Unipolar signal recording on plants

a_melisa_melis Italy
in Cyton

Hello,
I am trying to use a Cyton board to record surface potentials of plants. I need to do an unipolar measurement, using a reference electrode in the soil and a recording electrode on the plant tissue. Until now everything seemed to work fine (almost, since I could record the signals but the amplitude was way lower than expected) using an EEG configuration (SRB2 as a reference + bottom pin as a recording electrode). When I tried to connect three channels, at least two of them seemed to be recording the same thing even though they were connected to different leaves.
Is there a better way to perform this kind of measurements? What should I do?

Comments

  • wjcroftwjcroft Mount Shasta, CA

    Arianna, hi.

    What you are seeing with the same amplitude on different leaves, is likely because the 'impedance' or surface resistance in ohms of plant tissue, is very low. The plant cells, filled with water and dissolved minerals are essentially acting as one big 'electrolyte'. So appear to be the same 'skin surface' potential.

    https://www.google.com/search?q=recording+EEG+from+plant+leaves

    Some info above suggests that the electrode should be attached WITHOUT piercing the cell walls. A plain alligator clip with teeth would pierce to the interior cell fluids. You need a weaker clamp that only exerts mild downward pressure. They still recommend a separate electrolyte such as EEG gel / paste.

    William

  • a_melisa_melis Italy
    edited July 21

    Hi William,
    I am using proper electrodes with electrolytic interfaces and I am not piercing the plant tissue. It is not the first time I take this type of signal.
    Maybe I did not explain myself clearly. My question is: is the setup that I described the best one for this case? In my understanding, what I should see as a signal is BOTTOM PIN POTENTIAL - SRB2 POTENTIAL (I write bottom pin just so we are clear). Is there any possibility of cross talk between the channels there?
    Thank you
    Arianna

  • wjcroftwjcroft Mount Shasta, CA

    Your Cyton setup is the same as used in EEG. Yes, only the bottom pins are used and SRB2 is reference. Cross talk unlikely. What amplitudes are you seeing? Cyton is sensitive enough to measure down to low microvolts range, below say 4 uV. But also noise in that range. Especially easy to pickup environmental noise from EMF sources nearby. This usually shows up as mains noise at powerline frequencies.

    If you have done this before, seems like you should get similar amplitude signals as your other equipment. Is that not the case?

    I gave the search link above in case some of the results show adaptations using conventional EEG equipment. The people doing these plant measurements may have specialized electronics. Are you sure they are not measuring RESISTANCE, instead of voltage?

    https://www.google.com/search?q=can+plants+be+measured+with+EEG+machines,+or+should+resistance+be+measured+instead?

    AI response there suggests you want to be measuring resistance, not voltage see below. Cyton only measures microvolts.

    Plants do not have brains or nerves like animals do. Standard EEG machines cannot read thoughts or signals from them.
    Scientists measure electrical resistance (or electrical potential changes) with sensors instead to see how plants react to things like touch, water loss, or light.
    Why EEG Does Not Work on Plants
    No Brain: EEG tracks brain waves from nerve cells.
    No Neurons: Plants lack the central nervous systems that create those brain waves.
    Wrong Signals: Plant signals are slow chemical and hydraulic waves, not fast electrical spikes like in animal brains.
    How to Measure Plant Electricity
    Surface Electrodes: Scientists place small metal clips or patches on leaves or stems.
    Multimeters or Galvanometers: These tools measure changes in voltage or resistance.
    Action Potentials: Some plants, like the Venus flytrap, send fast electrical signals when touched. Simple sensors can track these specific events.
    If you want, tell me:
    Are you trying to build a plant-monitoring project?
    Do you want to know what specific equipment to buy?

  • a_melisa_melis Italy
    edited July 21

    So the configuration I am using should be right and what I see in the channels should be ok, that's great. Can it be a bug of the software when I see exactly the same thing on different channels?

    Plant surface potentials are very slow and the amplitude is tens of millivolts. Do you think it would be a problem for Cyton to detect them?
    I am trying to measure slow wave potentials similarly to this paper https://advanced.onlinelibrary.wiley.com/doi/10.1002/admt.71156. What I see is a likely shape of the signal but an amplitude way inferior (few millivolts instead of tens on millivolts). Do you have any idea of what the reason could be?

  • wjcroftwjcroft Mount Shasta, CA

    A true signal tens of millivolts is in the range of 10,000 uV for Cyton. This is easily seen. But you will need to turn off any high pass filters to see it. The default OpenBCI_GUI filter spec may be something like a bandpass from .5 Hz to 40 Hz.

  • a_melisa_melis Italy

    Ok, but you mean in the OpenBCI_GUI view options? I should still be able to see the signal in the raw data right? Or is there any filter applied by default already during acquisition?
    Thanks

  • wjcroftwjcroft Mount Shasta, CA

    https://docs.openbci.com/Software/OpenBCISoftware/GUIWidgets/#filters

  • wjcroftwjcroft Mount Shasta, CA

    Because your millivolts signal is so slowly moving, you must remove any filter that cuts off the sub 1 Hz frequencies.

    GUI displays have already applied the filters. This applies to all windows. However, the recordings are always raw, no filters.

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