Physiology and metabolomics reveal the accumulation patterns and tolerance mechanisms of energy grass Hybrid Pennisetum under elevated Cadmium stress

Energy grass has the characteristics of large biomass and rapid growth. If it also exhibits the ability to accumulate heavy metals, its efficiency in phytoremediation could be significantly enhanced. Previous studies on phytoremediation have predominantly focused on hyperaccumulators, with limited attention to energy grass. In this study, Hybrid Pennisetum, an energy grass plant, was used as a material to determine its accumulation patterns and tolerance mechanisms under a high concentration of cadmium (Cd) stress. The results showed that Hybrid Pennisetum is a Cd-tolerant plant and can survive under 300 mg/kg Cd stress. Under 100 mg/kg Cd stress, the underground biomass increased significantly by 83.66 %, while the aboveground biomass remained 80 % of the control level. In all treatment groups, the total Cd accumulation in the plant reached 300 μg. The enhanced Cd tolerance was attributed to factors including balancing the antioxidant enzyme system, regulating the chlorophyll content and sugar allocation, cell wall fixation, vacuole separation, synergistic interactions with endogenous metabolites, and efficient energy allocation. This study provides physiological and metabolomic insights into the accumulation patterns and tolerance mechanisms of the high-biomass plant Hybrid Pennisetum under elevated Cd stress, while proposing its dual-purpose potential for phytoremediation and bioenergy feedstocks. This integrative approach offers sustainable advantages compared to conventional remediation plants.