Influence of different spectral ranges of light and Ca2+ -channel blockers on Ca2+ and K+ levels in Phaseolus coccineus L. pulvini

Abstract

The effect of different spectral ranges of light on the modification of transport processes in isolated parts of Phaseolus coccineus pulvini was analysed in a bath medium by determining the Ca²⁺ and K⁺ contents. After 1 h incubation of separated fragments of the extensor and flexor in solutions containing deionized water, medium, or medium with verapamil or nifedipine, the investigated material was irradiated with monochromatic light of different wavelengths. The concentration of Ca²⁺, K⁺ and the pH value were determined in the medium. The obtained results suggest the occurrence of a specific coupling between the concentration of Ca²⁺ and K⁺ dependend on the wavelength of the applied light and part of the pulvinus. Certain spectral ranges of light brought about opposite effects on ion transport in opposite parts of the pulvinus. Changes in the pH of mediums containing isolated parts of the pulvini part to different effects of blue, red, and far-red light on the activity of H⁺-pumps located in the motor cells. The use of verapamil and nifedipine, specific Ca²⁺-channel blockers, made it possible to demonstrate the significant effect of Ca²⁺ on the activity and functioning of K⁺ -channels. The two types of inhibitors decreased the influx of Ca²⁺ and K⁺ to motor cells of the pulvini, however they did not limit the efflux of ions to the medium. The obtained results suggest that Ca²⁺ ions take part in transduction of the light signal. It seems probable that the action of blue light is also mediated by part of the Ca²⁺ ions.