Foliar biofortification with copper nanoparticles and its effect on phytochemical quality and enzymatic activity in lettuce

The objective of this study was to evaluate the foliar application of copper oxide nanoparticles (NPs-CuO) on the phytochemical quality, yield, catalase and peroxidase activity of the hydroponic lettuce crop. Five concentrations (5, 10, 15, 20 and 25 mg/L) of NPs-CuO and a control (0 mg/L) were compared. The experiment was established in a completely randomized design with five repetitions. Data were analyzed with analysis of variance and mean comparisons using Tukey's test (0.05). The results indicate that, under the hydroponic conditions, the lettuce plants showed a greater number of leaves, leaf width and the peroxidase enzyme activity was recorded with the concentration of 15 mg/L NPs-CuO. The concentration of 10 mg/L of NPs-CuO yielded higher contents of total phenols, total flavonoids and antioxidant capacity, being 46.63, 34.21 and 28.23% higher compared to the control treatment, respectively. Regarding the concentration of Cu in the lettuce leaf, the 20 mg/L treatment showed the highest concentration with a value of 9.93±2.40 µg/L DW. The use of copper nanoparticles could be an effective alternative to mitigate copper deficiency in the diet of the human population.