Glucose and Fulvic Acid Enhance Growth, Cadmium Tolerance, and Phytoremediation Potential in Mirabilis jalapa L.

Using ornamental plants for phytoremediation can not only remove pollutants from the environment but also beautify and purify it. The purpose of this study was to investigate the effects of exogenous spraying of transpiration regulators glucose (Glc) and fulvic acid (FA) on the growth, biomass, and cadmium (Cd) enrichment of Mirabilis jalapa L. It was found that Glc could promote the growth and biomass accumulation of M. jalapa L., whereas FA had no significant effect, with a particularly notable 77.3% increase in leaf biomass observed in the exogenous spraying of 4% Glc treatment compared with control. Glc promoted the translocation of Cd from roots to shoots by enhancing transpiration, whereas FA led to more Cd accumulation in roots. In the exogenous spraying of 4% Glc treatment, Cd enrichment in leaves increased by 138.6% compared with the control group. The bioconcentration factor and translocation factor of 4% Glc treatment were 2.4 and 2.2 times that of the control treatment, respectively. The removal rate was 2.35 times that of the control treatment. Further, both Glc and FA enhanced the antioxidant enzyme system of M. jalapa L. Exogenous spraying of Glc significantly increased the superoxide dismutase activity. Peroxidase activity increased by 58% of 4% Glc treatment compared with the control. In addition, exogenous spraying of Glc increased the net photosynthetic rate, 4% Glc treatment was 3.1 times higher than the control treatment, and the yield was 1.1 times greater in T1 treatment compared with control treatment. There was no significant effect on Pn at low concentration FA but a significant increase at high concentrations. In summary, exogenous spraying of 4% Glc can be used as an effective strategy to promote enrichment of Cd by M. jalapa L. and alleviate the oxidative stress caused by Cd, which provides a new method for phytoremediation of Cd-contaminated soil.