Interactive impacts of heat stress and microplastics contamination on the growth and biochemical response of wheat (Triticum aestivum) and maize (Zea mays) plants

The increasing global temperatures, driven largely by anthropogenic activities, pose a significant threat to crops worldwide, with heat stress (HS) emerging as one of the most severe challenges to agricultural productivity. Among the numerous human-induced pressures threatening terrestrial ecosystems globally, microplastics (MPs) represent one of the most persistent and urgent concerns. This study investigated the effects of heat stress (HS) at 35 °C and 40 °C (12 h exposure) on wheat (Triticum aestivum) and maize (Zea mays) grown in soil contaminated with polyethylene microplastics (PE-MPs; 0.01%, 0.1%, and 1% w/w), assessing their physiological and biochemical responses. The results indicated a significant (p < 0.05) reduction in plant height, root length, leaf area, chlorophyll content, and biomass of the selected plants due to MPs application. HS alone and in co-exposure with MPs caused damage to plant tissues as shown by significant (p < 0.05) reactive oxygen species (ROS) production, and lipid peroxidation. Under ROS induction, proline and antioxidant enzymes (CAT, POD, SOD) exhibited significantly (p < 0.05) higher levels in combined stress (HS + MPs) than in individual treatments. In conclusion, wheat exhibited higher levels of H2O2 and MDA stress markers indicating increased oxidative stress compared to maize. In contrast, maize showed elevated levels of proline, CAT, POD, and SOD, suggesting greater resistance to environmental stresses than wheat. Our results provide new understandings of sustainable agriculture practices and hold vast promise in addressing the challenges of HS and MP stresses in agricultural soils.