Improving our chemistry: challenges and opportunities in the interdisciplinary study of floral volatiles

Raguso, Robert A.; Thompson, John N.; Campbell, Diane R.

doi:10.1039/c4np00159a

Cited by 25 publications

(16 citation statements)

References 135 publications

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“…Variation in floral scent composition is commonly observed not only between species but also within a plant species (Delle-Vedove et al, 2017). With the exception of comparisons across times of day (Dötterl et al, 2005;Jürgens et al, 2014;Campbell et al, 2016;Chapurlat et al, 2018) however, remarkably little is known about sources of intraspecific variation in floral VOCs, including the roles of specific environmental conditions (Raguso et al, 2015). Understanding the potential for such phenotypic plasticity in response to the environment, and whether the plasticity is adaptive (Anderson et al, 2012), has become increasingly important with recent climate change (IPCC, 2014).…”

Section: Introductionmentioning

confidence: 99%

Phenotypic plasticity of floral volatiles in response to increasing drought stress

2018

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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.

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Section: Introductionmentioning

confidence: 99%

Phenotypic plasticity of floral volatiles in response to increasing drought stress

2018

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“…Testing these chemical and biosynthetic predictions even for a single plant-pollinator interaction is challenging. First, merely determining which of the often countless floral volatile compounds are biologically active is difficult, and this has only rarely been achieved even in more tractable systems [6,18]. Second, the elucidation of functional floral volatiles is likely to be strongly biased toward known and common compounds, leaving many cases where the chemistry of pollination is unknown.…”

Section: Introductionmentioning

confidence: 99%

Complex Sexual Deception in an Orchid Is Achieved by Co-opting Two Independent Biosynthetic Pathways for Pollinator Attraction

Bohman

Wong

et al. 2017

Current Biology

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Sexually deceptive orchids lure their specific male pollinators using volatile semiochemicals that mimic female sex pheromones. To date, the semiochemicals known to be involved consist of blends of chemically and biosynthetically related compounds. In contrast, we report that (S)-β-citronellol and 2-hydroxy-6-methylacetophenone, two biosynthetically distinct compounds, are the active semiochemicals in Caladenia plicata, which is pollinated by male Zeleboria sp. thynnine wasps. They are also sex pheromone components of the female Zeleboria. A 1:4 blend elicits a high rate of attempted copulation (∼70%) in bioassays, equivalent to rates observed at orchid flowers. Whereas β-citronellol is well known, 2-hydroxy-6-methylacetophenone appears to be previously unknown as a floral volatile. Production of the two compounds is restricted to glandular sepal tips; thus, differential expression analysis of contrasting floral tissue transcriptomes was employed to illuminate the biosynthesis. As expected, production of (S)-β-citronellol commences with the terpene synthase GES1 catalyzing the irreversible conversion of geranyl diphosphate (GPP) to geraniol. Contrary to prediction, biosynthesis subsequently proceeds in three steps, commencing with the oxidation of geraniol to geranial by alcohol dehydrogenase ADH3, followed by the enantioselective reduction of a double bond in geranial by geranial reductase GER1 to give (S)-β-citronellal. Finally, ADH3-catalyzed reduction of (S)-β-citronellal results in (S)-β-citronellol. In line with previous work on insects showing that 2-hydroxy-6-methylacetophenone is derived from a polyketide pathway, we report a differentially expressed polyketide synthase (PKS) gene candidate. Thus, in this unique example of sexual deception, pollination is achieved by co-opting and regulating two independent biosynthetic pathways of floral volatile compounds. VIDEO ABSTRACT.

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“…However, the development of relatively inexpensive headspace techniques and sensitive benchtop GC-MS systems has improved the accessibility of VOC analysis. Moreover, pollination ecologists can overcome many of these barriers by simply collaborating with chemists (Raguso et al, 2015). Despite these barriers, the study of floral VOCs is an exciting and rewarding endeavor and is more important than ever if we are to understand and mitigate pollinator declines and climate change impacts.…”

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confidence: 99%

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

Burkle

Runyon

2017

Appl Plant Sci

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As diverse environmental changes continue to influence the structure and function of plant–pollinator interactions across spatial and temporal scales, we will need to enlist numerous approaches to understand these changes. Quantitative examination of floral volatile organic compounds (VOCs) is one approach that is gaining popularity, and recent work suggests that floral VOCs hold substantial promise for better understanding and predicting the effects of environmental change on plant–pollinator interactions. Until recently, few ecologists were employing chemical approaches to investigate mechanisms by which components of environmental change may disrupt these essential mutualisms. In an attempt to make these approaches more accessible, we summarize the main field, laboratory, and statistical methods involved in capturing, quantifying, and analyzing floral VOCs in the context of changing environments. We also highlight some outstanding questions that we consider to be highly relevant to making progress in this field.

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Improving our chemistry: challenges and opportunities in the interdisciplinary study of floral volatiles

Cited by 25 publications

References 135 publications

Phenotypic plasticity of floral volatiles in response to increasing drought stress

Phenotypic plasticity of floral volatiles in response to increasing drought stress

Complex Sexual Deception in an Orchid Is Achieved by Co-opting Two Independent Biosynthetic Pathways for Pollinator Attraction

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

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