In defense of quaking aspen (Populus tremuloides): the distribution and roles of phenolic glycosides and extrafloral nectaries within and among trees

Abstract

"I studied the concentrations of phenolic glycosides (PGs) from leaves with and without extrafloral nectaries (EFNs) in Populus tremuloides during an outbreak of the aspen leaf miner, Phyllocnistis populiella, in interior Alaska. P. populiella feeds on the contents of epidermal cells from both top (adaxial) and bottom (abaxial) surfaces of P. tremuloides leaves. The objective of this study was to assess the association of chemical and biotic defenses in P. tremuloides and their interaction with the insect herbivore P. populiella. The concentration of PGs (salicortin and tremulacin) was approximately 70% greater in leaves bearing EFNs than in those without EFNs from short trees (<2.5 m); leaves with and without EFNs did not differ significantly in PG concentration for tall trees (5-8 m). Leaf mining caused the induction of the foliar PGs following eight days of mining. There was no difference in the ability of leaves with and without EFNs to induce PGs in response to mining. The extent of mining damage was significantly and negatively related to the PG concentration, whereas EFNs were not related to the extent of mining. At the site level, I found no evidence for a tradeoff between these two putative forms of defense in P. tremuloides"--Leaf iii