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.

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.