摘要：The main purpose of this study is to analyze whether Cd<sup>2+</sup> affects the absorption of Ca<sup>2+</sup> and Fe<sup>2+</sup> by the roots of five wetland plants and the toxic mechanism of cadmium on the subcellular structure. Five wetland plant samples were collected from the constructed wetland in the upper reaches of the Yangtze River. Based on the experiment and density function theory (DFT), we measured the Cd<sup>2+</sup> content in the root, stem, and leaf, the morphological dimensions of plants, and in the subcellular structure the electronic activity of Cd compound was calculated to describe the stability and activity of the products. In general, <i>Zephyranthes candida</i><i>,</i><i>Cynodon dactylon, Arundo donax</i>, and <i>Pontederia cordata</i> have distinct cadmium uptake characteristics, while <i>Phragmites communis</i> does not. The results indicated tolerance to cadmium in all but <i>Phragmites communis,</i> which was due to cadmium distribution through the process of transpiration and a mechanical interception. The simulation results showed that Cd<sup>2+</sup> imposed no obvious inhibition on the absorption of Ca<sup>2+</sup> and Fe<sup>2+</sup> in plants, as the energy barrier of the process is about 1–3 eV. Cd<sup>2+</sup> could improve the amount of pyruvate and glucose by 30% via <i>spd</i> orbital hybridization, making them more chemically reactive. At the same time, Cd<sup>2+</sup> could replace Mg<sup>2+</sup> in chlorophyll through a copper substitution reaction, making the electron energy of chlorophyll more concentrated. As a result, the valence-band electron at −40 eV was vacant. In conclusion, we determined that Cd<sup>2+</sup> has no obvious inhibitory effect on Ca<sup>2+</sup> and Fe<sup>2+</sup> in root absorption and that Cd<sup>2+</sup> could affect the properties of compounds of the subcellular structure and thus produce physiological toxicity.
