Abscisic acid improves the phytoremediation ability of the aquatic accumulator plant Nasturtium officinale R. Br. in cadmium-contaminated soil

Previous studies report significant contamination of farmland soil by cadmium (Cd). Cd contamination increases the risk of diseases after consumption of grain crops with high Cd levels. Hyperaccumulators or accumulators have been widely used to bioremediate Cd-contaminated farmland soil. Studies report that aquatic hyperaccumulators or accumulators are rarely used in phytoremediation, or their phytoremediation efficiencies are low. A pot experiment was carried out to explore the effects of abscisic acid (ABA) on the Cd accumulation (phytoremediation) of emerged aquatic accumulator plant Nasturtium officinale R. Br. Abscisic acid application increased the shoot biomass, peroxidase (POD) activity, superoxide dismutase (SOD) activity, catalase (CAT) activity, and soluble protein content of N. officinale under Cd-contamination condition. The application of ABA at 5, 10, and 20 μmol/L increased the chlorophyll and carotenoid contents in N. officinale. The application of ABA also increased the shoot Cd content and shoot Cd extraction of N. officinale. The application of ABA at 1, 5, 10, and 20 μmol/L increased the shoot Cd extraction by 11.65%, 25.27%, 37.91%, and 58.52%, respectively, compared with the control. In addition, ABA concentration had a linear regression relationship with the root biomass, shoot biomass, root Cd extraction, and shoot Cd extraction. Correlation, gray relational, and path analyses showed that the root biomass, shoot biomass, root Cd extraction, root Cd content, POD activity, SOD activity, and soluble protein content were significantly associated with the shoot Cd extraction. These findings indicate that ABA application can improve the phytoremediation ability of N. officinale under Cd-contaminated flooded fields.