Silver nanoparticles enter the tree stem faster through leaves than through roots

Abstract

A major environmental pollution problem is the release into the atmosphere of particulate matter, including nanoparticles (NPs), which causes serious hazards to human and ecosystem health, particularly in urban areas. However, knowledge about the uptake, translocation and accumulation of NPs in plant tissues is almost completely lacking. The uptake of silver nanoparticles (Ag-NPs) and their transport and accumulation in the leaves, stems and roots of three different tree species, downy oak (Quercus pubescens Willd.), Scots pine (Pinus sylvestris L.) and black poplar (Populus nigra L.), were assessed. In the experiment, Ag-NPs were supplied separately to the leaves (via spraying, the foliar treatment) and roots (via watering, the root treatment) of the three species. Uptake, transport and accumulation of Ag were investigated through spectroscopy. The concentration of Ag in the stem was higher in the foliar than in the root treatment, and in poplar more than in oak and pine. Foliar treatment with Ag-NPs reduced aboveground biomass and stem length in poplars, but not in oaks or pines. Species-specific signals of oxidative stress were observed; foliar treatment of oak caused the accumulation of H2O2 in leaves, and both foliar and root treatments of poplar led to increased O2− in leaves. Ag-NPs affected leaf and root bacteria and fungi; in the case of leaves, foliar treatment reduced bacterial populations in oak and poplar and fungi populations in pine, and in the case of roots, root treatment reduced bacteria and increased fungi in poplar. Species-specific mechanisms of interaction, transport, allocation and storage of NPs in trees were found. We demonstrated definitively that NPs enter into the tree stem through leaves faster than through roots in all of the investigated tree species.

The two faces of nanomaterials: A quantification of hormesis in algae and plants

“…The median for roots was 127.3% (geometric mean = 140.4%) whereas for foliage was 114.9% (geometric mean = 126.7%), and the two distributions differed significantly (Kruskal-Wallis, H = 11.79, P < 0.001). While nanoparticles may enter the tree stem faster when applied to leaves than when applied to roots (Cocozza et al, 2019), this analysis revealed that applying nanoparticles onto leaves does not necessarily yield higher MAX. Further, the root entries were grouped into two categories: a) those with plants grown in a liquid growing medium (hydroponic system, n = 88) and b) those with plants grown in soil substrate (no hydroponic system, n = 179).…”

To-Do and Not-To-Do in Model Studies of the Uptake, Fate and Metabolism of Metal-Containing Nanoparticles in Plants

“…On the other hand, NPs may undergo different transformations after their accumulation in roots, followed by their translocation to above-ground organs as it has been observed for selenium nanoparticles (Se NPs) and AgNPs in garlic and Arabidopsis plants, respectively [ 13 , 14 ]. Finally, it is worth mentioning the accumulation of AgNPs in stems of three different tree species was faster after foliar treatment compared to roots treatment [ 15 ].…”

Visualization and Localization of Submicron-Sized Ammonium Sulfate Particles on Needles of Japanese Larch (Larix kaempferi) and Japanese Cedar (Cryptomeria japonica) and Leaves of Japanese Beech (Fagus crenata) and Japanese Chinquapin (Castanopsis sieboldii) after Artificial Exposure

“…However, no significant changes in physiological data, such as net the photosynthetic rates, growth, leaf temperature, or plugging of stomata, were observed after the trees had been exposed to BC particles [16]. On the other hand, Cocozza et al [17] indicated that the foliar application of Ag-nanoparticles decreased the growth, aboveground biomass, and stem length in poplar, but not in oak and pine. These differences of results among tree species may be caused by the variation of the surface structures of leaves and needles.…”