Figure 6.

Changes in the photochemical fluorescence quenching, which is the relative reduction state of the plastoquinone (PQ) pool, reflecting the fraction of open PSII reaction centers (q_p) of young and mature Arabidopsis thaliana leaves measured (at 140 μmol photons m⁻² s^–1) 30 min, 90 min, 180 min, and 240 min after the foliar spay with 30 mg L⁻¹ of CuZn NPs or distilled water (control). Error bars on columns are standard deviations based on four to five leaves from different plants. Columns with different letter (lower case for young leaves and capitals for mature) are statistically different (p < 0.05). An asterisk (*) represents a significantly different mean of the same time treatment between young and mature leaves (p < 0.05).