Exogenous biostimulants: mechanisms and innovations for enhancing seed germination and resilience under abiotic...

Seed germination is a critical phase in the plant life cycle that is highly vulnerable to abiotic stresses such as drought, salinity, and extreme temperatures, posing a severe threat to global crop establishment and food security. Climate change is exacerbating these challenges, necessitating innovative strategies to enhance seed resilience.

This review comprehensively elucidates the physiological and biochemical mechanisms by which abiotic stress inhibits seed germination, focusing on disruptions in reactive oxygen species (ROS) homeostasis, phytohormone signaling, and energy metabolism. We further critically evaluate the potential of diverse exogenous substances including nanomaterials, phytohormones, metabolites, amino acids, and signaling molecules to mitigate these stresses.

We synthesize evidence demonstrating that exogenous substances can effectively enhance seed tolerance by modulating antioxidant defences, rebalancing hormonal crosstalk (particularly GA/ABA), and reprogramming energy metabolism. However, the transition from laboratory promise to field application faces significant hurdles, including cost-effectiveness, environmental safety, and short action cycles.

Looking beyond mere efficacy, this review proposes a transformative roadmap to overcome these limitations. We highlight the immense potential of integrating synthetic biology for sustainable biostimulant production, developing biosafe and biodegradable nanomaterials, and engineering stimulus-responsive nano-delivery systems for the targeted, on-demand release of active ingredients. We argue that the convergence of these multidisciplinary strategies is essential to bridge the lab-field gap and usher in a new era of intelligent, efficient, and sustainable seed technology, ultimately supporting the overarching goals of green agriculture and robust food systems.