Rapid changes in levels of mineral nutrients in root-tip cells following short-term exposure to aluminium

We investigated the rapid modification of plasma membrane and changes in mineral nutrients in root-tip cells of Al-tolerant rice and Al-sensitive barley following short-term exposure to Al (20 M Al, 1 h). The plasma membrane of the barley cells was significantly permeabilized when re-elongated in an Al-free Ca solution following a 1-h pre-treatment with Al, while that of rice cells was not affected at all. The elemental distribution and concentration in a 2-mm portion of the root apex were determined by electron probe X-ray microanalysis. Al was localized primarily to the epidermis and outer cortex cells in both species, and was much more abundant in barley than in rice. Al increased and decreased remarkably the intracellular K concentration in whole root-tip cells of rice and barley, respectively. In barley, the decrease in the concentration of Ca coincided with the accumulation of Al. Conversely, the intracellular concentration of P in the surface layers of root-tip cells increased with the accumulation of Al. The distribution and concentration of Ca and P in rice did not change after 1-h treatment with Al. These results suggest that the rapid modification of the plasma membrane of root-tip cells induced by Al affects the nutritional homeostasis in the cells.