β-Ocimene, a Key Floral and Foliar Volatile Involved in Multiple Interactions between Plants and Other Organisms

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Plants generally synthesize and emit species-specific floral volatile organic compounds (VOCs) mixtures to attract pollinators by mixing several of these common VOCs. Photo by Pexels

More than 1700 volatile organic compounds (VOCs) have been identified in the floral scents of flowering plants. These VOCs are not equally distributed across the phylogeny of flowering plants, so that the commonness and predominance of these compounds in floral scents varies widely among species. Common floral VOCs have a widespread phylogenetic distribution, which means that they are present in the floral scents of many species from different plant families. Instead, less common floral VOCs are only present in plants that are pollinated by specific pollinator groups with specific innate preferences for those VOCs.

β-Ocimene is a very common plant volatile released in important amounts from the leaves and flowers of many plant species. This acyclic monoterpene can play several biological functions in plants, by potentially affecting floral visitors and also by mediating defensive responses to herbivory.

In a new study in the journal Molecules authors indicated that the ubiquity and high relative abundance of β-ocimene in the floral scents of species from most plant families and from different pollination syndromes (ranging from generalism to specialism) strongly suggest that this terpenoid may play an important role in the attraction of pollinators to flowers.

In this study authors compiled abundant evidence from published studies that supports β-ocimene as a generalist attractant of a wide spectrum of pollinators. They found no studies testing behavioural responses of pollinators to β-ocimene, that could directly demonstrate or deny the function of β-ocimene in pollinator attraction; but “several case studies support that the emissions of β-ocimene in flowers of different species follow marked temporal and spatial patterns of emission, which are typical from floral volatile organic compound (VOC) emissions that are involved in pollinator attraction”, said Dr. Gerard Farré-Armengol from CREAF-CSIC Barcelona, now in the University of Salzburg.

Furthermore, important β-ocimene emissions are induced from vegetative plant tissues after herbivory in many species, which have relevant functions in the establishment of tritrophic interactions. Authors thus conclude that β-ocimene is a key plant volatile with multiple relevant functions in plants, depending on the organ and the time of emission.

Experimental behavioural studies on pure β-ocimene conducted with pollinating insects will be necessary to prove the assumptions made here. “In view of the presented indirect evidences, we strongly encourage the inclusion of β-ocimene alone or in combination with other floral volatiles in coupled gas chromatography electroantennographic detection (GC-EAD) analyses and behavioural tests when conducting future studies in order to provide a solid experimental proof for the assumptions made in the study”, said Prof. Josep Peñuelas from CREAF-CSIC Barcelona.

This study was funded by the European Research Council Synergy grant ERC-2013-SyG-610028, the Spanish Government project CGL2016-79835-P and the Catalan Government grant FI-2013

Journal Reference: Farré-Armengol, G., Filella, I., Llusià, J., Peñuelas, J. 2017. β-Ocimene, a Key Floral and Foliar Volatile Involved in Multiple Interactions between Plants and Other Organisms. Molecules 2017, 22, 1148; doi: 10.3390/molecules22071148.