Abstract
Aluminum (Al) causes root growth inhibition, but the toxicity mechanism has not been elucidated. In this study, a mechanism of the Al-induced inhibition of sucrose uptake was investigated in tobacco cells. Firstly, the characteristics of sucrose uptake was investigated in cells suspended in the calcium solution which contained various concentrations of 14C-Sucrose, but was adjusted osmolality with mannitol to the same level. The kinetics of sucrose uptake suggests two systems of high (at 1~3mM sucrose) and low (at 25~75mM sucrose) affinities. The high affinity uptake was inhibited almost completely with CCCP, but not with Wortmaninn, suggesting that high affinity uptake is via sucrose-proton cotransporter, but not endocytosis. Al inhibited both high and low affinity uptakes by more than 60% after 30 min exposure. These results suggest that tobacco cells have high and low affinity systems of sucrose uptake, and that Al immediately inhibits both systems.
