Figure 5.

Chlorophyll fluorescence kinetics in H. sativum leaves from plants germinated in the presence of different ZnO NP concentrations. Photoinduction curves averaged over 8 repetitions are shown. (a) 0 mg/L ZnO NPs (control); (b) 300 mg/L ZnO NPs; (c) 2000 mg/L ZnO NPs. F_p—peak (maximal) fluorescence level; F_s—steady-state fluorescence level. Curves were normalized by F_p. Fluorescence decrease ratios, R_fd = (F_p − F_s)/F_s, mean ± SD, were R_{fd 0} = 0.87 ± 0.05, R_{fd 300} = 0.45 ± 0.03, and R_{fd 2000} = 0.16 ± 0.02 at p = 0.05, n = 8.