Akademik Veri Yönetim Sistemi
INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY, cilt.23, sa.3, ss.1-20, 2026 (SCI-Expanded, Scopus)
Salt stress is one of the most important environmental factors limiting onion cultivation worldwide. This study investigated the effects of different doses of melatonin on some phenological characteristics and biochemistry of three onion genotypes with different dry skin colors under salinity stress. Onion seedlings treated with 0, 4, and 8 μM exogenous melatonin at certain stages of development were grown under stress conditions irrigated with 0, 150, and 300 mM NaCl. Phenotypic traits were evaluated, such as the number of leaves, length of the longest leaf, diameter of the white pseudostem, leaf erectness, whole-plant fresh weight, degree of leaf waxiness, and bulb weight. In addition, the total amount of phenolic substances, flavonoids, soluble protein, antioxidant capacity, and carotenoid and chlorophyll contents were also measured. Salt-induced phytotoxicity markedly affected the development and physiology of all onion cultivars. The degree of salt stress and the level of melatonin that provided the most effective response differed for each cultivar. For example, 8 µM melatonin supplementation was effective in the Burgaz cultivar to stop the decrease in whole plant weight under 300 mM salt stress conditions. In the Gence cultivar samples grown under 300 mM salt stress without melatonin addition, total phenolic matter content increased with the addition of 4 µM melatonin and decreased with the addition of 8 µM melatonin. Nevertheless, improvements in some morphological parameters, phenolic, flavonoid, and antioxidant contents, as well as higher chlorophyll contents in plant tissues, indicated that exogenous melatonin application may effectively enhance onions’ salt tolerance.