Impacts of root pruning intensity and direction on the phytoremediation of moderately Cd-polluted soil by Celosia argentea

Root pruning can impact the nutrient uptake capacity, photosynthetic efficiency, transpiration rate, root pressure, and biomass yield of various plants, which influence phytoremediation. A series of root pruning treatments with different combinations of direction (two-side pruning and four-side pruning) and intensity (10%, 25%, and 33% pruning) were performed on Celosia argentea. All two-side pruning treatments, regardless of intensity, decreased the dry biomass of the C. argentea roots at the end of the experiment relative to that of the control, and the lowest value occurred in the two-side-33% pruning treatment. However, the two-side-10% and two-side-25% pruning treatments stimulated the growth rate of the plant leaves significantly by 58.6% and 41.4%, respectively, relative to that of the control, and even offset the weight loss of the plant roots. Contrastingly, the two-side-33% pruning treatment reduced the biomass yield of leaves by 24.1%. For the four-side pruning treatments, low intensity increased the dry weight of both the plant roots and leaves, while both decreased under high intensity root pruning. The dry weight, Cd content, pigment level, and photosynthetic efficiency in the four-side-10% treatment were higher than those in the other treatments during the experiment, thereby corresponding to the best phytoremediation effect. Except for the two-side-33% pruning treatment, all the treatments increased the phytoremediation efficiency of C. argentea, thereby indicating that root pruning with a suitable combination of direction and intensity can positively influence the Cd removal ability of C. argentea.