Changes in yield and essential oil composition of fennel aerial parts across different growth stages in response to foliar application of pyrogallol

This study aimed to reduce the adverse effects of sandy soil stress on fennel (Foeniculum vulgare var. vulgare) plants (a natural source of essential oil) by applying pyrogallol to enhance their adaptation to such conditions. Plants were sprayed with pyrogallol at 50, 100, 150, and 300 mg L⁻¹, along with distilled water (as control). Aerial parts yield and essential oil composition were assessed across the vegetative, flowering, green fruiting, and mature fruiting stages. At mature fruiting stage, the greatest aerial part weight (108.15 g plant⁻¹) was obtained with 150 mg L⁻¹ pyrogallol, whereas the highest essential oil yield (1.96% and 1900.87 mg plant⁻¹) was observed in plants treated with 300 mg L⁻¹ pyrogallol. Limonene and estragole were found to be the dominant constituents, whereas monoterpene hydrocarbons and oxygenated monoterpenes constituted the primary groups. At mature fruiting stage, the maximum limonene content (270.3 mg plant⁻¹) was obtained with 100 mg L⁻¹ pyrogallol, while treatment with 300 mg L⁻¹ pyrogallol resulted in the highest levels of monoterpene hydrocarbons (243.2 mg plant⁻¹), estragole (1590.3 mg plant⁻¹), and oxygenated monoterpenes (1651.1 mg plant⁻¹).