Phenotypic plasticity of floral volatiles in response to increasing drought stress

Abstract

Background and Aims 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. Here quantitative relationships of floral volatile emissions to soil water content were analysed. Methods Plants of the sub-alpine herb Ipomopsis aggregata and hybrids with its closest congener were subjected to a progressive dry down, mimicking the range of soil moistures experienced in the field. Floral volatiles and leaf gas exchange were measured at four time points during the drought. Key Results As the soil dried, floral volatile emissions increased overall and changed in composition, from more 1,3-octadiene and benzyl alcohol to higher representation of some terpenes. Emissions of individual compounds were not linearly related to volumetric water content in the soil. The dominant compound, the monoterpene α-pinene, made up the highest percentage of the scent mixture when soil moisture was intermediate. In contrast, emission of the sesquiterpene (E,E)-α-farnesene accelerated as the drought became more intense. Changes in floral volatiles did not track the time course of changes in photosynthetic rate or stomatal conductance. Conclusions 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.

Plant Origin, but Not Phylogeny, Drive Species Ecophysiological Response to Projected Climate

“…In line with our expectation and previous studies (e.g., Pigliucci, 2001;Nicotra et al, 2010;Raabova et al, 2011;Campbell et al, 2019), we detected many significant effects of target climate indicating high phenotypic plasticity in majority of the traits. This indicates that the plasticity is more important than genetic differentiation for most of the traits measured in this study.…”

Flowers and climate change: a metabolic perspective

“…Modeling curves of VOC emission in response to abiotic stresses is therefore challenging. The chemical analysis of the scent of flowers exposed to heat and drought revealed complex bouquets, where some compounds showed positive and negative linear changes in response to the stress, whereas others exhibited loose and unpredictable trends (Farré‐Armengol et al ., ; Campbell et al ., ; see also Table ). Field measurements of floral VOC emissions in response to abiotic stresses are relatively well documented (Farré‐Armengol et al ., , ; Burkle & Runyon, ), although the molecular and biochemical mechanisms controlling for these changes are mostly unknown.…”

“…Studies conducted in petunia revealed transcriptional down‐regulation of enzymes of the phenylpropanoid and shikimate pathways and up‐regulation of their negative transcriptional repressors (Cna'ani et al ., ), leading to reduced VOC emission in response to heat (Sagae et al ., ). Through the course of evolution, floral emission of VOCs has been optimized to meet the requirements of temperature and rainfall typical of the blooming season of a given species (Farré‐Armengol et al ., ; Campbell et al ., ). Therefore, transcriptional and post‐transcriptional adjustments are expected to occur to cope with circumstances that interfere with this process.…”

Advanced phenology of intraguild predators shifts herbivore host plant preference and performance

“…Additionally, we sampled 20 ambient air controls both inside and outside of the field greenhouse. We measured soil moisture using a time-domain reflectometry probe (FieldScout TDR 100, Spectrum Technologies, Aurora, Illinois) as a covariate (Campbell et al, 2019). We sampled mirid addition and mirid-free control plants between 4 July and 17 July, 10 days after mirid addition.…”

“…Peaks were initially identified using the NIST14 mass-spectra library with a minimum similarity search of at least 70%. We exported peak areas to Excel and used a filtering script in R (Campbell et al, 2019). The script filtered out contaminant compounds by comparing peak areas of floral samples to ambient air controls, and only plant samples that passed the criterion were used in the final dataset.…”