The Telegraph Plant: Codariocalyx motorius (Formerly Also Desmodium gyrans)

Abstract

The telegraph plant (Codariocalyx motorius) has drawn much interest among plant physiologists because of its peculiar movements of the leaflets. While the terminal leaflets move from a horizontal position during the day and downward during the night, the lateral leaflets display rhythmic up and down movements in the minute range. The period length of the lateral leaflets is temperature dependent, while that of the terminal leaflet is temperature compensated. The movements of both the leaflets are regulated in the pulvini, a flexible organ between the leaflets and the stalk. Electrophysiological recordings using microelectrodes have revealed the physiological mechanisms underlying the leaflet movements. Early experiments related to effect of mechanical load, light, electric and magnetic fields on the leaflet oscillations by the Indian physicist Bose, and followed up by others, are presented. Experimental approaches are discussed and indicate, that Ca2+, various membrane channels, electric and osmotic mechanisms participate in the oscillating system. Modelling the pulvinus tissue would certainly aid in understanding the signal transduction during the movements. New approaches of modelling the mechanisms could further help in understanding the oscillations in the leaflet movements. Such oscillations might be of much broader relevance than known so far, although not as conspicuous as in the leaflet movements.