Some of the world’s oldest plants produce their own heat to beam out invisible infrared signals that draw in beetle pollinators.
The discovery focuses on cycads, ancient gymnosperms that rely on beetles for reproduction. Researchers found that these plants generate heat in their cones through mitochondrial processes, emitting infrared radiation that beetles detect using specialized antennae. The mechanism represents one of the earliest pollination signals, predating the colorful displays of modern flowers, according to a study by Wendy A. Valencia-Montoya of Harvard University and colleagues, published December 11 in Science.
Cycads, which date back more than 200 million years, are pollinated by animals and include over half of all known heat-producing plant species. Their cones, the reproductive structures, warm up in daily cycles, peaking in the evening when pollinators are active. This thermogenesis occurs only in organs involved in pollination, using starch as fuel and alternative oxidase proteins to convert energy into heat rather than chemical storage.
“Plant thermogenesis is controlled by mitochondrial respiration,” the researchers explain. “During this process, carbohydrates or lipids fuel heat production through alternative oxidase (AOX) or uncoupling proteins, which bypass adenosine 5′-triphosphate (ATP) synthesis to dissipate redox energy as heat.”
To explore the role of this heat, the team examined Zamia furfuracea and its beetle pollinator, Rhopalotria furfuracea. Thermal imaging showed that male cones, which produce pollen, heat up first, followed by female cones a few hours later. Beetles moved between them in sync with these temperature shifts, suggesting a “push-pull” system where cooling male cones prompt beetles to leave for warmer female ones.
Experiments isolated infrared as the key signal. Using 3D-printed cone models heated to match real cones, the team found beetles preferred the warm versions, even when covered to block conduction or convection. “We found that wild beetle pollinators were more attracted to heated female and male cone models compared with ambient temperature controls,” the authors report.
On the beetle side, the team identified adaptations for detecting this infrared. The tips of their antennae house thermosensitive structures with neurons that respond to heat. Transcriptome analysis pinpointed TRPA1 ion channels as the molecular sensors, tuned to the specific temperature ranges of their host plants. Blocking these channels eliminated the beetles’ response to infrared but not to scents.
“These findings point to an evolutionary shift in pollination signaling strategies that coincided with changes in dominant pollinator groups, each characterized by distinct sensory biases,” the team concludes.
Citations
W. A. Valencia-Montoya et al. Infrared Radiation Is an Ancient Pollination Signal. Science. Published online December 11, 2025. DOI: 10.1126/science.adz1728
