Potassium Chloride in the Motor Tissue of Stylidium

Abstract

Electron probe micro-analysis of the motor tissue in the column of S. graminifolium shows a relatively high concentration of potassium and chloride (about 600 mM) in the anterior cells of the tissue compared with other regions, prior to and immediately after the rapid movement of the column. The distribution of KCl is more widespread during the slower resetting movement of the column. It is suggested that the fast movement (a cross-fertilization mechanism) and the subsequent slow resetting movement are brought about by changes in turgor pressure in the anterior cells, with the principal osmoticum being KCl. The fast movement could be produced by a sudden loss of KCl and water from the anterior cells to the extra-cellular space, after which the KCl would diffuse into other regions of the column, while at the same time being reaccumulated into the anterior cells during the slower time of resetting of the column. When the column is fully reset, most of the KCl would again be in the anterior cells.