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Silver nanoparticles affect germination and induce oxidative stress in tobacco

Silver nanoparticles (AgNPs) are among the most widely used nanomaterials due to their excellent antimicrobial and antifungal properties. They can be found in various commercial products including textiles, paints and cosmetics. Increase in the production of AgNPs brings out concerns about their impact on the environment. Since plants have an important role in bioaccumulation of many environmentally released substances, they are likely to be influenced by AgNPs. In this study we have investigated the effects of three differently coated AgNPs [citrate, polyvinylpyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB)] and AgNO3 on germination and oxidative stress response of tobacco seedlings (Nicotiana tabacum L.). Five concentrations (25, 50, 75, 100 and 150 μM) of AgNPs and AgNO3, and two concentrations (10 and 25 μM) of surface coatings were tested. To evaluate the degree of oxidative damage, the content of malondialdehyde and protein carbonyls as well as the activity of antioxidant enzymes (pyrogallol peroxidase, ascorbate peroxidase, catalase and superoxide dismutase) was spectrophotometrically measured. Silver uptake in plant tissue was determined with inductively coupled plasma mass spectrometry (ICP-MS). The results showed that positively charged AgNPs- CTAB and CTAB coating have a negative effect on all the parameters of seed germination, while AgNPs-citrate and AgNPs-PVP as well as AgNO3 caused only a slight reduction of fresh weight and root length when applied in higher concentrations. Citrate and PVP surface coatings did not show any significant impact on seed germination. Protein carbonyl content was increased after treatments with AgNPs-PVP, AgNO3 and CTAB surface coating, while AgNPs- CTAB exhibited the opposite effect. Lipid peroxidation was detected after treatments with AgNPs-PVP and AgNPs-CTAB. All of the investigated antioxidant enzymes showed changes in activity implying the existence of oxidative stress. Silver uptake was the highest in AgNPs- CTAB treatment thus demonstrating that phytotoxicity of AgNPs directly correlates with their coating and surface charge.

Silver nanoparticles, germination, Nicotiana tabacum, oxidative stress

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