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X-ray spectroscopy uncovering the effects of Cu based nanoparticle concentration and structure on Phaseolus vulgaris germination and seedling development Nádia Marion Duran, Susilaine Maira Savassa, Rafael G. Lima, Eduardo de Almeida, Francisco Scaglia Linhares, Cornelis A.M. van Gestel, and Hudson W. Pereira de Carvalho J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.7b03014 • Publication Date (Web): 17 Aug 2017 Downloaded from http://pubs.acs.org on August 17, 2017
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Journal of Agricultural and Food Chemistry
X-ray spectroscopy uncovering the effects of Cu based nanoparticle concentration and structure on Phaseolus vulgaris germination and seedling development Nádia M. Durana, Susilaine M. Savassaa, Rafael Giovanini de Limaa, Eduardo de Almeidaa, Francisco S. Linharesb, Cornelis A. M. van Gestelc, and Hudson W. Pereira de Carvalhoa,*
a
Laboratory of Nuclear Instrumentation (LIN), Center of Nuclear Energy in Agriculture (CENA), University of São Paulo (USP), Piracicaba, SP, 13416000, Brazil.
b
Laboratory of Plant Development and Structure (LaBDEV), Center of Nuclear Energy in Agriculture (CENA), University of São Paulo (USP), Piracicaba, SP, 13416-000, Brazil.
c
Department of Ecological Science, Faculty of Earth and Life Sciences, Vrije Universiteit, De Boelelaan 1085, 1081HV Amsterdam, The Netherlands.
*Corresponding author: Email:
[email protected] Phone: + 55 19 3429 4737
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ABSTRACT
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Nanoparticles properties such as solubility, tunable surface charges and singular reactivity
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might be explored to improve the performance of fertilizers. Nevertheless, these unique
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properties may also bring risks to the environment since the fate of nanoparticles is poorly
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understood. This study investigated the impact of a range of CuO nanoparticles sizes and
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concentrations on the germination and seedling development of Phaseolus vulgaris L.
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Nanoparticles did not affect seed germination, but seedling weight gain was promoted by 100
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mg Cu L-1 and inhibited by 1,000 mg Cu L-1 of 25 nm CuO and CuSO4. Most of the Cu taken
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up remained in the seed coat with Cu hotspots in the hilum. X-ray absorption spectroscopy
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unraveled that most of Cu remained in its pristine form. The higher surface reactivity of the
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25 nm CuO nanoparticles might be responsible for its deleterious effects. The present study
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therefore highlights the importance of the nanoparticle structure for its physiological impacts.
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KEYWORDS:
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spectroscopy
Phaseolus
vulgaris,
CuO
nanoparticle,
germination,
X-ray
based
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INTRODUCTION
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In the past few years, a wide range of engineered nanoparticles, with unique physico-
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chemical properties, has been launched on the market and consequently to the environment.
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Such properties make these materials suitable for applications that substantially differ from
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those of the usual bulk form. The nanoscale particle size of these materials increases the
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surface to volume ratio, thus an important fraction of the atoms lies on the surface. These
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surface atoms have different properties that those in bulk, thus affecting their solubility, light
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scattering and absorbance, conductivity, melting point and catalytic properties1. Being present
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also in many daily life goods, nanoparticles can easily be released into the environment and
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reach the entire food chain. This possibility, which may result in toxicological effects on
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consumers2, remains so far uncertain, and has been a matter of intense debate in recent years.
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The development of nanotechnologies tailored for agricultural purposes can result in a more
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rational of use of pesticides, biocides and fertilizers3, 4 potentially reducing the usage of these
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hazardous products in agricultural practices. Such innovations could lead to cost reduction,
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less nutrient leaching and preservation of the desirable soil microbiota. In this context, we
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highlight the possibility of employing nanotechnology for seed coating5. Seed coating is an
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attractive way for micronutrient delivery. It has the potential to improve seedling growth and
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crop productivity6 while treated seeds generally germinate faster and more synchronized than
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non-treated seeds7. Compared to soil fertilization, seed treatment is an easier and cost-
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effective way requiring a lower quantity of nutrients6. A significant yield increase was
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observed when wheat seeds were treated with a low dose of Cu-EDTA (0.04 kg ha-1)8.
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The uptake of nanoparticles by plants occurs not only through the root system9, but also via
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leaves10 and seeds11. Studies regarding the effects of the interaction between nanoparticles and
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plants are not consensual. While some studies show that nano ZnO promoted root elongation
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in peanut12 and soybean13, and others showed similar results of nano CeO2 treatments on 3 ACS Paragon Plus Environment
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coriander14, corn and cucumber15, while studies on tobacco16 and basil17 showed detrimental
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effects on germination and growth upon exposure to nano TiO2.
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The effects of nanoparticle exposure do not only vary with the plant species, they also
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depend on the chemical composition, reactivity, size and morphology of the particles, as well
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as on aggregation state, applied concentration and experimental conditions. Inside living cells,
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they can interact with crucial processes like oxidative balance, genomic, proteomic and
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metabolomic. The nanoparticles can be internalized by an endocytosis and depending on their
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nature, can be located in different types of organelles. The entrance is controlled by biological
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and physicochemical attributes such as the cell type, surface chemistry and charge, size, shape
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and mechanical properties of the nanoparticles18.
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Specifically regarding the interaction of nanoparticles and seeds, the literature is still scarce.
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Table S119-27 in the electronic supplementary information (ESI) compiles some studies that
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investigated the effects of Ag, ZnO, Fe, and CuO nanoparticles on seeds. Depending on
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nanoparticle size, composition and concentration, germination and root elongation can be
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either favored or reduced. Studies on Cu-based nanoparticles are even scarcer.
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Nanometric copper is broadly used in catalysts, coatings, electronic components, medicines
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and lubricant compounds28. It means that regardless their potential application for seed
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treatment, copper-based nanoparticles will ultimately reach the environment and end up
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interacting with plants. Therefore, we must investigate and understand how these
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nanoparticles affect seed germination and seedling development. Albeit found only as a trace
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element in many plant tissues, copper is considered essential for vegetal life, being a
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transition metal involved in several metabolic processes like photosynthesis, mitochondrial
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respiration, oxidative stress protection, and protein synthesis29. Nonetheless, most reports in
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the literature show an increased toxicity in plants exposed to copper nanoparticles. These
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reports emphasize an inhibitory effect on seedling growth in different species such as black
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mustard30, green peas19, mung beans and wheat11.
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The present study aimed at investigating the effect of commercial Cu-based nanoparticles,
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used for seed priming, on the germination and seedling development of Phaseolus vulgaris,
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also known as common bean or kidney bean. In order to verify their potential use as seed
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fertilizer and the possible high doses impairments, we evaluated the impact of three
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nanoparticle sizes (25, 40 and