Seed priming with lavender essential oil increases germination and seedling growth in saline and potentially toxic elements-contaminated soils

Background Seed priming with natural compounds has emerged as a promising strategy to enhance plant tolerance to abiotic stresses. Among these, essential oils may mitigate the adverse effects of potentially toxic elements (PTEs) and salinity on seed germination and early growth. This study aimed to investigate the priming effects of Lavandula angustifolia Mill. essential oil on germination and seedling development of 3 Mediterranean aromatic species: Achillea millefolium L., Ocimum basilicum L., and Thymus vulgaris L. Methods Priming treatments were performed using different essential oil concentration (0.1%, 0.2%, 0.4%, 0.8%) with H 2 O and polysorbate P80 controls. Seed were grown on two heavy metal-polluted soils collected from abandoned mining sites (Montevecchio, HM1; Su Suergiu, HM2; Sardinia, Italy), a saline soil from Arborea in Sardinia (Sal) and an unpolluted sandy control soil. HM1 and HM2 soils were contaminated with arsenic (As), cadmium (Cd), lead (Pb), antimony (Sb) and zinc (Zn). Results Soil type, plant species, and priming conditions significantly affected germination rate, seedling vigor index, and fresh weight. Notably, 0.2% essential oil priming did not markedly enhance germination compared to controls, except for A. millefolium grown on the contaminated HM1 soil and T. vulgaris on control soil. Both A. millefolium and T. vulgaris showed significant higher soil tolerance indices in contaminated soils under 0.2% priming, while T. vulgaris also exhibited further improvement under 0.2–0.8% priming in control soil. Moreover, in Sal soil, germination and seedling development were generally inhibited across all species; however, L. angustifolia essential oil at 0.2% occasionally alleviated these negative effects. Conclusions Low-dose Lavandula angustifolia essential oil priming can improve germination and stress tolerance in certain aromatic species, representing a sustainable approach for the valorization of marginal and degraded lands.