The effect of ascorbic acid on flower yield, quantity and quality of rose essential oil

To investigate the effect of ascorbic acid on improving flower yield and the quantity and quality of rose essential oil, an experiment was designed in a randomized complete blocks design with four replications in a rose orchard in Hamoon County (Sistan Region, Iran) during the 2022–2023 year. The treatments studied were four different concentrations of ascorbic acid including 0, 50, 100 and 200 mg/L. Traits such as the number of flowers per plant, Fresh and dry petal yield per hectare, essential oil percentage, total phenol content, total flavonoid content, and antioxidant activity were measured. The chemical compounds of the flower essential oil were identified using a gas chromatography-mass spectrometer (GC-MS). The results showed that ascorbic acid at different concentrations increased the number of flowers per plant, fresh and dry petal yield, and essential oil content. However, the increase in traits depended on the concentration of this antioxidant, so that at the highest concentration, it caused a greater increase in all the mentioned traits. Fresh and dry petal yield increased by 25.08% and 27.72% under this treatment compared to the control. Total phenolic content, total flavonoid content, and antioxidant activity (DPPH) increased with an increasing ascorbic acid concentration. GC-MS results showed that the main compounds constituting the essential oil of the control plants (not sprayed with ascorbic acid) were d-Limonene, Phenylethyl Alcohol, Decane, 9,17-Octadecadienal, 1,2-Benzenedicarboxylic acid, 9,12-Octadecadienoic acid and Dodecane. The effect of ascorbic acid on the content of flower essential oil varied depending on the concentration of this antioxidant and led to an increase or decrease in compounds and the appearance of novel compounds such as Beta-Isobicyclogermacrene and Phthalic acid. Under ascorbic acid treatment at a concentration of 200 mg/L, the novel compounds were revealed that showed antimicrobial properties. Therefore, the antioxidant ascorbic acid can be used as a suitable solution to increase flower yield and the quantity and quality of rose essential oil for its commercialization.