Chemical Investigation and Dose-Response Phytotoxic Effect of Essential Oils from Two Gymnosperm Species ( var. Pall. and Mill.).

The chemical composition of the liquid and vapor phases of leaf essential oils (EOs) obtained from two species of Gymnosperms ( Willd. and Mill.) was investigated using the SPME-GC-MS technique. The results highlighted a composition characterized by 51 identified volatile compounds (34 in and 39 in ). In both bloils, monoterpenes prevailed over the sesquiterpenes, albeit with qualitative and quantitative differences. Sabinene (37.5% and 34.5%, respectively) represented the two most abundant components in the liquid and vapor phases of , and -pinene (51.0% and 63.3%) was the main constituent in The phytotoxic activity of the two EOs was assessed in pre-emergence conditions using three concentrations in contact (2, 5, 10 µL/mL) and non-contact (2, 20, 50 µL) tests against Lam. (Poaceae) and L. (Brassicaceae). Treatments were effective in a dose-dependent manner by significantly reducing the germination (up to 100% and 45-60%, respectively, with filter paper and soil as a substrate) and the seedling development (1.3 to 8 times) of both target species. Moreover, an exploratory survey on the residual presence of volatile compounds in the soil at the end of the tests was carried out.