Impact of Ag Nanoparticle Exposure on <i>p,p′</i>-DDE Bioaccumulation by Cucurbita pepo (Zucchini) and Glycine max (Soybean)

The effect of nanoparticle (NP), bulk, or ionic Ag exposure on dichlorodiphenyldichloroethylene (<i>p,p′</i>-DDE; DDT metabolite) accumulation by Glycine max L. (soybean) and Cucurbita pepo L. (zucchini) was investigated. The plants were grown in 125-mL jars of vermiculite amended with 500 or 2000 mg/L of bulk or NP Ag; ion controls at 5 and 20 mg/L were established. During 19 d of growth, plants were amended with solution containing 100 ng/mL of <i>p,p′</i>-DDE. Total shoot <i>p,p′</i>-DDE levels in non-Ag exposed G. max and C. pepo were 500 and 970 ng, respectively; total root DDE content was 13 700 and 20 300 ng, respectively. Ag decreased the <i>p,p′</i>-DDE content of G. max tissues by up to 40%, with NP exposure resulting in less contaminant uptake than bulk Ag. Total Ag content of exposed G. max ranged from 50.5 to 373 μg; NP-exposed plants had 1.9–2.2 times greater overall Ag than corresponding bulk particle treatments and also significantly greater relative Ag transport to shoot tissues. Bulk and NP Ag at 500 mg/L suppressed DDE uptake by C. pepo by 21–29%, although Ag exposure at 2000 mg/L had no impact on contaminant uptake. Similar to G. max, C. pepo whole plant Ag content ranged from 50.5 to 182 μg, with tissue element content generally being greater for NP exposed plants. These findings show that the Ag may significantly alter the accumulation and translocation of cocontaminants in agricultural systems. Notably, the cocontaminant interactions vary both with Ag particle size (NP vs bulk) and plant species. Future investigations will be needed to clarify the mechanisms responsible for the cocontaminant interactions and assess the impact on overall exposure and risk

Fullerene-Enhanced Accumulation of <i>p</i>,<i>p</i>′‑DDE in Agricultural Crop Species

The effect of C60 fullerene exposure on the accumulation of dichlorodiphenyldichloroethylene (p,p′-DDE; DDT metabolite) by Cucurbita pepo L. (zucchini), Glycine max L. (soybean), and Solanum lycopersicum L. (tomato) was determined. The plants were grown in 125 mL jars of vermiculite amended with 0 or 40 mg of C60 fullerenes. Prior to planting, the jars were amended with 40 mL solution containing 100 ng/mL of p,p′-DDE with 0 or 100 mg/L humic acid. During three weeks of growth, plants were watered with the same p,p′-DDE containing solutions. Total shoot p,p′-DDE levels in nonfullerene exposed tomato, soybean, and zucchini were 26.9, 131, and 675 ng, respectively; total root DDE content for the three plants was 402, 5970, and 5830 ng, respectively. Fullerenes increased the shoot p,p′-DDE content of zucchini by 29%; contaminant levels in soybean shoots were decreased by 48% but tomato shoot content was unaffected. The root and total plant p,p′-DDE content of all three species was significantly increased by fullerene exposure; enhanced contaminant uptake ranged from 30 to 65%. Humic acid, regardless of fullerene presence or plant type, significantly decreased the p,p′-DDE uptake. Fullerenes were detected in the roots of all plants but were not detected in plant shoots in the initial study. In a follow up study with zucchini designed to maximize biomass for extraction, over half the analyzed stems contained fullerenes at 60.5 to 4490 ng/g. These findings show that the carbon-based nanomaterials may significantly alter the accumulation and potentially the toxicity of cocontaminants in agricultural systems

Fullerene-Enhanced Accumulation of <i>p</i>,<i>p</i>′‑DDE in Agricultural Crop Species

The effect of C₆₀ fullerene exposure on the accumulation of dichlorodiphenyldichloroethylene (<i>p</i>,<i>p</i>′-DDE; DDT metabolite) by <i>Cucurbita pepo</i> L. (zucchini), <i>Glycine max</i> L. (soybean), and <i>Solanum lycopersicum</i> L. (tomato) was determined. The plants were grown in 125 mL jars of vermiculite amended with 0 or 40 mg of C₆₀ fullerenes. Prior to planting, the jars were amended with 40 mL solution containing 100 ng/mL of <i>p</i>,<i>p</i>′-DDE with 0 or 100 mg/L humic acid. During three weeks of growth, plants were watered with the same <i>p</i>,<i>p</i>′-DDE containing solutions. Total shoot <i>p</i>,<i>p</i>′-DDE levels in nonfullerene exposed tomato, soybean, and zucchini were 26.9, 131, and 675 ng, respectively; total root DDE content for the three plants was 402, 5970, and 5830 ng, respectively. Fullerenes increased the shoot <i>p</i>,<i>p</i>′-DDE content of zucchini by 29%; contaminant levels in soybean shoots were decreased by 48% but tomato shoot content was unaffected. The root and total plant <i>p</i>,<i>p</i>′-DDE content of all three species was significantly increased by fullerene exposure; enhanced contaminant uptake ranged from 30 to 65%. Humic acid, regardless of fullerene presence or plant type, significantly decreased the <i>p</i>,<i>p</i>′-DDE uptake. Fullerenes were detected in the roots of all plants but were not detected in plant shoots in the initial study. In a follow up study with zucchini designed to maximize biomass for extraction, over half the analyzed stems contained fullerenes at 60.5 to 4490 ng/g. These findings show that the carbon-based nanomaterials may significantly alter the accumulation and potentially the toxicity of cocontaminants in agricultural systems

Molecular Response of Crop Plants to Engineered Nanomaterials

Functional toxicology has enabled the identification of genes involved in conferring tolerance and sensitivity to engineered nanomaterial (ENM) exposure in the model plant Arabidopsis thaliana (L.) Heynh. Several genes were found to be involved in metabolic functions, stress response, transport, protein synthesis, and DNA repair. Consequently, analysis of physiological parameters, metal content (through ICP-MS quantification), and gene expression (by RT-qPCR) of A. thaliana orthologue genes were performed across different plant species of agronomic interest to highlight putative biomarkers of exposure and effect related to ENMs. This approach led to the identification of molecular markers in Solanum lycopersicum L. and Cucurbita pepo L. (tomato and zucchini) that might not only indicate exposure to ENMs (CuO, CeO₂, and La₂O₃) but also provide mechanistic insight into response to these materials. Through Gene Ontology (GO) analysis, the target genes were mapped in complex interatomic networks representing molecular pathways, cellular components, and biological processes involved in ENM response. The transcriptional response of 38 (out of 204) candidate genes studied varied according to particle type, size, and plant species. Importantly, some of the genes studied showed potential as biomarkers of ENM exposure and effect and may be useful for risk assessment in foods and in the environment