Chitooligosaccharide application enhanced the growth and phytoremediation efficiency of industrial hemp in Cd-contaminated soils

Hemp has been widely used for cadmium (Cd) remediation. However, its remediation efficiency needs to be improved. Chitooligosaccharides can enhance plant resistance and growth; however, their effects on hemp for Cd-remediation remain unclear. Herein, a greenhouse pot experiment was conducted to investigate the effects of three doses (0, 22.5, and 45 μg m^-2) of chitooligosaccharides (COS), chitin-oligosaccharides (NACOS), and hetero-chitooligosaccharides (HTCOS) on the growth and Cd-remediation efficiency of hemp. Results showed that chitooligosaccharides promoted the antioxidant system and aerial biomass (maximum 84 %) depending on doses and types. COS (22.5 μg m^-2 under 60 mg cadmium kg^-1 soil), NACOS, and HTCOS significantly elevated the Cd concentration in hemp. Consequently, NACOS and HTCOS (45 μg m^-2) significantly increased the average Cd removal up to 61 % and 81 %, respectively, compared with the control. Therefore, spraying chitooligosaccharides can enhance growth and phytoremediation efficiency of hemp by elevating aerial biomass and cadmium concentration of hemp.