Chemical defense ofPopulus balsamifera: A Clarification

Area of Science:

• Plant Chemistry
• Herbivore Interactions
• Forest Ecology

Background:

• Previous research suggested 2,4,6-trihydroxydihydrochalcone in juvenile Populus balsamifera deters snowshoe hares.
• This compound was thought to be responsible for differential palatability between juvenile and mature trees.

Purpose of the Study:

• To re-evaluate the role of 2,4,6-trihydroxydihydrochalcone in the feeding preferences of snowshoe hares for Populus balsamifera.
• To determine the actual distribution and concentration of this compound in different plant tissues and developmental stages.

Main Methods:

• Chemical analysis of Populus balsamifera tissues (internodes and buds) from juvenile and mature growth forms.
• Quantification of 2,4,6-trihydroxydihydrochalcone concentrations using established analytical techniques.

Main Results:

• 2,4,6-trihydroxydihydrochalcone is present in very low concentrations (<0.02% wet wt) in the internodes of Populus balsamifera.
• Concentrations of this compound are not significantly higher in juvenile internodes compared to mature ones.
• Conversely, 2,4,6-trihydroxydihydrochalcone is highly concentrated (20-25% wet wt) in the buds of Populus balsamifera.

Conclusions:

• The previously reported role of 2,4,6-trihydroxydihydrochalcone in juvenile Populus balsamifera palatability is incorrect.
• High concentrations of 2,4,6-trihydroxydihydrochalcone in buds likely serve as a deterrent to herbivores unable to access buds during foraging.
• Snowshoe hare feeding preferences are not explained by this compound in juvenile internodes.