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Silver nanoparticles affect germination and photosynthesis in tobacco

Nanotechnology has an impact on the food industry in all stages of production, from farming to processing. Silver nanoparticles (AgNPs) are the most common nanomaterial on the market due to their unique antibacterial and antifungal properties, often used in agriculture as vehicles for the delivery of fertilizers and pesticides. Since plants are involved in accumulation and biodistribution of many environmentally released substances, this can lead to an increased risk of human exposure to AgNPs through the food chain. 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 photosynthesis of tobacco seedlings (Nicotiana tabacum L.). The silver content in plant tissue was also determined. Five concentrations (25, 50, 75, 100 and 150 M) of AgNPs and AgNO3, and two concentrations (10 and 25 M) of surface coatings were applied. Chlorophyll fluorescence parameters were measured with fluorimeter using saturation pulse method, while photosynthetic pigments content was analysed by high-performance liquid chromatography (HPLC). 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. Photosynthesis efficiency was decreased in all the AgNPs and AgNO3 treatments, indicating a negative impact on photosynthetic apparatus. Surface coating treatments had no effect on photosynthesis efficiency parameters. Silver uptake was the highest in AgNPs-CTAB treatment thus demonstrating that phytotoxicity of silver nanoparticles directly correlates with their coating and surface charge.

silver nanoparticles, Nicotiana tabacum, germination percentage, chlorophyll fluorescence, photosynthetic pigments

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