Silver nanoparticles (AgNPs) are widely used in the different sections such as medical, agricultural, industrial, and environmental applications; and may be able to influence the toxicity on living organisms. Therefore, the purpose of this study was to evaluate the effects of AgNPs on photosynthetic pigments of an aquatic macrophyte, Brazilian elodea (Egeriadensa) under laboratory condition.Brazilian elodea was exposed to 0 (control), 0.2 and 2 mg/L AgNPs under continuous lighting. After 14 days of exposure, the total numbers of plants shoots were counted and concentrations of chlorophyll A and B as well as carotenoids were determined by spectrophotometry.According to the results, total numbers of plants shoots and concentrations of all measured photosynthetic pigments (chlorophyll A and B, carotenoids) of Brazilian elodea were decreased (p< 0.05) following fourteen days exposure to AgNPs in a concentration – dependent manner. Moreover, the Chlorophyll a/b ratio in Brazilian elodea after exposed to lower concentration (0.2 mg/l) and higher concentration (2 mg/l) were 2.13 ± 0.01 mg/l and 2.07 ± 0.03 mg/l respectively. The Chlorophyll a/b ratio in Brazilian elodea in both concentrations was higher than the control group (1.45 ± 04 mg/l). Carotenoid levels in Brazilian elodea after exposed to lower and higher concentrations of AgNPs (0.91 ± 0.01 and 0.51 ± 0.01) were lower than the control group (1.10 ± 0.13 mg/l). The results of present study revealed the toxic impact of AgNPs on photosynthesis of Brazilian elodea and Chlorophyll a/b ratio is considered a global indicator of photosynthetic activity.
