Thigmomorphogenesis: Electrical Resistance and Mechanical Correlates of the Early Events of Growth Retardation due to Mechanical Stimulation in Beans

Summary The early effects of mechanical stimulation of stems have been examined in Phaseolus vulgaris . Auxanometry has revealed that within 3 minutes after stimulation, there is a brief but significant 33 % stimulation of growth which ceases by 6 minutes. After this, there is complete cessation of elongation which lasts from 15 to 30 minutes, after which growth resumes at a little more than half of the pre-stimulus rate. During the brief period of stimulated growth, the electrical resistance of the tissue decreases within seconds after stimulation. This effect can also be detected at the cut base of excised plants as a decrease of the resistance of the solution bathing them. The resistance of the stem tissue recovers during the period of zero growth. These and other data indicate that electrolyte efflux coupled with decreases in the electrical resistance of cell membranes, are among the very early events of thigmomorphogenesis.