Melatonin as a plant biostimulant in crops and during post‐harvest: a new approach is needed

A great amount of data covering a wide variety of plant species and experimental conditions has demonstrated the beneficial actions that melatonin exerts on many aspects of plant development, including germination, photosynthesis and water economy. Melatonin behaves especially well as a plant biostimulator against biotic and abiotic stressors, increasing stress tolerance. The present contribution sets out possible future multidisciplinary studies, in which the impact of using melatonin with respect to agriculture, food technology, human nutrition and the environment needs to be clearly established. In crops, the effective dose and best formulations for individual plant species and cultivation conditions should be studied. As regards post‐harvest, the focus should be on the half‐life time of melatonin in fruits and water‐residue treatments. Detailed studies are lacking on the human intake of phytomelatonin in different diets. Studies on the metabolization of phytomelatonin and the combined effect with other phytonutrients such as carotenoids, chlorophylls, flavonoids, fibers, etc., would also be of interest. In soils, the possible interaction between melatonin and microbiome and non‐vertebrate animals is of primordial interest. In terms of the environment, although melatonin is classified as a non‐hazardous agent, its limitations as a possible animal hormone disruptor have been suggested. Specific studies on the permanence of melatonin in plant tissues, plant by‐products, soil, freshwater and honeybees, amongst others, are proposed to obtain crucial information. © 2021 Society of Chemical Industry.