Soil salinity, a major environmental concern, significantly reduces plant growth and production all around the world. Finding solutions to reduce the salinity impacts on plants is critical for global food security. In recent years, the priming of plants with organic chemicals has shown to be a viable approach for the alleviation of salinity effects in plants. The current study examined the effects of exogenous ethanol in triggering salinity acclimatization responses in soybean by investigating growth responses, and numerous physiological and biochemical features. Foliar ethanol application to saline water-treated soybean plants resulted in an enhancement of biomass, leaf area, photosynthetic pigment contents, net photosynthetic rate, shoot relative water content, water use efficiency, and K⁺ and Mg²⁺ contents, leading to improved growth performance under salinity. Salt stress significantly enhanced the contents of reactive oxygen species (ROS), malondialdehyde, and electrolyte leakage in the leaves, suggesting salt-induced oxidative stress and membrane damage in soybean plants. In contrast, ethanol treatment of salt-treated soybean plants boosted ROS-detoxification mechanisms by enhancing the activities of antioxidant enzymes, including peroxidase, ascorbate peroxidase, catalase, and glutathione S-transferase. Ethanol application also augmented the levels of proline and total free amino acids in salt-exposed plants, implying a role of ethanol in maintaining osmotic adjustment in response to salt stress. Notably, exogenous ethanol decreased Na⁺ uptake while increasing K⁺ and Mg²⁺ uptake and their partitioning to leaves and roots in salt-stressed plants. Overall, our findings reveal the protective roles of ethanol against salinity in soybean and suggest that the use of this cost-effective and easily accessible ethanol in salinity mitigation could be an effective approach to increase soybean production in salt-affected areas.

Metalloid pollution, including arsenic poisoning, is a serious environmental issue, plaguing plant productivity and quality of life worldwide. Biochar, a carbon-rich material, has been known to alleviate the negative effects of environmental pollutants on plants. However, the specific role of biochar in mitigating arsenic stress in maize remains relatively unexplored. Here, we elucidated the functions of biochar in improving maize growth under the elevated level of sodium arsenate (Na₂AsO₄, As^V). Maize plants were grown in pot-soils amended with two doses of biochar (2.5% (B1) and 5.0% (B2) biochar Kg⁻¹ of soil) for 5 days, followed by exposure to Na₂AsO₄ ('B1 + As^V'and 'B2 + As^V') for 9 days. Maize plants exposed to As^V only accumulated substantial amount of arsenic in both roots and leaves, triggering severe phytotoxic effects, including stunted growth, leaf-yellowing, chlorosis, reduced photosynthesis, and nutritional imbalance, when compared with control plants. Contrariwise, biochar addition improved the phenotype and growth of As^V-stressed maize plants by reducing root-to-leaf As^V translocation (by 46.56 and 57.46% in ‘B1 + As^V’ and ‘B2 + As^V’ plants), improving gas-exchange attributes, and elevating chlorophylls and mineral levels beyond As^V-stressed plants. Biochar pretreatment also substantially counteracted As^V-induced oxidative stress by lowering reactive oxygen species accumulation, lipoxygenase activity, malondialdehyde level, and electrolyte leakage. Less oxidative stress in ‘B1 + As^V’ and ‘B2 + As^V’ plants likely supported by a strong antioxidant system powered by biochar-mediated increased activities of superoxide dismutase (by 25.12 and 46.55%), catalase (51.78 and 82.82%), and glutathione S-transferase (61.48 and 153.83%), and improved flavonoid levels (41.48 and 75.37%, respectively). Furthermore, increased levels of soluble sugars and free amino acids also correlated with improved leaf relative water content, suggesting a better osmotic acclimatization mechanism in biochar-pretreated As^V-exposed plants. Overall, our findings provided mechanistic insight into how biochar facilitates maize’s active recovery from As^V-stress, implying that biochar application may be a viable technique for mitigating negative effects of arsenic in maize, and perhaps, in other important cereal crops. Graphical Abstract

Drought is recognized as a paramount threat to sustainable agricultural productivity. This threat has grown more severe in the age of global climate change. As a result, finding a long-term solution to increase plants’ tolerance to drought stress has been a key research focus. Applications of chemicals such as zinc (Zn) may provide a simpler, less time-consuming, and effective technique for boosting the plant’s resilience to drought. The present study gathers persuasive evidence on the potential roles of zinc sulphate (ZnSO₄·7H₂O; 1.0 g Kg⁻¹ soil) and zinc oxide (ZnO; 1.0 g Kg⁻¹ soil) in promoting tolerance of cotton plants exposed to drought at the first square stage, by exploring various physiological, morphological, and biochemical features. Soil supplementation of ZnSO₄ or ZnO to cotton plants improved their shoot biomass, root dry weight, leaf area, photosynthetic performance, and water-use efficiency under drought stress. Zn application further reduced the drought-induced accumulations of H₂O₂ and malondialdehyde, and electrolyte leakage in stressed plants. Antioxidant assays revealed that Zn supplements, particularly ZnSO₄, reduced reactive oxygen species (ROS) accumulation by increasing the activities of a range of ROS quenchers, such as catalase, ascorbate peroxidase, glutathione S-transferase, and guaiacol peroxidase, to protect the plants against ROS-induced oxidative damage during drought stress. Increased leaf relative water contents along with increased water-soluble protein contents may indicate the role of Zn in improving the plant’s water status under water-deficient conditions. The results of the current study also suggested that, in general, ZnSO₄ supplementation more effectively increased cotton drought tolerance than ZnO supplementation, thereby suggesting ZnSO₄ as a potential chemical to curtail drought-induced detrimental effects in water-limited soil conditions.