Differences between the leaf and stem essentials oils of domestic Mentha spicata var. spicata (L. 1753) plants
Résumé
Medauroidea extradentata (Brunner von Wattenwyl 1907) is a stick insect able to feed on a large variety of plants in captivity such as brambles and raspberries (Rubus spp. (L. 1753)) and hazels (Corylus maxima (Mill. 1768)) for the most common. When M. spicata var. spicata branches were presented, the stems were eaten and not the leaves (1). There are two possible explanations. The first one, is that the leaves and the stems have a different chemical composition. The second, and the more plausible, is that the essentials oils concentration is lower in the stems than in the leaves.
For that, the fresh plant was hydrodistilled according the Likens-Nickerson's method, followed by a gas chromatography (2). The results are that the chemical composition of the leaves and the stems is exactly the same, but the concentration of the essential oil is 6.86 times lower in the stems than in the leaves. So, it is probably the lower concentration in essential oil of the stems which is the answer to the question, why the stick insect M. extradentata prefers to eat stems instead of leaves from M. spicata var. spicata.
(1) Olive G., Zimmer J.-Y., Olive G. (2016). Mentha spicata var. spicata (L. 1753) and Raphanus sativus var. sativus (L. 1753) : survival meal for Medauroidea extradentata (Brunner von Wattenwyl 1907) (Phasmatodea: Phasmatidae). Communications in Agricultural and Applied Biological Sciences 81 (1), p. 190-193.
(2) Courtesy of Professor Marie-Laure FAUCONNIER (University of Liège, Gembloux Agro-Bio Tech, General and Organic Chemistry Unit).
Domaines
Chimie analytique
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