Effects of Melatonin and Sodium Nitroprusside (SNP) Spray on Salinity Adjustment and Improving the Morpho-physiological Traits of Cut Flower Gerbera Jamesonii

Melatonin has different physiological functions in plants, such as active growth regulator signal. A factorial experiment, based on randomized complete blocks design, was carried out in order to evaluate of the effect of melatonin and sodium nitroprusside (SNP) on morpho-physiological traits of cut flower Gerbera (Gerbera jamesonii cv. Malibu) under salinity stress. The first factor in this experiment was melatonin and SNP at 5 levels (control (without melatonin and SNP), 0.1 mM melatonin + 0 SNP, 0.1 mM melatonin + 10 µM SNP, 0.2 mM melatonin + 0 SNP, 0.2 mM melatonin + 10 µM SNP) and the second factor consisted of irrigation water with two levels of electrical conductivity (i.e., 2 and 4 dS/m). The studied traits consisted of soluble solids, cell membrane stability, leaf, shoot and root water potential, water use efficiency, reduced glucose, different kinds of chlorophyll, carotenoid, proline, superoxide dismutase, catalase, ascorbate peroxidase, polyphenol oxidase and total protein content. Based on the means’ comparisons, 0.1 mM melatonin + 10 μM SNP, 0.2 mM melatonin + 0 SNP and 0.2 mM melatonin + 10 μM SNP treatments had the highest membrane stability at 2 dS/m salinity level, and with increasing the salinity level to 4 dS/m, the membrane stability decreased. The amounts of chlorophylls a, b and total in the 0.1 mM melatonin + 10 μM SNP, 0.2 mM melatonin + 0 SNP and 0.2 mM melatonin + 10 μm SNP were significantly higher than control and 0.1 mM melatonin treatments. The amounts of SOD, CAT, and APX enzymes increased when combined with melatonin and SNP in comparison to the control. Therefore, melatonin and SNP can be recommended as an effective and very useful combination in the resistance of gerbera cut flower to salt stress conditions.