Researchers have tried hard to study the toxic effects of single pollutants like certain antibiotics and nanoplastic particles on plants. But we still know little about how these pollutants interact when they're together in the environment, and what combined toxic effects they have on plants. This study assessed the toxic effects of polystyrene nanoplastics (PS-NPs) and ciprofloxacin (CIP), both individually and in combination, on soybean (Glycine max L.) seedlings by various concentration gradients treatments of PS-NPs (0, 10, 100 mg/L) and CIP (0, 10 mg/L). The results indicated that high concentrations of PS-NPs significantly impeded soybean seedling growth, as evidenced by reductions in root length, plant height, and leaf area. CIP predominantly affected the physiological functions of leaves, resulting in a decrease in chlorophyll content. The combined exposure demonstrated synergistic effects, further intensifying the adverse impacts on the growth and physiological functions of soybean seedlings. Metabolomic analyses indicated that single and combined exposures markedly altered the metabolite expression profiles in soybean leaves, particularly related to amino acid and antioxidant defense metabolic pathways. These results indicate the comprehensive effects of NPs with antibiotics on plants and provide novel insights into toxic mechanisms.

Soil salinization negatively affects the growth and yield of economically valuable crops such as soybeans. New technologies are being developed to minimize the damage caused by saline stress and improve crop performance. Therefore, the use of biostimulants in agriculture may offer an alternative method to mitigate the deleterious effects of salinity. Extracts of the seaweed,Ascophyllum nodosum and humic substances (fulvic acids) are commonly used. Therefore, this study aimed to evaluate the action of a biostimulant composed of A. nodosum seaweed extract and fulvic acid applied at different phenological stages on the biometric, biochemical, and physiological parameters of soybeans (Glycine max) subjected to irrigation with saline water. The experimental design used was completely randomized in a 3 x 2 + 2 factorial scheme, referring to three applications of the biostimulant at different soybean phenological stages: V3, V3R1, and V3R1R4, two levels of electrical conductivity of irrigation water (ECw): 0.5 (S0) and 5.0 dS m-1 (S1), two additional controls, one with a positive control (PC) and the other with a negative control (NC). The experiment had five replicates with one plant per plot. The results of this study suggest that the application of the biostimulant can mitigate the harmful effects of salt stress in soybeans. The results obtained with V3R1 application in the parameters stem diameter, leaf area, shoot dry mass, electrolyte leakage, and chlorophyll b represent greater efficiency in mitigating the harmful effects of salinity in soybean cultivation.

Climate change has emerged as a challenge for soybean cultivation around the world, stimulating the development of technological alternatives that aim to mitigate the damage caused by water deficit. From this perspective, algae extract-based biostimulants have been tested to reduce water stress in several crops, but little is known about their effects on soybean. Thus, we hypothesize that a commercial biostimulant based on Ascophyllum nodosum can improve the physiological performance and water relations of Glycine max plants subjected to water deficit. To test this hypothesis, we set up an experiment in controlled conditions in a greenhouse, considering five treatments (control; application of biostimulant; water deficit (WD); WD + application of biostimulant; and WD + split application of biostimulant). The experiment was designed in completely randomized blocks with four replications per treatment and conducted in polyethylene pots containing 10 L of soil and three plants per pot. The irrigation was carried out daily; the water deficit was 50% soil moisture at field capacity, starting at the R1 stage (beginning of flowering, where there is at least one flower open at any node on the plant) and maintained for ten days. The biostimulant was applied concurrently with the onset of water deficit. We confirmed the hypothesis that foliar application of 1.0 L ha-1 of the biostimulant reduces the deleterious effects of the common water deficit at the beginning of the reproductive stage of soybean through the reduction of damage from oxidative stress (reduction of malondialdehyde synthesis by 31.2% in relation to the WD plants), maintenance of water potential and cellular homeostasis (10.2% increase in relative water content when compared with WD plants), and conservation of the contents of chlorophyll in leaves and stimulation of photosynthesis and carboxylation (68% increase in net photosynthetic rate and 49.3% increase in carboxylation efficiency in relation to WD plants). However, when applied in installments, the biostimulant was not efficient in reducing soybean water stress. Therefore, we conclude that the application of a biostimulant based on A. nodosum can help reduce the harmful effects of water deficit on soybean plants, opening up perspectives for the mass use of this extract in agricultural crops produced on a large scale.

Aluminum (Al) toxicity in acidic soils is a major abiotic stress that negatively impacts plant growth and development. The toxic effects of Al manifest primarily in the root system, leading to inhibited root elongation and functionality, which impairs the above-ground organs of the plant. Recent research has greatly improved our understanding of the applications of small molecule compounds in alleviating Al toxicity. This study aimed to investigate the role of boron (B), silicon (Si), and their combination in alleviating Al toxicity in soybeans. The results revealed that the combined application significantly improved the biomass and length of soybean roots exposed to Al toxicity compared to B and Si treatments alone. Our results also indicated that Al toxicity causes programmed cell death (PCD) in soybean roots, while B, Si, and their combination all alleviated the PCD induced by Al toxicity. The oxidative damage induced by Al toxicity was noticeably alleviated, as evidenced by lower MAD and H2O2 accumulation in the soybean roots treated with the B and Si combination. Moreover, B, Si, and combined B and Si significantly enhanced plant antioxidant systems by up-regulating antioxidant enzymes including CAT, POD, APX, and SOD. Overall, supplementation with B, Si, and their combination was found to alleviate oxidative damage and reduce PCD caused by Al toxicity, which may be one of the mechanisms by which they alleviate root growth inhibition due to Al toxicity. Our results suggest that supplementation with B, Si, and their combination may be an effective strategy to improve soybean growth and productivity against Al toxicity.

Water stress (WS) poses a significant threat to global food and energy security by adversely affecting soybean growth and nitrogen metabolism. This study explores the synergistic effects of exogenous salicylic acid (SA, 0.5 mM) and thiourea (TU, 400 mg L-1), potent plant growth regulators, on soybean responses under WS conditions. The treatments involved foliar spraying for 3 days before inducing WS by reducing soil moisture to 50% of field capacity, followed by 2 weeks of cultivation under normal or WS conditions. WS significantly reduced plant biomass, chlorophyll content, photosynthetic efficiency, water status, protein content, and total nitrogen content in roots and leaves. Concurrently, it elevated levels of leaf malondialdehyde, H2O2, proline, nitrate, and ammonium. WS also triggered an increase in antioxidant enzyme activity and osmolyte accumulation in soybean plants. Application of SA and TU enhanced the activities of key enzymes crucial for nitrogen assimilation and amino acid synthesis. Moreover, SA and TU improved plant growth, water status, chlorophyll content, photosynthetic efficiency, protein content, and total nitrogen content, while reducing oxidative stress and leaf proline levels. Indeed, the simultaneous application of SA and TU demonstrated a heightened impact compared to their separate use, suggesting a synergistic interaction. This study underscores the potential of SA and TU to enhance WS tolerance in soybean plants by modulating nitrogen metabolism and mitigating oxidative damage. These findings hold significant promise for improving crop productivity and quality in the face of escalating water limitations due to climate change.