Abiotic stress is characteristic of the semi-arid region, so fertilization with silicon (Si) can mitigate the damage caused by this stress, increasing yield and improving food quality. In this scenario, this study evaluated the agronomic performance and quality of onion bulbs as a function of Si doses in a semi-arid region of Brazil. A field experiment was conducted, designed in complete randomized blocks, testing Si doses (0, 42.6, 83.2, 124.8, and 166.4 kg ha-1), with four replicates. Dry mass, chlorophyll, nutrition, yield, and physicochemical quality of the bulbs were evaluated. Fertilization with Si increased the concentrations of P, N, K, Zn, and Cu in the leaves, indicating an improvement in the nutritional status. There was a decrease in the physicochemical characteristics of the bulbs, such as titratable acidity, soluble solids, total soluble sugars, ascorbic acid, and pyruvic acid, compared to the control. Fertilization with 68 and 72 kg ha-1 of Si, respectively, increased by 10% the commercial yield (81.49 t ha-1) and by 8% the total yield (87.96 t ha-1) of bulbs. The total and commercial yield of onion bulbs is increased with Si doses of 68 and 72 kg ha-1, respectively; however, Si reduces the concentration of physicochemical quality attributes of the bulbs.

High levels of Co(NO3)2 for living organisms are toxic. In this study, the protective effects of 2,6-dimethyl-morpholine dithiocarbamate (DMMDTC) against the toxicity of Co(NO3)2 on Allium cepa L. were investigated. Seven groups of onion bulbs were established to investigate the potential effects of DMMDTC against Co(NO3)2 exposure in root tips. These are a control group, two groups of DMMDTC alone in different concentrations, two groups of Co(NO3)2 in different concentrations, and finally, two groups of combined DMMDTC (1,2) + Co (1,2) in different concentrations were applied to onion roots. The effects of the chemicals on physiological parameters, Mitotic Index (MI), Micro Nucleus (MN), genotoxicity and Co(NO3)2 accumulation in the roots were examined. MI analysis revealed that Co(NO3)2 treatments reduced the MI compared to water control by 52.2-46.6%, depending on the concentration. The combinations of DMMDTC + Co(NO3)2 significantly increased MI while decreasing MN compared to the cobalt-only treatments. However the protective effect of DMMDTC against cobalt toxicity was limited when the data compared to the water control. The heavy damage to epidermis cells and nucleus was also observed in those cobalt applied groups. Co(NO3)2 accumulation in the roots, compared to water control, was also high in Co1-Co2 groups. The DMMDTC used in this study had effects similar to those of plant extracts in reducing genotoxic effects. Therefore, the research highlights the potential benefits of using synthesized DMMDTC on Allium cepa against the toxic effects of cobalt.

Large quantities of hazardous heavy metals found in industrial wastes and are adequate to make crops toxic and these noxious metals accumulate in plant tissues can cause deleterious effects in plants. The current investigation was carried out to assess the physiological response of onion plants in textile effluents contaminated soil and to determine the role of silicone in the onion plant under oxidative stress. The industrial effluent was used at the rate of control, 30 %, 60 % and 100 % effluents. Following treatment applications were made (30 % +Si, 60 % +Si, 100 % effluents + Si,0 % +Si). Various physiological and enzymatic parameters were studied. The complete randomized design (CRD) with triplicates was used for the experiment. Treatment T4 (seed + 100 % effluents) was most toxic and 43 % shoot length, 51 % root length, 47 % membrane damage,74 % chlorophyll a,67 % chl b, 82 %carotenoids, and 44 %, catalase inhibition was observed over (T1). Similarly, MDA content and membrane damage were also higher in T4 (237,189 %) as control. The (seed+ Si) was found most effective in terms of onion growth which increased the shoot length, root length, chl a, chl b, carotenoids, and SOD (34, 51,70,284, 175, and 174 %) higher as compared to T1 respectively. It is concluded from the current investigation that textile effluents contain various toxic materials, especially heavy metals which can adversely affect the onion plant and silicon suppressed the toxicity of effluents in plant, Si can be used l to overcome toxic effect of industrial waste and plant growth promotion

As the demand for fish increases, the amount of wastewater generated from fishponds is also increasing with potential environmental and public health effects from their indiscriminate disposal. This study aimed at comparative analyses of the physicochemical and heavy metal constituents and potential DNA damage by wastewaters from natural and artificial fishponds using Allium cepa assay. A. cepa were grown on 3.13, 6.25, 12.5, 25.0, and 50.0% (v/v; wastewater/tap water) concentrations of each wastewater. At 48 and 72 h, respectively, genotoxic and root growth inhibition analyses were carried out on the exposed onions. The onion root tips exposed to wastewaters showed a significant (P < 0.05) inhibition of root growth and cell division in a concentration-dependent manner. Additionally, chromosomal abnormalities like spindle disturbances, sticky chromosomes, micronucleus, bridges, and binucleated cells were observed in the exposed onions and their induction was higher significantly relative to the negative control. Generally, wastewater from the natural fishpond caused higher chromosomal aberrations than the wastewater from artificial fishpond. It is our belief that the cytotoxicity and genotoxicity observed in the onions were primarily caused by heavy metals like Cr, Cd, Fe, Pb, Cu, and Zn found in the wastewaters. These metals also showed a significant carcinogenic and non-carcinogenic risks in children and adults with Cd as the highest contributor to these detrimental risks. Ingestion route was the major exposure route to the toxic metals in these wastewaters. Wastewater from the natural fishpond showed a higher health risk than the wastewater from the artificial fishpond. These findings suggest that the wastewaters from natural and artificial fishpond contain compounds that might induce cytogenotoxicity in exposed organisms.

The ecotoxic effect of Zn species arising from the weathering of the marmatite-like sphalerite ((Fe, Zn)S) in Allium cepa systems was herein evaluated in calcareous soils and connected with its sulfide oxidation mechanism to determine the chemical speciation responsible of this outcome. Mineralogical analyses (X-ray diffraction patterns, Raman spectroscopy, scanning electron microscopy and atomic force microscopy), chemical study of leachates (total Fe, Zn, Cd, oxidation-reduction potential, pH, sulfates and total alkalinity) and electrochemical assessments (chronoamperometry, chronopotentiometry, cyclic voltammetry, and electrochemical impedance spectroscopy) were carried out using (Fe, Zn)S samples to elucidate interfacial mechanisms simulating calcareous soil conditions. Results indicate the formation of polysulfides (S-n(2-)), elemental sulfur (S-0), siderite (FeCO3)-like, hematite (Fe2O3)-like with sorbed CO32- species, gunningite (ZnSO4H2O)-like phase and smithsonite (ZnCO3)-like compounds in altered surface under calcareous conditions. However, the generation of gunningite (ZnSO4H2O)-like phase was predominant bulk-solution system. Quantification of damage rates ranges from 75 to 90% of bulb cells under non-carbonated conditions after 15-30 days, while 50-75% of damage level is determined under neutral-alkaline carbonated conditions. Damage ratios are 70.08 and 30.26 at the highest level, respectively. These findings revealed lower ecotoxic damage due to ZnCO3-like precipitation, indicating the effect of carbonates on Zn compounds during vegetable up-taking (exposure). Other environmental suggestions of the (Fe, Zn)S weathering and ecotoxic effects under calcareous soil conditions are discussed.

Heavy metals (HMs) are natural components of the Earth's crust that might originate from natural and anthropogenic sources. In excess quantities, the presence of these metals is harmful for both environment and human health. Taking this into account, various investigators examined bioaccumulator species in order to reduce environmental toxicity, among these Baccharis trimera. Therefore, the present study aimed to determine the capacity of B. trimera to bioaccumulate HMs and assess consequent cytogenotoxicity following exposure. B. trimera vegetative parts were collected from two groups (1) control, in which plants were cultivated in soil exposed to distilled water, and (2) exposed, in which plants were cultivated in soil exposed to HMs including manganese (Mn), iron (Fe), lead (Pb), copper (Cu), cobalt (Co), zinc (Zn), and chromium (Cr). HMs were quantified in cultivation soil and extracts (aqueous and ethanolic) as well as infusion of B. trimera vegetative parts. Root lengths and cytogenotoxic effects were determined using Allium cepa test. Results demonstrated that all HMs studied were absorbed and bioaccumulated by B. trimera. Root lengths were decreased when exposed to ethanolic extract of B. trimera cultivated in soil exposed to HMs solution, which was the extract that exhibited the highest cytogenotoxicity values. Thus, data demonstrated that B. trimera might serve as a bioaccumulator for the reduction of environmental toxicity associated with the presence of certain HMs.

With the expansion of urban areas, the amount of sludge produced by sewage treatment plants is increasing, raising big problems regarding the reintroduction of this sludge into nature in order to fully solve the wastewater problem. The application of sludge to agricultural surfaces or degraded land is a controversial solution since, despite the well-known benefits, sludge can, in certain cases, represent a real threat to both human health and the environment, with long-term harmful effects. The present study evaluates the potential genotoxicity of sludge using the Comet Test and three cellular bioindicators (lymphocytes, coelomocytes, and Allium cepa L.) for its quantification. To perform the tests, the soluble fraction of the sludge was used at concentrations of 25%, 50%, 75%, and 100%, as well as a negative control (H2O) and a positive control (H2O2). The Comet test indicated an increase in DNA damage among cells exposed for 4 h in the following order: coelomocytes, lymphocytes, and Allium cepa L. cells. Our results indicate that Allium cepa L. nuclei are more sensitive, with genotoxic effects being evident at concentrations as low as 25%. In coelomocytes, we recorded nuclear damage starting at a concentration of 75%. These results indicate the necessity of using multiple genotoxicity tests, combined in a test battery, to achieve a greater level of relevance. The concentration of the soluble fraction of the sludge has an inverse relationship with the auxin content in leaves and roots, suggesting varying levels of stress. The results of this study can contribute to the creation of a genotoxic profile of sewage sludge, facilitating decisions related to reducing its negative impact.