Physicochemical characterization of essential-oil nanoemulsions and their biostimulant effects on tomato (Solanum lycopersicum L.) seedling growth

Biostimulants are increasingly recognized as sustainable agents for improving plant growth and physiological performance. Among emerging formulations, nanoemulsions have gained considerable attention due to their enhanced stability, bioavailability, and potential to facilitate the delivery of bioactive compounds. In the present study, twelve nanoemulsions prepared from pure essential oil constituents (γ-terpinene, α-pinene, 1,8-cineole, cuminaldehyde, carvacrol, limonene, and cinnamaldehyde) and essential oils of medicinal plants ( Pimpinella anisum , Ferula assa-foetida , Zataria multiflora , Anethum graveolens , and Cuminum cyminum ) were investigated for their effects on the seedling growth of tomato ( Solanum lycopersicum L.). The nanoemulsions were applied as foliar sprays at concentrations of 50, 100, 200, and 400 µL L ^− 1 during the vegetative growth stage. The chemical composition of the essential oils was determined using gas chromatography mass spectrometry, while the physicochemical characteristics of the nanoemulsions, including particle size distribution and zeta potential, were analyzed. The results demonstrated that nanoemulsions containing 1,8-cineole exhibited a clear concentration-dependent stimulatory effect, increasing both root and shoot growth by up to 80%. Essential oils of Pimpinella anisum , Ferula assa-foetida , and Cuminum cyminum significantly enhanced root development at concentrations of 400, 100, and 200 µL L ^− 1 , respectively. In addition, nanoemulsions derived from Zataria multiflora , Anethum graveolens , and α-pinene significantly increased shoot biomass at concentrations of 100, 200, and 400 µL L ^− 1 , respectively. Overall, 1,8-cineole at the highest tested concentration was identified as the most effective treatment for promoting tomato growth. These findings highlight the potential of essential oil-based nanoemulsions as environmentally friendly biostimulants and support their prospective application in sustainable agricultural systems.