar cells regulating leaf movements.