Microflora volatiles as drivers of nutrient foraging in clonal plants

Background/Question/Methods

Studies on the foraging behavior of clonal plants have consistently shown that clonal plants preferentially place ramets in high light and/or high nutrient patches. For stoloniferous plants, placement of ramets in high light patches seems straightforward, but the ability to detect the nutrient quality of patches prior to rooting seems less clear. There is a positive correlation between patch quality and microflora activity. Furthermore, there is an increasing body of work that focuses on the emission of volatile organic compounds (VOCs) from varying sources, including soil microflora. We hypothesized that the nutrient foraging behavior of clonal plants and the ability of these plants to detect nutrient rich patches may be driven by volatile emissions from the microflora that colonize these high nutrient patches.

A greenhouse experiment was conducted in which 48 genetically identical ramets of Fragaria vesca were allowed to extend stolons over one of four substrate types (sterilized sand, soil, sterilized sand +litter, and soil + litter). Soil was collected from a field site rich with F. vesca. At no point were the developing daughter ramets allowed to root; contact between developing daughter ramets and substrate was prohibited. Once roots developed on daughter ramets, individuals were harvested, and plant organs were separated, dried and weighed. Headspace collection and GC-MS were performed on the substrates to determine a volatile profile. Chlorophyll content was measured in daughter leaves.

Results/Conclusions

We found a significantly higher allocation to root mass in daughter ramets that developed over non-sterilized (bacteria rich) substrates than sterilized substrates. We found a highly significant difference in root:shoot allocation; daughter ramets that developed over substrates that were non-sterilized displayed significant shifts in the root:shoot ratio indicative of not only an increased allocation to roots, but also a decreased allocation to shoots. Chlorophyll content is currently being analyzed. Volatile profiles are currently being analyzed, however preliminary results suggest that the volatile profiles of bacteria rich substrates are highly extensive compared to sterilized substrates.

In conclusion, we feel we have preliminary evidence to suggest that volatiles produced by nutrient rich patches may have an effect on resource allocation in F. vesca and that this can greatly influence foraging behavior. Specifically, stolons extending over nutrient rich patches may receive signals from belowground in the form of volatile emissions that can induce shifts in allocation from shoots to roots. Volatile analysis may also be able to elucidate which compounds are drivers of this change.