Fig. 2. Chlorophyll a fluorescence parameters: (A) ratio of variable (F_v) to maximum (F_m) fluorescence and (B) efficiency of quantum yield of electron flow throughout Photosystem II (PSII) measured on leaves of wooly digitalis cultivated with wastewater (filled circles) and nutrient solution (open circles) and foxglove cultivated with wastewater (filled triangles) and nutrient solution (open triangles). Values are means ± standard deviations; n = 20.