Distribution and mobility of aluminium in an Al-accumulating plant, Fagopyrum esculentum Moench.

Buckwheat (Fagopyrum esculentum Moench. cv. Jianxi) accumulates high concen trations of Al in the leaves without showing any toxicity. To understand th e accumulation mechanism of All in buckwheat, the distribution and mobility of Al in buckwheat were investigated. Relatively long-term treatment (28 d ) with Al led to a decrease in Al concentration from old to young leaves, w hile a short-term (1 d) exposure to Al resulted in a uniform distribution o f All in the leaves. When the fourth leaf was wrapped inside a transparent plastic bag to suppress transpiration, the Al concentration of this leaf wa s only one-quarter of that in the corresponding leaf without wrappng. Wit i n a leaf, the Al concentration at the margins was much higher than that in the centre. These results indicate that Al distribution in the leaves is co ntrolled by both rate and duration of transpiration. The mobility of Al bet ween old and new leaves was studied by first growing plants in a solution w ith Al, followed by culture in a solution without Al. The Al content in the two new leaves appeared after removal of external Al was very low, whereas that in the old leaves did not decrease but continued to increase. The inc reased Al content was found to be translocated from Al remaining in the roo ts. It is concluded that Al is not mobile once it is accumulated in the lea f.