Amendments with activators or microorganisms to enhance phytoremediation in toxic-metal-polluted soils have been widely studied. In this research, the production of indoleacetic acid, siderophore, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase by phosphate-solubilizing bacteria was investigated during a pure culture experiment. Pot experiments were performed using Cd-polluted soil with the following treatments: control (CK, only ultrapure water), orange-peel-based activator (OG), and a combination of phosphate-solubilizing bacteria (Acinetobacter pitti) and OG (APOG). Ryegrass plant height and fresh weight, Cd content in ryegrass, total and available Cd soil content, soil enzyme activity, and soil bacterial diversity were determined in this work. The findings showed that the height of ryegrass in OG and APOG increased by 14.78% and 21.23%. In the APOG group, a decreased ratio of Cd was 3.37 times that of CK, and the bioconcentration factor was 1.28 times that of CK. The neutral phosphatase activity of APOG was 1.33 times that of CK and catalase activity was 1.95 times that of CK. The activity of urease was increased by 35.48%. APOG increased the abundance of beneficial bacteria and Proteobacteria was the dominant bacterium, accounting for 57.38% in APOG. Redundancy analysis (RDA) showed that nutrient elements were conducive to the propagation of the dominant bacteria, the secretion of enzymes, and the extraction rate of Cd in the soil. The possible enhancement mechanism of phytoremediation of cadmium by A. pitti combined with OG was that, on the one hand, APOG increased soil nutrient elements and enzyme activities promoted the growth of ryegrass. On the other hand, APOG activated Cd and boosted the movement of Cd from soil to ryegrass. This research offers insight for the combination of phosphate-solubilizing bacteria with an orange-peel-based activator to improve phytoremediation of Cd-contaminated soils and also provides a new way for the resource utilization of fruit residue.

Koelreuteria paniculata demonstrates significant potential for remediating manganese (Mn)-contaminated soils, particularly in mining areas. This study investigated its tolerance and enrichment mechanisms through pot experiments under varying Mn stress (0–15 mmol·L⁻¹). The results revealed a typical “low-promotion and high-suppression” response, with optimal growth observed at 5 mmol·L⁻¹ Mn. The species exhibited a strong capacity for Mn accumulation, primarily in the roots (up to 2910.24 mg·kg⁻¹), though the enrichment factor decreased at higher concentrations. Physiological and subcellular distribution analyses indicated that low Mn levels enhanced chlorophyll content and antioxidant enzyme activities, while excessive stress induced membrane lipid peroxidation. Crucially, tolerance was attributed to effective Mn immobilization in root cell walls (46–76%) and vacuolar compartmentalization in leaves (46–52%), which prevented metal translocation to sensitive organelles. These findings clarify the physiological mechanisms behind Mn tolerance in K. paniculata and support its use in practical Mn phytoremediation.