Wenjuan Tan

Interaction of metal oxide nanoparticles with higher terrestrial plants: Physiological and biochemical aspects.

Multiple applications of metal oxide nanoparticles (MONPs) could result in their accumulation in soil, threatening higher terrestrial plants. Several reports have shown the effects of MONPs on plants. In this review, we analyze the most recent reports about the physiological and biochemical responses of plants to stress imposed by MONPs. Findings demonstrate that MONPs may be taken up and accumulated in plant tissues causing adverse or beneficial effects on seed germination, seedling elongation, photosynthesis, antioxidative stress response, agronomic, and yield characteristics. Given the importance of determining the potential risks of MONPs on crops and other terrestrial higher plants, research questions about field long-term conditions, transgenernational phytotoxicity, genotype specific sensitivity, and combined pollution problems should be considered.

Copper nanoparticles/compounds impact agronomic and physiological parameters in cilantro (Coriandrum sativum)

The environmental impacts of Cu-based nanoparticles (NPs) are not well understood. In this study, cilantro (Coriandrum sativum) was germinated and grown in commercial potting mix soil amended with Cu(OH)2 (Kocide and CuPRO), nano-copper (nCu), micro-copper (μCu), nano-copper oxide (nCuO), micro-copper oxide (μCuO) and ionic Cu (CuCl2) at either 20 or 80 mg Cu per kg. In addition to seed germination and plant elongation, relative chlorophyll content and micro and macroelement concentrations were determined. At both concentrations, only nCuO, μCuO, and ionic Cu, showed statistically significant reductions in germination. Although compared with control, the relative germination was reduced by ∼50% with nCuO at both concentrations, and by ∼40% with μCuO, also at both concentrations, the difference among compounds was not statistically significant. Exposure to μCuO at both concentrations and nCu at 80 mg kg(-1) significantly reduced (p≤ 0.05) shoot elongation by 11% and 12.4%, respectively, compared with control. Only μCuO at 20 mg kg(-1) significantly reduced (26%) the relative chlorophyll content, compared with control. None of the treatments increased root Cu, but all of them, except μCuO at 20 mg kg(-1), significantly increased shoot Cu (p≤ 0.05). Micro and macro elements B, Zn, Mn, Ca, Mg, P, and S were significantly reduced in shoots (p≤ 0.05). Similar results were observed in roots. These results showed that Cu-based NPs/compounds depress nutrient element accumulation in cilantro, which could impact human nutrition.

Interaction of titanium dioxide nanoparticles with soil components and plants: current knowledge and future research needs – a critical review

Titanium dioxide nanoparticles (nano-TiO2), one of the most produced engineered nanoparticles (ENPs), are used in pigments, photocatalysis, food additives, and personal care products. This broad variety of applications has led to the unusual and widespread distribution of nano-TiO2 in several environmental sectors, with different effects on living organisms. In the last decade, several publications have shown fragments of information about the interaction, detection, uptake, and translocation of nano-TiO2 in plants. This review includes a discussion of the current knowledge about factors affecting the interaction of nano-TiO2 with soil and plants. We also discuss the role of particle size, crystal phase, surface coating, and techniques employed to study the interaction of these nanoparticles with plants. Concluding results from synchrotron based, microscopic, physiological, and biochemical analyses of plants exposed to nano-TiO2 are presented. However, the current information leaves no doubt that there are still many aspects in need of additional investigations to fully understand the effects of nano-TiO2 in plants. For instance, little is known about the transgenerational effects of nano-TiO2 exposure and the changes at agronomical and physiological levels. The effects of such ENPs in proteins and other metabolites are also not well understood. In addition, more information is needed about the interaction of nano-TiO2 with other ENPs-and-organic co-contaminates and the effects of plants. Since nano-TiO2 have been found in edible tissues, it is expected that they will be in the food chain; thus, studies on their trophic transfer are required. The authors hope that, besides contributing to a better understanding of current data about the effects of nano-TiO2 in soil and plants, this review will help to drive future investigations and will contribute to the general knowledge on the environmental interactions of engineered nanomaterials.

Physiological and biochemical effects of nanoparticulate copper, bulk copper, copper chloride, and kinetin in kidney bean (Phaseolus vulgaris) plants

It is essential to understand the interactions of engineered nanoparticles (ENPs) with additives used in agriculture and their impacts on crop plants. In this study, kidney bean (Phaseolus vulgaris) plants were grown in potting soil amended with either nano copper (nCu), bulk copper (bCu), or copper chloride (CuCl2) at 0, 50, and 100mg/kg, combined with 0, 10, or 100μM of kinetin (KN). Plant growth, Cu, micro and macroelement concentrations, chlorophyll content, and enzymatic activity were examined in 55-day old plants. Results showed that root Cu content was at least 10-fold higher, compared to other tissues. Accumulation of Cu in roots was decreased by 100μM KN up to 25%. A concentration-dependent increase of Cu content in leaves by Cu×KN was observed. Chlorophyll production was diminished by CuCl2+KN between 22 and 30%, showing a hormetic response. Catalase activity was repressed by 65% to 82% in bCu and CuCl2 treatments. From all essential elements, Ca, Mn, and P were reduced by 33% to 97% in bCu, CuCl2, and CuCl2+KN treatments. However, this did not impact stem elongation and tissue biomass that increased up to 55% under exposure to bCu and CuCl2. Our results demonstrate that KN combined with ionic Cu could have negative implications in kidney bean plants, since this combination impacted chlorophyll production and nutrient element accumulation.

Differential effects of copper nanoparticles/microparticles in agronomic and physiological parameters of oregano (Origanum vulgare)

The effects of metallic copper nanoparticles (nCu) in plants are not well understood. In this study, soil grown oregano (Origanum vulgare) was exposed for 60days to nCu and Cu microparticles (μCu) at 0-200mgCu/kg. At harvest, Cu accumulation, biomass production, nutrient composition, and Cu fractions in soil were measured. Except for μCu at 50mg/kg, both nCu and μCu increased root Cu (28.4-116.0%) and shoot Cu (83.0-163.0% and 225.4-652.5%, respectively), compared with control. Copper accumulation from μCu increased as the external μCu increased. nCu and μCu did not affect shoot length, malondialdehyde, or chlorophyll, but increased water content (6.9-12.5%) and reduced shoot biomass (21.6-58.5%), compared with control. In addition, at 50mg/kg, μCu decreased root biomass and length (48.6% and 20.5%, respectively) and water content (1.8% and 3.9% at 100 and 200mg/kg, respectively). All treatments modified root and shoot Ca, Fe, Mg, and Mn (p≤0.05). Additionally, all Cu treatments decreased starch (33.9-58.5%), total sugar (39.5-55.7%), and reducing sugar (13.6-33.9%) in leaves. Results showed that metallic Cu nanoparticles/microparticles affected agronomical and physiological parameters in oregano, which could impact human nutrition. However, smaller size particles do not necessarily imply greater toxicity.

Foliar Exposure of Cu(OH)2 Nanopesticide to Basil (Ocimum basilicum): Variety-Dependent Copper Translocation and Biochemical Responses

In this study, low and high anthocyanin basil ( Ocimum basilicum) varieties (LAV and HAV) were sprayed with 4.8 mg Cu/per pot from Cu(OH)2 nanowires, Cu(OH)2 bulk (CuPro), or CuSO4 and cultivated for 45 days. In both varieties, significantly higher Cu was determined in leaves of CuSO4 exposed plants (691 and 672.6 mg/kg for LAV and HAV, respectively); however, only in roots of HAV, Cu was higher, compared to control ( p ≤ 0.05). Nanowires increased n-decanoic, dodecanoic, octanoic, and nonanoic acids in LAV, but reduced n-decanoic, dodecanoic, octanoic, and tetradecanoic acids in HAV, compared with control. In HAV, all compounds reduced eugenol (87%), 2-methylundecanal (71%), and anthocyanin (3%) ( p ≤ 0.05). In addition, in all plant tissues, of both varieties, nanowires and CuSO4 reduced Mn, while CuPro increased chlorophyll contents, compared with controls ( p ≤ 0.05). Results suggest that the effects of Cu(OH)2 pesticides are variety- and compound-dependent.

Effects of the exposure of TiO 2 nanoparticles on basil ( Ocimum basilicum ) for two generations

There is a lack of information about the transgenerational effects of titanium dioxide nanoparticles (nano-TiO2) in plants. This study aimed to evaluate the impacts of successive exposure of nano-TiO2 with different surface properties to basil (Ocimum basilicum). Seeds from plants exposed or re-exposed to pristine, hydrophobic, or hydrophilic nano-TiO2 were cultivated for 65 days in soil unamended or amended with 750 mg·kg-1 of the respective particles. Plant growth, concentration of titanium and essential elements, as well as content of carbohydrates and chlorophyll were evaluated. There were no differences on Ti concentration in roots of plants sequentially exposed to pristine or hydrophobic nano-TiO2, or in roots of plants exposed to the corresponding particle, only in the second cycle. However, sequential exposure to hydrophilic particles resulted in 65.2% less Ti in roots, compared to roots of plants exposed the same particles, only in the second cycle. The Ti concentrations in shoots were similar in all treatments. On the other hand, pristine and hydrophilic particles reduced Mg in root by 115% and 81%, respectively, while pristine and hydrophobic particles reduced Ni in shoot by 84% and 75%, respectively, compared to unexposed plants in both cycles. Sequential exposure to pristine nano-TiO2 increased stomatal conductance (214%, p ≤ 0.10), compared to plants that were never exposed. Hydrophobic and hydrophilic nano-TiO2 reduced chlorophyll b (52%) and total chlorophyll (30%) but increased total sugar (186%) and reducing sugar (145%), compared to unexposed plants in both cycles. Sequential exposure to hydrophobic or hydrophilic nano-TiO2 resulted in more adverse effects on photosynthesis but in positive effects on plant growth, compared to pristine nano-TiO2.

Terrestrial Nanotoxicology: Evaluating the Nano-Biointeractions in Vascular Plants

The effects of engineered nanoparticles (ENPs) in living organisms are described in a myriad of articles. Most of the literature on this topic is devoted to plants of different gender and species. Studies from laboratories and greenhouse facilities highlight effects on chlorophyll production, plant growth, stress enzyme activities, phytotoxicity, cytotoxicity, and genotoxicity. With few exceptions, research reports show that toxic effects of ENPs on plants are associated with particle size, phase, surface properties, exposure concentration, and soil chemistry. ENPs have been found to be taken through roots from soilless/soil media and translocated to the aboveground organs. However, the uptake and translocation can occur in reverse if important amounts of ENPs are exposed to the foliage. This chapter includes an analysis of the most recent and relevant information about the interaction of ENPs with vascular plants. Most of the reviewed literature refers to highly produced and used ENPs. Data about exposure to carbon nanotubes (CNTs), cerium dioxide (nano-CeO2), titanium dioxide (nano-TiO2), zinc oxide (nano-ZnO), copper oxide (nano-CuO), gold (nano-Au), iron (nano-Fe3O4), silver (nano-Ag), and others ENPs are discussed.

Biophysical Methods of Detection and Quantification of Uptake, Translocation, and Accumulation of Nanoparticles

Manufactured nanomaterials (MNMs) are more frequently found in consumer products as well as in industrial and agricultural applications. The high volume of production, use, and disposal of MNM-containing wastes increase the probability of release of these products to the environment. An ever-increasing number of articles have shown that MNMs impact plants and other organisms in different ways. In this chapter, we discuss the biophysical methods currently used to measure the uptake, translocation, accumulation, and speciation of MNMs within plants. We included methods used to analyze plants exposed to carbon-based and metal-based MNMs. Advantages and disadvantages of each analytical technique are discussed.