Improvement of nutrient elements and allicin content in green onion (Allium fistulosum) plants exposed to CuO nanoparticles

With the exponential growth of nanomaterial production in the last years, nano copper (Cu)-based compounds are gaining more consideration in agriculture since they can work as pesticides or fertilizers. Chinese scallions (Allium fistulosum), which are characterized by their high content of the antioxidant allicin, were the chosen plants for this study. Spectroscopic and microscopic techniques were used to evaluate the nutrient element, allicin content, and enzyme antioxidant properties of scallion plants. Plants were harvested after growing for 80 days at greenhouse conditions in soil amended with CuO particles [nano (nCuO) and bulk (bCuO)] and CuSO4 at 75–600 mg/kg]. Two-photon microscopy images demonstrated the particulate Cu uptake in nCuO and bCuO treated roots. In plants exposed to 150 mg/kg of the Cu-based compounds, root Cu content was higher in plants treated with nCuO compared with bCuO, CuSO4, and control (p ≤ 0.05). At 150 mg/kg, nCuO increased root Ca (86%), root Fe (71%), bulb Ca (74%), and bulb Mg (108%) content, compared with control (p ≤ 0.05). At the same concentration, bCuO reduced root Ca (67%) and root Mg (33%), compared with control (p ≤ 0.05). At all concentrations, nCuO and CuSO4 increased leaf allicin (56–187% and 42–90%, respectively), compared with control (p ≤ 0.05). The antioxidant enzymes were differentially affected by the Cu-based treatments. Overall, the data showed that nCuO enhances nutrient and allicin contents in scallion, which suggests they might be used as a nanofertilizer for onion production. [Display omitted] •None of the Cu-based compounds produced visible signs of toxicity.•Allicin, Ca, Fe, Mg, and Mn contents were improved by nCuO, but not by bCuO.•Nano CuO increased root GPOX and leaf APOX, but reduced CAT in roots and leaves.•Cu was translocated to leaves dependent on the Cu compound exposure manner.•Cu uptake distribution from bCuO and nCuO treatments indicated an apoplastic pathway.