Figure 2.

Differences in activites of (A) superoxide dismutase (SOD), (B) pyrogallol peroxidase (PPX), (C) ascorbate peroxidase (APX), and (D) catalase (CAT) in leaves of tobacco plants 7 days after exposure to 25, 50, and 100 μM AgNP–PVP, AgNP–CTAB, and AgNO₃, applied either alone or in combination with 125, 250, and 500 μM cysteine (cys). Values are the means ± SE of three biological replicates, each with six technical replicas. If columns are marked with different letters, the treatments are significantly different at p ≤ 0.05 (a two-way ANOVA followed by Duncan’s post hoc test); small letters mark the differences among different concentrations of the same treatment type as well as control; capital letters mark the differences among different treatment types of the same concentration; asterisk (*) denotes significant differences among treatments with and without cysteine of the corresponding concentration, while hash sign (#) denotes significant difference between each treatment with cysteine and control.