Phenotypic plasticity of floral volatiles in response to increasing drought stress

Flowers emit a wide range of volatile compounds which can be critically important to interactions with pollinators or herbivores. Yet most studies of how the environment influences plant volatiles focus on leaf emissions, with little known about abiotic sources of variation in floral volatiles. Understanding phenotypic plasticity in floral volatile emissions has become increasingly important with globally increasing temperatures and changes in drought frequency and severity. Campbell et al. analysed the quantitative relationships of floral volatile emissions to soil water content.

The authors did this by subjecting plants of the sub-alpine herb Ipomopsis aggregata and hybrids with its closest congener to a progressive dry down, mimicking the range of soil moistures experienced in the field. They measured floral volatiles and leaf gas exchange at four time points during the drought.

This study shows responses of specific floral volatile organic compounds to soil moisture. The non-linear responses furthermore suggest that extreme droughts may have impacts that are not predictable from milder droughts. Floral volatiles are likely to change seasonally with early summer droughts in the Rocky Mountains, as well as over years as snowmelt becomes progressively earlier. Changes in water availability may have impacts on plant–animal interactions that are mediated through non-linear changes in floral volatiles.