Copper Oxide Nanoparticle Foliar Uptake, Phytotoxicity, and Consequences for Sustainable Urban Agriculture

Abstract

Throughout the world, urban agriculture supplies fresh local vegetables to city populations. However, the increasing anthropogenic uses of metal-containing nanoparticles (NPs) such as CuO-NPs in urban areas may contaminate vegetables through foliar uptake. This study focused on the CuO-NP transfer processes in leafy edible vegetables (i.e., lettuce and cabbage) to assess their potential phytotoxicity. Vegetables were exposed via leaves for 5, 10, or 15 days to various concentrations of CuO-NPs (0, 10, or 250 mg per plant). Biomass and gas exchange values were determined in relation to the Cu uptake rate, localization, and Cu speciation within the plant tissues. High foliar Cu uptake occurred after exposure for 15 days for lettuce [3773 mg (kg of dry weight)] and cabbage [4448 mg (kg of dry weight)], along with (i) decreased plant weight, net photosynthesis level, and water content and (ii) necrotic Cu-rich areas near deformed stomata containing CuO-NPs observed by scanning electron microscopy and energy dispersive X-ray microanalysis. Analysis of the CuO-NP transfer rate (7.8-242 μg day), translocation of Cu from leaves to roots and Cu speciation biotransformation in leaf tissues using electron paramagnetic resonance, suggests the involvement of plant Cu regulation processes. Finally, a potential health risk associated with consumption of vegetables contaminated with CuO-NPs was highlighted.

Are Cerium Oxide Nanoparticles Transferred from Plants to the Aphid Myzus persicae (Hemiptera: Aphididae)?

“…Even though chemical images show the presence of Ce on the leaves, we cannot state whether the nano-CeO 2 was present on the surface or within the leaves. Several studies investigated the foliar uptake of nanoparticles, and neither the mechanisms behind the phenomenon nor size exclusion limits are clear yet (Larue et al 2012;Raliya et al 2016;Xiong et al 2017).…”

The Role of Nanotechnology in the Fortification of Plant Nutrients and Improvement of Crop Production

“…However, some reactions may lead to release of copper ions inside the plant cells that could be toxic. Toxicity of copper nanomaterials results from their solubility in the medium of application and redox processes arising from their interactions with other substances [3].…”

“…CuO NPs tend to be more toxic than copper nanoparticles due to their oxidative nature, even at low concentrations, but positively impact on the photosynthetic process of the plant. CuO NPs have also been reported to exhibit antimicrobial activities, which affect the microbial reactions in the soil as some are resistant while others are not [3]. The resistance could be a result of release of Cu 2+ ions, which bind with the cellular membrane of microorganisms thereby causing damage.…”

“…Urban agriculture that makes use of recent nanotechnologies has the potential to contribute immensely to food security and healthy nutrition. Although there are associated risks from chemicals which may have emanated from soils, water or air [3], the ultimate goals for application of nanomaterials in agriculture spans reducing hazard chemicals, nutrient losses, pest control and crop yield improvement [4].…”

Structural and Microstructural Analysis for CuO Nanoparticles Prepared by Precipitation Method.

“…Copper oxide nanoparticles (CuO-NPs) are being increasingly used in many agrochemicals such as pesticides, herbicide, fertilizers, antimicrobial, additives and growth regulators [1]. The wide use of CuO-NPs leads to their release into the environment, which is of concern due to their potential risk to biological processes [2]. Previous studies have assessed the impact of various NPs including CuO on soil microbial communities, finding that the effects strongly depend on the characteristics of the NPs, such as size, shape, composition, and morphology [3].…”