Talking trees always seemed to be a figment of Tolkien-esque fantasy, rather than reality. In the 80′s, this changed as biologists began to realize that many plants were in fact communicating with one another. Small amounts of airborne chemicals – odors that we are unable to detect with our limited sense of smell – were being exchanged regularly between plants, resulting in changes in behavior. Specifically, when some plants get attacked by insects, they release volatile chemicals into the surrounding atmosphere. These chemicals are picked up by nearby trees, which turn on internal chemical defenses to quickly deter insect herbivores that may be soon encroaching.
As research expanded on plant volatiles, it soon became obvious that they were ubiquitous, and might serve other defensive purposes for plants. At least in some cases, volatiles can be used as a type of alarm call. Plants can release volatiles when they are being attacked by herbivores, which call in parasitoids and predators of that herbivore. It’s the old adage “the enemy of your enemy is your friend.” Here, plants can recruit insect defenders simply through smelling different.
Though this type of indirect defense has been shown in a number of systems, we still know very little about what causes variation in the chemical signals produced by plants in nature. Do things like temperature or air humidity modify a signal, and do rapid changes in these factors result in noise for insects that are trying to pick them up? How effective are insect predators and parasitoids at filtering this noisy signal? These are questions I hope to answer in my dissertation work.