Genotypic Differences and Prior Defoliation Affect Re-Growth and Phytochemistry after Coppicing in Populus tremuloides

Abstract

Although considerable research has explored how tree growth and defense can be influenced by genotype, the biotic environment, and their interaction, little is known about how genotypic differences, prior defoliation, and their interactive effects persist in trees that re-grow after damage that severs their primary stem. To address these issues, we established a common garden consisting of twelve genotypes of potted aspen (Populus tremuloides) trees, and subjected half of the trees to defoliation in two successive years. At the beginning of the third year, all trees were severed at the soil surface (coppiced) and allowed to regenerate for five months. Afterwards, we counted the number of root and stump sprouts produced and measured the basal diameter (d) and height (h) of the tallest ramet in each pot. We collected leaves one and two years after the second defoliation and assessed levels of phenolic glycosides, condensed tannins, and nitrogen. In terms of re-growth, we found that the total number of sprouts produced varied by 3.6-fold among genotypes, and that prior defoliation decreased total sprout production by 24%. The size (d(2)h) of ramets, however, did not differ significantly among genotypes or defoliation classes. In terms of phytochemistry, we observed genotypic differences in concentrations of all phytochemicals assessed both one and two years after the second defoliation. Two years after defoliation, we observed effects of prior defoliation in a genotype-by-defoliation interaction for condensed tannins. Results from this study demonstrate that genotypic differences and impacts of prior defoliation persist to influence growth and defense traits in trees even after complete removal of above-ground stems, and thus likely influence productivity and plant-herbivore interactions in forests affected by natural disturbances or actively managed through coppicing.

Cytotype differences in radial increment provide novel insight into aspen reproductive ecology and stand dynamics

“…Aspen frequently show pronounced phenotypic and chemical differences among genets (Stevens et al 2012;Kanaga et al 2008;Osier and Lindroth 2004). Collectively, the triploid stems in the current study belonged to four genotypes (clones), whereas the diploids stems belonged to 13 genotypes.…”

Influence of Genotype, Environment, and Gypsy Moth Herbivory on Local and Systemic Chemical Defenses in Trembling Aspen (Populus tremuloides)

“…The patterns of carbon-based phytochemical production among these genotypes were consistent with previous observations . Salicinoids and condensed tannins are both formed via the shikimate-phenylpropanoid pathway (Tsai et al 2006), and the inverse correlation (R=−0.40, P<0.001) between concentrations of these compounds has been reported elsewhere for aspen (Couture and Lindroth 2012;Hemming and Lindroth 1995;Stevens et al 2012). Collectively, the patterns of expression of carbon and protein-based defenses among different aspen genotypes may represent a genetically-determined and/or physiological tradeoff between production of different classes of secondary metabolites.…”

Genetic Modification of Lignin in Hybrid Poplar (Populus alba × Populus tremula) Does Not Substantially Alter Plant Defense or Arthropod Communities

“…All trees were coppiced and allowed to reflush before surveys in 2010 and 2011, but not in 2012. Coppicing “resets” tree age and chemistry responds accordingly ( Stevens et al 2012 ) effectively making our trees phenologically ∼1-year-old in 2010 and 2011 but 2-years-old in 2012. Lines represent mean chemistry levels of each transgenic or wild-type (WT) poplar tree ( n = 7–10 replicate trees) at each date.…”