Bismuth exposure affects morpho-physiological performances and the ionomic profile in garden cress (Lepidium sativum L.) plants

Environmental pollution caused by heavy metals has long been considered a relevant threat to ecosystem survival and human health. The use of safer substitutes for the most toxic heavy metals in many industrial applications is discussed as a potential way to face this issue. In this regard, Bi has been proposed for replacing Pb in several production processes. However, few literature records reported on the effects of Bi on living organisms, particularly on plants. In this study, garden cress (Lepidium sativum L.) plants were exposed to different concentrations of Bi nitrate added to soil in growth chambers for 21 days. Results evidenced the toxic effect of Bi on shoot growth, regardless of the Bi nitrate concentration in the soil, paralleled by a similar reduction in the chlorophyll and carotenoid content, a decrease in the nitrogen balance index values, and an impairment of the photosynthetic machinery evaluated by chlorophyll fluorescence image analysis. The presence of Bi in the soil was shown to affect element accumulation in roots and translocation to shoots, with micronutrient content particularly reduced in the leaves of Bi-treated plants. A dose-dependent plant accumulation of Bi to metal concentration in the soil was observed, even if very low metal bioconcentration ability was highlighted. The reduced Bi translocation from roots to shoots in plants exposed to increasing Bi concentrations in the soil is discussed as a possible defense mechanism likely associated with the observed increase of anthocyan and flavonol contents and the activation of photoprotection mechanisms preventing higher damages to the photosynthetic apparatus

Morpho-Physiological and Metal Accumulation Responses of Hemp Plants (Cannabis Sativa L.) Grown on Soil from an Agro-Industrial Contaminated Area

Hemp is a promising plant for phytomanagement. The possibility to couple soil restoration to industrial crop cultivation makes this plant attractive for the management of contaminated sites. In this trial, Cannabis sativa L. plants were grown in a greenhouse on soils from two sites of “Valle del Sacco” (Lazio Region, Italy), a wide area contaminated by agro-industrial activities. One site was representative of moderate and diffuse metal(loid) multi-contamination, above the Italian concentration limit for agriculture (MC—moderately contaminated). The second site showed a metal(loid) content below the aforementioned limit, as a typical background level of the district (C—control). After 90 days, biometric and physiological parameters revealed satisfactory growth in both soil types. MC-grown plants showed a slight, but significant reduction in leaf area, root, and leaf biomass compared with C-grown plants. Chlorophyll content and chlorophyll fluorescence parameters, namely the quantum yield of primary photochemistry (Fv/Fm) and the Performance Index (PIABS), confirmed the good physiological status of plants in both soils. Metal(loid) analyses revealed that As, V, and Pb accumulated only in the roots with significant differences in MC- and C-grown plants, while Zn was found in all organs. Overall, preliminary results showed a satisfactorily growth coupled with the restriction of toxic metal translocation in MC-grown hemp plants, opening perspectives for the phytomanagement of moderately contaminated areas

Morpho-physiological and molecular responses of Lepidium sativum L. seeds induced by bismuth exposure

Bismuth (Bi) is considered a “green metal” as its toxicity has been reported to be lower than other metals, particularly lead. Even though the low presence in the environment, an increase of Bi concentrations in soil and wastewater is predictable due to its enhanced uses for many industrial and medical applications. Therefore, given the little literature on the matter, particularly in plants, information on the effects of Bi on living organisms is needed. In this study, seeds of garden cress (Lepidium sativum L.), a model plant for ecotoxicological assays (OECD), were exposed to increasing Bi concentrations (0 to 485 mg L−1 Bi(NO3)3·5H2O in deionised water) in petri plates. After 72 h, the percent germination index (GI%) revealed no effects at the lowest Bi concentrations, while a slight toxicity occurred at 242 and 485 mg L−1 Bi nitrate. A significant reduction of the root length was observed in Bi-treated seedlings, especially at the highest Bi concentrations. Consistently, the Alkaline Comet Assay revealed a genotoxic effect induced by Bi exposure in garden cress seedlings. A Bi concentration-dependent metal accumulation in plantlets was also observed, with a Bi concentration higher than 1200 mg kg−1 found in plantlets at the highest Bi concentration assayed. The toxicity effects observed in the study were discussed, as contribution to the expansion of knowledge on Bi ecotoxicity and genotoxicity in plants

Nature Based Solutions on the river environment: an example of cross-disciplinary sustainable management, with local community active participation and visual art as science transfer tool

An attempt to link phytomanagement, art and social involvement is presented. The “Remediation” Project started up from the search of sustainable solutions for the management of a riparian area in the city of Rome. With the participation of citizens, researchers carried out a preliminary survey on the presence of metals within the target ecosystem and a demonstrative experiment on phytoremediation. Several social and cultural events have been organized in connection with the scientific part of the project: a public debate, an art exposition, a performance and two workshops at the experimental field. The Project demonstrated that through art it is possible to raise curiosity on scientific issues; the participated survey on metal pollution highlighted the strict interconnection among environmental matrices (soil/water/bioma) and thus the risk of contamination transfer; the demonstrative experiment, even if very basic in order to be easily approached by citizens, showed the great potential of Nature Based Solutions

Microcosm Experiment to Assess the Capacity of a Poplar Clone to Grow in a PCB-Contaminated Soil

Polychlorinated byphenyls (PCBs) are a class of Persistent Organic Pollutants extremely hard to remove from soil. The use of plants to promote the degradation of PCBs, thanks to synergic interactions between roots and the natural soil microorganisms in the rhizosphere, has been proved to constitute an effective and environmentally friendly remediation technique. Preliminary microcosm experiments were conducted in a greenhouse for 12 months to evaluate the capacity of the Monviso hybrid poplar clone, a model plant for phytoremediation, to grow in a low quality and PCB-contaminated soil in order to assess if this clone could be subsequently used in a field experiment. For this purpose, three different soil conditions (Microbiologically Active, Pre-sterilized and Hypoxic soils) were set up in order to assess the capacity of this clone to grow in the polluted soil in these different conditions and support the soil microbial community activity. The growth and physiology (chlorophyll content, chlorophyll fluorescence, ascorbate, phenolic compounds and flavonoid contents) of the poplar were determined. Moreover, chemical analyses were performed to assess the concentrations of PCB indicators in soil and plant roots. Finally, the microbial community was evaluated in terms of total abundance and activity under the different experimental conditions. Results showed that the poplar clone was able to grow efficiently in the contaminated soil and to promote microbial transformations of PCBs. Plants grown in the hypoxic condition promoted the formation of a higher number of higher-chlorinated PCBs and accumulated lower PCBs in their roots. However, plants in this condition showed a higher stress level than the other microcosms, producing higher amounts of phenolic, flavonoid and ascorbate contents, as a defence mechanism

FT-ICR-MS based untargeted metabolomics of Melilotus officinalis plants grown in different soil treatments

This study reports the application of the leguminosae Melilotus officinalis in soil recovery and as a source of bioactive compounds. Plants were cultivated in semiarid soil under four different fertilizer treatments: urban waste compost at 10 t/ha (C-Low) and 20 t/ha (C-High), inorganic fertilizer (Inorg) and a Control (without any fertilizer). Metabolite composition of plants' leaves was analyzed through Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Metabolite extraction was performed from frozen lyophilized leaf samples (eight biological replicates per treatment) with 1 mL of 50% methanol/water (LC–MS grade, Merck). Then, the methanolic sample extract was diluted 1000-fold in methanol and analysed by direct infusion on a 7-Tesla SolariX XR Fourier Transform Ion Cyclotron Resonance Mass Spectrometer, equipped with a ParaCell (FT-ICR-MS, Brüker Daltonics). Leucine enkephalin (YGGFL, Sigma Aldrich) was added as internal standard ([M+H]+ =556.276575 m/z), at a concentration of 0.1 µg/mL, and formic acid (Sigma Aldrich, MS grade) was added at a final concentration of 0.1% (v/v) to all samples. Spectra were acquired in positive electrospray ionization (ESI+), in magnitude mode, with an acquisition size of 4M, and recorded between 100 and 1500 m/z. The accumulation time was 0.1 seconds, and 100 transients were accumulated for each spectrum, zero-filled and apodised (half-sine). Online calibration was performed using the monoisotopic m/z value of leucine enkephalin. The software Bruker Compass data Analysis 5.0 (Brüker Daltonics, Bremen, Germany) was used to process and retrieve the mass lists, considering peaks with a minimum signal-to-noise ratio of 4. The alignment of the raw data from the different replicas for each spectrum dataset was performed with Metaboscape 5.0 (Brüker Daltonics, Bremen, Germany) using T-ReX 2D (MRMS single spectrum) algorithm, with the intensities normalized to the sum of all intensities in each sample. M/z values that appeared only in one analysed sample were removed from the table.</p