Abstract

The column of the flower of S. crassifolium when mechanically stimulated moves through an angle of about 4 rad in 15 ms and then resets more slowly in several hundred seconds. The rates of the firing and resetting as a function of temperature have been investigated. Arrhenius plots of these rates are approximately straight lines yielding energies of activation of ~ 8 kJ mol^-1 for firing and ~72 kJ mol^-1 for resetting. These results suggest that resetting is the 'active' part of the movement, and is closely linked to the metabolic energy supply. The rate of firing is more likely limited by friction within the cell walls of the motor tissue, or possibly by the viscosity of extracellular water.