Effects of decapitation and root cutting on phytoremediation efficiency of Celosia argentea

Decapitation and root cutting can influence plant physiological features, such as height, dry weight, and transpiration rate, which partly determine the success of phytoremediation. In this study, the effects of three root cutting intensities (10%, 25%, and 33%), decapitation, and their combination on the phytoremediation efficiency of Celosia argentea were evaluated. Decapitation increased the biomass yield of C. argentea roots and leaves and significantly improved the species' Cd decontamination ability. Root cutting, especially 33% cutting treatment, decreased the root dry weight. The 10% and 25% root cutting treatments increased the leaf biomass yield by 58.6% and 41.4%, respectively, compared with the untreated control, even compensating for the loss of roots, but 33% root cutting decreased the leaf dry weight. Low and moderate root cutting intensity (10% and 25%) increased the leaf Cd content by 33.4% and 24.9%, respectively, and was associated with improved transpiration rate. The highest root and leaf dry weights were observed for the combination of decapitation and 10% root cutting, which increased the biomass yield of underground and aerial parts by 109.9% and 286.2%, respectively. In addition, decapitation offset the negative effects of 33% root cutting on plant growth, indicated by the higher dry weight relative to the control. Decapitated C. argentea accumulated 11.0, 7.5, and 0.7 times more Cd with the 10%, 25%, and 33% root cutting treatments, respectively, compared with the control. The combination of root cutting and decapitation was a practicable and economical method of enhancing the Cd decontamination capacity of C. argentea.