Effect of synthetic and biosynthesized silver nanoparticles on growth, physiology and oxidative stress of water hyacinth: Eichhornia crassipes (Mart) Solms

Silver (Ag) nanoparticles (NPs) are synthesized by several methods and are being widely used in various fields of science. In recent times, evaluation of their toxicological effects on environment, especially to the plant ecosystems has attained special attention. In this study, effect of synthesized AgNPs [chemically (S-AgNPs) and/or biologically (B-AgNPs)] on the growth and physiology of an aquatic plant water hyacinth-Eichhornia crassipes (Mart) Solms was evaluated. Water hyacinth plants were treated with S-AgNPs and B-AgNPs at different concentrations of 1, 10 and 100 mg L-1 and growth was monitored for 5 days. Decreased growth of hyacinth was observed only on fifth day in treatments with S-AgNPs treatment alone but not for B-AgNPs. Further, the atomic absorption spectroscopy results (at 100 mg L-1 concentration) showed a higher accumulation of S-AgNPs over the B-AgNPs in various parts of the treated plants. Biochemical analysis on day five in B-AgNPs treated leaf extracts revealed an increase in carbohydrate and protein levels, and a decrease in phenol and chlorophyll content. In contrary, S-AgNPs treated leaf extracts did not show any significant changes in carbohydrate and protein levels, however, observed a significant increase in phenol and chlorophyll content. Interestingly, S-AgNP treatment increased the activities of antioxidative enzymes, such as catalase, peroxidase and superoxide dismutase. No significant differences were measured in plants treated with B-AgNPs when compared to normal plants which may reveal that these B-AgNPs instead enhanced the plant growth with a fewer minor effects on water hyacinth plants over S-AgNPs.