Photosynthetic variation and detoxification strategies based on cadmium uptake, non-protein thiols, and secondary metabolites in Miscanthus sacchariflorus under cadmium exposure

Miscanthus sacchariflorus is previously demonstrated to be a potential candidate for remediation of cadmium (Cd) pollution. To explore its resistance strategy to Cd, a hydroponic experiment was conducted to determine the variations of photosynthetic activity in leaves and physiological response in roots of this plant. Results showed that the root of M. sacchariflorus was the primary location for Cd accumulation. The bio-concentration factor in the roots and rhizomes was >1, and the translocation factor from underground to aboveground was <1. Throughout the experimental period, treatment with 0.06 mM Cd2+ did not significantly alter the contents of chlorophyll a, chlorophyll b, or carotenoid. By contrast, treatment with 0.15 and 0.30 mM Cd2+ decreased the contents of chlorophyll a, chlorophyll b, and carotenoid; caused the deformation of the chlorophyll fluorescence transient curve; reduced the photochemical efficiency of photosystem II; and increased the contents of non-protein thiols, total flavone, and total phenol. These results indicate that M. sacchariflorus has good adaptability to 0.06 mM Cd2+. Moreover, the accumulation of the non-protein thiols, total flavone, and total phenol in roots may promote the chelation of Cd2+, thus alleviating Cd toxicity. This study provides theoretical support for using M. sacchariflorus to remediate Cd-polluted wetlands.