A plant’s aroma is part of the way it communicates with its surroundings. Just like humans or other animals, a smell is here to tell us something. Perfumes evolved exactly for this reason. Today perfume developers must understand various characteristics when designing an aroma that will send other people specific information. Aroma helps us to interpret who the person in front of us is, their expectations, self-esteem, desires and other information besides what is seen.
The central nervous system in any animal relies on smell much more than in humans. Some species hold dozens of thousands of smells receptors, which reflect most of the animal’s perception. Smell disorder impairs their ability to survive.
The plant kingdom is almost exclusively the source of aroma compounds in nature. As we mentioned earlier, these compounds are part of secondary metabolites, which means the plant invest energy to produce these compounds, although they aren’t utilized in the primary plant cycle.
There are two emerging themes in the study of plant chemical ecology:
(a) Most secondary compounds have multiple and context-dependent functions.
(b) Many info-chemicals appear as deadly toxins, which through co-evolutionary processes come to be utilized as signals and cues by organisms that develop a tolerance to them.
Linalool is a noncyclic monoterpenoid that usually constitutes 5% or less of cannabis essential oil (Ross and ElSohly 1996). It is a great example of this kind of multifunctional agent. Linalool, widespread in most floral scents, can act as deadly cell killer, a signal for herbivores to get away and attract others for a tasty meal.
Researchers from the departments of neuroscience and entomology at the University of Arizona studied the relationship between Jimsonweed (Datura wrightii) and the nocturnal moth, Carolina sphinx (Manduca sexta) in the Southwestern USA. They traced that Linalool has two different odorant coding messages in the moth antennal lobe. Linalool got two enantiomers, which means they are a mirror image. This is just as our left and right hands are the same, except for being reversed along one axis (the hands cannot be made to appear identical simply by reorientation). Results show that one Linalool structure effects only on the female lobe, causing her to lay eggs. The other mirror structure affects both male and female in feeding signals. This odorant compound controls the behavioral communication, through two different neural pathways.
Linalool and other terpenes have evolved to affect neurons in trace amounts. They will continue to cause much interest in the study of the role of odorants, especially cannabis based, for medical and pharmaceutical developments.