A recent study on the titan arum, popularly referred to as the corpse flower due to its foul smell resembling decomposing flesh, reveals key genetic pathways and biological processes that generate heat and smelly compounds during the plant’s blooming period. This research sheds light on the flower’s unique ability to generate warmth before it opens, a phenomenon known as thermogenesis, which is relatively rare among plants and not well understood. Additionally, the study identifies a new ingredient in the corpse flower’s scent—a chemical called putrescine.
The corpse flower, famous for its distinct odor that mimics decaying flesh, attracts large crowds to greenhouses worldwide during its scarce blooming events. Scientists are particularly fascinated by the plant’s capability to elevate its temperature right before it blooms through thermogenesis, an unusual feature in the plant kingdom that remains largely enigmatic.
Recently, a study led by Dartmouth examined the inner workings of the corpse flower, uncovering essential genetic pathways and biological functions responsible for heat generation and the emission of odorous substances during blooming. Published on November 4 in PNAS Nexus, the research led by G. Eric Schaller, who is a professor of biological sciences, also revealed a new component contributing to the corpse flower’s scent—an organic compound known as putrescine.
Schaller and his team utilized several blooms of Morphy, Dartmouth’s 21-year-old corpse flower residing in the Life Sciences Greenhouse, for gathering tissue samples for both genetic and chemical analysis.
Interestingly, the titan arum isn’t simply one flower; rather, it consists of numerous smaller flowers enveloped within a towering central stalk referred to as the spadix. This spadix can reach heights of up to 12 feet, making it a visually striking feature of the plant. The titan arum can remain unbloomed for years, with a typical interval of 5 to 7 years, yet when it does bloom, the process occurs overnight. “These rare blooms are fleeting, giving us only a brief opportunity for study,” notes Schaller.
A wavy layer of petals at the base of the spadix, called the spathe, opens up to form a cup surrounding the central stalk, displaying deep red or maroon colors inside. As the spadix heats up—sometimes rising by as much as 20 degrees Fahrenheit above the ambient temperature—it shortly follows with the release of the plant’s unique scent, which consists of a mixture of sulfur-based compounds designed to attract flies and carrion beetles for pollination.
During Morphy’s bloom in 2016, researchers collected nine tissue samples over three nights, starting when the temperature of the spadix peaked, focusing on the spathe’s lip and base, as well as the appendix at the top of the spadix. They later supplemented their samples with two additional leaves.
Alveena Zulfiqar, who was a visiting research scholar at Schaller’s lab, successfully extracted high-quality RNA from the tissue, which allowed the team to perform RNA sequencing analyses to uncover the role of specific genes in temperature regulation and odor production.
“This enables us to observe which genes are expressed and particularly active during the heating and odor emission from the appendix,” explains Schaller, who specializes in how plant hormones influence growth and environmental responses. He also writes short horror fiction: “The corpse flower uniquely bridges both my scientific and literary interests,” he adds.
While thermogenesis is a common feature in animals, it is quite rare in plants. In animal cells, a group of proteins known as uncoupling proteins alter the process of storing chemical energy, instead releasing it as heat, according to Schaller.
The RNA analysis indicated that genes linked to the plant equivalents of uncoupling proteins, referred to as alternative oxidases, displayed increased activity in the tissues collected during the onset of flowering—particularly in the appendix region. Additionally, genes linked to sulfur transport and metabolism were also active at this time.
To better understand the mechanisms activated by these genes, the team isolated plant tissues during another bloom and collaborated with the University of Missouri, employing mass spectrometry to identify and assess the levels of various amino acids—components of proteins—in the tissues.
As anticipated from their RNA findings, they identified heightened amounts of a sulfur-containing amino acid called methionine, which is a precursor to sulfur-based compounds that readily evaporate when heated, resulting in strong odors. The levels of methionine rapidly declined in tissues sampled a few hours later.
A surprising discovery was the detection of increased quantities of another amino acid from spathe samples, which provides a precursor for producing putrescine, a scent associated with decaying animals.
This study marks a pioneering effort to decode the molecular mysteries of the corpse flower’s scent, unveiling how the titan arum manages its temperature and the specific roles that different parts of the flower cluster play in creating the foul smell that attracts pollinators.
Schaller indicates that Morphy still holds many secrets, as he turns his attention to uncovering the factors that trigger blooming and investigating whether plants housed together might synchronize their flowering to amplify the scent, further attracting pollinators.
