Contamination by heavy metals has severely hampered agricultural productivity across the world. Cadmium (Cd) is one of the most dangerous heavy metals to plants. Melatonin (ME), a stress-relief hormone, has been extensively utilized to reduce phytotoxicity caused by heavy metals. In this work, we examined how ME reduced Cd damage in strawberry seedlings. The results revealed that Cd stress dramatically reduced growth characteristics (fresh and dry weight, root and shoot length), leaf gas exchange elements, and pigments content (chlorophyll a and chlorophyll b) in strawberry seedlings. In contrast, ME application efficiently enhanced growth and biomass production, increased net photosynthetic rate, and improved pigments molecules in strawberry seedling under Cd toxicity. Cadmium treatment effectively improved the level of malondialdehyde (MDA) and hydrogen peroxide (H2O2), whereas ME strictly counterbalanced these oxidative stress markers. Furthermore, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), were dominantly increased by ME. Additionally, ME supplementation significantly improved secondary metabolites (phenols, anthocyanin, and flavonoids) content, and these metabolites potentially restricted excess H2O2 accumulation. In conclusion, our results revealed that ME might help to reduce Cd-induced phytotoxicity in strawberry seedlings by increasing growth, photosynthesis, redox homeostasis, and secondary metabolites.
