Voltage

Action Potential in Plants

Plants lack a nervous system, yet they communicate through electrical signals. Their cells generate action potentials, just like animal neurons, enabling rapid, coordinated responses to environmental stimuli.

More Information

Event	Molecules / Ions Involved	Type of Process
Stimulus	Sensory mechanisms	Channel opening
Ca²⁺ influx, K⁺ and Cl⁻ efflux	Ions	Passive diffusion
Depolarization	—	Action potential
Potential restoration	ATP, H⁺ pumps, ion exchangers	Active transport

Action Potential in Plants

Plants' cells generate action potentials strikingly similar to those of animal neurons, enabling rapid and coordinated responses to environmental stimuli. This process is driven by calcium, chloride, and potassium ions: when calcium concentration exceeds a critical threshold, depolarization propagates from cell to cell without direct energy consumption, following the electrochemical gradient.

Specialized intercellular structures, analogous to animal synapses, ensure efficient transmission of information throughout the organism. Reactive oxygen species, produced by redox reactions, further amplify the electrical signal. Remarkably, glutamate (the primary neurotransmitter in animal nervous systems) performs the same function in plants, activating calcium channels and coordinating responses across the entire organism.

Bioelectric Reaction

Mathematical Analysis & Automatic Fitting for Voltage Signals

A dedicated analysis module allows quantitative characterization of plant electrical signals:

Automatic Signal Classification

Auto-detection of signal type from shape: Exponential Return vs Action Potential
Based on peak structure, rebound ratio, and temporal ordering of events
3σ baseline noise threshold for robust detection

Analysis

Fitted to the decay phase from the peak:

\[ V(t) = A \cdot e^{-\,(t - t_0)\,/\,\tau} + V_{\text{baseline}} \]

Extracts: amplitude A, time constant τ, peak time t₀, baseline V_baseline
Physical meaning: membrane relaxation after mechanical/hydraulic stimulus

Analysis

A physiologically motivated two-phase model:

\[\begin{aligned} V(t) &= A_{\text{sin}} \cdot \sin\!\bigl(2\pi f\,(t - t_0) + \varphi\bigr) && \text{for } t < t_{\text{peak}} \quad [\text{depolarization}] \\[6pt] V(t) &= A_{\text{exp}} \cdot e^{-\,(t - t_{\text{peak}})\,/\,\tau} + V_b && \text{for } t \geq t_{\text{peak}} \quad [\text{repolarization}] \end{aligned}\]

Extracts: 7 parameters (amplitude, frequency, phase, time constant, baseline)
Physical meaning: fast oscillatory depolarization + exponential repolarization

Voltage Instrumentation

The system evolved from a manually assembled prototype with discrete components to a compact dedicated PCB. This transition improved reliability, reduced size and noise, and allowed the integration of signal acquisition, processing, and communication into a single board.

More Information Full Hardware Report on GitHub

Voltage Instrumentation

The PlantLeaf ESEB V1.0 is a custom PCB designed with KiCad to acquire and process the very weak electrical signals generated by plants (10–150 mV). The signal is first amplified and filtered by the INA128 instrumentation amplifier, then further conditioned using the LMC6484 operational amplifier and passive RC filters to reduce high-frequency noise.

Finally, the STM32F411CEU6 microcontroller performs the analog-to-digital conversion, processes the data, and transmits it to the PlantLeaf application for visualization and analysis.

Experiments

Voltage Experiments

The experiments focused on capturing and analysing electrical signals generated by plants in response to different types of environmental stress. The plant chosen for initial tests was the Dionaea muscipula, selected for its particularly short reaction time to stimuli. Across 20 independently recorded responses, the models described above achieved a mean R² (Goodness of the Fit) of 0.9757 and a median of 0.9832 s, confirming strong agreement between the mathematical model and the observed physiology.

Mechanical stress

The obtained graphs show characteristic electrical responses: rapid depolarization followed by a slower repolarization phase, similar to action potentials described in scientific literature.

Light stress

A second type of experiment investigated the plant's response to sudden exposure to intense light. The plant was initially placed inside a dome darkened with a black cloth. The sudden removal exposed the plant to strong light intensity, simulating a rapid transition from shade to direct sunlight. The recording showed a significant and rapid variation, with a depolarization peak followed by a gradual return to the baseline potential.

Action Potential in Plants

Action Potential in Plants

Mathematical Analysis & Automatic Fitting for Voltage Signals

Exponential Return Model

Action Potential Model

Analysis

Analysis

Voltage Instrumentation

Voltage Instrumentation

Voltage Experiments

Mechanical stress

Light stress