Combined Effect of CuO Nanoparticles and Lighting on the Growth and Antioxidant Potential of Lettuce in CEA

Nanoparticles (NPs) are becoming more commonly used in agricultural practices for cultivating plants under Controlled Environment Agriculture (CEA). The foliar application of copper oxide (CuO) NPs can enhance the production of bioactive compounds in lettuce without adversely affecting yield. However, there is a lack of data regarding the effects of NPs on plants under various lighting conditions, which is a crucial aspect of CEA. The study aims to find out how different lighting conditions can lead to Cu accumulation, to determine the effects of CuO NPs on lettuce growth, antioxidant potential and mineral elements, and to investigate the potential risk of these NPs’ uptake to human health. Plants were grown in Ebb-type hydroponic systems with red-blue and white-red-blue LED lighting at daily light integral 8.64 and 14.4, sprayed with aqueous suspensions of CuO NPs (40 nm, 30 ppm). The influence was determined on lettuce growth, the enzymatic (GR, APX, CAT, SOD, MDHAR, DHAR) and non-enzymatic (TPC, DPPH, ABTS, FRAP) antioxidants, mineral elements and hazard quotients. Our study showed the synergistic effect of foliar application of CuO NPs and lighting on lettuce. We found that CuO NPs positively influenced lettuce growth and stimulated the antioxidant system, particularly the non-enzymatic components such as phenols, carotenoids, and total antioxidant capacity. This effect was enhanced under a broader wavelength range of white-red-blue light and with a higher daily light integral value of 14.4. The application of CuO NPs significantly increased the Cu content in lettuce. Importantly, the concentration of the used CuO NPs did not reach the limit of Cu ions dangerous to humans, as the calculated intake level remained below safe limits, but it is not determined how much of them remained in the form of NPs.