Plants form and emit a wide variety of volatile organic compounds. Volatiles from flowers attract pollinators and increase the fitness of plants by promoting efficient reproduction, and those from fruits attract seed-dispersing animals and help plants to find new habitats (Dudareva et al., 2013). Vegetative organs, such as leaves, stems, and roots, also produce and emit volatiles, and this process generally is induced by various types of biotic and abiotic stresses as a defense response (Pierik et al., 2014).Green leaf volatiles (GLVs) are expressed ubiquitously with other groups of volatile compounds, such as terpenoids and amino acid derivatives. GLVs are derivatives of fatty acids and include six-carbon (C6) aldehydes, alcohols, and esters (Fig. 1; Matsui, 2006; Scala et al., 2013). In intact and healthy plant tissues, GLV levels generally are low, but when tissues suffer stresses associated with the disruption of cells, such as herbivore damage or attack by necrotrophic fungi, GLV-forming pathways are activated rapidly to yield large quantities of GLVs at damaged tissues (Matsui, 2006; Scala et al., 2013; Ameye et al., 2017). GLVs at damaged tissues participate in direct plant defense by preventing the invasion of harmful microbes (Shiojiri et al., 2006a;Kishimoto et al., 2008). GLVs also function

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Since the levator and frontalis muscles lack interior muscle spindles despite being antigravity mixed muscles to involuntarily sustain eyelid opening and eyebrow lifting, this study has proposed a hypothetical mechanism to compensate for this anatomical defect. The voluntary contraction of fast-twitch fibres of the levator muscle stretches the mechanoreceptors in Müller's muscle to evoke proprioception, which continuously induces reflex contraction of slow-twitch fibres of the levator and frontalis muscles. This study confirmed the presence of cell bodies of the trigeminal proprioceptive neurons that transmit reflex contraction of the levator and frontalis muscles. After confirming that severing the trigeminal proprioceptive fibres that innervate the mechanoreceptors in Müller's muscle induced ipsilateral eyelid ptosis, Fluorogold was applied as a tracer to the proximal stump of the trigeminal proprioceptive nerve in rats. Fluorogold labelled the cell bodies of the trigeminal proprioceptive neurons, not in any regions of the rat brain including the trigeminal ganglion, but in the ipsilateral mesencephalic trigeminal nucleus neighbouring the locus ceruleus. Some Fluorogold particles accumulated in the area of the locus ceruleus. The trigeminal proprioceptive neurons could be considered centrally displaced ganglion cells to transmit afferent signal from the mechanoreceptors in Müller's muscle to the mesencephalon, where they may be able to make excitatory synaptic connections with both the oculomotor neurons and the frontalis muscle motoneurons for the involuntary coordination of the eyelid and eyebrow activities, and potentially to the locus ceruleus.

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