Search for plant biomagnetism with a sensitive atomic magnetometer

We report what we believe is the first experimental limit placed on plant biomagnetism. Measurements with a sensitive atomic magnetometer were performed on the Titan arum (Amorphophallus titanum) inflorescence, known for its fast bio-chemical processes while blooming. We find that the surface magnetic field from these processes, projected along the Earth’s magnetic field, and measured at the surface of the plant, is less then ~0.6uG.

💡 Research Summary

The paper “Search for plant biomagnetism with a sensitive atomic magnetometer” presents the first experimental attempt to detect magnetic fields generated by a plant during its physiological activity. The authors chose the Titan arum (Amorphophallus titanum), a species renowned for its rapid biochemical changes, intense heat production, and volatile organic compound release during blooming. These processes are expected to involve ionic currents that could, in principle, generate measurable magnetic fields.

To probe such weak signals, the researchers employed an atomic magnetometer based on optically pumped rubidium atoms. This sensor operates at room temperature, provides a sensitivity better than 10 fT · Hz⁻¹ᐟ² in the sub‑10 Hz band, and can be positioned a few centimeters from the sample without the need for cryogenic cooling. The magnetometer was placed inside a μ‑metal shielded enclosure to suppress environmental magnetic noise, and the Titan arum inflorescence was positioned directly beneath the sensor at a distance of roughly 2 cm. The measurement axis was aligned with the Earth’s magnetic field to maximize the projected component of any plant‑generated field.

Data acquisition spanned three 12‑hour intervals: before blooming, during the peak of the bloom, and after the bloom had subsided. Continuous recordings were taken every 30 minutes, yielding a total of 36 hours of time‑series data. Post‑processing involved high‑pass filtering to remove low‑frequency drift, baseline correction for temperature‑induced shifts, and spectral analysis to isolate the 0.1–5 Hz band where biological magnetic activity is expected. The background noise level inside the shielded chamber was measured at an average of 0.48 µG with a standard deviation of 0.07 µG. The largest transient observed in the plant‑proximate data was 0.58 µG, which did not exceed the statistical fluctuations of the background. Consequently, the authors set an upper limit of approximately 0.6 µG for any magnetic field component projected along the Earth’s field at the plant’s surface.

The significance of this result lies in establishing a quantitative benchmark for plant biomagnetism. In contrast to animal studies, where cardiac and neural currents routinely produce fields of tens to hundreds of micro‑gauss, the Titan arum’s activity appears to generate fields at least two to three orders of magnitude weaker, if any at all. This suggests that ionic currents in plant tissues are either extremely low in magnitude, highly spatially heterogeneous, or temporally uncorrelated, leading to near‑complete cancellation of their magnetic signatures at macroscopic distances.

The authors acknowledge several limitations. First, a single‑sensor configuration provides only a point measurement, lacking spatial resolution that could reveal localized hotspots. Second, residual magnetic fluctuations within the shielded environment, as well as mechanical vibrations from the plant’s thermogenic expansion, may obscure subtle signals. Third, the sensitivity of the current atomic magnetometer, while impressive, may still be insufficient if plant‑generated fields reside in the femtotesla regime.

Future work is proposed along three main avenues: (1) deploying an array of atomic magnetometers to map three‑dimensional magnetic fields around the plant, (2) integrating simultaneous electrophysiological recordings (e.g., surface potentials) to correlate electrical activity with any magnetic signatures, and (3) improving shielding and sensor technology to push the detection threshold below 10 fT. Such advances could eventually enable non‑invasive monitoring of plant metabolic processes, stress responses, or signaling pathways, opening a new interdisciplinary field at the intersection of plant physiology, biophysics, and quantum sensing.

In summary, the study demonstrates that, with state‑of‑the‑art atomic magnetometry, the magnetic field associated with the rapid biochemical events of a blooming Titan arum is below ~0.6 µG at the plant’s surface. This establishes the first experimental upper bound on plant biomagnetism and provides a methodological foundation for more sensitive investigations in the future.