The effect of Ascorbic acid and Melatonin on Morphophysiological Characteristics and Salinity Tolerance of Miniature Rose (Rosa chinensis var. minima)

Soil salinity is a major abiotic constraint affecting crop yield and quality of ornamental plants. The current study aimed to investigate the melatonin and ascorbic acid regulator on the morphological and physiological characteristics of miniature roses under salinity stress, in the research greenhouse of Agriculture and Natural Resources Campus, University of Tehran, located in Karaj, on biennial cuttings of miniature roses, in plastic pots with a diameter of 14 cm containing cocopeat and perlite (1: 1), in the randomized complete block design with four replications, in the spring of 2018. The studied factors included foliar application of melatonin (at four concentrations of 0, 1, 10, and 100 μM) and ascorbic acid (at three concentrations of 0.5, 1.5, and 3 mM) and combined treatment containing two levels of melatonin 1 μM × ascorbic acid 0.5 mM and melatonin 1 μM × ascorbic acid 1.5 mM and salinity stress at three levels of zero, four and eight dS/m. The results showed that the salinity stress generally reduced morphological characteristics; in this study, the most effective treatment in the foliar application was observed with 3 mM ascorbic acid treatment, which increased the number of flowers and branch height by 36% and 86%, respectively, compared to the control. Foliar application of melatonin 100 μM showed the highest effect on the concentration of nitrogen and potassium equal to 43% and 11% as compared to the control, respectively. Accumulation of soluble sugars during salinity stress conserving osmotic potential and reducing dehydration, and the leaf soluble sugar increased by 11% as compared to the control and proline was observed in foliar application with 1 μM melatonin treatment. The results of this study showed that the ability of this antioxidant (Ascorbic acid 3 mM) can be used to improve the growth and development of miniature roses under salinity stress.