Metal nanoparticles (NPs) are finding ever-wider applications in plant production (agricultural and forestry-related) as fertilisers, pesticides and growth stimulators. This makes it essential to examine their impact on a variety of plants, including trees. In the study detailed here, we investigated the effects of nanoparticles of silver and copper (i.e., AgNPs and CuNPs) on growth, and chlorophyll fluorescence, in the seedlings of Scots pine and pedunculate oak. We also compared the ultrastructure of needles, leaves, shoots and roots of treated and untreated plants, under transmission electron microscopy. Seedlings were grown in containers in a peat substrate, prior to the foliar application of NPs four times in the course of the growing season, at the four concentrations of 0, 5, 25 and 50 ppm. We were able to detect species-specific activity of the two types of NP. Among seedling pines, the impact of both types of NP at the concentrations supplied limited growth slightly. In contrast, no such effect was observed for the oaks grown in the trial. Equally, it was not possible to find ultrastructural changes in stems and roots associated with the applications of NPs. Cell organelles apparently sensitive to the action of both NPs (albeit only at the highest applied concentration of 50 ppm) were chloroplasts. The CuNP-treated oaks contained large plastoglobules, whereas those dosed with AgNP contained large starch granules. The NP-treated pines likewise exhibited large numbers of plastoglobules, while the chloroplasts of NP-treated plants in general presented shapes that changed from lenticular to round. In addition, large osmophilic globules were present in the cytoplasm. Reference to maximum quantum yields from photosystem II (Fv/Fm)—on the basis of chlorophyll a fluorescence measurements—revealed a slight debilitation of oak seedlings following the application of both kinds of NP at higher concentrations. In contrast, in pines, this variable revealed no influence of AgNPs, as well as a favourable effect due to the CuNPs applied at a concentration of 5 ppm. Our research also showed that any toxic impact on pine or oak seedlings due to the NPs was limited and only present with higher concentrations.

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Recent research points to the possibility of nanoparticles being used as fertilisers, growth stimulators, and promoters of plant resistance or pesticides. In this study, we sought to determine the influence of nanoparticles of silver and copper (AgNPs and CuNPs) on growth parameters and spontaneous mycorrhizal colonisation of roots in 2-year-old container-grown seedlings of Scots pine. Foliar applications of nanoparticles were made through two growing seasons, four times a season, at concentrations of 0, 5, 25 and 50 ppm. Comparisons of the ultrastructures characterising the needles, stems and roots of the treated or untreated pines were conducted with transmission electron microscopy (TEM). The deployed CuNPs stimulated mycorrhizal colonisation at all concentrations, although the growth of seedlings was only promoted at a concentration of 25 ppm. Higher concentrations of AgNPs (25 and 50 ppm) inhibited the formation of mycorrhizae, though the lowest concentration (5 ppm) produced an increase in both mycorrhizal colonisation and the dry mass of roots. The species of ectomycorrhizal fungi found were Thelephora terrestris, Suillus bovinus and Sphaerosporella brunnea. The TEM results comparing treated and control (untreated) needles revealed changes in the chloroplasts from lensshaped to spherical. Furthermore, an increase in the number of plastoglobules and the presence of large osmophilic globules in the cytoplasm associated solely with the needles of pines receiving 50 ppm nanoparticles were observed. In contrast, ultrastructural changes in stems and roots associated with the applications of NPs were not found. Overall, the results indicated that CuNPs and AgNPs could be used as stimulators of growth in general, and mycorrhizal colonisation in particular, among container-grown Scots pines. However, further work is needed to determine their optimal doses and concentrations.Citation: Aleksandrowicz-Trzcinska M, Szaniawski A, Studnicki M, Bederska-Blaszczyk M, Olchowik J, Urban A (2018). The effect of silver and copper nanoparticles on the growth and mycorrhizal colonisation of Scots pine (Pinus sylvestris L.) in a container nursery experiment. iForest

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