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Summary Roots of garden cress ( Lepidium sativum L., Einfache Gartenkresse) were incubated in an A23187, CaCl 2 and EGTA-containing medium in order to elevate the free cytoplasmic Ca 2+ concentration in statocytes. If the Ca 2+ -concentration exceeded 0.1 mM, after 15min the distal complex of endoplasmic reticulum (ER) disintegrated and was displaced towards the anticlinal by the sedimenting amyloplasts. After 2h the ER formed whorls and was further displaced within the statocytes. The calmodulin antagonists, Calmidazolium, W-7 and Compound 48/80, had no effect on the ER-distribution if added for 15min. After 2h, however, the polarity of the statocytes, as indicated by a distinct ER-distribution, was disturbed by all antagonists. It is suggested that the short-term effects of Ca 2+ -elevation are caused by a direct Ca 2+ action on the cytoskeleton. Long-term Ca 2+ -elevation and calmodulin antagonists most probably interfere with a Ca 2+ -pump/-channel based polar transport of Ca 2+ . |
