Plant Electricity

A plant is not only stuff with mass, nor only chemistry, nor only biology. You may look at a plant as well from an electrical point of view. Bio-electronics is an emerging way to better understand the plant’s world. For example, researchers –among others at the Dutch Koppert Biological Systems – explore ways to strengthen the robustness of plants and their resistance against disease and plagues. Ed Moerman is focussing on this domain. He likes to quote Albert Szent-Gyorgyi:

WHAT DRIVES LIFE IS A LITTLE ELECTRIC CURRENT, KEPT UP BY THE SUNSHINE. ALL THE COMPLEXITIES OF INTERMEDIARY METABOLISM ARE JUST ‘MINOR’ ADDITIONAL PHENOMENA.

Moerman starts at the very beginning: with photosynthesis. He even calls that plant grower a ‘chlorofyll-manager’. Sunlight, entering a plant leaf, excites electrons and this process may induce some fluorescence and a little loss of heath, but it mainly stores energy and delivers it to other parts of the plant by photochemistry. He mentions a series of electrical parameters that are relevant in plant production systems, like Ampere, Volt and Ohm (impedance), and how they relate to pH, redox potential, Brix and frequency.

A list of electronic parameters in the plant. Source: Ed Moerman.

These parameters offer an extra indicator for the health of the plant. “All the magic that we know is in the transfer of electrons. Reduction (gaining electrons) and oxidation (the loss of electrons) combine to form redox-chemistry, which contains the majority of chemical reactions. As electrons jump from atom to atom, they carry energy with them, and that transfer of energy is what makes all life on earth possible.” A farmer who understands these electrical signals, will complement his knowledge of the more familiar hydraulic and chemical signals in the plant. This complementarity is shown in the picture below.

The combination of electric with hydraulic and chemical signals in a plant gives a more complete picture of the plant’s health. Source: Ed Moerman.

In the article “Long­distance plant signaling pathways in response to multiple stressors: The gap in knowledge”, Bauerle (2016) from Cornell University, mentions a series of electrical signals in plants: ‘action potential’, ‘slow wave potential’, ‘system potential’ and ‘wound potential’. Each one of them has its own preferred location in and routing through the plant.

Illustrated representation of electrical signals in plants. Action potentials (APs), slow wave potentials (SWPs), system potentials (SPs), and wound potentials (WPs) are common electrical signals in plants. Source: Bauerle (2016).

In a plant, the electric potentials are very low, between 30 and 600 milliVolt. Nevertheless these low differecnes in potential have a lot of meaning. We’ll explore this meaning further.

There is a nice picture (below) of the relation between Volt, Ampere and Ohm. Mister Volt pushes mister Ampere through the narrow belt of mister Ohm. As such processes also happen in plants, you can design an electric diagram of a plant, as is shown in the right hand part of the picture below. Many devices are available to measure these variables in plants.

The basic law of electricity correlates the electrical current (Ampere) with the electrical tension (Voltage) and the resistance or impedance (Ohm). The right hand part of the picture shows how you can perceive a plant as an electrical system. Source: Moerman, Koppert.

Moerman presents two examples of how electrical phenomena can play a role in agriculture and horticulture. In 2012, in South Africa, dr. Pieter van Zyl obtained his doctorate on the effect of electric current on the growth and production of tomato plants. Van Zyl experimented with three different ways of administration of electrical frequencies. All three resulted in higher production than untreated tomatoes (which supplied 1284 grams/plant), i.e. 1395, 1603 and 2003 grams/plant. Van Zyl seeks an explanation in the enhanced activities of potassium and calcium ions at the border of the cells. These ions are important for the exchange of ions through the cell wall. His thesis is that the frequency resonating with 16 Hz increases the activity of potassium ions and also – but slightly less – activates the calcium ions, which are especially sensitive to 32 Hz. Exposing plants to such frequencies – from the elctrical current – would speed up the exchange of ions through the cell wall. At this level of the very small ‘particles’ such as electrolytes, electrons and protons, the quantum laws are valid.

As a second example of bioelectronics, Moerman shows a color picture of the electric potential and the electric field strength around blossoming flowers. The proposition here is that bees observe this gradient of electrical voltage around the flower and they do not only react on the frequency of color or smell.

Electric Potential lines (Volt) and Electric Field lines (Volt/meter) around flowers.

Source: http://science.sciencemag.org/content/suppl/2013/02/20/science.1230883.DC1 “Detection and Learning of Floral Electric Fields by Bumblebees”, School of Biological Sciences, University of Bristol, UK.

This kind of electrical approach of physiological processes in plants has already lead to many measurements. For example, trees show very clear variations in voltage, that may be related to the internal metabolism as well to its physiological reactions on changing environmental conditions! One nice example is a simple midi-synthesizer that transforms the plants electrical signals into tones and pitches. And the plant makes music! You will find more under SOUND.

Henk Kieft