Do silver nanoparticles stimulate the formation of ectomycorrhizae in seedlings of pedunculate oak (Quercus robur L.)?

Abstract

Metal nanoparticles are gaining ever-wider application in agriculture and forestry, as alternatives to chemical agents used as fertilisers, growth stimulators and pesticides, establishing a need for eco-toxicological risk assessment of these agents. We tested the effects of foliar-applied silver nanoparticles (AgNPs) on chlorophyll a fluorescence and on abundance and species composition of ectomycorrhizal (ECM) colonisation. The application of AgNPs at concentrations of 5, 25 and 50 ppm was found to stimulate the formation of mycorrhizae in seedlings of pedunculate oak, with the highest effect at intermediate concentrations (25 ppm). There were non-linear effects on the relative abundance of ECM fungal species. The proportion of dominant T. terrestris was highest in the control group, whereas the shares of ECM formed by the two other species, S. brunnea and P. involutus, were higher in the treatments with intermediate and maximal concentrations of AgNPs, respectively. Maximum quantum yield of photosystem II (Fv/fm) assessed by chlorophyll a fluorescence measurements revealed slight debilitation of oak seedlings irrespective of the application of AgNPs and their concentrations. This result offered an indirect indication that photosynthesis capacity had no influence on the level of mycorrhization. We hypothesise that foliar AgNPs treatments at concentrations below thresholds of acute toxicity and in the absence of significant effects on chlorophyll a fluorescence may still exert significant influence on biotic interactions including mycorrhizal symbioses by impacting plant hormonal balance, particularly ethylene, and regulatory pathways involved in host control of ECM colonisation.

Nanotechnology in plants: recent advances and challenges

“…167 Likewise, Ag NPs (20.4 ± 3.2 nm) caused similar effects, generating plant growth inhibition and decreased root mycorrhizal colonization rate. 168 However, recent studies showed beneficial effects: Ag NPs (5 nm mean size) stimulated the formation of mycorrhizae in seedlings of pedunculate oak (Quercus robur L.), 169 and biologically synthesized TiO 2 NPs (68 nm mean size) enhanced root colonization of common bean (Phaseolus vulgaris L.) with the arbuscular mycorrhizal fungi (Funneliformis mosseae) and improved salinity tolerance compared to inoculation with arbuscular mycorrhizal fungi alone. 170 These seemingly contradictory results expose the complexity of the relations involved and highlight the necessity to consider every experimental parameterin particular, precise optimization of doses and modes of application.…”

“…170 These seemingly contradictory results expose the complexity of the relations involved and highlight the necessity to consider every experimental parameterin particular, precise optimization of doses and modes of application. 169,170…”

CuO Nanoparticle-Mediated Seed Priming Improves Physio-Biochemical and Enzymatic Activities of Brassica juncea

“…Research is underway to develop NPs that can improve the nutrient and pesticide delivery to plants [ 4 ]. NPs are used in agriculture as nano-fertilizers to increase plant growth, as pesticides to manage the harmful effects caused by pests on the crop, and sometimes also as sensors to monitor the soil quality and plant health [ 5 ]. The extensive use of NPs in various fields raises the concern that they are released into the environment and interact with the plant through their shoot part or root part positively or negatively [ 6 , 7 ].…”