Comparative Effectivness of Metal Ions in Inducing Curvature of Primary Roots of Zea mays

We used five cultivars of Zea mays (Bear Hybrid WF9 ^* 38MS, B73 ^* Missouri 17, Yellow Dent, Merit, and Great Lakes Hybrid 422) to reinvestigate the specificity of metal ions for inducing root curvature. Of 17 cations tested, 6 (Al³⁺, Ba²⁺, Ca²⁺, Cd²⁺, Cu²⁺, Zn²⁺) induced curvature. Roots curved away from Al³⁺, Ba²⁺, and Cd²⁺. Roots curved away from low (0.1 millimolar) concentrations of Cu²⁺ but toward higher (1-5 millimolar) concentrations. Roots initially curved away from Zn²⁺ but the direction of the subsequent curvature was unpredictable. In most cases, roots of all cultivars curved towards calcium. However, in some tests there was no response to calcium or even (especially in the cultivars Merit and B73 ^* Missouri 17) substantial curvature away from calcium. The results indicate that the induction of root curvature is not specific for calcium. The results are discussed relative to the possible role of calmodulin as a mediator of ion-induced root curvature.