Abstract:In order to explore the tolerance mechanism and dynamic migration of Zn in torpedograss (Panicum repens), the accumulation and transport capacity of Zn in roots, stems and leaves, as well as the distribution characteristics of Zn subcellular and chemical states were studied by hydroponic pot experiment. The results showed that the maximum Zn contents in roots, stems, and leaves were 2 728.38, 388.63 and 1 199.07 mg/kg, respectively, and their enrichment factors (with a maximum of 3.11) all exceeded the international limit for super-accumulating plants. The average migration rate from root to leaf (264.99%) was much higher than that from stem to leaf (14.16%). With the extension of stress time and the increase of Zn concentration, the Zn contents in stems and leaves significantly increased (P<0.05). However, the change in Zn content of root showed a “Λ” type, reaching the highest value at 21 days. The roots and leaves were detoxicated mainly by cell wall fixation (more than 58%), while the stems were detoxicated mainly by vacuole compartments. The Zn in the roots and leaves mainly exists in the NaCl extraction state, with the highest proportions of 75.40% and 61.05%, respectively, followed by organic state (HAc and HCl), which mainly reduces the damage by allocating more Zn to the less active chemical state storage. The Zn in stems is mainly in the form of ethanol and d-H2O with high activity, and the higher fluidity of Zn ions enhances the transport from stem to leaf, resulting in higher Zn content in leaves. Therefore, Panicum repens exhibits strong Zn tolerance and accumulation capacity, and has the potential and advantage of ecological remediation of heaviy Zn-contaminated water-level-fluctuation zones in tropical and subtropical regions.
