The Effects Of Silver Nanoparticles On The Vegetative Growth And Flowing Of Arabidopsis Thaliana

The small size, structure and surface characteristics of nanoparticles confer novel physical and chemical properties that are not shared by bulk particles of the same material. Because of their particular properties, NPs are used in a variety of applications, from cosmetics to medicine. Silver nanoparticles (AgNPs) are one of the most important nanomaterials in consumer product inventories due to their known antimicrobial properties and usefulness in personal care products, food service, building materials, medical instruments, and textiles. Given that the increase in production of commercial AgNPs may have potential negative impacts on ecosystems, our knowledge regarding the toxicity of AgNPs must be broadened to predict the environmental and human health risks associated with these materials.The aim of the present study was to elucidate the toxic effects of AgNPs on the level of morphology, physiology, cell ultrastructure and gene transcription in Arabidopsis thaliana, by comparing with the toxicity of Ag+.The results showed that the fresh weight and root length decreased 53.9% and 41.4% respectively after treated with 3.0mg/L AgNPs for 2 weeks, while they were not change by the treatment of Ag+. Meanwhile, the anthocyanine content was increased to 5.99- and 3.8-fold of the control, and the total chlorophyll content decreased to 36.5% and 18.8% of the control after AgNPs and Ag+ treatment, respectively. We also measured the absorption of metal ion in the leaves, and the results showed that the Ag content reached 3137μg/g and 804.7μg/g after treated with 2.5mg/L AgNPs and Ag+ for 2 weeks. Furthermore, the K, Fe, Zn content were reduced to 71.4%,50.3% and 49% in the AgNPs treatment group, while did not change significantly in the Ag+ treatment group. The results of transmission electron microscopy (TEM) and metal content analysis showed that 3.0mg/L AgNPs could be accumulated in leaves. These absorbed AgNPs disrupted the thylakoid membrane structure and decreased chlorophyll content, which can inhibit plant growth. The gene expression results showed that the antioxidant enzyme genes (SOD, APX, etc.) and aquaporins genes (PIP2, SIPl,etc.) had changed; and the inhibition of flowering pathway genes (AP1,FT, FLC) due to the changing expression of vernalization pathway genes (VIN3, VRN2, FRI) by AgNPs was the main reason to the delaying of flowering. Compared with the toxicity of Ag+from physiological, ultrastructural and molecular levels, this study suggests that AgNPs was more toxicity than Ag+, and it inhibits plant growth, damages cell structure and changes gene transcript via nanoparticles themselves, not the dissolved silver released from AgNPs.