Potential of plant growth regulators associated with nanostructures for sustainable agriculture

The growing demand for more productive and sustainable agricultural systems has driven the use of plant growth regulators (PGRs), essential in coordinating physiological processes such as germination, root development, hormonal signaling, antioxidant defense, and photosynthesis. However, significant limitations—such as chemical instability, rapid degradation, low release efficiency, and sensitivity to environmental factors—reduce the performance of conventionally applied PGRs. In this scenario, nanostructures emerge as strategic tools to optimize the action of PGRs, offering greater stability, molecular protection, controlled release, and efficient targeting to plant tissues. Recent evidence demonstrates that nanocarriers can increase vigor, productivity, stress tolerance, and metabolic efficiency of plants by modulating physiological pathways, balancing reactive species, and enhancing the internal translocation of compounds. Despite the advances, negative responses are also reported, highlighting the importance of controlling the physicochemical properties of nanoparticles to ensure safety and efficacy. This study aims to discuss the potential and challenges of nanoformulations in promoting more efficient, resilient, and environmentally sustainable agriculture. Comprehensively compile and integrate current knowledge on: (i) biosynthesis, signaling, and functions of major classes of phytohormones; (ii) interactions between nanostructures and plants, including absorption, translocation, and physiological effects; (iii) encapsulation technologies and release mechanisms of plant growth regulators; and (iv) impacts of nanostructures on germination, growth, antioxidant systems, reactive species, and photosynthesis. By critically gathering and interpreting recent results, this work offers an updated overview of the potential, limitations, and prospects of integrating nanomaterials and growth regulators for applications in sustainable agriculture.