Seed Bio-priming to Improve Germination, Seedling Growth and Essential Oil Yield of Dracocephalum Kotschyi Boiss, an Endangered Medicinal Plant in Iran

The study was conducted to evaluate the effects of 10 and 20min seed soaking in Azotobacter chroococcum and Bacillus polymixa suspension culture on seed germination, seedling growth and essential oil yield of Dracocephalum kotschyi Boiss. Up to day 13, 20min of B. polymixa suspension culture soaking seeds had shown germination more than 20%, whereas control seeds did not begin germination until day 13. The highest germination rate (1.67) was observed with 20min of B. polymixa suspension culture soaking seeds. B. polymixa improved seedling length and vigour index more than those of A. chroococcum suspension culture soaking seeds. The highest fresh (81.06g) and dry weight (11.76g), relative leaf chlorophyll content (42.24) and Fv/Fm ratio (0.66) of emerging D. Kotschyi seedlings were recorded with seed bio-priming with B. polymixa for 20min. The main components affected by B. polymixa and A. chroococcum were limonene, alpha-pinene, gamma-terpinene, caryophyllene oxide, germacrene D and terpinen-4-ol. The highest percentage of essential oil constituents (97.6%) of D. Kotschyi seedlings were observed with 20min of B. polymixa suspension culture soaking seeds. The results indicated that seed bio-priming with B. polymixa for 20min was more effective than the other treatments concerning seed germination, seedling growth and essential oil yield of D. Kotschyi.