Changes in Metal Distribution, Vegetative Growth, Reactive Oxygen and Nutrient Absorption of Tagetes patula under Soil Cadmium Stress

Phytoremediation with hyperaccumulator plants has been recognized as a potential way for the clearing of cadmium (Cd)-contaminated soil. In this study, hyperaccumulator Tagetes patula was treated with seven concentrations of Cd, ranging from 0 to 300 mg kg−1. The Cd enrichment and nutrient contents in different organs during different growth phases were investigated. Under Cd concentrations ≤75 mg kg-1, the morphological growth of T. patula did not change significantly regardless of growth stage. However, when Cd concentration exceeded 150 mg kg−1, the morphological growth was remarkedly inhibited. The root/shoot ratio remained unchanged except for at 300 mg kg−1. In addition, Cd negatively influenced the flowering process at the concentration of 300 mg kg−1. Cd content increased significantly in Cd-treated plants. Nitrogen absorption was increased under Cd treatments, and phosphorus content was also increased under concentration ≤150 mg·kg−1. However, the potassium content in the flower was decreased under 300 mg kg−1. Furthermore, the contents of H2O2, O2− and malondialdehyde were increased during the seedling phase, especially when Cd concentration was ≥150 mg kg−1. In summary, T. patula showed a strong ability to tolerate Cd, and such ability might be explained by nutrient absorption and reactive oxygen clearness.