Involvement of receptor potentials and action potentials in mechano-perception in plants

The rapid turgor movements of Mimosa pudica and some carnivorous plants hav e long stimulated the interest of botanists. In addition, it is becoming ev ident that slower responses of plants to mechanical stimuli, such as coilin g of tendrils and thigmomorphogenesis, are common phenomena. Electrophysiol ogical studies on mechano-perception have been carried out in M. pudica and carnivorous plants, and have established that the response to mechanical s timulation is composed of three steps: perception of the stimulus, transmis sion of the signal, and induction of movement in motor cells. The first ste p is due to the receptor potential, the second and third steps are mediated by the action potential. In this article, the mechanisms of responses to m echanical stimuli of these plants are considered. Since higher plants are c omposed of complex tissues, detailed analysis of electrical phenomena is ra ther difficult, and so the mechanism for generating the receptor potential had not yet been studied. Characean cells have proved to be more amenable t o the study of the electrophysiology of plant membranes because of their la rge cell size and the ease by which single cells can be isolated. Recent pr ogress in studies of the receptor potential in characean cells is also disc ussed.