PS 30-112 - Measuring leaf and root plant functional traits uncovers multidimensionality of plant responses to arbuscular mycorrhizal fungi

Background/Question/Methods

Plant responses to mycorrhizal mutualisms are most often characterized by simple measures of plant biomass. While mycorrhizal fungi influence plant biomass by increasing nutrient uptake, we also appreciate that mycorrhizal fungi may provide diverse benefits to their plant hosts. As a result, we expect plant species’ responses to mutualisms may be much more complex than increased biomass. To understand how plant traits are influenced by mycorrhizal colonization, we measured leaf and root functional traits in 27 prairie plant species when grown with and without mycorrhizal fungi.

Results/Conclusions

When using traits from plants not colonized by mycorrhizal fungi, the first principal component (PC) described the tradeoff between leaf tissue quality and aboveground growth rate. This PC was strongly correlated with mycorrhizal growth response (R² = 0.82, p < 0.001), such that plants that invest in high quality tissues when uncolonized have larger biomass responses when colonized by mycorrhizal fungi. When we consider how these functional traits change when plants are colonized by mycorrhizal fungi, we find that there are two distinct PCs, representing 33% and 21% of variance explained, that describe changes in quantity and quality of leaf tissue, respectively. The third PC, representing 16% of the variance in the data set, described the deviation of root traits from their expected aboveground correlates, suggesting that mycorrhizal colonization can also shift the proportion of resources allocated above and belowground. These results indicate that there are multiple dimensions of plant response to mycorrhizal fungi. Mycorrhizal fungi not only affect how much aboveground biomass a plant produces but also affect aboveground tissue quality and allocation belowground. These results provide a trait-based mechanism for other benefits that mycorrhizal fungi provide to a plant, such as drought tolerance and disease resistance.