Gas chromatography-mass spectrometry analysis of variations in the essential leaf oil of 6 Eucalyptus Species and allelopathy of mechanism 1,8-cineole

The Eucalyptus plant releases allelopathic chemicals into the environment mostly through the essential oils volatilized from the leaves. This study discussed the composition of the leaf oils of few seven-year-old varieties like Eucalyptus pellita (E. pel), Eucalyptus camaldulensis (E. cama), Eucalyptus grandis (E. gra), Eucalyptus dunni (E. dun), Eucalyptus saligna (E. sal), and E. grandis × E. urophylla (E. gra×E. uro) and three-year-old E. grandis × E. urophylla (E. gra × E. uro (three)). It determined the allelopathic mechanism and the types of chemical components playing the leading role. Essential oil was obtained by hydrodistillation and analyzed by the Gas Chromatography-Mass Spectrometry (GC-MS) method. In order to determine the effect of allelopathy, seed germination experiments were carried out at different concentrations (10-100 mL/L) of the E. Gra × E. uro leaf oil (EO) and the major components. The wheat seeds germinated by adding 1,8-cineole were used to determine the activity of α-amylase. Moreover, the mRNA expression of α-amylase in seeds was studied. The major chemical class in the essential oil was oxygenated monoterpene; 1,8-cineole (20.2-67.5%) displayed the highest content. Other substances that were high in content and ubiquitous included α-pinene (0.3-21.8%), α-terpineol (0.44-19.24%), and borneol (0.81-3.05%). The four chemical constituents and EO influenced the germination and growth of the three plants. Among them, 1,8-cineole exhibited the strongest inhibitory effect. The α-amylase activity of the 1,8-cineole-treated wheat seeds had decreased significantly. Molecular evidence suggested that 1,8-cineole decreased the α-amylase gene (AMY) expression.