Potential use of Rorippa sylvestris (L.) Besser. as a cadmium hyperaccumulator for phytoremediation

Rorippa sylvestris (L.) Besser. (yellow fieldcress) is a hyperaccumulator of cadmium (Cd) discovered recently. There are several studies in the topic of Cd tolerance capacity and detoxification mechanism of plants, but the detoxification mechanism of R. sylvestris is not clear. Root tiller seedlings of R. sylvestris were planted in the brown bottles filled with culture solution containing different levels of Cd (0, 10, 25, 50, 100, 200 μmol·L⁻¹, respectively) for 8 days in order to make sure the physiological responses, Cd subcellular distribution and chemical forms under Cd stress. The results showed that the growth increased in lower Cd concentration and declined in higher Cd concentration. Physiological characteristics such as photosynthesis and MDA were not significantly affected compared with the control at Cd concentratetion ≤ 50 μmol·L⁻¹. The content of soluble sugar and free proline increased with the increasing of Cd concentration for the purpose of reducing the Cd toxicity to plant. R. sylvestris had a strong capability of Cd accumulation in different Cd treatments. The concentration of Cd in plant tissues (root, stem, leaf) was in the order of root>stem>leaf. The Cd subcellular distribution in plant tissues of R. sylvestris was in the order of soluble fractions>cell wall>protoplast>mitochondria. Cd was mainly extracted by deionized water and 80% ethanol (60.91–69.76%), followed by sodium chloride (16.14–25.12%), which indicated that R. sylvestris achieved to enhance Cd tolerance capacity and detoxification mechanism through root retention and vacuolar compartmentalization.