Vapor and Liquid Phase Profiles of Essential Oils from Abies , Picea and Pinus Species and Their Phytotoxic Interactions with Weed Growth in Pre- and Post-Emergence Conditions.

The chemical content of essential oils (EO) obtained from the leaves of four Pinaceae ( Abies alba , Picea abies , Pinus cembra and Pinus mugo ) was investigated by SPME-GC-MS technique. The vapor phase was characterized by the monoterpenes with values higher than 95.0%. Among them, α -pinene (24.7-48.5%), limonene (17.2-33.1%) and β -myrcene (9.2-27.8%) were the most abundant. The monoterpenic fraction prevailed over the sesquiterpenic one (≥74.7%) in the EO liquid phase. Limonene was the major compound in A. alba (30.4%), P. abies (20.3%) and P. mugo (78.5%), while α -pinene in P. cembra (36.2%). Regarding the phytotoxic properties, EOs were studied at different doses (2-100 μL) and concentrations (2-20/100 μL/mL). All EOs were found to be significantly active ( p -value ˂ 0.05) against the two recipient species in a dose-dependent way. In pre-emergence tests, germination of Lolium multiflorum and Sinapis alba was reduced by up to 62-66% and 65-82%, respectively, as well as their growth by up to 60-74% and 65-67%, due to the effects of compounds in both the vapor and liquid phases. In post-emergence conditions, at the highest concentration, the phytotoxicity of EOs caused heavy symptoms and, in the case of S. alba , A. alba EO completely destroyed (100%) the treated seedlings.