Differential Cadmium Accumulation and Tolerance Among Mirabilis jalapa L. from Diverse Seed Sources

Mirabilis jalapa L., an ornamental plant, exhibits robust adaptability to diverse environmental conditions and is widely distributed across various regions of China. Seeds from different geographical origins may differ in growth and Cd accumulation characteristics. The present study aimed to evaluate differences in cadmium (Cd) accumulation among M. jalapa L. from four seed sources originating from geographically distinct regions with contrasting climatic and edaphic conditions (Heilongjiang, Gansu, Jiangsu, and Inner Mongolia). Pot experiments were conducted using both artificially Cd-spiked soils and field-contaminated soils, along with hydroponic cultures. Cd concentrations in roots, stems, and leaves were measured, and accumulation capacity was assessed using growth parameters, bioconcentration factors (BCF), translocation factors (TF), and tolerance indices. The results revealed that the Jiangsu (JS) seed sources exhibited significantly higher Cd BCF and tolerance indices compared to the other seed sources. In spiked soils with Cd concentrations below 50 mg·kg−1, no significant differences in Cd extraction rates were observed among seed sources; however, the extraction rate declined markedly when soil Cd exceeded this threshold. In field-contaminated soils, no significant variation in Cd extraction rates was detected among seed sources. A significant negative correlation was identified between Cd extraction rate and soil Cd content. Under hydroponic conditions, the Inner Mongolia (NM) seed sources exhibited a higher root tip number and tolerance index than the other seed sources. Integrated across the pot and hydroponic experiments, these results indicate that the Cd accumulation and tolerance strategies of different M. jalapa L. seed sources were different. Further research is needed to verify the internal mechanism. Soil Cd concentration threshold and Cd speciation differences are critical factors determining the phytoremediation efficiency of M. jalapa L., and low-concentration Cd-contaminated soil is more suitable for its phytoremediation application. Therefore, the selection of appropriate seed sources should be matched to soil Cd level and Cd speciation for sustainable phytoremediation. These findings improve our understanding of the variation in Cd accumulation among M. jalapa L. seed sources from different geographical origins and provide new insights into the phytoremediation of Cd-contaminated soils, as well as the selection of suitable seed sources for the sustainable utilization of contaminated agricultural and urban soils.