Multi-omics technologies reveal the Cd toxicity alleviating effect of zinc oxide nanoparticles on Cannabis sativa L. by improving plant growth and antioxidant activity

Cadmium (Cd) toxicity inhibits plant growth and threatens agricultural sustainability and human health. Although zinc oxide nanoparticles (nZnO) have shown potential in mitigating heavy metal stress, their effectiveness in reducing Cd toxicity in hemp ( Cannabis sativa L.) has yet to be explored. Here, we evaluated the response of foliar-applied nZnO at different concentrations (0, 50, 100, and 200 mg L –1 ) on the growth of hydroponic hemp cuttings exposed to Cd stress (200 μM CdCl 2 ). Results demonstrated a clear dose-dependent response; nZnO (50 mg L –1 ) significantly enhanced growth or recovery under Cd stress, increasing plant height by 26.1 %, leaf dry weight by 62.4 %, Fv/Fm by 14.1 % and reducing the DAB-stained area by 55.1 % and Cd content by 21.8 %. By contrast, a high concentration (200 mg L –1 ) induced phytotoxic effects, as evidenced by decreased biomass and chlorophyll content. Moreover, 50 mg L –1 nZnO enhanced the accumulation of key antioxidant metabolites, including terpenoids (e.g., cannabigerolate and dihydroartemisinic acid), amino acids (e.g., L -leucine, tryptophan, and glutathione), and phenolic acids (e.g., caffeate) in response to Cd stress. Integrated transcriptomic and metabolomic analyses further revealed that genes such as CsPER57 , CsNRAMP5 , CsHIPP39 , CsIAA14 , and CsABCC1 may be upregulated by bHLH62, bZIP34, and MYB77, enhancing the antioxidant system. This study demonstrated a dose-dependent protective role of nZnO in alleviating Cd toxicity, highlighting its beneficial and regulatory effects on growth and antioxidant metabolism and providing a theoretical foundation for its application in sustainable hemp cultivation and heavy metal stress management. • Cd stress reduced hemp seedling height, leaf area, biomass, pigment, and induced ROS accumulation. • 50–100 mg L −1 nZnO enhanced growth performance and biomass; 200 mg L −1 showed phytotoxicity. • Genes CsPER57, CsHIPP39 , CsNRAMP5 , CsABCC1 are implicated in nZnO-mediated Cd detoxification and antioxidant defense. • nZnO alleviated Cd toxicity via increased alkaloids, phenolic acids, terpenoids and amino acids.