Aluminum contents of the edible portions of the winged bean, Psophocarpus tetragonolobus (L.) DC. (Fabaceae): field study and caveat.

The winged bean, Psophocarpus tetragonolobus (L.) DC has been widely recognised as a potentially useful source of protein for tropical regions of the world. A neglected aspect of the plants nutritional quality has been the reporting of the accumulation of aluminum (Al) in the edible parts of the plant; the leaves, pods, seeds and tubers. The accumulation of Al in the plant on acidic tropical soils and the implication of Al to human health problems further justified the inclusion of Al in nutritional analysis. Field experiments on two varieties of the winged bean, the USDA-release Hi-Flyer and an unnamed variety from the Phillipines, showed that all edible portions of the plant accumulate Al from high to very high levels when compared to an average of usually less than 300 ppm in other crop plants. Aluminum accumulation is generally highest in the youngest tissues particularly in the young roots with levels recorded as high as 25,000 ppm and these contents are as high as levels for recognised 'Al accumulators' such as the leaves of Pinus and tea. Future improvement breeding programs for the winged bean will necessarily require identifying and taking advantage of possible variation in Al accumulation between varieties.