Poster: Root Biology

Abs # 528: Lanthanum uptake in root protoplasts and its effects on root growth of Zea mays L.

Presenter:	Liu, Min , mxl3440@louisiana.edu
Authors	Liu, Min  (A)   Hasenstein, Karl H (A)
Affiliations:	(A): University of Louisiana at Lafayette

The calcium channel blocker and antagonist lanthanum induces growth inhibition in a concentration- and time dependent manner. La³⁺ also promotes the formation of root hairs and the initiation and maturation of xylem. However, the mechanism of lanthanum effects is still poorly understood. To test whether or not La³⁺ can cross the plasma membrane, we conducted uptake studies in corn root protoplasts in the presence of 1 µM to 1mM La³⁺ between five minutes and five hours. Our data suggest that La³⁺is taken up by corn protoplast and affects the level of Ca²⁺ and K⁺. The rate of La³⁺ uptake was proportional to the tested concentration and time. Time course studies indicate that La³⁺ binds to and saturates the membrane before entering the cell. The La³⁺ content in the protoplast was about 0.65, 38.01, 205.99 µg x10^-6 protoplasts five hours after application of 1, 100 and 1000 μM LaCl₃ to Ca²⁺ free medium. In the presence of 1 mM Ca²⁺, La³⁺ uptake was reduced but showed similar kinetics. The data suggest that La³⁺ exerts complex effects on root growth and interacts with calcium-dependent events.