Present evidence suggests the following picture for cell wall extension: there is the possibility that auxin acts to induce synthesis of nucleic acids and proteins which presumably are envolved in cell enlargement through enzyme activation and cell wall components synthesis. Rapid responses to auxin may be through the auxin activation of a proton pump on the plasmalemma. The resultant lowering of the pH in the wall enhances the activity of wall-loosening enzymes there promoting cell wall enlargement. A schematic representation of the mechanism concerning the action of auxin in elongation growth is presented.