Brassinosteroids as phytohormonal shields against micro- and nanoplastic stress in plants
Microplastics (MPs) and nanoplastics (NPs) are biologically active stressors in agricultural soils, where they alter soil physical structure, disrupt rhizosphere processes, impair water and nutrient acquisition, and provoke oxidative and hormonal disequilibrium in plants. Brassinosteroids (BRs), particularly brassinolide and 24-epibrassinolide, have recently emerged as modulators of plant responses to plastic-particle stress. Current evidence indicates that BRs do not detoxify plastics directly. Instead, they reorganize plant performance across interconnected layers: aquaporin-linked NP transport, antioxidant and ascorbate-glutathione metabolism, photosystem II function, hormone crosstalk, secondary metabolism, and rhizosphere feedbacks. In tomato, BRs reduced polystyrene-NP accumulation in edible tissues by suppressing aquaporin genes. In Pinellia ternata and rice, BRs attenuated MP/NP-induced growth inhibition by restoring photosynthetic efficiency and redox control. This mini review synthesizes these findings and frames BRs as eco-hormonal regulators of the plant-plastic-soil interface, while highlighting priorities for field-realistic validation.