Early events induced by aluminum stress in elongating cells of wheat root

The relation between the toxic effects of alminum (Al) on growth and cell viability in roots of wheat (Triticum aestivum L. cv Atlas 66) was investigated. Root elongation of wheat was reduced after 3 h of treatment with 50 pM AlCl₃ at pH 4.7. Only the apical region of the root treated with Al was stained with hematoxylin. Al treatment decreased the length and increased the diameter of the cells at the elongation zone of the root. Staining with propidium iodide which can permeate through only a damaged plasma membrane showed that treatment with Al for longer than 3 h decreased cell viability. These findings suggest that inhibition of cell elongation by Al is partially accompanied by cell death. Lignin was deposited in the cell wall of the second and third layers of the cortex in the elongation zone of the root. Also the disruption of microtubules ocurred in elongating cells treated with 50 μM Al for 3 h. The effects of Al stress on root elongation and cell viability in the elongation zone were inhibited by 1 mM Ca. In conclusion, inhibition of root elongation by Al is strongly related to the inhibition of cell elongation, accompanied by decreased cell viability, lignin deposition and the disruption of microtubules.