Spatiotemporal Floral Scent Variation of Penstemon digitalis

Abstract

Variability in floral volatile emissions can occur temporally through floral development, during diel cycles, as well as spatially within a flower. These spatiotemporal patterns are hypothesized to provide additional information to floral visitors, but they are rarely measured, and their attendant hypotheses are even more rarely tested. In Penstemon digitalis, a plant whose floral scent has been shown to be under strong phenotypic selection for seed fitness, we investigated spatiotemporal variation in floral scent by using dynamic headspace collection, respectively solid-phase microextraction, and analyzed the volatile samples by combined gas chromatography-mass spectrometry. Total volatile emission was greatest during flowering and peak pollinator activity hours, suggesting its importance in mediating ecological interactions. We also detected tissue and reward-specific compounds, consistent with the hypothesis that complexity in floral scent composition reflects several ecological functions. In particular, we found tissue-specific scents for the stigma, stamens, and staminode (a modified sterile stamen common to all Penstemons). Our findings emphasize the dynamic nature of floral scents and highlight a need for greater understanding of ecological and physiological mechanisms driving spatiotemporal patterns in scent production.

The smell of environmental change: Using floral scent to explain shifts in pollinator attraction

“…But we might also expect the past and current environmental conditions in which a plant is growing to influence its floral volatiles (e.g., Majetic et al, 2008, 2009a). Additionally, floral volatiles of an individual might change over the course of a day, over the lifetime of a flower (e.g., after ovules within a flower become fertilized), over the flowering season of an individual, or over the lifetime of a plant individual (e.g., Schiestl et al, 1997; Burdon et al, 2015). There may be interactions between typical temporal rhythms of floral volatile production and composition of a plant and the environmental conditions that it is experiencing, but this is poorly understood.…”

More lessons from linalool: insights gained from a ubiquitous floral volatile

“…Of these, the furanoid linalool oxides may give rise to 16 possible stereoisomeric aldehydes and alcohols, collectively known as 'lilac compounds', owing to their discovery in the floral scent of Syringa vulgaris [(13; see 52)]. Lilac compounds attract specific functional groups of pollinators, such as noctuid moths [14,15] and long tongued fungus gnats [16 ] in different floral contexts.…”

“…One recent study demonstrated that variation in floral scent was significantly associated with seed fitness in a day-blooming, bee pollinated plant, Penstemon digitalis, identifying (S)-(+)-linalool as the target of phenotypic selection [51]. Further analyses identified the nectar spur as the source of this VOC [52], suggesting that (S)-(+)-linalool might function as an honest indicator of the presence of nectar, or might enhance floral constancy by pollinators, or might protect nectar from microbial infestation. Floral constancy is likely to result from a learned association of the consistent relationship between nectar availability and linalool, either as a scent or a flavor.…”

Bumblebees require visual pollen stimuli to initiate and multimodal stimuli to complete a full behavioral sequence in close‐range flower orientation

“…Whereas colored bracts or petals are mostly large‐sized to attract flower visitors from some distance, color patterns of the petals and other flower organs are small and more important for orientation at close range. This visual color pattern is paralleled by an olfactory, gustatory and tactile pattern (Burdon, Raguso, Kessler, & Parachnowitsch, ). Studies of flower odor chemistry suggest that nectar and pollen rewards frequently differ in the quantity and composition of volatile compounds compared to other floral tissues, and that such within‐flower spatial variation may function as odor guides to direct pollinators to nectar (Dötterl & Jürgens, ) or pollen rewards (Bergström et al., ; Dobson, Danielson, & Van Wesep, ).…”