Compartmentation of aluminium in leaves of an Al-accumulator, Fagopyrum esculentum Moench.

Buckwheat (Fagopyrum esculentum Moench.) is an Al-accumulating plant, but the internal mechanism(s) of detoxification of Al is not fully understood. We investigated the subcellular localization of Al in the leaves of this plant (cv. Jianxi) by directly isolating protoplasts and vacuoles. Pure protoplasts and vacuoles from the leaves of buckwheat, grown hydroponically in Al solution, were obtained based on light-microscopic observation and the activities of marker enzymes of cytosol and vacuoles. More than 80% of total Al in the leaves was present in the protoplasts, and was identified as an Al-oxalate complex (1:3 ratio) by ²⁷A1-nuclear magnetic resonance. Oxalate and Al in the protoplasts was localized in the vacuoles. These results suggest that internal detoxification of Al in the buckwheat leaves is achieved by both complexation with oxalate and sequestration into vacuoles.