  Upon stimulation, plants elicit electrical signals that can travel within a
cellular network analogous to the animal nervous system. It is well-known that
in the human brain, voltage changes in certain regions result from concerted
electrical activity which, in the form of action potentials (APs), travels
within nerve-cell arrays. Electrophysiological techniques like
electroencephalography, magnetoencephalography, and magnetic resonance imaging
are used to record this activity and to diagnose disorders. In the plant
kingdom, two types of electrical signals are observed: all-or-nothing APs of
similar amplitudes to those seen in humans and animals, and slow-wave
potentials of smaller amplitudes. Sharp APs appear restricted to unique plant
species like the "sensitive plant", Mimosa pudica, and the carnivorous Venus
flytrap, Dionaea muscipula. Here we ask the question, is electrical activity in
the Venus flytrap accompanied by distinct magnetic signals? Using atomic
optically pumped magnetometers, biomagnetism in AP-firing traps of the
carnivorous plant was recorded. APs were induced by heat stimulation, and the
thermal properties of ion channels underlying the AP were studied. The measured
magnetic signals exhibit similar temporal behavior and shape to the fast de-
and repolarization AP phases. Our findings pave the way to understanding the
molecular basis of biomagnetism, which might be used to improve
magnetometer-based noninvasive diagnostics of plant stress and disease.
