Inhibition of Adventitious Root Growth in Tradescantia by Calmodulin Antagonists and Calcium Inhibitors<xref ref-type="fn" rid="fn1"><sup>1</sup></xref>

Abstract

When cuttings of Tradescantia fluminensis stem were incubated in distilled water, the buds located at the node grew into adventitious roots. The root growth could be inhibited by calmodulin antagonists, trifluoperazine, chlorpromazine, compound 48/80 and calmidazolium, in a concentration-dependent manner. The divalent cation chelator ethyleneglycol-bis-(β-aminoethyl ether)-N, N, N, N-tetraacetic acid had no effect, however, the intracellular chelator TMB-8 completely inhibited root growth. The growth was also inhibited by calcium ionophore A23187, lanthanum, a competitive inhibitor of Ca2+ uptake and verapamil, a calcium channel inhibitor. A Western blot of the adventitious root extract followed by immunostaining with an anti-spinach calmodulin antibody clearly showed the presence of calmodulin in this tissue. These results strongly suggest the involvement of calmodulin and calcium in the growth of Tradescantia advenitious roots.