DISTRIBUTION OF ALUMINUM IN ACCUMULATOR PLANTS BY X-RAY-MICROANALYSIS IN RICHERIA-GRANDIS VAHL LEAVES FROM A CLOUD FOREST IN VENEZUELA

The leaf cells of a tropical tree which accumulates more than 1 mg per gram dry weight of A1 in its leaves were studied by X-ray microanalysis. The analyses made in cell walls, vacuoles and chloroplasts of a mature leaf showed that A1 is accumulated preferentially in the cell wall. In the pre-senescent leaf, Al also invades the interior of cells and is deposited in chloroplasts and vacuole. Aluminium was found also in xylem vessels but only in traces in phloem tissue. It was not found in spongy parenchyma cells. The observed A1 distribution, i.e. at the adaxial leaf face, coincides with observed damage in tissues of pre-senescent leaves. The means by which this plant copes with Al under natural conditions seems to be partially preventing it from entering the cell by deposition in cell walls. A hypothesis about the pathways of A1 in accumulator plants is proposed.