Ellen Phiddian
Cosmos science journalist
A huge, stinking corpse flower is blooming in Geelong – an event that only lasts for a few days, roughly every 5 years.
The corpse flower, also called the titan arum or Amorphophallus titanum, has become a public spectacle for botanic gardens over the last decade.
The rare bloom is accompanied by rare “thermogenesis” – internal temperatures in the flower reach 40°C – and a smell like rotting corpses, to attract pollinating flies.
While the plants have grown well in botanic gardens (this Geelong flower has been propagated from a population grown in Adelaide), they’re still endangered in their native Sumatra.
And there is still much to understand about them: for instance, how do they produce all that heat and stink?
A new Amorphophallus titanum study, published in PNAS Nexus, has some answers.
The researchers examined a corpse flower named Morphy at Dartmouth College, USA, when it bloomed in 2016 and 2022.
“The blooms are rare and also short-lived, so we only get a small window to study these phenomena,” says co-author Professor Eric Schaller, a molecular biologist at Dartmouth.
When the titan arum blooms, a sheaf called the “spathe” appears overnight, unfurling to reveal a huge yellow “spadix”, covered in tiny yellow flowers. Spadices can reach 2m in height, and are the source of the plant’s heat and smell.
The team collect 9 tissue samples from Morphy over its 3 nights of blooming in 2016: from the lip and base of the spathe, and the top of the spadix. They also collected 2 samples from the plant’s leaf after it bloomed, in 2017.
They extracted genetic material from each sample – specifically, RNA forming the intermediate step between DNA and the proteins it codes for.
“This helps us see what genes are being expressed and to see which ones are specifically active when the appendix heats up and sends out odour,” says Schaller.
They found that genes for certain proteins, called alternative oxidases, were being promoted more at the beginning of flowering, and especially at the top of the spadix. These genes are responsible for the plant’s heat.
Genes related to sulphur transport and metabolism were also more active.
The team then took tissues from Morphy in its 2022 bloom, and analysed the amounts of amino acids (the molecules which proteins are made from) inside them.
In pre-blooming tissue, they found very high levels of the amino acid, methionine, which contains sulphur and which is known to turn readily into foul-smelling sulphur-based compounds.
Methionine levels were lower in post-bloom tissues, which is explained by the high levels of stinky dimethyl disulphide and dimethyl trisulphide produced during the bloom.
The researchers were expecting methionine changes, but they also found similar patterns in another, sulphur-free amino acid: arginine.
Arginine serves as a precursor to the compound putrescine, which produces the rotting corpse smell. Putrescine had not previously been noted by corpse flower scientists, but this team found it in the titan arum’s odour.
Next, the team is working to find out if there are any chemical indicators that might signal a flower is about to bloom. They’re also looking at synchronous blooming in specimens housed together.
