Cadmium accumulation and main rhizosphere characteristics of seven French marigold (Tagetes patula L.) cultivars.

The study was conducted to determine Cd accumulation and Cd fraction in the rhizosphere soil of seven Tagetes patula cultivars (Little Hero Orange, Durango Yellow, Janie Yellow Bright, Lucifer Yellow, Hero Flame, Hongyun Red, Konghuang Yellow). T. patula cultivars showed strong tolerance and accumulation to Cd. The highest Cd concentration (273.77 mg kg) in shoots was observed in Little Hero Orange when treated with Cd100. For most cultivars, Cd treatments significantly affected rhizosphere pH values, but had a slight effect on dissolved organic carbon (DOC). pH were negatively correlated with Cd accumulation and Cd percentages in the exchangeable fraction in the rhizosphere soil of Little Hero Orange, Durango Yellow, and Konghuang Yellow. No significant correlation was observed between DOC, Cd accumulation and Cd percentage in the exchangeable fraction in the rhizosphere soil, except for Konghuang Yellow. The results suggested that pH might be related to Cd bioavailability and their uptake by T. patula. Among seven cultivars, Little Hero Orange showed the greatest pH decrease, highest shoot Cd accumulation and Cd percentage in the exchangeable fraction, suggesting the difference in pH responses to Cd levels among T. patula might be responsible for their different ability of Cd activation.