Effects of Calmodulin Inhibitors and Blue Light on Rhythmic Movement of Robinia pseudoacacia Leaflets

Abstract— The effect of several calmodulin (CAM) antagonists, blue light and an intracellular calcium inhibitor, on the circadian rhythm of Robinia pseudoacacia leaflet movement has been studied. The CAM antagonists, chlorpromazine (CPZ), trifluoperazine (TFP), calmidazolium and N -(6-aminohexyI)-5-chloro-1-naphthalenesulfonamide (W₇) shifted the phase of the circadian rhythmic movement while W₅, an inactive analogue of W₇, had no effect. Two hour pulses of calmidazolium (10–50 μ M ) gave rise to a phase-response curve with maximum advances (up to 9 h) at circadian time (CT) 6 and maximum delays (up to 7 h) at CT 22. No effect was found on transition from subjective day to subjective night and vice versa. The TFP (10–50 μ M ), applied as 2 h pulses during the circadian cycle, shifted the phase of the circadian leaflet movement and also produced maximum advances in the middle of subjective day. Two hour blue light pulses shifted the phase of leaflet rhythmic movement. The phase-response curve obtained showed maximum advances (up to 5 h) in the middle of subjective day and maximum delays on transition from subjective day to subjective night. Two hour pulses of 50 μ M 8-(diethylamino)octyl 3,4,5-trimethoxybenzoate hypochloride (TMB-8), an intracellular calcium inhibitor, caused the same type of phase-response curve, with maximum advances and delays occurring at the same time as those produced by blue light. These results indicate that CAM might be involved in controlling the circadian oscillator that drives Robinia leaflet movement. The relationship between CAM and calcium with red and blue light is discussed.