Effect of Putrescine and Nitric Oxide on Morphological, Biochemical and Postharvest Characteristics of Rose ‘Avalanche’

 The genus Rosa from the family Rosaceae with over 150 species is one of the most important ornamental plants in the world. From a commercial point of view, cut roses play a key role in trade of cut flowers. Nitric oxide regulates key physiological processes that depend on the concentration of this compound such as hypocotyls growth, defensive responses, growth and development, photosynthesis, and phytoalexin generation in stressful conditions. Polyamines are key biomolecules that have a role to play in the regulation of many plants’ growth and development processes and their responses to different environmental stimuli. This study was performed to investigate the effect of foliar application of sodium nitroprusside (as a NO donor) and putrescine (as a polyamine) on ‘Avalanche’ rose in hydroponic conditions.

 This study was conducted in the research and production greenhouses of Urmia University and the research laboratory of the Department of Horticultural Sciences of the Faculty of Agriculture in 2019-2020 on rose (Rosa hybrida ‘Avalanche). This experiment was conducted as a factorial trial based on completely randomized design with two factors including sodium nitroprusside in four concentrations of 0, 50, 100 and 200 μM and putrescine in four concentrations of 0, 1, 2 and 4 mM with 3 replications as a foliar application under hydroponic conditions in greenhouses and in pots. The treatments were applied two weeks after transplantation, every 15 day-interval for 4 months. In order to investigate the effects of putrescine and sodium nitroprusside on some morphological and physiological characteristics of plants, two weeks after the end of treatments, sampling was performed to measure morphological and physiological characteristics. The measured indicators included: fresh and dry weight of flowering stem, chlorophyll a, b and total chlorophyll, carotenoids and also in the postharvest stage were guaiacol peroxidase and ascorbate peroxidase enzymes activity and bending of flowering stem. The SAS software version 9.2 was used to analyze the variance and compare the mean of the studied traits. Comparison of means was performed using the Tukey’s range test method at a probability level of 1 and 5%. Also, Excel (2016) software was used to draw the graph.

 According to the means comparison of measured parameters, sodium nitroprusside along with putrescine increase the flowering stem fresh and dry weight, photosynthetic pigments of leaves and antioxidant enzymes activities at the postharvest stages. Sodium nitroprusside at a concentration of 50 μM with 4 mM putrescine increased the fresh and dry weight of the flowering stem. Also, the concentration of 100 μM sodium nitroprusside with 4 mM putrescine significantly increased chlorophyll a, b, total chlorophyll and carotenoid content compared to control. It should be noted that preharvest application of sodium nitroprusside along with putrescine cause to improve postharvest characteristics of rose. In this research, application of 100 and 200 μM SNP alone or with different concentrations of putrescine increased guaiacol peroxidase and ascorbate peroxidase activity and reduced bending of flowering stem of rose ‘Avalanche’ at the postharvest stage. Probably polyamines (such as putrescine) and nitric oxide increase photosynthesis potential with increasing photosynthetic pigments and protecting cell membranes thus increase growth and flowering traits of plants such as increasing the flowering stem weight of rose in this research. At postharvest stage, senescence of flowers is an inevitable phenomenon that cause to produce free radicles in plants. Free radicles injure the plant membranes lipids and change the antioxidant enzymes activities. This despite the fact that nitric oxide and putrescine protect antioxidant enzymes against free radicles as a result can improve vase life of rose.   

 Based on the results of the present study, it can be concluded that putrescine, with SNP, improves growth characteristics as well as increases the postharvest traits and quality of cut flowers of rose.  According to the results, it is observed that among the different concentrations of putrescine, the concentration of 4 mM had the greatest effect on the growth and physiological parameters of rose while the concentration of 100 and 200 μM sodium nitroprusside had a greatest effect on physiological characteristics and postharvest traits of rose. In general, both SNP and putrescine had a positive and favorable effects on improving growth and postharvest indices, but the effective concentration varied depending on the type of parameter.