Exogenous foliar application of melatonin mitigates salt induced oxidative stress and promotes growth in Gerbera jamosonii.

• Salt stress resulted in reduction of growth, chlorophyll contents. • MT treatment alleviated the oxidative damage of gerbera. • MT regulates ion homeostasis and antioxidant strategy in response to salt stress. • MT pretreatment improves growth and biomass of gerbera under salt stress. Salt stress is a major abiotic stress factor that is increasing at a continuos pace and pressurizing global food security in view of climate change. Therefore, plant scientists are developing strategies to ameliorate the negative effects of salt stress on crop production. Melatonin (N-acetyl-5-methoxytryptamine; MT) is a vital biological hormone in plants that modulates growth, development, and tolerance to extreme environmental conditions. Its exogenous application is used to improve resistance to various stressors. Gerbera (Gerbera jamosonii L. cv. Yunnanhong) is a vital ornamental flower crop moderately sensitive against salt stress. A series of experiments were conducted on gerbera plants grown under NaCl stress (150 mM) with or in the absence of MT at 0.1 and 0.2 mM. It was shown that salt stress reduced growth and physiological traits but also caused oxidative stress, as recorded by the induction of oxidative stress markers in cell tissues. Foliar application of MT, especially at the concentration of 0.2 mM, boosted plant growth, biomass production, photosynthetic pigments, and ameliorated oxidative stress. The decrease in oxidative stress was associated with improved antioxidant activity linked to the production of the enzymes catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD). Exogenous MT also improved potassium (K+) uptake and restricted sodium (Na+) uptake in the leaves of gerbera. In conclusion, optimal MT application may serve as a potential ameliorator of salt-induced oxidative stress and help in the regulation of salinity for gerbera production under the threat of climate change. [ABSTRACT FROM AUTHOR]