Compositional changes of the floral scent volatile emissions from Asian skunk cabbage (Symplocarpus renifolius, Araceae) over flowering sex phases

Abstract

Introduction Flowering of the Asian skunk cabbage (Symplocarpus renifolius, Araceae) shows a sequential expression of female, bisexual and male sex phases. The protogynous thermogenic inflorescence has unpleasant odours, but the contributing chemical composition is poorly understood. Objective To determine the volatile composition of odour emissions from each S. renifolius flowering phase. Methodology The dynamic headspace method was used to collect floral volatiles from six intact S. renifolius inflorescences in their natural habitat. Collected volatiles from the three flowering phases were analysed using gas chromatography–mass spectrometry/olfactometry (GC–MS/O). Results Female‐phase inflorescences were characterised by an earthy‐rotten‐minty odour, while male‐phase inflorescences typically exhibited a rotten‐oily odour. Approximately 160 compounds were detected in volatiles from the three phases. Common to all phases were 3‐methylbutyl 3‐methylbutanoate, 1,8‐cineole, dimethyl disulphide and sabinene, together accounting for 52 to 54% of total volatiles. GC–MS/O revealed that at least 28 volatiles including eight S‐containing compounds contributed to the unpleasant odour of S. renifolius. Among them, dimethyl disulphide (onion‐like), methional (potato‐like), and the tentatively identified methyl dithioformate (garlic‐like) were intense odour‐active compounds in each floral phase. Additionally, 2‐isopropyl‐3‐methoxypyrazine (IPMP) was a major contributor to the earthy odour that was characteristic of the female phase. Conclusions No marked changes were observed in floral volatile compositions over the three flowering phases of S. renifolius. Instead, flower phase‐dependent proportional changes of minor components (e.g. IPMP and 2,3‐butanedione) altered the odour characteristics between the female and male phases.

Identification of Odor-Active Compounds Released from a Damaged Plant of the Asian Skunk Cabbage Symplocarpus renifolius

“…Forty compounds, 28 of them odor-active, were identified by GC–MS–O. Four of the compounds, namely, 3-methylbutyl 3-methylbutanoate, 1,8-cineole, dimethyl disulfide, and sabinene, were commonly found in all phases, collectively accounting for 52–54% of the total volatiles . An odor emitted from the damaged part of skunk cabbages, remains to be investigated.…”

“…In the analyses of floral scent volatiles from the intact inflorescences of S. renifolius, odorant 8a was detected as the odor-active component in GC−MS−O analyses and tentatively identified as methyl dithioformate. 5 These findings in S. renifolius are the first to suggest the presence of methyl dithioformate as a natural product. The compound, however, was synthesized as an intermediate in organometallics.…”

“…Between the two types of odors from the different plant organs of S. renifolius, our group analyzed floral volatiles from the intact inflorescences over three flowering phases in previous research. 5 The inflorescences in the female phase had an earthy−rotten−minty odor, whereas those in the male phase changed to a rotten−oily odor. Forty compounds, 28 of them odor-active, were identified by GC−MS−O.…”

“…Four of the compounds, namely, 3-methylbutyl 3-methylbutanoate, 1,8cineole, dimethyl disulfide, and sabinene, were commonly found in all phases, collectively accounting for 52−54% of the total volatiles. 5 An odor emitted from the damaged part of skunk cabbages, remains to be investigated. Our group ■ RESULTS AND DISCUSSION Identification of Odor-Active Compounds.…”

Protoplast-Based Transient Expression Combined with Plant Cultivation Systems as a Valuable Tool for Floral Thermogenesis Studies in Aroids

“…Increased temperature in their owers or cones enables them to effectively diffuse volatile odor components (VOCs) as attractants, which renders this ability to produce heat, also known as thermogenesis, an important reproductive strategy to attract pollinators (Meeuse and Raskin 1988). The principal composition of VOCs emitted from the in orescences was revealed in several thermogenic species, such as aroids (Kite and Hetterscheid 2017;Marotz-Clausen et al 2018;Oguri et al 2019;Shirasu et al 2010;Stensmyr et al 2002) and cycads (Azuma and Kono 2006;Salzman et al 2020;Terry et al 2007). In the cycad Macrozamia lucida, speci c pollinator thrips (Cycadothrips chadwickii) are attracted ("pulled") by lower concentrations of the dominant VOCs, b-myrcene, and repelled ("pushed") by higher concentrations of the same compound (Terry et al 2007).…”