Comparison of the Aluminum Tolerance ofMiscanthus sinensisAnderss. andMiscanthus sacchariflorusBentham in Hydroculture

Miscanthus sinensis Anderss. and Miscanthus sacchariflorus Bentham are typical perennial species that are widely distributed throughout Japan. Miscanthus sinensis dominates seminatural grasslands and grows on acid soil. By contrast, M. sacchariflorus grows on fertile lowlands and alluvial plains. The two species are sometimes distributed in the same area, but the more Al‐tolerant species might be expected to dominate with increasing acidity of the soil. To assess the tolerance to Al of the two closely related species of Miscanthus, an analysis was made of dry‐mass allocation and production of organic acids, which are involved in mechanisms of Al tolerance, using hydroponic culture. Plants were grown at seven (M. sinensis) and six (M. sacchariflorus) concentrations of Al. After 42 d, the dry mass of shoots and roots of M. sinensis was lower ($$P< 0.05$$) at 5 mg Al L−1 as compared to controls. Dry mass of M. sacchariflorus was lower ($$P< 0.01$$) at 2 mg Al L−1. The ratio of shoot to root dry mass (S/R) increased more in M. sacchariflorus at >5 mg Al L−1 than in M. sinensis. Miscanthus sinensis excreted twice as much citric acid from its roots (45 mg L−1 d−1), to form an Al‐chelate, as did M. sacchariflorus. Because of the higher excretion rate of citric acid from its roots, M. sinensis might tolerate Al better than M. sacchariflorus.