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Given the existing and potential impact of NP-formulations on agricultural production, safety, and consumer perception, the primary objectives for this work are to: <OL> <LI> Develop a baseline assessment of response of plants and associated microbial flora to a range of metal oxide NP, and in parallel<LI> Develop analytical and bio-reporter methods for detecting and tracking nano-materials in agriculturally relevant settings. </OL> These two primary objectives support our long-term goal of understanding and advancing nano-technology applications in agriculture through knowledge of basic biological activity coupled with development of sensitive reporting and tracking methods.<P>
The following outputs are anticipated from this research: <OL> <LI> Characterize the impact of as-manufactured and modified NP on two rhizosphere pseudomonads, one of which is modified to act as a sentinel for NP. <LI> Characterize the impact of as-manufactured and modified NP plant-rhizosphere microbe interactions that induce improved growth and stress tolerance. <LI> Characterize NP evolution and biological activity following exposure to humic acid and surfactants using Field Flow Fractionation (FFF) coupled with ICP-MS and supporting techniques. <LI> Determine the optimum combination of field flow fractionation techniques coupled with ICP-MS and other detectors to characterize the as-made NP and their modification after exposure to the rhizosphere microbes and plants (biotic modification) and abiotic modification with humic acids and surfactants.
NON-TECHNICAL SUMMARY: Nano-scale materials and devices are found in a growing number of applications, offering numerous opportunities as well as challenges. The allure of materials and particles having dimensions below 100 nm is their unique properties that arise from high surface area to volume ratio and/or quantum mechanical effects. The potential benefits of nano-technology will continue to drive this growing market into all realms of society including agriculture and food science. This work focuses on detecting and monitoring effects of metal and metal-oxide nanoparticle (NP) interactions on plants, their native rhizosphere microbes, and plants amended with microbes that impart drought, stress, and disease resistance properties on the plant. The consequences of abiotic and biotic modifications of NP will be investigated. We will focus on NP of CuO, ZnO, and Ag as a relevant subset of the metal and metal oxide class of NP.
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APPROACH: We will initially investigate as-made "pristine" NP from the manufacturers. Nanopowders of CuO (nominal size of 30 nm) and ZnO (nominal size 50-70 nm) are available from Sigma-Aldrich, and Attostat Ag (10 nm) from NCL Laboratories (Salt Lake City), prepared using a laser ablation method ensuring an absence of contaminating organic molecules. The as-manufactured NP will be applied to (a) bacteria (KT2240 / PcO6), (b) plants (barley, cucumber, tobacco), (c) plants with roots colonized with PcO6. Bacteria and plant morphological studies (root / shoot length) will be conducted followed by bacteria and plant fractionation to determine the location of the NP and provide materials for chemical analysis. FFF-ICP-MS analysis of the fractions will reveal NP uptake, distribution, and aggregation state. Biotic modification of NP will be revealed by comparing with FFF-ICP-MS fractograms of as-manufactured NP. Abiotic NP modifications will be carried out by coating NP with humic acids and resulting NP activity analyzed. For all experimental procedures at least three independent studies will be performed with three replicates of each treatment.