Fig. 3

Native PAGE analysis of SOD forms in iceberg lettuce plants treated with different concentrations of putrescine and the chitosan–putrescine nanocomposite: Put 1 mM–1 mM putrescine; Ch–Put 1 mM–1 mM chitosan–putrescine nanocomposite; Put 2.5 mM–2.5 mM putrescine; Ch–Put 2.5 mM–2.5 mM chitosan–putrescine nanocomposite; deionized water served as a control—Control; temperatures 4 °C and 20 °C. Only the upper and lower parts of the gel, which did not show any bands, were cropped. The original gels are shown in the supplementary figure (Figure S1).