Stephen Graham Jones
Pinyon pines respond chemically to above- and belowground herbivory and pathogens by synthesizing and emitting secondary compounds known as monoterpenes (C10). However, whether aboveground herbivory can alter belowground monoterpene concentrations and the ecological importance of this potential systemic response remain uncertain. The overarching goal of my thesis is to determine whether foliar damage elicits an induced response by altering monoterpene concentrations in needles and roots, thus potentially changing the susceptibility of pinyon pines to needle herbivores and root pathogens. I used mechanical damage (M), the application of methyl jasmonate (MeJA) and the combination of the two treatments (MeJA+M) on pinyon pine seedlings as proxies for foliar herbivore damage and assessed needle and root monoterpene concentrations periodically over 20 days following the treatments. Overall, my results show that simulated foliar herbivory significantly induced monoterpene production in both needles and roots. However, the specific compounds induced differed between needles and roots, and the direction and magnitude of these changes resulted in a significant damage effect on total needle monoterpenes, but not on total root monoterpenes. The significant increase observed for most of the needle and root individual compounds was due to the application of MeJA. Time and interaction of time and damage treatment did not exhibit a significant effect on most monoterpene compounds, which may be due to variation among individual seedlings at each time interval, resulting substantial variation in monoterpene concentrations. For future work, more detailed analyses are needed to be able to assess the time effect. Moreover, the effectiveness of the induced responses in both needles and roots in defense against future herbivory and root pathogens should be a focus of future investigations.
Possehl, Caitlyn, "Samuel and his Magic" (2013). Undergraduate Honors Theses. 468.