Effect of nitrogen application on seedling growth and cadminm uptake and distribution in Acacia mangium × Acacia auriculiformis under cadmium stress

ObjectivesThe adaptation and bioremediation capability of Acacia mangium × Acacia auriculiformis were studied under different nitrogen and cadmium stress levels for providing support for scientific fertilization of the target cultivation of Acacia mangium × Acacia auriculiformis.

MethodsA pot experiment was carried out with two cadmium stress levels of Cd²⁺ 30 and 60 mg/kg and two urea levels of 0.4 and 0.8 g/kg soil. The accumulation and distribution of dry matter, N, P, K and Cd in shoots and roots of the trees were analyzed.

ResultsThe cadmium stress significantly inhibited dry matter accumulation in roots, stems and leaves of Acacia mangium × Acacia auriculiformis, and also reduced the N, P and K absorption and accumulation. The Cd transfer coefficients of the plant were from 0.044 to 0.224 when treated with different Cd concentrations. The concentrations of Cd in roots were significantly higher than those in stems and leaves, and the accumulation ability of Cd in roots was higher than that in shoots. In order to adapt to the environment better, the Acacia mangium × Acacia auriculiformis transferred more Cd from roots to shoots under the high Cd stress. Under the Cd²⁺ stress of 30 mg/kg, the high N increased P and K contents and accumulations in shoots, while the low N increased P and K contents in roots. The high N was more efficient in accumulation and distribution of dry matter in shoots, while the low N showed the same performance in roots. The nitrogen fertilization promoted the absorption and accumulation of Cd in the plants and improved the Cd transfer coefficients when treated with different Cd concentrations. The low nitrogen significantly promoted the Cd accumulation in roots, leaves and plants, and the high nitrogen significantly promoted the Cd accumulation in stems and the allocation proportion of Cd in stems and leaves.

ConclusionsNitrogen fertilization could alleviate the limitation of N and K absorption of Acacia mangium × Acacia auriculiformis in 30 mg/kg Cd concentration and promote accumulation of dry matter, N, P, K and Cd. The low nitrogen is good for better growth of the plant, and the high nitrogen performs better in promoting the transferring of Cd to the aboveground of Acacia mangium × Acacia auriculiformis, which is required for the ability of the Cd bioremediation.