Regulating Oxidative Stress and Enzymatic Antioxidants Under Saline Stress in <i>Washingtonia filifera</i> Using Melatonin

Abstract The current study was performed in the canopy in Coll. of Agric., Univ. of Basrah during the season (1-10-2023 to 30-5-2024), to investigate the effect of foliar application of melatonin at three concentrations (0, 50 and 100 mg L −1 ) and irrigation with water with salinity (2, 6 and 12 mS cm −1 ) on Washingtonia filifera seedlings. The results showed significant effects of melatonin and saltstress on oxidative stress indicators and enzymatic antioxidants. Irrigation led to water with a salinity of 12 mS cm −1 reduced the MSI rat (71.920) % and an increase in H 2 O 2 levels (0.8956) micromole g −1 and MDA (2.4733) nanomolegm −1 , as well as increasing the effectiveness of antioxidant enzymes POD, Super Oxidase and GPx, which reached (25.023, 3.8100 and 17.822) units minute −1 g −1 , respectively. Spraying melatonin at 100 mg − l increased MSI (80.244%) and reduced H 2 O 2 levels (0.7334) micromole g −1 and MDA (1.9167) nanomole gm −1 , as well as increasing the effectiveness of the antioxidant enzymes POD, Super Oxidase and GPx, which reached (26.318, 3.8133 and 18.288) units minute −1 g −1 , respectively Additionally, the majority of the features under study increased as a result of the combined interaction between salinity and melatonin, particularly at high concentrations, whereas some other qualities, such H 2 O 2 and MDA, decreased.