Abstract
The phytotoxicity and eco-compatibility of essential oils (EOs) from Eucalyptus gunnii (EG) and E. pulverulenta ‘Baby Blue’ (EP), cultivated in Italy for their cut foliage, were investigated. Leaf micromorphology, EOs phytochemical characterization, and phytotoxicity were analysed. EP revealed a significantly higher oil gland density and a higher EO yield with respect to EG. In both EOs, 1,8-cineole was the major compound (~75%), followed by α-pinene in EG (13.1%) and eugenol in EP (7.5%). EO phytotoxicity was tested on both weeds (Lolium multiflorum, Portulaca oleracea) and crops (Raphanus sativus, Lactuca sativa, Lepidium sativum, Solanum lycopersicum, Pisum sativum, Cucumis sativus). EG EO inhibited germination of P. oleracea, R. sativus, and S. lycopersicum seeds (ranging from 61.5 to 94.6% for the higher dose used), while affecting only radical elongation in S. lycopersicum (ranging from 66.7 to 82.6%). EP EO inhibited germination of P. oleracea and R. sativus (ranging from 41.3 to 74.7%) and affected radical elongation of L. sativum and L. multiflorum (ranging from 57.4 to 76.0%). None of the EOs affected the germination and radical growing of L. sativa, P. sativum, and C. sativus. Moreover, EP EO was more active than EG EO in inhibiting α-amylase, a key enzyme for seed growth regulation. Brine shrimp lethality assay showed that both EOs are safe for aquatic organisms, suggesting their high eco-compatibility. The data collected provide useful information for future applications of these EOs in agriculture as safe and selective bioherbicides.
Highlights
Native from Australia, the genus Eucalyptus (Myrtaceae) contains about 800 species and is largely cultivated around the world in commercial plantations for several applications, such as cellulose, pulp, gum, essential oils, and honey production, as well as for construction and as ornamental plants [1,2].In Italy, several Eucalyptus species were introduced at the beginning of the 1800s by plant collectors to be used as ornamental trees in private gardens [3]
Our study investigated the micromorphology, phytochemistry, phytotoxic activity, and eco-compatibility of E. gunnii (EG) and E. pulverulenta ‘Baby blue’ (EP) essential oils (EOs)
The comparison between the two species showed that EP had a higher oil gland density as well as a higher yield in EO with respect to EG
Summary
Native from Australia, the genus Eucalyptus (Myrtaceae) contains about 800 species and is largely cultivated around the world in commercial plantations for several applications, such as cellulose, pulp, gum, essential oils, and honey production, as well as for construction and as ornamental plants [1,2]. In Italy, several Eucalyptus species were introduced at the beginning of the 1800s by plant collectors to be used as ornamental trees in private gardens [3]. Is the leader in Europe in terms of the production and export of eucalyptus cut foliage, which is mainly sold on the Northern European market, where fresh and dried branches are used in floral compositions [6]
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