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Nasturtium officinale is a cadmium (Cd) accumulator plant, but its phytoremediation capacity is low compared to other hyperaccumulators. To improve the phytoremediation capacity, the seedlings of N. officinale was grown in Cd-contaminated paddy soils, and the effects of diethyl aminoethyl hexanoate (DA-6) on N. officinale growth and Cd accumulation were studied. DA-6 increased the shoot biomass of N. officinale, and had a quadratic polynomial regression relationship with root and shoot biomass. DA-6 had no significant effects on chlorophyll a, chlorophyll b, and carotenoid contents, increased peroxidase, superoxide dismutase, and catalase activities, and decreased the soluble protein content. DA-6 also increased the Cd content and Cd extraction of N. officinale to some extent, and had a quadratic polynomial regression relationship with the root Cd content, shoot Cd content, root Cd extraction, and shoot Cd extraction. Significant correlations were found among plant biomass, chlorophyll content, Cd content, Cd extraction, and antioxidant enzyme activity. Furthermore, soluble protein content and soil exchangeable Cd was significantly correlated with plant Cd content and Cd extraction. Therefore, DA-6 can promote N. officinale growth and improve its phytoremediation capacity for Cd-contaminated paddy soils, with a recommend optimum dose of 20 mg/L. [ABSTRACT FROM AUTHOR]

To assess the effects of brassinolide (BR) on the growth and phytoremediation ability of cadmium (Cd) accumulator plants, different BR concentrations were applied to emerged accumulator plant Nasturtium officinale growing in Cd-contaminated soil. Brassinolide application increased the biomass, photosynthetic pigment content, and antioxidant enzyme activity of N. officinale. When N. officinale was treated with 1.5 mg L−1 of BR, the highest shoot biomass was obtained, recording an increase of 26.06%, compared to the control. In addition, BR treatment decreased the Cd contents in the shoots of N. officinale, and the BR concentrations of 0.5, 1.0, 1.5, and 2.0 mg L−1 decreased the Cd content in shoots by 10.49%, 12.11%, 20.13%, and 17.23%, respectively, compared to the control. Brassinolide treatment also slightly inhibited the transportation of Cd from the roots to shoots. The findings revealed that BR had no significant effects on the Cd extraction amounts by stems, leaves, and shoots of N. officinale. However, BR promoted the growth of N. officinale and inhibited the Cd uptakes in the above-ground part of N. officinale. Thus, N. officinale could be used as a wild vegetable in the Cd-contaminated soil, although not suitable for phytoextraction as an accumulator plant. [ABSTRACT FROM AUTHOR]