2 LEGUMINOUS TREE SPECIES DIFFER IN GROWTH AND ION UPTAKE IN HOAGLANDSOLUTION - PHOSPHORUS TOXICITY IN AMUR-MAACKIA

Hydroponic culture of tree seedlings is used commonly to study root bi ology; however, we have found that two species of woody legumes differ in their responses to this practice. Seedlings of Amur maackia (Maack ia amurensis Rupr. & Maxim.) and black locust (Robinia pseudoacacia L. ) were culture in 1, 5, 10, 25, 50, and 100% Hoagland solution #1 for 5 weeks. Total drug mass of black locust increased with increasing sol ution concentration up to 50%. Amur maackia dry mass was greatest in 5 % solution. Bronzing, chlorosis and necrosis occurred on leaves of Amu r maackia in solutions 10% and symptom severity increased with solutio n strength. Leaf phosphorus (P) content of Amur maackia increased from 0.40 to 1.95% of dry mass as solution strength increased from 5 to 50 %. Amur maackia grown in a soil-based medium and irrigated with 50% so lution showed no foliar toxicity symptoms, and P content of the leaves of these plants was 0.279%. Laminae of Amur maackia had higher mangan ese (Mn) content than laminae of black locust at solution concentratio ns above 5%. Levels of calcium (Ca) and magnesium (Mg) in laminae of A mur maackia suggest an enhanced ability of this species to absorb ions from its medium. Results indicate no elemental deficiencies for eithe r species. We conclude that black locust can be grown hydroponically u sing standard methods. However, growth of Amur maackia in solution is inhibited at concentrations of Hoagland solution #1 > 10%, suggesting a sensitivity to the availability of ions and perhaps an enhanced abil ity to sequester ions from its medium.