Melatonin, a molecule initially discovered in animals, has gained increasing importance in recent decades due to its wide range of functions in the plant kingdom. This review examines the role of melatonin in crops, from its biosynthesis to its effects on various stages of plant development, including germination, vegetative growth, flowering, and senescence. Melatonin has been shown to act as a biostimulant in plants, enhancing germination, improving tolerance to abiotic stresses such as drought and salinity, and boosting both photosynthesis and biomass production. Recent studies have underscored its importance in regulating the circadian cycle and the plant’s antioxidant response. Notable advances include research on high-value commercial crops, such as rice (Oryza sativa L.) and maize (Zea mays L.), where the exogenous application of melatonin has increased yield by 15% to 20% under stress conditions. The findings presented in this review highlight melatonin's potential, not only as a stress mitigator but also as a key component in the agronomic management of crops, enhancing productivity and sustainability in the face of current climate challenges. However, further research is needed to better understand its interactions with other phytohormones and its effectiveness across different agricultural species.
