Plant-derived smoke enhances maize tolerance to industrial effluent-induced oxidative stress

Industrial activities, particularly those in the sugar industry, generate large volumes of wastewater that threaten crop production and soil health. Maize, a major cereal crop, is highly sensitive to such stress conditions. This study aimed to determine the influence of sugar mill effluents (SME) at five concentrations (10, 25, 50, 75, and 100%) on the growth of maize and physiological, nutritional, and antioxidant parameters in the presence of plant-derived smoke (PDS) solution (1:500). It was found that a low concentration of SME (10%) had a significant positive effect on seed germination, root and shoot fresh weight, plant height, root number, chlorophyll a/b, carotenoids, and crude fiber content, but a high concentration (25-100) had a significant negative effect on these characteristics. Oxidative stress was also strongly induced by high SME concentrations because they induced antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). Notably, PDS co-application mitigated the adverse impacts of increased concentrations of SMEs by enhancing growth, photosynthetic pigments and regulating antioxidant enzymes activities. Further, physiochemical analysis of Chashma sugar mill effluent (SME) revealed that there were major deviations of WHO standards and high temperature, conductivity, turbidity, organic load, and heavy metals (Fe, Zn, Cd, Cu, Cr, Pb). Exposure of SME decreased the germination, growth, photosynthetic pigments, antioxidant activities and nutritional content of maize seeds in a concentration-dependent fashion. Plant-derived smoke (PDS, 1:500) reduced these effects, and improved germination, biomass, plant height, root number, pigments, antioxidants, and nutritional quality, fresh weight of roots under 100% SME, which improved by an average of 41%. PDS is an effective reliever of the phytotoxicity of the SMEs in maize. These results indicate that SME exerts a dual influence on maize, showing beneficial effects at lower concentrations and inhibitory effects at higher concentrations, while PDS application partially alleviated SME-induced stress and improved maize tolerance under controlled conditions.