Use of nanoparticles as nano copper (nCu) may be useful in agriculture. The objective of the present study was to evaluate responses in plant growth and antioxidants in tomato fruits upon application of nCu absorbed on chitosan hydrogels. The study was performed in two stages. The first stage, with tomato seedlings, was done to determine the most appropriate nCu concentration. nCu was absorbed on a chitosan hydrogel at 100 mg nCu kg-1 of hydrogel, and five different treatments of hydrogel were applied to the substrate prior to transplantation: 0.3, 0.15, 0.06, 0.03 and 0.015 g L-1, plus a control. The second stage evaluated the best treatment results from the previous stage, a chitosan treatment without nCu and a control. Effects of the treatments on antioxidants in the leaves and fruit were evaluated, along with fruit quality. The results from the first stage demonstrated that 0.06 g L-1 nCu-chitosan hydrogel treatments had better results. Outcomes from the second stage demonstrated that treatment with nCu had the best results for most of the plant growth variables, with differences in catalase activity in the leaves and lycopene concentration in the fruit. Application of chitosan hydrogels with nCu was favorable to tomato growth and quality
