Influence of Silver Nano-particles on the Salt Resistance of Tomato

Silver nanoparticles (AgNPs) have been implicated to enhance seed germination and plant growth, improve photosynthetic quantum efficiency and act as antimicrobial agents to manage plant diseases. The role of nanoparticles in the improvement of plant tolerance to environmental stresses such as drought and salinity remains unclear. In this study, we examined the effects of AgNP dose on the salt tolerance of tomato (Solanum lycopersicum L.) plants during germination. Tomato seeds were treated with different AgNP doses and germinated under salinity stress. Five concentrations of AgNPs (0.05, 0.5, 1.5, 2 and 2.5 mg L-1) and two levels of NaCl (150 and 100 mM) were tested. Seed germination and seedling growth of tomato plants were markedly inhibited by salt stress, and this effect was alleviated by exposure to AgNPs. The germination percentage, germination rate, root length and seedling fresh and dry weight of tomato were improved after exposure to AgNPs under NaCl stress. The expression of salt stress genes was investigated by semi-quantitative RT-PCR. Of the examined salt stress genes, four genes, AREB, MAPK2, P5CS and CRK1, were up-regulated by AgNPs under salt stress, and three genes, TAS14, DDF2 and ZFHD1, were down-regulated in response to AgNPs. The gene expression patterns associated with AgNP exposure also suggest the potential involvement of AgNPs in response to stress, indicating that they might be useful for improving plan