An intense smell reminiscent of rotting meat is thought to signal to pollen-carrying insects on behalf of the titan arum. But does the plant keep releasing the same odor throughout its brief flowering period?
A study published in 2025 by Rose K. Rossell and colleagues continuously measured compounds released by a single plant in a greenhouse. The researchers wanted to understand how the amount and composition of its odor change during flowering, and how much that signal is altered by chemical reactions in the air.
A Night for Receiving Pollen and a Night for Releasing It
What looks like one enormous flower is an “inflorescence,” a collection of small flowers. Inside it are female and male flowers. The female flowers first become receptive to pollen from other plants, and the male flowers release pollen the following night.
The researchers studied a plant that flowered at Colorado State University in the United States in May 2024. A sampling inlet placed approximately 3 meters downwind of the plant measured airborne volatile compounds every second. Air was also collected by another method to cross-check compound identities. These repeated measurements came from the same single plant, not a comparison of multiple plants or wild populations.
Sulfur Compounds Dominate the First Night; the Next Is Less Intense and More Diverse
On the first night, when the female flowers were active, sulfur-containing volatile compounds made up a large proportion of the emissions. Methanethiol was particularly abundant. Previous studies had emphasized dimethyl disulfide and dimethyl trisulfide, but the authors suggest that conventional sampling methods may not have captured highly volatile methanethiol adequately.
The sulfur compounds did not all reach their maxima simultaneously. Small releases as the inflorescence began opening were followed by larger peaks at different times for different compounds. Their sequence did not simply match the order of volatility. The authors suggest that production or metabolism within the plant contributes to these temporal changes, rather than stored odor merely escaping into the air.
On the following night, when the male flowers were active, sulfur-compound concentrations fell and the mixture became more balanced, including other classes of compounds. Substances known from floral scents, such as benzyl alcohol and monoterpenes, were detected on both nights. Several groups of compounds thus overlapped within a single carrion-like impression.
Calculations using the greenhouse volume and ventilation rate estimated first-night methanethiol emissions at approximately 12 grams per hour expressed as sulfur mass. This was an estimate derived from air measurements and ventilation conditions, not a direct weighing of the material released by the plant.
Keeping the Insects Attracted on the First Night Until the Next?
These differences between nights led the authors to consider a mechanism in which a strong odor attracts insects on the first night, the insects remain inside through the day, and they leave carrying pollen the following night. This would reduce the need to produce another large odor signal and attract new insects during the male-flower stage. The interpretation is that the resources invested in a large inflorescence and its scent could thereby be used efficiently for reproduction.
However, this experiment did not track insects to verify their trapping and release. The temporal changes in compounds are consistent with that mechanism, rather than demonstrating it. The idea that strong carrion odors and other, more conventionally floral compounds divide the tasks of attracting insects from a distance and guiding them inside is also a hypothesis for future testing.
Changes in the Air Can Change the Proportions in the Signal
Odors are not simply diluted by the wind. When they encounter highly reactive substances in the air, their components break down at different rates. If insects use combinations of compounds as cues, preserving their proportions matters as well as preserving the total amount.
The researchers calculated what would happen if the measured odor were exposed for three hours to nitrate radicals, oxidants active at night. Under conditions intended to represent a relatively unpolluted forest, the first night’s odor retained its component proportions relatively well even as its total amount declined, because its main compounds degraded at similar rates. By contrast, the following night’s mixture was more prone to changes in proportions because its components differed greatly in their reaction rates.
However, when oxidant levels were increased to represent urban air pollution, both the amount and composition of the odor changed substantially for both nights. Even the first night’s signal became less able to retain its chemical profile. These were model calculations, not field measurements of reduced insect flight or pollination.
Summary
The titan arum’s odor was a signal that changed over time, with large releases of sulfur compounds on the first night and a different amount and mixture on the next. The hypothesis that insects attracted on the first night are used again on the following night links this emission difference with the calculations showing that the first night’s component ratios are relatively persistent.
The authors also highlight another problem: even when a flower can produce an odor, its signal may not remain intact until it reaches the intended recipient. Air pollution combined with forest fragmentation could disrupt the chemical communication connecting plants far apart. The study proposes that conserving these enormous flowers requires attention not only to their habitat but also to changes in the air linking flowers and insects.
References
Rossell, R. K., Riches, M., Koss, A. R., Brenner, T., & Farmer, D. K. (2025). Efficient Pollination Stinks: Corpse Flowers Use Floral Trapping and Persistent Emissions. Geophysical Research Letters, 52, e2025GL117021. DOI: 10.1029/2025GL117021 / Full original article.
The research was supported by the US National Oceanic and Atmospheric Administration, the Alfred P. Sloan Foundation, and the US National Science Foundation. One coauthor is affiliated with the instrument manufacturer TOFWERK; the other authors declare no competing financial interests. Original article: © 2025 The Author(s), Creative Commons Attribution–NonCommercial (CC BY-NC).
