Use of compost in the uptake mitigation of arsenic in Beta vulgaris L. var. cicla.

BACKGROUND: Arsenic (As) may represent a risk for crop yield quality and human health since it may accumulate in the edible plant organs with the potential of leading to acute or chronic toxic effects in varied segments of the population. Management of soil fertility through compost has proven to be a valuable practice for increasing and maintaining soil organic matter, with nutritional benefits for crops. This work aimed to evaluate Swiss chard yield and the change in the bioavailability, bioaccumulation, and partitioning of As in the response of the use of compost or conventional mineral fertilization in an open-field trial conducted in a volcanic area in central Italy characterized by the natural contamination of As in soil. RESULTS: Compost treatment led to a short-term increase trend in soil organic carbon, total nitrogen, and available phosphorus in a significant way. In the compost-amended plots, the mitigation of the As uptake was detected in leaves, which are the edible part of Swiss chard. The As bioaccumulation factor in leaves of Swiss chard and the translocation factor for leaves/roots were also decreased using compost. CONCLUSION: Fertilization by compost can improve soil fertility, sustain Swiss chard production, and mitigate As accumulation in leaves of this crop grown in a naturally As-contaminated soil. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Mechanisms of arsenic assimilation by plants and countermeasures to attenuate its accumulation in crops other than rice.

Arsenic is a ubiquitous metalloid in the biosphere, and its origin can be either geogenic or anthropic. Four oxidation states (-3, 0, +3 and + 5) characterize organic and inorganic As- compounds. Although arsenic is reportedly a toxicant, its harmful effects are closely related to its chemical form: inorganic compounds are most toxic, followed by organic ones and finally by arsine gas. Although drinking water is the primary source of arsenic exposure to humans, the metalloid enters the food chain through its uptake by crops, the extent of which is tightly dependent on its phytoavailability. Arsenate is taken up by roots via phosphate carriers, while arsenite is taken up by a subclass of aquaporins (NIP), some of which involved in silicon (Si) transport. NIP and Si transporters are also involved in the uptake of methylated forms of As. Once taken up, its distribution is regulated by the same type of transporters albeit with mobility efficiencies depending on As forms and its accumulation generally occurs in the following decreasing order: roots > stems > leaves > fruits (seeds). Besides providing a survey on the uptake and transport mechanisms in higher plants, this review reports on measures able to reducing plant uptake and the ensuing transfer into edible parts. On the one hand, these measures include a variety of plant-based approaches including breeding, genetic engineering of transport systems, graft/rootstock combinations, and mycorrhization. On the other hand, they include agronomic practices with a particular focus on the use of inorganic and organic amendments, treatment of irrigation water, and fertilization.

Effects of ground transport on the presence of heavy metals in selected honeybee products.

Honeybees are insects very sensitive to environmental pollution and at the same time very good indicators of the pollution levels for certain types of pollutants. The morphology and ethology of these insects make them perfect vectors for dust and substances, including heavy metals produced by anthropic activities or naturally generated and deposited on foraged flora. When bees are raised to produce foods such as honey and pollen, they can easily transfer pollutants collected from contaminated flower affecting the quality of these products. However, depending on geographical location of the apiaries and their distance from pollution sources, the risk to contaminate bee products can be higher or lower requiring deep investigations. In this study, two apiaries were built near ground transport infrastructures and used as monitoring stations for investigating heavy metal presence in beehive products such as bee wax, pollen, and honey. Another apiary was placed between these two locations at a distance of 500 m from each one and used as central node to asses possible diffusion trends. Parallel, air quality was monitored in the proximity of each apiary to verify the air pollution of the environments close to these sites. The results of the study suggest that the presence of the highway and the train station affected the levels of heavy metal presence in the apiary products. Air quality near apiaries was also negatively affected by ground transport, especially in proximity of the highway. Wax resulted significantly more polluted in the apiary close to train station with elements such as Al, Zn, and Ni, while honey and pollen were significantly more polluted in the proximity of the highway with elements such as Al, Fe, Cu, and Zn. Honey was the product suffering less the contamination by heavy metals while pollen was the worse. In conclusion, the presence of transportation nodes determined a higher accumulation of heavy metals in beehive products respect the apiary placed in between, suggesting to pay particular attention in the site selection for the placement of apiaries to protect both bees and human health.

Cynara cardunculus L. var. scolymus L. Landrace "Carciofo Ortano" as a Source of Bioactive Compounds.

The preservation of agricultural biodiversity and socioeconomic development are relevant both to enhance domestic production and to support innovation. In the search for new biomolecules, we have focused on the "Carciofo Ortano" landrace, growth in the northern part of the Lazio region. Artichoke cultivation generates substantial by-products, including leaves, stems, and roots, which could serve as valuable sources of biomolecules and prebiotic dietary fiber. To valorize the leaf waste of the "Carciofo Ortano" landrace, a multidisciplinary approach was applied. Chemical analysis using HPLC-DAD identified mono-O- and di-O-caffeoylquinic acids and the sesquiterpene cynaropicrin in all artichoke leaf extracts. SPME-GC/MS analyses detected aliphatic alcohols in the fresh leaf samples. Antiproliferative and cytotoxic studies on cancer (SH-SY5Y, MCF-7, MDA) and normal (MCF-10A) human cell lines revealed that leaf extracts induced a selective dose and time-dependent biological effect. While showing slight activity against environmental bacterial strains, artichoke leaf extracts exhibited significant antifungal activity against the phytopathogenic fungus Alternaria alternata. Overall, the results highlight the potential of "Carciofo Ortano" cultivation by-products as a rich source of biomolecules with versatile applications in humans, animals, and the environment.

Use of Air-Classification Technology to Manage Mycotoxin and Arsenic Contaminations in Durum Wheat-Derived Products.

Mycotoxins are the most common natural contaminants and include different types of organic compounds, such as deoxynivalenol (DON) and T-2 and HT-2 toxins. The major toxic inorganic elements include those commonly known as heavy metals, such as cadmium, nickel, and lead, and other minerals such as arsenic. In this study, micronisation and air classification technologies were applied to durum wheat (Triticum turgidum ssp. durum L.) samples to mitigate inorganic (arsenic) and organic contaminants in unrefined milling fractions and final products (pasta). The results showed the suitability of milling plants, providing less refined milling products for lowering amounts of mycotoxins (DON and the sum of T-2 and HT-2 toxins) and toxic inorganic elements (As, Cd, Ni, and Pb). The results showed an As content (in end products) similar to that obtained using semolina as raw material. In samples showing high organic contamination, the contamination rate detected in the more bran-enriched fractions ranged from 74% to 150% (DON) and from 119% to 151% (sum of T2 and HT-2 toxins) as compared to the micronised samples. Therefore, this technology may be useful for manufacturing unrefined products with reduced levels of organic and inorganic contaminants, minimising the health risk to consumers.

Identification of Resistance Genes and Response to Arsenic in Rhodococcus aetherivorans BCP1.

Arsenic (As) ranks among the priority metal(loid)s that are of public health concern. In the environment, arsenic is present in different forms, organic or inorganic, featured by various toxicity levels. Bacteria have developed different strategies to deal with this toxicity involving different resistance genetic determinants. Bacterial strains of Rhodococcus genus, and more in general Actinobacteria phylum, have the ability to cope with high concentrations of toxic metalloids, although little is known on the molecular and genetic bases of these metabolic features. Here we show that Rhodococcus aetherivorans BCP1, an extremophilic actinobacterial strain able to tolerate high concentrations of organic solvents and toxic metalloids, can grow in the presence of high concentrations of As(V) (up to 240 mM) under aerobic growth conditions using glucose as sole carbon and energy source. Notably, BCP1 cells improved their growth performance as well as their capacity of reducing As(V) into As(III) when the concentration of As(V) is within 30-100 mM As(V). Genomic analysis of BCP1 compared to other actinobacterial strains revealed the presence of three gene clusters responsible for organic and inorganic arsenic resistance. In particular, two adjacent and divergently oriented ars gene clusters include three arsenate reductase genes (arsC1/2/3) involved in resistance mechanisms against As(V). A sequence similarity network (SSN) and phylogenetic analysis of these arsenate reductase genes indicated that two of them (ArsC2/3) are functionally related to thioredoxin (Trx)/thioredoxin reductase (TrxR)-dependent class and one of them (ArsC1) to the mycothiol (MSH)/mycoredoxin (Mrx)-dependent class. A targeted transcriptomic analysis performed by RT-qPCR indicated that the arsenate reductase genes as well as other genes included in the ars gene cluster (possible regulator gene, arsR, and arsenite extrusion genes, arsA, acr3, and arsD) are transcriptionally induced when BCP1 cells were exposed to As(V) supplied at two different sub-lethal concentrations. This work provides for the first time insights into the arsenic resistance mechanisms of a Rhodococcus strain, revealing some of the unique metabolic requirements for the environmental persistence of this bacterial genus and its possible use in bioremediation procedures of toxic metal contaminated sites.

Influence of organic management on As bioavailability: Soil quality and tomato As uptake.

The research studied the effects of organic vs. conventional management of soil quality and tomato yield quality, cultivated in a geogenic arsenic contaminated soil. The chemical and biochemical properties were analyzed to evaluate soil quality, arsenic mobility and its phyto-availability, as well as arsenic accumulation in the tomato plant tissues and if tomatoes cultivated in arsenic rich soil represents a risk for human health. A general improvement of tomato growth and soil quality was observed in the organic management, where soil organic carbon increased from 1.24 to 1.48% and total nitrogen content. The arsenic content of the soil in the organic management increased from 57.0 to 65.3 mg kg-1, probably due to a greater content of organic matter which permitted the soil to retain the arsenic naturally present in irrigation water. An increase of bioavailable arsenic was observed in the conventional management compared to the organic one (7.05 vs 6.18 mg kg-1). The bioavailable form of metalloid may affect soil microbial community structure assessed using El-FAME analysis. The increase of the total arsenic concentration in the organic management did not represent a stress factor for soil microbial biomass carbon (Cmic), which was higher in the organic management than in the conventional one (267 vs. 132 µg Cmic g-1). Even if the organic management caused an increase of total arsenic concentration in the soil due to the enhanced organic matter content, retaining arsenic from irrigation water, this management mitigates the arsenic uptake by tomato plants reducing the mobility of the metalloid.

On the interactions among zinc availability and responses to ozone stress in durum wheat seedlings.

Seedlings of durum wheat [Triticum turgidum subsp. durum (Desf.) Husn] were exposed to zinc nutrition and to ozone (O3) in a factorial combination: adequate (+Zn treatment) or no Zn (-Zn) in the nutrient solution, followed by exposure to either ozone-free air (filtered air, FA) or to 150 nL L-1 ozone (O3) for 4 h. Although omitting Zn from the nutrient solution failed to impose a genuine Zn deficiency, -Zn*FA durum wheat seedlings showed a typical deficiency behaviour, i.e. Zn mobilisation from root to shoot. Such inter-organ Zn redistribution, however, did not occur in -Zn*O3 plants. Exposure to each stress singly decreased the activity and the protein amount of foliar plasma membrane H+-ATPase, but not stress combination, which even increased the H+-ATPase expression with respect to control. In the -Zn*O3 plants, moreover, the foliar activities of the plasma membrane-bound NAD(P)H-dependent superoxide synthase and of Cu,Zn-superoxide dismutase, and the transcripts abundance of the luminal binding protein and of the protein disulphide isomerase, were also stimulated. It is proposed that, even in the absence of actual Zn starvation, the perception of deficiency conditions could trigger changes in redox homoeostasis at the plasma membrane level, helpful in compensating an O3-dependent oxidative damage.

Different compensatory mechanisms in two metal-accumulating aquatic macrophytes exposed to acute cadmium stress in outdoor artificial lakes.

Mechanisms underlying cadmium (Cd) detoxification were compared in two aquatic macrophytes commonly used in phytoremediation, namely Pistia stratiotes L. and Eichhornia crassipes (Mart.) Solms. To simulate Cd pollution in the open environment, plants growing in outdoor artificial lakes were exposed for 21d to either 25 or 100microM Cd, in two consecutive years. Toxicity symptoms were absent or mild in both species. Metal accumulation was much higher in the roots of P. stratiotes, whereas in E. crassipes a comparatively higher fraction was translocated to the leaves. In both species, Cd was neither included in phenolic polymers or Ca-oxalate crystals, nor altered the levels of Cd-complexing organic acids. Glutathione levels were constitutively remarkably higher and much more responsive to Cd exposure in P. stratiotes than in E. crassipes. Abundant phytochelatin synthesis occurred only in P. stratiotes, both in roots and in leaves. In E. crassipes, on the other side, the constitutive levels of some antioxidant enzymes and ascorbate were higher and more responsive to Cd than in P. stratiotes. Thus, in these two aquatic plants grown in the open, different detoxification mechanisms might come into play to counterbalance Cd acute stress.

On the role of H2O2 in the recovery of grapevine (Vitis vinifera cv. Prosecco) from Flavescence dorée disease.

In the present work, we compared hydrogen peroxide (H2O2) localisation and the activities/contents of antioxidant enzymes and metabolites in the leaf tissues of grapevine (Vitis vinifera L. cv. Prosecco) plants showing different sanitary status, namely diseased by Flavescence dorée, healthy or recovered. Polymerase chain reaction analysis revealed that the pathogen associated with Flavescence dorée (proposed as 'Candidatus Phytoplasma vitis') was detected in the leaf tissues of symptomatic plants, but was not observed in either the healthy or recovered plants. Hydrogen peroxide accumulated in the phloem plasmalemma of recovered grapevine leaves, but was not detected in either healthy or diseased material. When compared to diseased or healthy plants, recovered plants had distinctly lower extractable levels of catalase and ascorbate peroxidase, two enzymes primarily involved in the scavenging of excess H2O2 generated in different cell compartments. Among healthy, diseased and recovered leaves there was no significant difference in the amount of 2-thiobarbituric acid-reactive substances, which are assumed to reflect the extent of peroxidative breakdown of membrane lipids. Therefore, it is suggested that recovery from Flavescence dorée disease in grapevine might be associated with a long-term, sustained and tissue-specific accumulation of H2O2 in leaves, which reduces numbers or prevents further infection by Flavescence dorée phytoplasma. Recovered grapevine plants might be able to achieve such H2O2 accumulation through a selective and presumably stable downregulation of enzymatic H2O2 scavengers, without altering the levels of other antioxidant systems and without incurring an increased oxidative risk.

Cell wall immobilisation and antioxidant status of Xanthoria parietina thalli exposed to cadmium.

Total and cell wall-bound cadmium and the major antioxidants were measured in thalli of the lichen Xanthoria parietina (L.) Th. Fr. exposed to two Cd concentrations, namely 4.5 or 9.0 µm, in liquid medium during exposure periods of either 24 or 48 h. Total Cd in the thalli was within the range of previous field measurements and was proportional to the exposure concentration, but less than proportional with respect to exposure duration. More than half of the total Cd was immobilised by the cell wall. The adopted conditions of Cd stress caused: (i) no changes in dry weight and protein concentration; (ii) an increase in the level of ascorbic acid and a decrease in that of reduced glutathione, as well as an increase in guaiacol peroxidase activity; (iii) no changes or moderate decreases in the activities of superoxide dismutase, catalase, dehydroascorbate-, NADPH-dependent glutathione disulfide-, and monodehydroascorbate reductases and of ascorbate peroxidase; (iv) an increase of the level of thiobarbituric acid-reactive substances, assumed to reflect malondialdehyde formation arising from membrane lipid peroxidation. Thus, X. parietina might withstand realistic levels of Cd stress by: (1) intercepting the heavy metal at cell wall level, (2) the intervention of antioxidant metabolites, and (3) a moderate increase in guaiacol peroxidase activity.

Responses of Xanthoria parietina thalli to environmentally relevant concentrations of hexavalent chromium.

Thalli of the lichen Xanthoria parietina (L.) Th. Fr. were soaked for either 24 or 48 h in a buffered medium in the presence of environmentally relevant concentrations (4.8 and 9.6 µM) of hexavalent chromium [Cr(VI)]. Treatment effects on the antioxidant status, differential distribution and fate of Cr(VI) among the mycobiont and the photobiont cells, and potential damage to cell ultrastructure in the two bionts, were evaluated. The adopted conditions of low Cr(VI) stress caused: (i) an increase in the level of ascorbic acid and a decrease in that of reduced glutathione, as well as a moderate increase in guaiacol peroxidase activity, only observed after treatment with 9.6 µM Cr(VI); (ii) no changes in malondialdehyde content; (iii) a remarkable Cr accumulation in the mycobiont cytosol and compartmentalisation in the mycobiont vacuoles;(iv) a modest apoplastic Cr immobilisation by the outer part of the cell walls, of both the mycobiont and the photobiont. The response of X.parietina to low concentrations of Cr(VI) appears to be a complex phenomenon, which might reflect maintenance of cellular homeostatic equilibria, rather than specific response pathways.