Effect of external calcium on the control of stamen movement inBerberis vulgaris L.

Abstract

The mechanical stimulation of the sensitive internal lower part of Berberis vulgaris stamen resulted in its rapid bending. In the present study we have examined the influence of external Ca²⁺ concentration on stamen movement. The external Ca²⁺ reduced the extent of the response and the effect was dependent on Ca²⁺ concentration and duration of the treatment. Addition of calcium ionophore A 23187 to the medium reduced the response and the effect was dependent on the external Ca²⁺ concetration. This result might suggest an increase in Ca²⁺ level in cytosol. The inhibitory effect of higher Ca²⁺ concentration on stamen bending was cancelled by Ca²⁺-chelating agents. Ca²⁺-channel blockers prevented the stamen response in higher external Ca²⁺ concentration with different effectiveness. In these conditions, during 4-h experiments, La³⁺, verapamil and nifedipine gave ability of stamen movement at about 85 %, 58 % and 10 %, respectively. An energy-dependent Ca²⁺ efflux was confirmed in experiments by using vanadate, a non-specific ATPase inhibitor. The lack of inhibition of stamen bending after application of calmodulin antagonists suggests that it might not be directly involved in regulation of the response. The inhibitory effect of higher Ca²⁺ concentration on stamen movement might result from: (a) the binding with cell wall materials, (b) changes of structure of cytoplasm and metabolic activity and (c) influence on transport processes.