La3+ uptake and its effect on the cytoskeleton in root protoplasts of Zea mays L.

La3+ ions are known to antagonize Ca2+ and are used as a Ca2+ channel blocker but little is known on the direct effects of La3+. Micromolar La3+ concentrations promoted root growth while higher concentrations were inhibitory. The uptake of La3+ in maize root protoplasts revealed a membrane binding component (0.14 and 0.44 pmol min−1 protoplast−1 for 100 and 1,000 μM La3+) followed by a slower concentration and time-dependent uptake. Uptake was reduced by Ca2+, but had no substantial effect on other ions. La3+ shifted microtubule organization from random to parallel but caused aggregation of microfilaments. Our data suggest that La3+ is taken up into plant cells and affects growth via stabilization of the cytoskeleton.