Co-application of biochar and selenium nanoparticles improves yield and modifies fatty acid profile and essential oil composition of fennel (Foeniculum vulgare Mill.) under cadmium toxicity.

Fatty acids and essential oils (EOs) are the primary variables that influence the quality of fennel (Foeniculum vulgare Mill.). Soil toxicity to cadmium (Cd) is the main environmental issue facing fennel, and priming methods like soil amendments and nanoparticles (NPs) are commonly utilized to deal with it. The goal of the current study was to examine the effects of biochar (BC) and selenium nanoparticles (Se NPs) on fennel plants in Cd-contaminated soils. The pot experiment was conducted with Cd stress at 0, 10, and 20 mg kg-1 soil, BC at 5% (v/v), and foliar-spraying Se NPs at 40 mg L-1 as a factorial completely randomized design (CRD) at a greenhouse condition in 2022. The findings demonstrated that Cd toxicity significantly decreased plant performance, while BC and Se NPs enhanced it. Without BC and Se NPs, Cd toxicity at 20 mg kg-1 soil decreased biological yield (39%), seed yield (37%), EO yield (32%), and monounsaturated fatty acids (14%), while increased saturated fatty acid (26%) and polyunsaturated fatty acids (40%) of fennel. The main EO profile was anethole (65.32-73.25%), followed by limonene (16.12-22.07%), fenchone (5.57-6.83%), and estragole (2.25-3.65%), which mainly were oxygenated monoterpenes. The combined application of BC and Se NPs improved the yield, EO production, and fatty acid profile of fennel plants under Cd stress, increasing the plants' resistance to Cd toxicity.