Morphogenetic, Ontogenetic and Diurnal Variability in Antimicrobial Activity of Bitter Fennel (Foeniculum vulgare Miller var. vulgare) Essential Oil

Background: There has been considerable interest in antimicrobial activity of plant essential oils in recent years. Objectives: This research was carried out to determine morphogenetic, ontogenetic and diurnal variability in antimicrobial activity of bitter fennel essential oil. Methods: To specify morphogenetic variability, leaf and root-bulb-stalk samples taken at pre-, full and post-flowering, flower samples picked at full flowering and seed samples gathered at two seed growth stages were used. For ontogenetic and diurnal variability, whole plant samples were taken at pre-, full and post-flowering and at 9:00 am, 1:00 pm and 5:00 pm. A total of 10 microorganisms have been used to determine antimicrobial activity of essential oils with disc-diffusion and microdilution broth methods. Results: The highest inhibitory effect among leaf essential oils was observed from post-flowering samples, but essential oils of root-bulb-stalk samples of pre-flowering produced the highest antimicrobial activity. Whole plant essential oils of post-flowering samples produced higher antimicrobial activity than those of pre- and full flowering samples. Generally, inhibitory effect of seed essential oils extracted at the beginning of seed formation was higher than those of seed maturity. Daily harvesting time caused no effect on antimicrobial activity of essential oils of whole plant samples. Conclusion: The present study reveals that antimicrobial activity of bitter fennel essential oil significantly vary based on plant parts and growth stages.