Polyamine defense shield of plants against biotic and abiotic stress

• Polyamines (PAs) are critical defense system in plants • PAs enhance stress tolerance under biotic and abiotic stress conditions. • PA biosynthesis modulates stress resilience and plant growth trade-offs. • PAs interact with ROS, phytohormones, and nitric oxide to modulates stress responses. • PA-mediated stress amelioration is important for plant growth and climate-resilience. Adverse environmental conditions impair plant growth and development, leading to reduced biodiversity and threatens global food security. Polyamines (PAs) are essential nitrogenous compounds, play a pivotal role in plant stress physiology, acting as a plants defense shield against biotic and abiotic stressors. PAs function in maintaining cellular integrity, modulating antioxidant defenses, and regulating gene expression, which are vital for plant survival under adverse environmental conditions and their combinations. PAs stabilize cellular structures, protect proteins, and interact with signaling molecules such as reactive oxygen species (ROS) and phytohormones, thereby enhancing stress tolerance. However, the biosynthesis of PAs is metabolically costly, requiring significant energy and resource allocation, which impact plants growth and reproduction. The balance between the metabolic costs and the benefits of enhanced stress tolerance is crucial for plant fitness and productivity. Recent advancements in genetic and molecular engineering, including overexpression and knockout studies, have demonstrated the potential of manipulating polyamine biosynthesis to improve stress resilience in plants. Despite these advancements, the intricate molecular mechanisms underlying polyamine-mediated stress responses remain poorly understood. Future research should focus on elucidating these mechanisms, optimizing polyamine levels to enhance stress tolerance without compromising growth, contribute to the development of resilient crop varieties capable of sustaining food security in the face of climate change and increasing environmental stressors. This review underscores the importance of PAs in plant stress physiology and provides a comprehensive framework for future research aimed at enhancing crop resilience, ecosystem biodiversity and food security under biotic and abiotic stresses and their combinations.