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Chemical Identity of a Rotting Animal-Like Odor Emitted from the Inflorescence of the Titan Arum (Amorphophallus titanum)

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The titan arum, Amorphophallus titanum, is a flowering plant with the largest inflorescence in the world. The flower emits a unique rotting animal-like odor that attracts insects for pollination. To determine the chemical identity of this characteristic odor, we performed gas chromatography-mass spectrometry-olfactometry analysis of volatiles derived from the inflorescence. The main odorant causing the smell during the flower-opening phase was identified as dimethyl trisulfide, a compound with a sulfury odor that has been found to be emitted from some vegetables, microorganisms, and cancerous wounds.
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Chemical Identity of a Rotting Animal-Like Odor Emitted
from the Inflorescence of the Titan Arum (Amorphophallus titanum)
Mika SHIRASU,1Kouki FUJIOKA,2Satoshi KAKISHIMA,3Shunji NAGAI,4Yasuko TOMIZAWA,5
Hirokazu TSUKAYA,6Jin MURATA,3Yoshinobu MANOME,2and Kazushige TOUHARA1;y
1Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences,
The University of Tokyo, Tokyo 113-8657, Japan
2Department of Molecular Cell Biology, Institute of DNA Medicine, Jikei University School of Medicine,
Tokyo 105-8461, Japan
3Botanical Gardens, Graduate School of Science, The University of Tokyo, Tokyo 112-0001, Japan
4National Cancer Center, Hospital East, Chiba 277-8577, Japan
5Department of Cardiovascular Surgery, Tokyo Women’s Medical University, Tokyo 162-8666, Japan
6Department of Biological Science, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
Received September 28, 2010; Accepted November 3, 2010; Online Publication, December 7, 2010
[doi:10.1271/bbb.100692]
The titan arum, Amorphophallus titanum, is a flower-
ing plant with the largest inflorescence in the world. The
flower emits a unique rotting animal-like odor that
attracts insects for pollination. To determine the chemi-
cal identity of this characteristic odor, we performed gas
chromatography-mass spectrometry-olfactometry anal-
ysis of volatiles derived from the inflorescence. The
main odorant causing the smell during the flower-
opening phase was identified as dimethyl trisulfide, a
compound with a sulfury odor that has been found to be
emitted from some vegetables, microorganisms, and
cancerous wounds.
Key words: Amorphophallus titanum; odor; gas chroma-
tography-mass spectrometry; olfactometry;
dimethyl trisulfide
The genus Amorphophallus is well known for the
characteristic odor of its inflorescence.
1)
Among the
species of the genus Amorphophallus,Amorphophallus
titanum (Becc.) Becc. ex Arcangeli is famous for the
large size of the inflorescence (Fig. 1A) and for emitting
a rotting animal-like odor.
2,3)
This odor probably attracts
pollinators such as carrion beetles and flies.
1)
Previous
studies using gas chromatography-mass spectrometry
(GC-MS) have identified several odorants, including
dimethyl oligosulfides, that are emitted from A. tita-
num,
1)
but it is not certain whether these odorants reflect
the odor of the flower as humans experienced it. In
addition, due to the rarity of flowering events, detailed
study of this species was limited until recently. In the
Botanical Gardens of The University of Tokyo, on July
22, 2010, we had an opportunity to analyze the smell of
the inflorescence of an A. titanum plant. The GC-MS-
olfactometry (GC-MS-O) technique allowed us to
analyze emitted odorous compounds that contribute to
the rotting animal-like smell during the flowering
period.
First we evaluated the intensity and quality of the
odors emitted from the inflorescence of A. titanum
during flowering by human nose (Fig. 2A). At the
beginning of flowering, a faint rotten fruit-like odor was
detected occasionally. Then the odor emitted from the
flower gradually intensified. During full opening of the
spathe, a strong rotting animal-like odor was emitted
constantly. In addition, infrared radiation from the
surface of the inflorescence was measured with a
thermograph (Neothermo TVS-600; Avionics Japan,
Tokyo), as described elsewhere.
4,5)
The odor became
stronger with heat production from the spadix, as
previously reported (Fig. 2B and C).
3,6)
After the peak
of the spadix temperature, the inflorescence began to
secrete a fluid from the spadix in which a rotten fish-like
odor was sensed.
Next we collected volatile compounds emitted from
the A. titanum. The volatiles derived from the inflor-
escence were absorbed directly to Carboxen/PDMS
(Carboxen/Polydimethylsiloxane) SPME (solid phase
micro extraction) fibers (SUPELCO, Bellefonte, PA)
that had been placed inside of the inflorescence from
21:00 to 23:00 on July 22 (Figs. 1B(a) and 2A). The
compounds on the SPME fibers were then analyzed by
GC-MS-O which enabled us to examine the mass spectra
and odor qualities of individual GC-separated odorants
simultaneously. Shimadzu GCMS-QP2010 (Shimadzu,
Kyoto) (a stabilwax column of 60 m 0.32 mm i.d.
with a film thickness of 0.5 mm) was combined with a
sniffing port equipped with a Sniffer9000 system
(Brechbuhler, Houston, TX) in splitless mode (MS and
sniffing port at ratio of 1:4.7). The column temperature
was programmed to rise at 5 C/min from 50 C (2-min
hold) to 230 C (30-min hold) (total run time, 68 min).
The interface temperature was maintained at 200 C and
the ion source temperature at 230 C. Mass spectra were
obtained in full scan mode (range 20–400) by electron
impact using the NIST library database.
yTo whom correspondence should be addressed. Fax: +81-3-5841-8024; E-mail: ktouhara@mail.ecc.u-tokyo.ac.jp
Abbreviations: GC-MS, gas chromatography-mass spectrometry; GC-MS-O, GC-MS-olfactometry; TIC, total ion chromatogram; RT, retention
time; DMTS, dimethyl trisulfide; DMDS, dimethyl disulfide
Biosci. Biotechnol. Biochem.,74 (12), 2550–2554, 2010
Communication
Figure 3A shows total ion chromatograms (TIC) of a
SPME-absorbed sample collected by the method shown
in Fig. 1B(a). The odor characters sensed at the sniffing
port are described under the chart. GC-MS-O analysis
and evaluation of odors were performed by three
persons. The sensory characters of the odor-positive
peaks and the identified odorants are summarized in
Fig. 3D. The characteristic rotting animal-like surfury
odor, which was identical to the odor we sensed in the
inflorescence during the opening of the spathe, came
out at a retention time (RT) of 18.79 min. The mass
spectrum of the peak predicted the structure of dimethyl
trisulfide (DMTS) (Fig. 3C). The mass spectrum and the
retention time of authentic DMTS (Wako, Tokyo) were
identical to those of the peak compound, confirming
that the sulfury odor at RT ¼18:79 min was DMTS
(Fig. 3C).
In addition, the gaseous odor (RT ¼9:06 min) was
identified as methyl thiolacetate, and the cheesy, foot-
like valerian odor (RT ¼25:93 min) was identified as
isovaleric acid (Fig. 3A). The green odor at RT ¼16:19
could not be identified due to low concentration or to
overlapping peaks in the TIC. Dimethyl disulfide
(DMDS), which has been reported to be a major odorant
emitted from A. titanum, was also detected abundantly
at RT ¼9:80 min, but we could not sense the odor by
GC-MS-O analysis due to a high threshold,
7,8)
suggest-
ing that the contribution of DMDS to human olfactory
perception is not significant. The presence of a large
amount of DMDS, however, is plausible, because
DMDS is thought to be a precursor of DMTS which is
biosynthesized from methionine or S-methyl-L-cysteine
sulfoxide via methanethiol, which was also detected by
GC-MS (Fig. 3A).
9,10)
Considering that GC-MS-O anal-
ysis directly identifies crucial volatiles that contribute to
the quality of the smell that humans sense, these results
suggest that the main odorous component of A. titanum
is DMTS. GC-MS-O analysis of another flowering
A. titanum cultivated in a greenhouse at Flower Park
Kagoshima gave the same results (flower opening on
August 2, 2010) (data not shown).
At the end of the flower-opening phase, the odor
quality of the inflorescence changed gradually following
secretion of the odorous fluid from the spadix. The fluid
secreted from the spadix was collected from 1:00 to 3:00
on July 23, and head-space volatile compounds from a
10 ml sample enclosed in a 40 ml glass vial were absorbed
to SPME fibers for 7 h (Fig. 1B(b)). GC-MS-O analysis
of the SPME sample showed a strong rotten fish-like
odor similar to the odor we sensed at the end of the
flower-opening phase at RT ¼3:33 min, and this was
identified as trimethylamine (Fig. 3B, inset). Green,
burnt odor (RT ¼6:13 min) was identified as 3-methyl
butanal, and a vinegary odor (RT ¼20:47 min) as acetic
acid (Fig. 3B).
Time Event Odor quality
14:00 Opening of the spathe Slight rotten fruit-like odor
16:00
18:00
Yellow pickled radish
Spathe full opened Rotting animal-like odor
20:00
22:00 Spadix warming phase
0:00
Fluid exuded from the spadix
2:00
Rotten fish, Rotten egg
4:00
6:00
8:00 Closing of the spathe
Strong rotting animal-like odor
Rotten egg
daytime
nighttime
daytime
28oC35oC
19:47
0:47
ABC
18:00
22:00
2:00
6:00
-2
0
2
4
6
28
30
32
34
36
Spadix temperature (oC)
16:00
20:00
0:00
4:00
8:00
Spadix temp - ambient temp (oC)
July 22
July 23
Fig. 2. Scheme of the Flowering Behavior, Odor Quality and Thermogenesis of A. titanum.
(A) Flowering events and characteristic odors of A. titanum. The darkness of the gray indicates the intensity of the rotting animal-like odor.
(B) Time course record of spadix temperature (black line). Difference between the spadix and the ambient temperature (red line).
(C) Representative thermographic images (top, taken at 19:47 on July 22, 2010; bottom, taken at 0:47 on July 23, 2010). Scale bar, 20 cm.
Spadix
Spathe
AB
Fluid
Gas
SPME
SPME
(a)
(b)
Spadix
Spathe
Fig. 1. Odor Sampling from a Flower of Amorphophallus titanum.
(A) Full opening of the spathe of an A. titanum with a height of
1.6 m in the Koishikawa Botanical Gardens in July 2010. Scale bar,
20 cm. (B) Methods of collecting volatiles emitted from A. titanum.
(a) Volatile compounds from the inflorescence were directly
absorbed to SPME fibers placed between the spadix and the spathe.
(b) A fluid secreted onto the spadix was collected, and the head-
space volatiles from the fluid were absorbed to SPME fibers. Scale
bar, 20 cm.
Odor from a Flower of the Titan Arum 2551
Finally, we attempted to evaluate flower odor objec-
tively by using an electronic nose, FF-2A (Shimadzu,
Kyoto).
11,12)
The device contains electronic sensors with
various sensitivities and selectivities for volatile com-
pounds, and is standardized with nine gases (hydrogen
sulfide, methylmercaptan, ammonia, trimethylamine,
propionic acid, butylaldehyde, butylacetate, toluene,
and heptane), the odor quality of which can be
categorized into nine groups (hydrogen sulfide, sulfur,
ammonia, amine, organic acid, aldehyde, ester, aromatic
group and carbon hydrate). The flower smell was
collected directly into a 2 L tedlar bag (SUPELCO,
Bellefonte, PA) with a sampling pump (GL Sciences) at
21:00 on July 23. The collected air was diluted 5-fold
with odorless nitrogen gas and injected into the FF-2A.
Various concentrations of DMTS and DMDS were also
applied to the device. The virtual odor index in terms of
the nine aromatic categories is plotted in Fig. 4. For the
sample of A. titanum, the sulfur category was identified
as the highest odor index, and organic acid, aldehyde,
amine, and ester categories constituted lower index
categories (Fig. 4A). In a series of diluted DMTS, the
chart pattern of 0.01 ppm DMTS was similar to that of
the A. titanum sample (Fig. 4), which was fairly
consistent with the approximate concentration of DMTS
emitted as calculated at the basis of the GC-MS analysis
(data not shown). The chart pattern of DMDS was also
similar to that of the A. titanum sample, but the overall
odor intensity was weaker than that of DMTS (see
Fig. 4B and E). These results again confirm that DMTS
is the major contributor to the flower smell for human
olfactory sensation.
In conclusion, simultaneous evaluation of odor qual-
ity and the molecular masses of volatiles by GC-MS-O
enabled us to identify DMTS as the main odorant that
causes the rotting animal-like odor of A. titanum during
CD
126
15 32
45
64
79
111
100
80
60
40
20
0
20 40 60 80 100 120
m/z
Intensity (%)
126
32
45
64
79
111
100
80
60
40
20
0
20 40 60 80 100 120
m/z
Intensity (%)
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
0.0×10 -00
1.0×10 07
2.0×10 07
Time (min)
Intensity
Green
Sulfury
Valerian
Gaseous
A
S O SSS
O
OH
Gas-SPME
RT=18.8 min
Authentic DMTS
B
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
0.0×10 -00
1.0×10 07
2.0×10 07
Time (min)
Intensity
Rotten fish
Acidity
Sulfury
Green, burnt
O
OH
O
N
Fluid-SPME
Gas Fluid
3.33 Rotten fish Trimethylamine - ++
6.13 Green, burnt 3-Methyl-butanal - +
9.06 Gaseous Methyl thiolacetate + -
16.19 Green + -
18.79 Surfury Dimethyl trisulfide ++ +
20.47 Acidity Acetic acid - +
25.93 Valerian, cheese, feet Isovaleric acid + -
RT Odor character Odorant Odor intensity
2 3 4 5
0
5.0×10 06
1.0×10 07
1.5×10 07
TIC
2 3 4
0
5.0×10 06
1.0×10 07
1.5×10 07
5
TIC
m/z
EI
C
EI
C
SCH3H
SS
Fig. 3. GC-MS-O Analysis of SPME-Absorbed Head-Space Volatiles Emitted from A. titanum.
(A) Total ion chromatogram of volatile compounds absorbed to SPME fibers by the method described in Fig. 1B(a). Characteristics of odors
sensed at the sniffing port of GC-MS-O are described at the bottom of the chart. (B) Total ion chromatogram of head-space volatiles emitted from
the fluid of spadix, as described in Fig. 1B(b). Inset in (A) and (B) is the close-up TIC from 2 min to 5 min. The light gray and dark gray lines
indicate extracted ion chromatograms of the molecular ion peaks of trimethylamine (m=z59) and methanethiol respectively (m=z48)
respectively. (C) Mass spectrum of the peak at 18.8 min of TIC in Fig. 3A (top). Mass spectrum of authentic DMTS (bottom). (D) Retention
times (RTs), odor characters, and chemical identities of odor-positive peaks by GC-MS-O analysis. The intensities of the odors at the odor-
positive peaks in Fig. 3A (odor intensity, Gas) and 3B (odor intensity, Fluid) are categorized into three groups: not detected (), slight (þ),
strong (þþ).
2552 M. SHIRASU et al.
the opening of the spathe. Trimethylamine was found to
be the odorant that caused the rotten-fish odor at the end
of flowering. We also identified several other com-
pounds contributing to the odor of the inflorescence,
including methyl thiolacetate, 3-methyl butanal, acetic
acid, and isovaleric acid.
DMTS has been reported to be present in volatiles
emitted from vegetables such as cooked onion and
cabbage, decayed meats, and fermented food and drink,
which usually cause fly attraction.
13,14)
Indeed, oligo-
sulphides emitted from the flower of dead-horse arum
(Helicodiceros muscivorus) have been reported to be
attractants for flies,
15)
suggesting that A. titanum also
fools flies into pollinating it by mimicking the odors of
fermented products and rotting animal bodies. On the
other hand, an interesting coincidence is that DMTS is
known to be the main source of the malodor of fungating
cancer wounds in human.
16)
Indeed, the odor index
pattern of the head-space volatiles of a gauze pad placed
on a breast cancer wound was very similar to that of
A. titanum on electronic nose FF-2A (Fig. 4G). It is an
intriguing question how mechanisms of producing
DMTS have been acquired in various organisms as a
signal for various purposes during the process of
evolution.
Acknowledgment
We are grateful to Tadashi Yamaguchi (Botanical
Gardens, Graduate School of Science, the University of
Tokyo) for the photograph of A. titanum in Fig. 1A.
This research was approved by the Research Ethics
Committee of the University of Tokyo. It was supported
in part by grants from the Ministry of Education,
Culture, Sports, Science, and Technology (MEXT) of
Japan.
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... The scents emitted by Amorphophallus species are reminiscent of carrion, various forms of excrements, fish, sewerage, nauseating gases, rancid cheese, fermenting fruit and mushrooms. [34][35][36][37][38][39][40][41] Table S1 lists all the investigated Amorphophallus species, the analyzed voucher and sampling time and the identified scent compounds in their relative amount as well as the subjective perception. ...
... Dimethyl oligosulphides are characteristic of the decomposition of various organic matters, ranging from sulfur-rich vegetables, to cancerous wounds and most importantly cadaveric decomposition and carnivore dung. 10,41,44 They are released in various plant lineages and represent well-known attractants for various copro-necrophagous beetles and flies. [45][46][47] Furthermore, two distantly related Amorphophallus clades, comprising a handful of species each, were found to be characterized by the emission of benzenoid compounds, which are considered to be strongly evolutionarily constrained. ...
... The documented variation can obviously at least partly be accounted for by different study methodologies 37,38,40 or because of different sampling times or sample overloads, etc. 38 Particularly, the sampling time seems to be a critical aspect, as the variation in scent composition may strongly vary during anthesis. 13,38,41,55 Thus, whenever possible, a consistent sampling protocol was ensured, minimizing the influence of the sampling time. 38 However, some individuals reveal a broader intraspecific variation or scent polymorphism. ...
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Caryocar brasiliense is a flagship species of the Brazilian Cerrado. It produces flowers with a strong peculiar scent, which are pollinated by bats and occasionally moths with short mouthparts. However, the cues responsible for attracting these nocturnal pollinators remain unknown. We aimed to identify osmophores of C. brasiliense, describe the ultrastructure of the cells involved in the synthesis and release of floral odour, and identify the constituents of the floral bouquet. We performed field observations and histochemical and ultrastructural analyses of flowers focusing on the androecium. Gas chromatography-mass spectrometry was used to analyse the scents emitted. Filament epidermal cells were found to possess an unusual shape and be responsible for the main production and release of odour. These cells, called foraminous cells, are elongate and possess pores where their cell walls are abruptly thin. The cuticle is practically absent over the pores, which facilitates odour emission. The foraminous cells have conspicuous nuclei and organelle-rich cytoplasm where oil droplets can be seen prior to anthesis. The features of these cells remain similar during anthesis, but many vesicles fuse with the plasma membrane and the number of oil droplets in the cytosol decreases. Twenty-nine components were found in the scent, especially fatty acid derivatives and N- and S-bearing compounds. Our analyses revealed that the androecium of C. brasiliense has a particular structure that acts as an osmophore. The scent from the androecium resembles that of the entire flower, which is an unprecedented finding for a plant with single flowers as the pollination unit.
... The spadix is divided into a lower pistillate zone, followed by an upper staminate zone and finally on top, a sterile appendix that serves scent volatilization (Mayo et al., 1997;Kite & Hetterscheid, 2017). Scent volatilization is known to be promoted by heat generation in the appendix, at least in some species (Skubatz et al., 1990;Barthlott et al., 2009;Lamprecht & Seymour, 2010;Shirasu et al., 2010). ...
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Encompassing ca. 200 species distributed in paleotropical Africa and Asia, Amorphophallus is one of the largest genera of Araceae. In spite of a great economic interest for its glucomannan production, only few studies have attempted to grasp the evolutionary history of this genus. In the current state of knowledge, four main clades, mostly linked to biogeographical delineation, have been identified from phylogenies based on few genes. However, relationships among and within these clades still remain unclear, due to the rapid radiation that occurred during the early evolutionary history of the genus. Here, we generated genome skimming libraries for 43 specimens from 36 species distributed across the four clades, which allowed us to produce a phylogenetic matrix for a set of 71 plastid genes. Our phylogenies confirm the monophyly of these clades but show a new and well‐resolved arrangement among these clades. Our analyses therefore provide a new scenario and timeline for the evolution of the main Amorphophallus clades, consistent with the morphological characteristics of the clades. The inferred scenario is also in agreement with climate dynamics and the onset of long‐distance dispersal by the earliest migratory birds near the Oligocene/Miocene transition around 23 million years ago. Our study provides an up‐to‐date baseline to understand biogeographic and ecological processes that shaped the current diversity and distribution of Amorphophallus, paving the way for larger‐scale phylogenomic studies based on plastid and nuclear genomes. This article is protected by copyright. All rights reserved.
... Increased temperature in their flowers 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 inflorescences 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 dioecious cycads, such as Macrozamia lucida and Zamia furfuracea, male cones regulate the concentration of the dominant VOCs by oscillating their internal temperature. ...
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Key message Floral thermogenesis is an important reproductive strategy for attracting pollinators. We developed essential biological tools for studying floral thermogenesis using two species of thermogenic aroids,Symplocarpus renifolius and Alocasia odora. Abstract Aroids contain many species with intense heat-producing abilities in their inflorescences. Several genes have been proposed to be involved in thermogenesis of these species, but biological tools for gene functional analyses are lacking. In this study, we aimed to develop a protoplast-based transient expression (PTE) system for the study of thermogenic aroids. Initially, we focused on skunk cabbage (Symplocarpus renifolius) because of its ability to produce intense as well as durable heat. In this plant, leaf protoplasts were isolated from potted and shoot tip-cultured plants with high efficiency (ca. 1.0 × 10⁵/g fresh weight), and more than half of these protoplasts were successfully transfected. Using this PTE system, we determined the protein localization of three mitochondrial energy-dissipating proteins, SrAOX, SrUCPA, and SrNDA1, fused to green fluorescent protein (GFP). These three GFP-fused proteins were localized in MitoTracker-stained mitochondria in leaf protoplasts, although the green fluorescent particles in protoplasts expressing SrUCPA-GFP were significantly enlarged. Finally, to assess whether the PTE system established in the leaves of S. renifolius is applicable for floral tissues of thermogenic aroids, inflorescences of S. renifolius and another thermogenic aroid (Alocasia odora) were used. Although protoplasts were successfully isolated from several tissues of the inflorescences, PTE systems worked well only for the protoplasts isolated from the female parts (slightly thermogenic or nonthermogenic) of A. odora inflorescences. Our developed system has a potential to be widely used in inflorescences as well as leaves in thermogenic aroids and therefore may be a useful biological tool for investigating floral thermogenesis.
... The scent compounds of nearly a hundred Amorphophallus species have been analysed Hetterscheid 1997, 2017;Kite et al. 1998;Kakishima et al. 2011;Lamprecht and Seymour 2010;Shirasu et al. 2010;Chen et al. 2015;Raman et al. 2017) and most species release scent types that include "carrion, faeces, urine, dung, fishy, sewerage, nauseating gaseous, rancid cheese, fermenting fruit and mushrooms" (Kite and Hetterscheid 2017). These odour types are effective cues for insects that search for such substrates for feeding, mating or breeding, indicating the deceptive nature of the majority of Amorphophallus species (Kite et al. 1998;Jürgens et al. 2006Jürgens et al. , 2013Vereecken and McNeil 2010;Urru et al. 2011;Johnson and Schiestl 2016;Kite and Hetterscheid 2017). ...
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The genus Amorphophallus encompasses some 230 species and is one of the largest genera of the Araceae family. Most species release scents, smelling of carrion, faeces, dung and similar nauseating odours for pollinator attraction and are therefore considered to have evolved a deceptive pollination syndrome. Some of the most iconic members of the genus, such as the A . titanum and A . gigas , are considered to be carrion mimics. Copro-necrophagous insects, beetles and flies in particular, are attracted by these scents and are therefore assumed to act as pollinators. However, many reports and observations on Amorphophallus pollinators are anecdotal in nature or do not distinguish between legitimate pollinators and non-pollinating visitors. Moreover, some published observations are not readily accessible as they are many decades old. Therefore, the available data and information about insect visitors and/or pollinators in the genus Amorphophallus is compiled, reviewed and discussed.
... It is likely that these plants evolved to mimic the stage that attracts the highest number of deceived pollinators during active decay (see Kočárek 2003) rather than a fresh carcass that would attract a limited number of early colonizers (reviewed in Jürgens and Shuttleworth 2015). MeSAc is also produced by corpse-mimicking plants, but its role has not been explored (Kite and Hetterscheid 2017;Shirasu et al. 2010). We recently uncovered evidence that MeSAc has a powerful enhancer effect as a synergist of DMTS, attracting nonparental silphine beetles that specialize on the active decay stage (Trumbo and Dicapua 2020). ...
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When burying beetles first emerge as adults, they search for well-rotted carcasses with fly maggots on which to feed. After attaining reproductive competence, they switch their search and respond to a small, fresh carcass to prepare for their brood. Because the cues used to locate a feeding versus a breeding resource both originate from carrion, the beetles must respond to subtle changes in volatiles during decomposition. We investigated cues used to locate a fresh carcass in the field by (1) a general subtractive method, applying an antibacterial or antifungal compound to reduce microbially derived volatiles, and (2) a specific additive method, placing chemical supplements near a fresh carcass. Five sulfur-containing compounds, known to result from bacterial metabolism of sulfur-containing amino acids, were studied: dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), methyl thiolacetate (MeSAc, also known as S-methyl thioacetate), and methyl thiocyanate (MeSCN). When a carcass aged for 48 h was treated with an antibacterial compound to reduce volatiles, there was a 59% decrease in beetles discovering the resource. The addition of the chemical supplement MeSAc had no effect on discovery of a fresh carcass, while DMS and DMDS had a limited ability to attract breeding beetles. The chemical that was least well known, MeSCN, increased beetle numbers by 200–800% on a fresh carcass and almost guaranteed discovery. DMTS, which is known to attract a variety of carrion insects, was the only compound to significantly reduce beetle presence at a fresh carcass. A laboratory experiment demonstrated that DMTS does not directly inhibit breeding, suggesting that DMTS deters breeding beetles while they fly.
... This velvety, leathery structure might be to mimic animal skin and, combined with its odor, might be used to attract potential pollinators. Therefore, it is possible that there is odor-emitting chemical secretion from epidermal cells, similar to Amorphophallus titanum, such as methyl thiolacetate, dimethyl trisulfide, and isovaleric acid (Shirasu et al. 2010). However, we were unable to locate secretory cells in this study. ...
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Main conclusion: A histological study of Rafflesia patma revealed the simplicity of a flower's vascular tissue and epidermal features of flower organs, including their structures and pigmentation. Rafflesia is an endophytic holoparasitic plant that infects Tetrastigma. In a previous study, we characterized the shape of the strands of an endophyte (Rafflesia patma Blume) and hypothesized their distribution. In this study, we deepened our analysis by assessing parts of flower tissue sampled during anthesis, performed surface casting of the abaxial and adaxial sides of the perigone lobe to profile their surface features, and histologically characterized the perigone lobe, perigone tube, and central column base, including the anther and cupula region. The objective of these observations was to compare tissues from different organs and the distribution of cells staining positive for tannin, suberin, and lignin. Observable features in this study were vascular and epidermal tissue. We also observed reduced vascular tissue with xylem and vascular parenchyma in multiple organs. The adaxial epidermis found in the perigone lobes and tube had papillate cells, and their function might be to assist with the emission of odor through chemical evaporation. The abaxial epidermis, also found in perigone lobes and tube, had flattened cells. These, combined with the nearby flattened parenchyma cells, especially in the outermost, early perigone lobe, might provide a tougher (stiffer) outer protective barrier for the flower. The accumulation of tannin in perigone lobes might offer protection to the flower from herbivores prior to anthesis. Although a previous observation indicated the possibility of stomata on the surface of Rafflesia flowers, no stomata were found in this study.
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Covering: up to 2019 Soon after the birth of gas chromatography, mass spectrometry and olfactometry were used as detectors, which allowed impressive development to be achieved in the area of odorant determinations. Since the mid-80s, structured methods of gas chromatography-olfactometry have appeared, allowing the determination of which odor constituents play a key role in materials. Progressively, numerous strategies have been proposed for sample preparation from raw materials, the representativeness evaluation of extracts, the identification of odor constituents, their quantification, and subsequently, the recombination of the key odorants to mimic the initial odor. However, the multiplicity of options at each stage of the analysis leads to a confusing landscape in this field, and thus, the present review aims at critically presenting the available options. For each step, the most frequently used alternatives are described, together with their strengths and weaknesses based on theoretical and experimental justifications according to the literature. These techniques are exemplified by many applications in the literature on aromas, fragrances and essential oils, with the initial focus on wine odorants, followed by a short overview on the molecular diversity of key odorants, which illustrates most of the facets and complexities of odor studies, including the issues raised by odorant interactions such as synergies.
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Thermologic investigations were carried out on three species of Amorphophallus: A. konjac, A. paeoniifolius and A. titanum, all the three strongly thermogenic. Moreover, their breeding system is described as protogynous, the heat production occurs in the appendix and male florets, no warming is seen in the female florets and pollen is shed after the end of heat dissipation. All the three have large, impressive inflorescences developed from big corms and have considerable sizes. During their inflorescence, they have a strong scent like rotting meat with carrion smell. Amorphophallus konjac (K. Koch) has a large, exposed appendix that produces a disgusting scent during the day of the female phase of blooming. The appendix produces about 3 W for several hours, and the temperature elevation is about 2.9 K. The low temperature elevation is attributed to a high surface area and a high evaporative heat loss from the appendix. During the male phase of blooming, a second episode of thermogenesis occurs during the same time of day, apparently from the male florets, reaching a maximum of 1.6 W. Amorphophallus paeoniifolius (Dennst.) Nicolson has a spadix that varies considerably from that of A. konjac and A. titanum with an amorphous upper end of the appendix like a shrunken red pepper instead of cone-like appendices for the two others. It shows thermogenic temperature increases of up to +9.1 K in the male florets and +2.6 K for a short time in the appendix. Amorphophallus titanum (Becc.) Becc. ex Arcang is the largest inflorescence of the world, growing up to 300 cm high and 250 cm across. A much smaller plant was observed during its thermogenic period by means of infrared (IR) thermography, IR thermometry, and thermometric data logger. The temperature maximum showed 36.6 °C at ambient 24.0 °C, which means a temperature difference of about +12.6 K. In the morning of the next day, all temperatures are back to ambient at about 24 °C. Estimates of the heat production (about 74 W) were made from the geometric data and special assumptions with respect to the heat transfer.
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Smell provides important information about the quality of food and drink. Most well-known for their expertise in wine tasting, sommeliers sniff out the aroma of wine and describe them using beautiful metaphors. In contrast, electronic noses, devices that mimic our olfactory recognition system, also detect smells using their sensors but describe them using electronic signals. These devices have been used to judge the freshness of food or detect the presence of pathogenic microorganisms. However, unlike information from gas chromatography, it is difficult to compare odour information collected by these devices because they are made for smelling specific smells and their data are relative intensities. Here, we demonstrate the use of an absolute-value description method using known smell metaphors, and early detection of yeast using the method. This technique may help distinguishing microbial-contamination of food products earlier, or improvement of the food-product qualities.
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Mechanisms for the formation of methanethiol, dimethyl disulfide, and dimethyl trisulfide in disrupted cabbage tissues were investigated. Dimethyl disulfide was produced in both air- and nitrogen-saturated disrupted cabbage tissues without significant differences (p ≤ 0.05), which indicated that air oxidation of methanethiol is not the predominant mechanism for the formation of dimethyl disulfide. These results favored the mechanism in which the formation of dimethyl disulfide occurs from chemical disproportionation of methyl methanethiosulfinate. Methanethiol and dimethyl trisulfide were formed rapidly in model systems containing either methyl methanethiosulfinate or methyl methanethiosulfonate and hydrogen sulfide. This indicated that the reactions of the thiosulfinate and thiosulfonate compounds with hydrogen sulfide are prominent mechanisms for the formation of methanethiol and dimethyl trisulfide following the action of cysteine sulfoxide lyases. Methyl methanethiosulfinate and methyl methanethiosulfonates were found to possess characterizing sauerkraut aroma notes.
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An outstanding flagship species in the plant kingdom is the Titan arum (Amorphophallus titanum), which produces a fountain-like bloom up to 3 m high. The unique appearance of three simultaneous inflorescences in May 2006 was a chance to analyse the flowering behaviour and thermogenesis of this giant. For the first time, the heating of the central column (spadix) could be documented using a high-performance thermographic camera. Time series analyses of the infrared image sequences revealed that the 3-m high spadix surface heats up in pulses emanating from the base of the inflorescence. The surface temperature reaches over 36 degrees C, compared to the ambient temperature of 27 degrees C. Waves of the carrion-like odour are synchronised with these heat pulses. The combination of heat pulses, the fountain-like shape plus the enormous size lead to a unique type of 'convection flower'. On the basis of our observations, we assume that Amorphophallus titanum is able to overcome thermodynamic decoupling by a self-produced convective process.
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Dimethyl trisulfide (DMTS) is involved in the unpalatable aroma of stale sake, called "hineka"; however, the mechanism underlying the formation of DMTS during the storage of sake has not been elucidated. This paper investigates the precursors of DMTS in sake. An experiment using [methyl-d(3)]-methionine showed that Strecker degradation of methionine plays a minor role in the formation of DMTS. Separation of components in sake by cation exchange resin revealed that DMTS precursors are present in the acidic/neutral fraction rather than in the basic one. Purification of the DMTS precursor compounds was carried out through several chromatographic steps, measuring DMTS-producing potential as an index. High-resolution ESI-MS and 1D/2D NMR experiments enabled the identification of one of the precursor compounds as 1,2-dihydroxy-5-(methylsulfinyl)pentan-3-one.