Dopamine and GR24 Alleviate Cadmium Stress and Reduce Cadmium Uptake in Grapevines

To alleviate cadmium (Cd) stress and reduce Cd uptake in fruit trees, the effects of dopamine (100 μmol/L, based on previous studies) and strigolactone analog GR24 (1 μmol/L, based on previous studies) on the growth and Cd accumulation of grapevines under Cd stress (5 mg/L, based on preliminary study) were investigated. Compared with control, Cd treatment inhibited grapevine growth by decreasing the plant height, root length, biomass, and photosynthetic capacity. In contrast, under Cd stress, treatments with dopamine or GR24 increased the plant height, root length, biomass, and photosynthetic capacity compared with Cd treatment. Dopamine and GR24 treatments also affected the activities of antioxidant enzymes (peroxidase, superoxide dismutase, and catalase) and the levels of osmotic regulatory substances (soluble protein, proline, and soluble sugar) in different ways. Moreover, dopamine and GR24 treatments reduced the Cd content and translocation factor in grapevines under Cd stress. Specifically, compared with Cd treatment, dopamine treatment reduced root Cd content by 18.92% and shoot Cd content by 35.18%, whereas GR24 treatment reduced root Cd content by 10.93% and shoot Cd content by 22.61%. In conclusion, both dopamine and GR24 treatments can mitigate Cd stress, promote growth, and reduce Cd uptake in grapevines.