Movement of Potassium Ions in the Motor Tissue of Stylidium

Abstract

In the flower of the trigger plant, Stylidium, the filaments and style are fused together into a column, sensitive to mechanical stimulation by nectar-gathering insects. A bend ini the column at the throat of the flower contains motor tissue of specialized anatomy, which changes curvature on stimulation, producing a rapid angular movement (in -20 ms) of the column followed by a recovery comprising a slow movement (in - 500 s) back to its original position and then a gradual return, within about 1 h, of its ability to again respond to stimuli. Associated with the recovery are changes in distribution of K+ within the motor tissue. After stimulation of the column there is a net movement of K+ from the morphologically anterior side of the column (on the convex side of the bend after the fast movement) to the posterior side, which continues for some time after the column has returned to its original position. The K+ then returns to the anterior side, now on the concave side of the column, as the ability of the column to respond to stimuli is slowly regained. Under some conditions, the column may commence oscillatory movements with a period of about 1000 s. During these oscillations there are small oscillatory changes in the distribution of K+ within the column.