Evaluation of parameters influencing plant response to carbon nanotube contamination

Carbon nanotubes (CNTs) are among the most used nanomaterials (NMs) thanks to their excellent physicochemical properties. All along their lifecycle, they may be spread unintentionallyor intentionally in the environment. It is thus essential to assess their behavior and potential impacts on ecosystems and particularly on crop plants. Overall, behaviour and effects of CNTs in plants are not well understood and still very controversial. In this work, we aimed to assess the influence of several parameters on plant response after exposure in a CNT-contaminated soil. We first focused on the analytical challenge of detecting CNT in biological matrices and tested several spectroscopic techniques. Then, we evaluated the response of tomato plants to two different NMs (CNTs and TiO2-NPs). Our results highlight that despite being different for several parameters (i.e. shape, size, surface chemistry), CNT exposure led to a similar response in tomato plants, in particular on the alteration of plant cell wall components. The study of different plant species (tomato, canola, maize and cucumber) exposed to DWCNT contamination highlighted different responses according to plant species, maize (monocot) being the most sensitive. Different types of CNTs are currently available. Five types of CNTs varying in diameter, functionalization and length were used to investigate their impact on canola. Canola was more sensitive to CNTs with the smallest diameters, but it was also observed that the functionalization greatly modulated the plant response. Finally, we tested the impact of a combined stress: canola plants grown in optimal growth conditions were not impacted by CNT exposure at the tested dose, while we observed that plants were more sensitive to CNTs when submitted to a concomitant heat stress

Carbon nanotubes: Impacts and behaviour in the terrestrial ecosystem - A review

For more than twenty years, nanotechnologies have arisen a huge interest and are used in numerous fields. Carbon nanotubes (CNTs) are one of the most used nanomaterials thanks to their excellent optical, mechanical, electrical and thermal properties. All along their lifecycle, CNTs may be spread in the environment during production, use, destruction, reuse or potential accidents in production units or during transportation. For this reason, it is essential to evaluate their behaviour and potential impacts on ecosystems and particularly on the terrestrial ecosystem. After a brief summary of CNT properties, synthesis methods, and applications as well as detection and characterisation techniques, this review will focus on impacts of CNTs on the terrestrial ecosystem, discussing their behaviour in soil, plants and interactions with other pollutants as well as their impacts on soil microbiota, macrobiota and plants

Toxicité des nanotubes de carbone envers l'homme et l'environnement

Du fait d'un nombre grandissant d'applications commerciales des nanotubes de carbone, les questions relatives à leur impact potentiel sur la santé humaine et sur l'environnement sont toujours d'actualité et font encore l'objet de recherches très actives. Cet article fait le point sur les connaissances actuelles en prenant en compte la diversité des nanoparticules qui se cachent sous la dénomination générale de "nanotubes de carbone". Il ambitionne de traiter la question de manière générale, de l’échelle cellulaire, sur cultures in vitro, à l’échelle complexe de l’écosystème par des approches simplifiées en micro et mésocosmes, notamment

Assessing the impacts of sewage sludge amendment containing nano-TiO2 on tomato plants: A life cycle study

Increasing evidence indicates the presence of engineered nanoparticles (ENPs) in sewage sludge derived from wastewater treatment. Land application of sewage sludge is, therefore, considered as an important pathway for ENP transfer to the environment. The aim of this work was to understand the effects of sewage sludge containing nano-TiO2 on plants (tomato) when used as an amendment in agricultural soil. We assessed developmental parameters for the entire plant life cycle along with metabolic and bio-macromolecule changes and titanium accumulation in plants. The results suggest that the sewage sludge amendment containing nano-TiO2 increased plant growth (142% leaf biomass, 102% fruit yield), without causing changes in biochemical responses, except for a 43% decrease in leaf tannin concentration. Changes in elemental concentrations (mainly Fe, B, P, Na, and Mn) of plant stem, leaves and, to a lesser extent fruits were observed. Fourier-transformed infrared analysis showed maximum changes in plant leaves (decrease in tannins and lignins and increase in carbohydrates) but no change in fruits. No significant Ti enrichment was detected in tomato fruits. In conclusion, we evidenced no acute toxicity to plants and no major implication for food safety after one plant life cycle exposure

Evaluation des paramètres susceptibles d'influencer la réponse des plantes à une exposition aux nanotubes de carbone

Les nanotubes de carbone (NTC) sont parmi les nanomatériaux (NM) les plus utilisés grâce à leurs excellentes propriétés physico-chimiques. Tout au long de leur cycle de vie, ils peuvent se répandre dans l'environnement, de façon involontaire ou intentionnelle. Il est donc essentiel d'évaluer leur comportement et leurs impacts sur les écosystèmes et en particulier sur les plantes agricoles. A ce jour, le comportement et les effets des NTC chez les plantes ne sont pas bien compris et sont sujet à controverses. Dans ce travail, nous avons cherché à évaluer l'influence de plusieurs paramètres sur la réponse des plantes exposées à des sols contaminés en NTC. Dans un premier temps, nous nous sommes penchés sur le défi analytique de la détection des NTC dans les matrices biologiques en comparant plusieurs techniques spectroscopiques. Nous avons ensuite évalué la réponse de plants de tomate à deux types de NM différents (NTC et TiO2-NP). Nos résultats mettent en évidence que même si les deux NMs diffèrent sur de nombreux paramètres (forme, taille, chimie de surface), les plantes ont présenté une réponse commune, en particulier avec une altération au niveau des composants pariétaux. L’étude des impacts de NTC sur 4 espèces végétales différentes (tomate, colza, maïs et concombre) a permis de mettre en évidence des réponses variant selon l'espèce végétale, le maïs (monocotylédone) semblant être l’espèce la plus sensible. De nombreux types de NTC sont actuellement disponibles. Cinq d'entre eux, dont le diamètre, la fonctionnalisation et la longueur varient, ont été utilisés pour étudier leurs impacts sur le colza. Le colza était plus sensible aux NTC ayant les diamètres les plus petits, mais nous avons aussi observé que la fonctionnalisation modulait grandement la réponse de la plante. Enfin, l'exposition aux NTC combinée à un stress environnemental a montré que les plantes étaient plus sensibles aux NTC lorsqu'elles étaient soumises à un stress thermique concomitantCarbon nanotubes (CNTs) are among the most used nanomaterials (NMs) thanks to their excellent physicochemical properties. All along their lifecycle, they may be spread unintentionallyor intentionally in the environment. It is thus essential to assess their behavior and potential impacts on ecosystems and particularly on crop plants. Overall, behaviour and effects of CNTs in plants are not well understood and still very controversial. In this work, we aimed to assess the influence of several parameters on plant response after exposure in a CNT-contaminated soil. We first focused on the analytical challenge of detecting CNT in biological matrices and tested several spectroscopic techniques. Then, we evaluated the response of tomato plants to two different NMs (CNTs and TiO2-NPs). Our results highlight that despite being different for several parameters (i.e. shape, size, surface chemistry), CNT exposure led to a similar response in tomato plants, in particular on the alteration of plant cell wall components. The study of different plant species (tomato, canola, maize and cucumber) exposed to DWCNT contamination highlighted different responses according to plant species, maize (monocot) being the most sensitive. Different types of CNTs are currently available. Five types of CNTs varying in diameter, functionalization and length were used to investigate their impact on canola. Canola was more sensitive to CNTs with the smallest diameters, but it was also observed that the functionalization greatly modulated the plant response. Finally, we tested the impact of a combined stress: canola plants grown in optimal growth conditions were not impacted by CNT exposure at the tested dose, while we observed that plants were more sensitive to CNTs when submitted to a concomitant heat stress

Phytoremediation studies: comparison between in situ and ex situ experiments results

ACTIInternational audienceWorldwide, a large number of contaminated site are reported due to anthropogenic activities and the intense use of chemicals. These sites need an appropriate management and remediation options that take in consideration, not only environmental risks, but also the linked socio-economic aspects. In the last years, phytoremediation techniques have been studied and selected as suitable and environmentally-friendly method to restore contaminated ecosystems. The selection of plants for phytoremediation is mostly done through ex situ pots experiments in greenhouse, growth chambers or in hydroponic conditions. Moreover, pots experiments are usually short-term study, while in situ experiments can last several years or even decades. For these reasons, the aim of this work was to compare plant response to heavy metal stress using plants grown directly on the contaminated fields and plants grown in pots containing soil from the same contaminated site. Among different species of studied plants, Miscanthus x giganteus seems to be a promising crop thanks to its demonstrated capacity to combine both environmental and economic benefits. In this experiment plants have grown in the Metaleurop Nord site, in Northern France, which has been suffering for more than a century for atmospheric emissions from two smelters present in the area. In this site, soils present a concentration of heavy metal which is 20 to 50 times higher than the regional background. In parallel to the in situ experiments, a two years ex situ experiment have been set up. Miscanthus plants were grown in pots containing contaminated soils from the Metaleurop site. The purposes were to evaluate (i) heavy metal uptake, (ii) translocation to different plant organs, (iii) and the metal impacts on plant health, using a set of biomarkers (evaluation of oxidative stress, DNA degradation, alteration of photosynthetic pigments, and production of secondary metabolites…). Results showed significant differences in almost each biomarker considered, demonstrating lower metal uptake, better adaptation, and a lower stress level in plants grown in field. Moreover, it is important to highlight that after several months, plants in pots demonstrated stress even in control samples compared to the in situ plants. This suggests that pot experiments do not reveal what happens on the field, by overestimating plant metal uptake capacity but also by modifying plant response to metal stress. This work demonstrates the importance of leading in situ experiment to understand fully how plants behave and adapt to site conditions, and to select better plants suitable for phytomanagement. More generally, it raises the question of the relevance of selecting plants with pots experiments

Response of Three Miscanthus × giganteus Cultivars to Toxic Elements Stress: Part 1, Plant Defence Mechanisms

International audienceMiscanthus × giganteus demonstrated good phytostabilization potentials in toxic element (TE) contaminated soils. However, information about its tolerance to elevated concentrations is still scarce. Therefore, an ex-situ pot experiment was launched using three cultivars (termed B, U, and A) grown in soils with a gradient Cd, Pb and Zn concentrations. Control plants were also cultivated in non-contaminated soil. Results show that the number of tillers per plant, stem diameter as well as leaf photosynthetic pigments (chlorophyll a, b and carotenoids) were negatively impacted by soil contamination. On the other hand, phenolic compounds, flavonoids, tannins, and anthocyanins levels along with the antioxidant enzymatic activities of superoxide dismutase, ascorbate peroxidase and glutathione reductase increased in the plants grown on contaminated soils. Altogether, these data demonstrate that miscanthus is impacted by concentrations of toxic elements yet is able to tolerate high levels of soil contamination. These results may contribute to clarifying the miscanthus tolerance strategy against high contamination levels and its efficiency in phytoremediation

Comparative study of response of four crop species exposed to carbon nanotube contamination in soil

Crop plants are exposed to a variety of contaminants through sewage sludge spreading but very little is known about the impact of emerging contaminants such as nanomaterials. To date their impact on plants is still very controversial with many works claiming negative impacts while some authors suggest their use as plant growth regulator in agriculture. In this study, aiming to better understand where these discrepancies may come from, we investigated the influence of plant species (tomato, rapeseed, cucumber and maize) on plant response to a carbon nanotube contamination in soil condition. Our results demonstrate that the same CNT contamination can lead to different effects depending on plant species with positive impacts on cucumber and rapeseed (more than 50% increase in leaf biomass and surface area and 29% increase in chlorophyll for cucumber) but negative impact on maize (−14% for plant height), while tomato was insensitive. FTIR analysis of biomacromolecule composition suggested that these differences could be related with plant cell wall composition (in particular: pectins, xyloglucans and lignins). As a summary, no overall conclusion can be drawn about the toxicity of a specific nanomaterial for all plant species

Response of Three <i>Miscanthus</i> × <i>giganteus</i> Cultivars to Toxic Elements Stress: Part 2, Comparison between Two Growing Seasons

The positive impact on restoring soil functionality, decreasing toxic elements (TE) bioaccessibility, and enhancing soil physicochemical and biological parameters established a consensus on considering a Miscanthus × giganteus convenient species for phytomanaging wide TE contaminated areas. Nevertheless, information about the plant’s mode of reaction to elevated soil multi-TE concentrations is still scarce. For the sake of investigating the miscanthus response to stressful TE concentrations, an ex-situ pot experiment was initiated for 18 months, with three miscanthus cultivars referred to as B, U, and A planted in soils with gradient Cd, Pb, and Zn concentrations. A non-contaminated control soil was introduced as well, and plants were cultivated within. Results revealed that the long exposure to increasing soil TE concentrations caused the number of tillers per plant to decline and the TE concentrations in the leaves to boost progressively with the soil contamination. The photosynthetic pigments (chlorophyll a, b, and carotenoids) were negatively affected as well. However, the phenolic compounds, flavonoids, tannins, and anthocyanins, along with the antioxidant enzymatic activities of superoxide dismutase, ascorbate peroxidase, and glutathione reductase elevated progressively with the TE concentration and exposure duration. Conclusively, miscanthus plants demonstrated an intensified and synchronized antioxidative activity against the TE concentration

Can Zn pollution of soil promote adaptive evolution in plants? Insights from a one-generation selection experiment

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