Effect of melatonin on the contents of fatty acids and antioxidants of saffron.

Early leaf senescence at the end of the growing season poses a significant challenge in saffron cultivation. While changes in leaf composition during senescence have been extensively documented in various plants, similar studies on saffron remain unexplored. Furthermore, there has been no investigation into the potential role of melatonin in delaying leaf senescence in saffron. This study aimed to examine the changes in saffron leaf composition and evaluate the effects of melatonin foliar application during the late growth stage. The research was conducted over two consecutive cropping years (2020-2021 and 2021-2022). In the first experiment, five concentrations of melatonin (0, 50, 100, 150, and 200 μM) were applied as foliar sprays to assess their effects on fatty acid composition and plant greenness. The second experiment involved varying melatonin concentrations and two application timings (124 and 131 days after germination) to study their impact on antioxidant enzyme activity. Both experiments were designed as factorial trials within a completely randomized block design with three replicates. The results demonstrated that treatment with 100 μM melatonin significantly increased the production of fatty acids, including C8:0 (67.60 %), C10:0 (98.66 %), C12:0 (40.73 %), and C18:0 (35.32 %) compared to the untreated control. Also, the highest activities of ascorbate peroxidase and catalase enzymes were observed with 100 μM melatonin applied 124 days after germination. On the same day, the highest total protein content was recorded with 50 μM melatonin, although it was not significantly different from the 100 μM treatment. In conclusion, the 100 μM melatonin treatment was found to be the most effective in enhancing plant greenness, modifying fatty acid composition, boosting antioxidant enzyme activity, and increasing total protein content. However, the timing of melatonin application emerged as a critical factor warranting careful consideration. These findings highlight the promising role of melatonin in improving the physiological and biochemical attributes of saffron plants.