Snapdragon is an herbaceous annual plant with large diversities in color and shape and a long flowering period; it is a resistant and semi-resistant plant from scrophulariaceae family. It is used as either cut flower or garden plant. The use of fertilizers with no side effects is necessary for the nature. Humic acid has been named amongst the nature-friendly organic fertilizers. In the present study, the effects of on-soil humic acid application in four concentrations (0mg/l, 50mg/l, 100mg/l

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... 200mg/l) and foliar iron oxide nanoparticles' foliar sprays in four levels (0mg/l, 150mg/l, 300mg/l and 450mg/l) have been investigated on the quantitative and qualitative traits of snapdragon, Montego Rose Bicolor Variety. To do so, a factorial experiment within the format of complete randomized block design was carried out in three replications. The measured variables were plant height, number of florets, the emergence time of the first florets, wet and dry weights of the aerial organs and root, electrolyte leakage, total phenol, amount of soluble sugar, chlorophyll content and anthocyanin amount. Based on the results obtained from variance analysis, the mutual effect of humic acid and iron oxide nanoparticles was significant increase in the percentages of such traits as the length of the flower cluster, flower persistence, wet root weight, dry root weight, dry weight of the aerial organs, chlorophyll a, chlorophyll b, total chlorophyll, sugar content and electrolyte leakage in a 1% level. The effect of iron oxide nanoparticles alone was also significant increase in a 1% level in such traits as the wet weight of the aerial organs, total phenol content and anthocyanin amount but the plant height, number of ancillary branches, number of nodes, number of open florets, number of closed florets, the total number of florets and the time of the second series of flowering were not influenced by any of the applied treatments. The maximum amounts of the dry weight of the aerial organs (0.032g), the amount of chlorophyll b (16.91mg/g.wet weight) and sugar content (0.76mg/g.wet weight) were observed in Fe300Hu50 treatment; the maximum amounts of phenol (2.88mg/g.wet weight) and flower persistence (95.66 days) were observed in Fe150Hu0 treatment and the highest rates of total chlorophyll (30.78mg/g.wet weight), length of the flower cluster (5.9cm) and the lowest electrolyte leakage (21.23%) were seen in Fe300Hu100, Fe450Hu50 and Fe450Hu100 treatments. Keywords: dry weight of the aerial organs, photosynthetic pigments, electrolyte leakage, nutrition Introduction: The population increase and expansion in the urban and industrial life not only causes decrease in the natural green spaces but it also brings about an increase in the pollutants and threatens the physical and psychological health of the human beings. Therefore, the expansion of the green spaces and the use of ornamental plants in parks and urban spaces are being increased for reducing the pollutions and enhancing the human health. Nowadays, besides satisfying the psychological and mental needs worldwide, the ornamental plants bring billions of dollars to the producing countries in the global markets and this has enticed a larger deal of attention in the countries to these plants . In Iran, the flowers and plants have been commonly used in designing green spaces since 3000 years ago but the commercial production of them dates back to 90 years ago. Foreign currency spent on ornamental plants is equivalent to one percent of production expenses and this is reflective of the very low cost of producing them in contrast to the other agricultural crops.