The effects of foliar application of some micronutrient elements on the content and composition of the essential oil of Damask rose (Rosa damascena Mill.)

The present study was conducted to investigate the effects of micronutrient elements (Fe, Cu, Zn and Mn) application on the content and composition of essential oil of Damask rose (Rosa damascena Mill.) flowers in southwestern Iran (Shahrekord) in 2019 and 2020. Four foliar fertilizers including Librel Fe-Lo, Librel Cu, Librel Zn and Librel Mn were applied as mineral fertilizers. Librel Fe-Lo contains 13.2% chelated iron, Librel Zn is a foliar fertilizer with 14% Zinc in chelated form, Librel Cu has 14% copper in chelated form, and Librel Mn is comprised of 13% Mn chelated with EDTA. Results obtained from gas chromatography/mass spectrometry (GC-MS) showed 36 essential oil components. The highest (0.11-0.14%) and lowest (0.03-0.05%) levels of essential oil content were obtained from combined Fe, Cu, Zn and Mn treatment and control treatment, respectively. Plants treated by the combinations of 40 ppm of micronutrients (Fe3Cu3Zn3Mn3 treatment) and control produced the greatest and lowest amounts in most essential oil components, respectively. The predominant components of the essential oil included oxygenated monoterpenes including beta-citronellol (22.5-28.1%), geraniol (15.1-23.1%), camphor (0.86-2.3%), citronellol (0.4-1.9%), trans-geraniol (0.5-2.1%), together with aliphatic hydrocarbons  including nonadecane (11.1-13.3%), pentadecane (3.55-8.9%), and heneicosane (4.5-8.7%). Application higher than 40 ppm of micronutrients, most possibly due to toxicity, lowered both content and composition of essential oil.