In seeds treated with CuO NPs, 30-50% of seeds germinated on the second day of the experiment, while control seeds started germinating only on the third day, a result that was also reflected in the 2.26-fold increase observed in the GSI. In the case of lettuce seeds, the treatment of 25 mg/L presented a significantly higher germination percentage than the control on the first day (p < 0.05). About 80% of seeds treated with 25 mg/L of CuO NPs germinated, while 57% of seeds germinated in the control (Figure ).