Intraspecific and interspecific variation in phenolic root exudate profiles
Root exudates compose a highly diverse group of chemicals, which may affect the rhizosphere environment in different ways. While the chemical composition of root exudates are expected to vary greatly among tree species, direct root exudate samples of trees have not been collected and analyzed for chemical characteristics. In this lab, we are particularly interested in phenolic exudates since their effects on the rhizosphere can range from microbial food source and signaling compound to toxicity, influence soil extracellular enzyme activity, and precipitate nitrogen out of solution. Moreover, since phenolic compounds are secondary metabolites, we expect them to show higher variation between and even within tree species than primary metabolites such as sugars.
We have found and modified a method for root exudate collection and HPLC analysis that allows us to measure phenolic compound diversity. Currently, we are analyzing 1) the variation in phenolic exudate profiles among different temperate forest tree species and 2) genotypic variation in phenolic exudate profiles in willow shrubs under drought.
Next steps are to analyze the role of phenolic root exudate diversity identified by these two experiments in root priming and shaping rhizosphere microbial community composition.