Objective Accumulation and distribution of different forms of zinc in Myriophyllum spicatum L. were examined for applying the aquatic plant to remove the heavy metal in water.

Method A hydroponic experimentation was conducted to determine the biomass, height, leaf epidermal cell variation, and antioxidant enzyme activities of the plants grown in water under varied zinc concentrations. Subcellular distribution and chemical forms of Zn in the roots, stems, and leaves of the plant were analyzed.

Result M. spicatum plants survived in the water under the spiked Zn. At the Zn concentration of 50 mg·L⁻¹（Z1）, the plant height significantly increased by 22.87% and the biomass 10.06% over control with no significant differences on chlorophyll and MDA contents in the roots and leaves. On the other hand, the SOD activities in the roots and leaves of the treatment plants were significantly elevated. At 200 mg·L⁻¹（Z2）, the plant height and biomass showed no significant differences, but chlorophyll was significantly lowered by the treatments, and the MDA content and SOD activity in the roots and leaves were significantly increased by the treatments. Depending upon the treatments, the Zn contents in the roots of the aquatic plants ranged 55.48–242.44 mg·kg⁻¹, in the stems 14.78–31.02 mg·kg⁻¹, and in the leaves 18.01–69.79 mg·kg⁻¹. Those under the Z1 and Z2 treatments were significantly higher than the others, and that in the roots significantly higher than that in the leaves or stems. The subcellular Zn in M. spicatum was mainly located in the leaf cell walls, which accounted for 32.56%–49.50%, and stem cell walls, which accounted for 41.21%–43.52%. In the roots, Zn was mostly in the soluble fractions that comprised 32.10%–50.48% of total. The NaCl-, HAc-, and HCl-extractable Zn were predominant at 77.00%–86.00% in the leaves and at 81.00%–86.38% in the stems. Whereas the water and NaCl-soluble Zn were mostly found in the roots at 59.71%–63.65%.

Conclusion M. spicatum extracted Zn from the environment and stored in various forms more in the roots than the stems and leaves. The ability of the aquatic plant in accumulating Zn with tolerance might come from the cell wall retention and vacuoles segregation (soluble components), and in part, due to the low-reactivity forms of the heavy metal it absorbed.