Nitrogen fertilization promotes the phytoremediation of cadmium in Pentas lanceolata

Abstract

The star cluster (Pentas lanceolata) cv. Butterfly was planted in a medium that contained 25 mg/kg cadmium (Cd) with application of varying nitrogen concentrations (0 mM, 8 mM, 16 mM, 24 mM and 32 mM) weekly. Regardless of whether nitrogen was applied, the length of stems, roots, the number of nodes, and thickness of leaves of the test seedlings were inhibited by the presence of Cd in the medium. Initially the Cd in the soil caused the chlorophyll meter readings (CMR) of plants to decrease to an abnormal level. The CMR values of the injured plants then recovered to normal levels after 28 days of 32 mM or 24 mM nitrogen addition (CMR levels 29.4 and 25.7 respectively), while the controls had a CMR of only 15.7. The 32 mM nitrogen treatment obtained the maximum accumulation of Cd concentration (622.9 mg/kg) in the root of the testing plants with a total Cd amount of 27.9 μg. Briefly, nitrogen treatment can improve the phytoremediation of Cd, also can promote the recovery of chlorophyll in leaves. Without inhibition of the flowering, the Pentas lanceolata could preserve their function in the landscape even during the process of phytoremediation.