Genetic variation in the phenolic concentration and inducibility in explanding leaves of Populus tremuloides.

Abstract

The co-existence of plants and herbivores has resulted in various chemical and mechanical adaptations in plants. Phenolics form one of the largest groups of defensive chemical compunds and are ubiquitous among all plants. Plants are able to induce these chemical defenses in response to herbivorous attack. Studies show that trembling aspen (Populus tremuloides) exhibit genetic plasticity in constituitive phenolic levels among clones. However, little is known about the relationship between genotype and the ability to induce defenses. The focus of this study was to determine whether variable phenolic levels are genetically determined and whether a correlation exists between constituitive levels and inducibility in young aspen leaves. We tested for constituitive and induced phenolics in clones located on the Pellston Plain in northern, lower Michigan. Our results show a significant difference between constituitive and induced levels (t-test, p=0.016), which indicates that the clones responded to mechanical damage. However, the overall change in phenolic concentrations was negative (paired t-test, mean=-0.413). We found no genetic variation among clones for constituitive phenolic levels (Kruskal-Wallis, p=0.329) nor for their absolute induction values (Kruskal-Wallis, p=0.424). We believe these results may indicate that plant defensive strategies for younger leaves differ from older, fully expanded leaves.