Assessing the Biostimulant Effects and Antimicrobial Activity of Lavandula Angustifolia Essential Oil

Abstract Biostimulation is a well-known method for enhancing plant growth. Several natural and artificial compounds have demonstrated efficacy in promoting plant growth and development by initiating specific physiological processes. The main objective of this research was to evaluate the antimicrobial activity and the biostimulant effect of Lavandula angustifolia essential oil on radish, which was selected as representative vegetable crop species. The chemical composition of the lavender essential oil (LEO) was characterized and used for antimicrobial assays on 6 microorganisms at different concentrations (2.0, 4.0 and 8.0%) and biostimulant tests (0.5, 1.0, 2.0 and 4.0%). LEO biostimulant effect was tested on two independent radish cycles performed in a Mediterranean greenhouse. LEO was mainly constituted by oxygenated monoterpenes including Linalool (36.81%) and Linalyn acetate (41.0%) and, in minor concentration, by other monoterpenes such as Limonene, Camphor, Endo-Borneol, Eucalyptol and β-Mircene 1.49%. The antimicrobial activity of LEO showed an inhibition index that increased proportionally to LEO concentration. Staphylococcus aureus showed the highest growth inhibition (about 89%) at 8.0% of LEO. All biometric and biomass parameters (plant height, leaf length, average leaf area, aerial and radish fresh weight) increased in both cycles with a LEO concentration till 4.0% ( p < 0.05). Chlorophyll index, radish macro and micronutrient content did not differ significantly in both cycles based on the LEO content. The advantages of LEO as biostimulant can be promising in enhancing growth and yield of radish under the maximum dosage of 2.0%, while higher concentrations (≥ 4.0%) caused phytotoxic effects. Further investigations could be conducted applying multiple low-dose foliar concentrations in other horticultural crops, to assess the potential application of LEO as natural herbicide for use in sustainable and organic farming.