When applied to pulvini ofMimosa pudica, jasmonic acid (JA) affected neither proton fluxes nor the membrane potential of the motor cells. When added to leaflets ofCassia fasciculata, JA increased the rate of dark-induced pulvinar movements in a concentration-dependent manner. This effect was observed within as little as 15 min after a 1-h treatment that preceded the inducing signal. Treatments in buffered media at acidic pH resulted in the greatest physiological responses. Light-induced pulvinar movements were considerably reduced under the same conditions. With continuous illumination, JA induced a closing movement of the leaflets in a concentrationdependent manner. These results are discussed in relation to the ionic changes in the pulvinar motor cells and in relation to results obtained previously upon treatment ofCassiaplants with ABA. Although ABA and JA have similar physiological effects on the dark-induced closure, they differ in the type of response elicited by brief treatment and with respect to light-induced opening.
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