Identification of Salvia miltiorrhiza Bunge with high and low cadmium accumulation and insight into the mechanisms of cadmium accumulation

Salvia miltiorrhiza Bunge is used as a Chinese herbal medicine (CHM) particularly its roots. No relevant reports at home and abroad have been made on the mechanism of cadmium (Cd) accumulation in S. miltiorrhiza. The Cd accumulation characteristics of S. miltiorrhiza from main cultivation areas in China were evaluated for the first time to obtain high and low Cd accumulation in S. miltiorrhiza roots. Results showed obvious differences in the Cd enrichment capacity of S. miltiorrhiza from different cultivation areas. We took the lead in identifying the germplasm resources of S. miltiorrhiza with high and low Cd accumulation, that is, S. miltiorrhiza roots from Pingyi Shangdong (SDPY) belongs to the resource with high Cd accumulation (SDPY-H) and that from Zhongjiang Sichuan (SCZJ) is the resources with low Cd accumulation (SCZJ-L) based on relevant physiological and biochemical indexes. Although the Cd content of SDPY-H was apparently higher than that from SCZJ-L, its translocation factor from root to aboveground part is significantly lower than that in SCZJ-L. Therefore, planting SCZJ-L is not only an economic and effective way to use Cd in slightly and moderately polluted soil, but also its aboveground part can be used for phytoremediation. Changes in Cd content before and after the use of transpiration inhibitor indicate that SDPY-H enriched Cd through the symplastic pathway, whereas SCZJ-L mainly enriched Cd through the apoplastic pathways. In addition, the role of the symplastic pathway in SCZJ-L is weaker than that in SDPY-H, which were preliminarily revealed by fluorescent quantitative polymerase chain reaction. The significant reduction of the SmNramps transcription expression amount is one of the reasons for the low Cd accumulation of SCZJ-L.