Phytochemistry
To compare the effects of cytotype and genotypic variation on
phytochemistry in response to environmental stress, leaves were
harvested between August 17-24, 2018. Leaves were collected evenly
across the different treatments. From each tree, three fully expanded,
young leaves without petioles were collected from the upper third of the
tree crown. All leaves collected from defoliated trees showed signs of
damage. Leaves from all mesocosms were collected under wet soil
conditions. Total condensed tannins were analyzed using the acid butanol
method of Porter, Hrstich, and Chan (1985) standardized against purified
condensed tannins from P. tremuloides . Levels of the salicinoid
phenolic glycosides tremulacin, tremuloidin, salicin and salicortin were
quantified using ultra-high-performance liquid chromatography-mass
spectrometry as described by Rubert‐Nason, Couture, Gryzmala, Townsend,
and Lindroth (2017). Leaf nitrogen was measured using near-infrared
reflectance spectroscopy (Rubert-Nason et al., 2013) verified against a
subset of the samples analyzed using combustion gas chromatography
(Thermo Flash EA1112 elemental analyzer [Thermo Finnigan, Milan,
Italy]).