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\DOI{10.5802/crmeca.331}
\datereceived{2025-08-27}
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\dateposted{2026-02-23}
\begin{document}

\begin{noXML}

\CDRsetmeta{articletype}{review}

\title{From electroculture to plasma agriculture: a three-century arc
bridging Bertholon's legacy with contemporary farming advances}

\alttitle{De l'\'{e}lectroculture \`{a} la plasma-agriculture : un arc
de trois si\`{e}cles reliant l'h\'{e}ritage de Bertholon aux
avanc\'{e}es contemporaines en agriculture}

\author{\firstname{Thierry} \lastname{Dufour}\CDRorcid{0000-0002-0397-368X}}
\address{Laboratoire de Physique des Plasmas, 4 Place Jussieu, 75005 Paris, 
Sorbonne Universit\'{e}, CNRS, \'{E}cole polytechnique, France}
\email{thierry.dufour@sorbonne-universite.fr}

\keywords{\kwd{Electroculture}
\kwd{Plasma agriculture}
\kwd{Cold atmospheric plasma}
\kwd{Abb\'{e} Bertholon}
\kwd{Reactive oxygen and nitrogen species}
\kwd{Seed priming}
\kwd{Sustainable agriculture}}

\altkeywords{\kwd{\'{E}lectroculture}
\kwd{Agriculture plasma}
\kwd{Plasma froid atmosph\'{e}rique}
\kwd{Abb\'{e} Bertholon}
\kwd{Esp\`{e}ces r\'{e}actives de l'oxyg\`{e}ne et de l'azote}
\kwd{Amorçage des semences}
\kwd{Agriculture durable}}

\begin{abstract} 
This review traces the historical trajectory of electricity in
agriculture, from the earliest observations of electrical phenomena to
the emergence of cold plasmas. Looking back to Antiquity and then to
the Enlightenment, it underlines Abb\'{e} Bertholon's 18th-century
efforts to channel atmospheric electricity to stimulate crops, using
devices such as the electro-v\'{e}g\'{e}tom\`{e}tre. Although these
early electroculture experiments relied on neither quantitative
dosimetry nor rigorous methodology, they foreshadowed the idea of a
controlled transfer of electrical energy to plants. Then the review
examines the historical development of galvanism, electrochemistry, and
the physics of gaseous discharges throughout the 19th and 20th
centuries, which collectively laid the foundations for contemporary
cold-plasma technologies. In the 21st century, plasma agriculture has
emerged as an interdisciplinary approach integrating electrical,
chemical, radiative, thermal, and fluid-mechanical effects.
Applications include seed treatment (preconditioning, seed priming),
stimulation of plant growth, soil and water treatment, and
decontamination of agri-food products. The review thus reassesses
Abb\'{e} Bertholon's contributions as those of a methodological
precursor and shows how his intuition of a ``vivifying electricity''
resonates with modern cold-plasma science. Finally, it argues that
plasma agriculture can transform an Enlightenment intuition into a
reproducible experimental framework for sustainable agriculture and
food safety. 
\end{abstract} 

\begin{altabstract} 
Cette revue retrace la trajectoire historique de l'\'{e}lectricit\'{e}
en agriculture, depuis les premi\`{e}res observations des
ph\'{e}nom\`{e}nes \'{e}lectriques jusqu'\`{a} l'\'{e}mergence des
plasmas froids. En remontant \`{a} l'Antiquit\'{e} puis au Si\`{e}cle
des Lumi\`{e}res, elle met en lumi\`{e}re les efforts de l'abb\'{e}
Bertholon au XVIII\textsuperscript{e} si\`{e}cle pour canaliser l'\'{e}lectricit\'{e}
atmosph\'{e}rique afin de stimuler les cultures, au moyen de
dispositifs tels que l'\'{e}lectro-v\'{e}g\'{e}tom\`{e}tre. Bien que
ces premi\`{e}res exp\'{e}riences d'\'{e}lectroculture ne reposent ni
sur une dosim\'{e}trie quantitative ni sur une m\'{e}thodologie
rigoureuse, elles pr\'{e}figurent l'id\'{e}e d'un transfert
contr\^{o}l\'{e} d'\'{e}nergie \'{e}lectrique vers les plantes. Le
r\'{e}cit suit ensuite l'essor du galvanisme, de l'\'{e}lectrochimie
et de la physique des d\'{e}charges dans les gaz aux XIX\textsuperscript{e} et XX\textsuperscript{e}
si\`{e}cles, jusqu'\`{a} l'\'{e}mergence des technologies de plasma
froid. Cette revue permet de mettre en avant qu'au XXI\textsuperscript{e} si\`{e}cle,
l'agriculture plasma appara\^{i}t comme une solution
interdisciplinaire, int\'{e}grant des effets \'{e}lectriques,
chimiques, radiatifs, thermiques et de m\'{e}canique des fluides. Les
applications couvrent le traitement des semences
(pr\'{e}conditionnement, amorçage des semences), la stimulation de la croissance
v\'{e}g\'{e}tale, le traitement des sols et de l'eau, ainsi que la
d\'{e}contamination des produits agroalimentaires. Cette revue
r\'{e}\'{e}value ainsi les apports de l'abb\'{e} Bertholon comme
pr\'{e}curseur m\'{e}thodologique, et montre comment son intuition
d'une \og \'{e}lectricit\'{e} vivifiante \fg
trouve un \'{e}cho dans la science moderne des plasmas froids. Enfin,
elle d\'{e}fend l'id\'{e}e que l'agriculture plasma peut transformer
une intuition des Lumi\`{e}res en un cadre exp\'{e}rimental
reproductible, pour une agriculture durable et la s\'{e}curit\'{e}
alimentaire.
\end{altabstract} 

%\input{CR-pagedemetas}

\editornote{Article submitted by invitation}
\alteditornote{Article soumis sur invitation}

\maketitle

\end{noXML}

\section{Electricity and agronomy: a historical trajectory from
Antiquity to the 21st century}\label{sec1}

\subsection{Electricity (Antiquity-18th century): from experimental
spectacle to metrological\newline instrumentation}\label{sec1.1} 

From Antiquity to the end of the 18th century, the study of electrical
phenomena evolved from a qualitative curiosity to a quantitative,
instrument-based practice. Early authors such as Theophrastus
(\textit{De lapidibus}) and Pliny the Elder (\textit{Natural History})
noted the attraction of straw and other light objects by rubbed amber
(\={e}lektron) and jet (gagates), while medical authors 
(e.g.,~Scribonius Largus, Galen) reported the analgesic use of electric fish 
(torpedoes)~\cite{1,2,3}. Medieval lapidaries and encyclopedias widely
transmitted these observations in descriptive form, with Albertus
Magnus' \textit{De mineralibus} being the emblematic  example~\cite{4}.
During the Renaissance, Girolamo Cardano (\textit{De subtilitate},
1550) and Giambattista della Porta (\textit{Magia naturalis},
1558/1589) expanded the inventory of ``electric bodies'' (amber, jet,
diamond, sapphire) capable of attracting small particles after 
friction~\cite{5,6}. The thread of observation thus remained continuous
until the end of the 16th century, but was essentially qualitative:
there were no calibrated instruments and procedures were poorly
standardized.

A conceptual consolidation began with William Gilbert's work \textit{De
Magnete} (1600), who coined the term ``electricus'' and clearly
distinguished electrical attractions from  magnetism~\cite{7}. In the
17th and early 18th centuries, friction machines multiplied
demonstrations and made the production of charges more reliable and
visually convincing: Otto von Guericke's sulfur globe (1660s) and
Francis Hauksbee's luminous glass globes (1705--1710) are canonical 
examples~\cite{8,9}. Stephen Gray's experiments (1729) established
conduction and insulation as distinct behaviors and
Charles-Fran\c{c}ois de Cisternay du Fay (1733) organized the effects
under a ``vitreous/resinous''  duality~\cite{10,11}. Nevertheless,
according to subsequent metrological standards and in the absence of
sustainable charge storage and common measurement conventions,
electricity remained a theater of demonstration (sparks, ``electric
kiss'', bristling hair).

It was only in the 1740s that advances in instrumentation created the
conditions for cumulative experiments and comparative methods. The
Leyden jar, developed independently by \mbox{E.-G. von Kleist} and P. van
Musschenbroek (1745--1746), was the first reliable device for storing
electrical charge, making it possible to repeat protocols and compare
outcomes systematically  
\mbox{(Figure~\ref{fig1}a)}. Linking several jars in
parallel to form a ``battery'' further increased storage capacity and
enabled more powerful discharges  (Figure~\ref{fig1}b)~\cite{12,13,14}.
At the same time, electrostatic machines became both more standardized
and more powerful, exemplified by Nairne's cylinder (1773; 
Figure~\ref{fig1}c) and van Marum's monumental generator (1784). These
devices reflected not only the growing technical capacity of the
sources but also a nascent ambition to measure and quantify electrical 
effects~\cite{15,16}. Public demonstrations provided a bridge between
spectacle and experiment: on March 14, 1746, Abb\'{e} Nollet famously
discharged a Leyden jar through a chain of the king's guards at
Versailles and then through Carthusian monks. Such iconic moments
dramatized electricity as a visible, collective phenomenon while
simultaneously consolidating experimental techniques and a shared
community of  practice~\cite{17,18}.

\begin{figure}
\includegraphics{fig01}
\caption{\label{fig1}(a)~Leyden jar: a glass vessel acting as the
dielectric, with an inner tin-foil lining connected by a chain to the
top terminal; an outer foil (grounded, not shown here) forms the second
armature. Charge is stored between the two foils separated by the
glass~\cite{19}.  (b)~Battery of Leyden jars (``Franklin battery'') in
a wooden case. The inner electrodes of the jar are bus-bar connected;
the outer foils are commoned through the box, forming a parallel array
that increases total capacitance and stored energy for stronger 
discharges~\cite{19}. Nairne's cylinder electrical machine (c.\ 1770s).
Hand-cranked glass cylinder rubbed by a cushioned exciter generates
charge; collecting combs feed the insulated prime conductors
(foreground bars). Polarity can be selected by connecting either end of
the cylinder and a Leyden-jar terminal allows storage and discharge for
demonstrations and  experiments~\cite{20}.}
\end{figure}

In parallel, metrological tools multiplied and gradually shifted
attention from spectacle to measurement. Franklin's demonstration of
the equivalence between lightning and electricity and his promotion of
the lightning rod (1750--1752), redirected interest toward the
controlled delivery of charge. These claims also sparked a widely read
debate with  Nollet~\cite{17,21,22}. Building on this shift toward
quantification, Lane's spark-reading electrometer (1767) allowed the
quantification of Leyden jar discharge, while the Henley quadrant
(1770) introduced a single-index measure of repulsion that was rapidly
disseminated by Nairne and documented by Priestley 
(1772)~\cite{23,24,25}. H.-B. de Saussure extended electrometers to
atmospheric studies during the  1760s--1780s~\cite{26}. This quantitative
turn culminated with Coulomb’s torsion balance (1785), which yielded the first precise
law of electrical  forces~\cite{27}. At the same time, synthesis works
such as Priestley's \textit{History and Present State of Electricity}
(1767/1769), Cavallo's \textit{Complete Treatise of Electricity} (1777)
and Beccaria's \textit{Dell'elettricismo artificiale e naturale} (1753)
organized the expanding literature and, crucially, framed
``artificial'' and atmospheric electricity within a single analytic 
perspective~\cite{14,28,29,30}. Collectively, these developments
established a proto-metrology of electricity: systematic measurement
practices and conceptual unification were now in place, even if
standardized units and calibrated scales were only beginning to emerge.

Having established tools for storage, delivery and measurement, the
first applications to living systems began to emerge. In 1783,
Bertholon's \textit{De l'\'{e}lectricit\'{e} des v\'{e}g\'{e}taux}
introduced the ``electro-v\'{e}g\'{e}tom\`{e}tre,'' a device designed
to capture and channel atmospheric electricity toward crop beds, as
detailed in  Section~\ref{sec2.3}~\cite{31}. In his treaty, Bertholon
mentions a broader set of contemporary experiments that suggested
electricity had a stimulating effect on vegetation. Stephen Demainbray
in the 1740s electrified myrtles and observed accelerated growth,
results confirmed by Abb\'{e} Nollet on mustard seeds and Jean
Jallabert on hyacinth and daffodil bulbs. Georg Matthias Bose and
Abb\'{e} Menon described similar effects on shrubs and buds. Later,
Edouard-Fran\c{c}ois Nunebert compared electrified and non-electrified onion bulbs, noting faster germination and taller stems, while Abb\'{e}
d'Ormoy reported thicker bases and stronger roots across several
species. Jean-Paul Marat claimed positive results on cress and lettuce
and Franz Karl Achard made similar observations on crop 
plants~\cite{31}. 

By the close of the 18th century, a rudimentary metrology of
electricity had thus taken shape: storage through the Leyden jar,
delivery via standardized machines and conductors and measurement with
electrometers and the torsion balance. This transition, from
spectacular display to instrumented practice, prepared the ground for
the galvanic and electrochemical breakthroughs of the 1790s
(Section~\ref{sec1.2}) and, more broadly, for later process-oriented
uses where measurable inputs and controlled exposures would become
central.

\subsection{1790--2000: From galvanism to controlled discharges and
their processes}\label{sec1.2} 
Following the debates at the end of the 18th-century debates, Volta's
invention of the pile (1799--1800;  Figure~\ref{fig2}a) marked a
decisive turning point. For the first time, experimenters had access to
a continuous, controllable and reproducible source of 
current~\cite{32}. Through the 19th century, this foundation was
reinforced by the standardization of instruments and units: precision
galvanometers and bridges, standard cells and the practical
volt--ohm--ampere system together provided a calibrated metrological
framework. Electricity, once confined to episodic demonstrations, was
transformed into a measurable flow, available on demand and suitable
for serial, comparable protocols.

\begin{figure}
\includegraphics{fig02}
\caption{\label{fig2}(a)~Voltaic pile (1800): column of alternating
zinc-copper disks separated by brine-soaked washers. Polarity is set by
couple orientation: the end toward the zincs is negative, toward the
coppers positive (modern convention). Removing terminal plates does not
change polarity. Side leads provide  $({+})/({-})$ connections~\cite{20}. 
(b)~Bose's apparatus for simultaneous mechanical and electrical
responses: an induction-coil stimulator; a mirror galvanometer records
the electrical trace, an optic levers the movement; lamp-reflected
beams write on a rotating kymograph; latency yields stimulus-response 
relations~\cite{35}.  (c)~Crookes tube (high vacuum): a phosphorescent
screen and a slotted mica diaphragm form a beam of cathode rays; a
magnet deflects the beam, demonstrating negative charge and magnetic
sensitivity~\cite{40}. (d)~Werner von Siemens's first ozonizer (1857):
glass discharge tube operating a ``silent'' dielectric-barrier
discharge; dry air/oxygen traverses the annular gap where ozone is 
\mbox{produced~\cite{41}}.}
\end{figure}

On this basis, Faraday formalized the laws of electrolysis in the
1830s, establishing both a conceptual and an operational framework for
the conversion of electricity into  chemistry~\cite{33}. In biology,
the same stability of supply opened up new paths. In 1873,
Burdon-Sanderson recorded action potentials in \textit{Dionaea
muscipula}, showing that plant movements could be associated with
discrete electrical  signals~\cite{34}. A generation later, Bose
extended this program into plant electrophysiology, developing
instruments and methods to detect, transmit and analyze plant signals 
(Figure~\ref{fig2}b)~\cite{35}. The idea that an electrical stimulus
could modulate measurable plant functions (movements, conduction,
responses to stress) was thereby firmly established, laying the
groundwork for systematic bioelectrical experimentation.

From the second half of the 19th century, a true metrology of
discharges began to emerge, extending far beyond the simple spark. In
1889, Paschen formulated his law relating breakdown voltage to pressure
and electrode spacing, giving experimenters a predictive tool for
designing and scaling  apparatus~\cite{36}. A decade later, Townsend's
ionization theory (1897--1901) clarified the avalanche multiplication
of electrons and established the different regimes of gaseous 
discharge~\cite{37,38}. In parallel, new instruments opened wider
experimental spaces: Geissler's tubes and Crookes's rarefied-gas
experiments  (Figure~\ref{fig2}c) revealed the diversity of luminous
and conductive phenomena under reduced  pressure~\cite{39,40}. As early
as 1857, Werner von Siemens described the dielectric barrier discharge
(DBD) also known as ``silent discharge'', as a practical source for
ozone generation  (Figure~\ref{fig2}d)~\cite{41}. By 1928, Langmuir
gave this domain its modern vocabulary, introducing the term
\textit{plasma} to describe a quasi-neutral ionized  gas~\cite{42}.
Taken together, these advances transformed the conception of electrical
discharge. What had once been understood as a fleeting spark now
appeared as a controllable medium, with stabilizable regimes and
tunable energy input.

On this metrological foundation, structured chemical applications
quickly followed. Siemens's dielectric barrier discharge ozonizers,
developed in the late 19th century, enabled large-scale water ozonation
and gave the ``silent discharge'' its first industrial 
role~\cite{43,44}. A few years later, the Birkeland--Eyde arc (1903,
Figure~\ref{fig3}a) harnessed high-temperature plasmas to oxidize
atmospheric nitrogen, producing nitrates and nitrous acids as
precursors for  fertilizers~\cite{45}. Alongside these advances,
low-pressure mercury-vapor lamps systematized the germicidal use of
ultraviolet radiation: their characteristic 254~nm emission was applied
to air and water disinfection in experimental setups such as
Rentschler's  (Figure~\ref{fig3}b)~\cite{46,47,48}.

\begin{figure}
\includegraphics{fig03}
\caption{\label{fig3}(a)~Birkeland--Eyde disc flame. An AC arc between
water-cooled copper tips is blown into a rotating circular sheet by a
transverse magnetic field between the pole faces. The time-averaged
luminous disc is the hot reaction zone used to form NO in 
air~\cite{45}.  (b)~UV-germicidal aerosol test duct (15 ft ${\times}$ 1
ft): room air seeded with atomized \textit{E. coli} passes a mixing box
and a low-pressure mercury lamp (UV-C ${\approx}$ 254~nm); a perforated
copper traverse tube feeds Wells air centrifuges; a tantalum photocell
monitors irradiance; an axial fan sets the flow~\cite{48}.}
\end{figure}

At the beginning of the 20th century, electroculture experienced
renewed interest, with attempts to exploit atmospheric electricity as a
stimulus for plant growth. Devices ranged from Lemstr\"{o}m's overhead
networks of charged wires above fields to Christofleau's so-called
``atmospheric''  antennas~\cite{49,50}. As shown in 
Figure~\ref{fig4}a, the latter were designed to channel ``natural
electricity'' from diverse sources (wind, clouds, sunlight, rain and
even telluric currents) into the soil. In practice, however, the
antenna functioned primarily as a charged conductor exposed to
atmospheric potential gradients, behaving more like a lightning rod
than a genuine energy transfer system. Though scientifically unfounded,
such instruments helped popularize the notion of directing ``sky
electricity'' toward crops.  Figure~\ref{fig4}b depicts their
application to grapevines, while  Figure~\ref{fig4}c illustrates
reports of enhanced bean growth compared with controls fertilized only
with manure. Yet these outcomes must be interpreted with caution:
fertilization regimes, soil heterogeneity, seasonal effects, rainfall
and cultivation practices were poorly controlled and device geometries
and polarities varied considerably. Consequently, these trials are best
understood as part of a genealogy of ideas and technical imagination,
rather than as rigorous demonstrations of efficacy. Their true legacy
lies in shaping the concept of a controlled transfer ``sky
${\rightarrow}$ soil/plant'' and in fostering agronomic observation
(emergence, yields), foreshadowing later, quantitatively controlled
approaches based on explicit, traceable dose metrics.

\begin{figure}
\includegraphics{fig04}
\caption{\label{fig4}(a)~Schematics diagram introducing Christofleau's
atmospheric antenna: a passive mast with pointed collector, galvanic
wire and ground network, claiming to harness atmospheric,
thermoelectric, rain-galvanic and telluric sources to deliver weak
fields/currents to crops~\cite{50}. (b)~Christofleau-style atmospheric
antenna for vines: mast tipped with a multi-point collector feeds a
down-lead to a trellised network of horizontal wires around grapevines,
forming a passive aerial-ground circuit intended to deliver weak
atmospheric fields/currents to the crop. Adapted from~\cite{50}.
(c)~Digitally-restored photograph (for clarity) of beans either grown
with manure (left) or grown without manure but under Christofleau's
atmospheric electroculture antenna (right). Adapted  from~\cite{50}.}
\end{figure}

This historical current of electroculture, however, did not directly
evolve into or compete with plasma-based technologies. The latter
emerged independently much later, at the end of the 20th century,
driven not by the legacy of ``sky electricity'' but by advances in
plasma physics and its biomedical applications. Whereas electroculture
remained speculative and pre-metrical, cold plasma research developed
within a rigorous framework of controlled discharges and quantitative
dosimetry. Hence, from the 1970s onward, cold plasmas began to be
investigated as low-temperature agents for sterilization and surface
decontamination. Initial work focused on low-pressure plasmas to
inactivate microorganisms on medical materials and devices. By the
1990s, these methods entered healthcare practice, most notably through
hydrogen peroxide gas-plasma sterilizers for heat-sensitive 
instruments~\cite{51,52}. In the mid-to-late 1990s, a further step was
achieved with the emergence of atmospheric sources (including DBDs,
glidarc reactors, plasma jets and RF discharges) that operated directly
in open air. These systems demonstrated robust microbial inactivation
and, crucially, allowed treatment conditions to be parameterized in
terms of applied power, frequency, working gas and exposure 
time~\cite{53}. This trajectory, from biomedical sterilization tools to
well-characterized atmospheric plasmas, laid the groundwork for
extending plasma technologies into agronomy, giving rise to the modern
field of plasma agriculture.

\subsection{The 21st century: the rise of plasma agriculture in a
physico-chemical framework}\label{sec1.3} 
Plasma agriculture designates a contemporary research field that
applies cold plasma sources (and their derivatives such as afterglows
and plasma-activated water) to seeds, plants, soils, irrigation systems
and agri-food chains. Unlike earlier traditions of electroculture or
electrostatic spraying, which relied on static fields or charge
deposition, plasma agriculture is explicitly grounded in plasma
chemistry, physico-chemical dosimetry and dose--response control.
Bibliometric analysis  (Figure~\ref{fig5}a) shows that the term
``plasma agriculture'' gained traction only after the mid-2010s,
marking the consolidation of a distinct research community and
vocabulary.

\begin{figure}
\includegraphics{fig05}
\caption{\label{fig5}(a)~Annual number of publications (1990--2024)
containing the exact expression ``plasma agriculture,'' as indexed by
Google Scholar (Results retrieved on 18 August 2025, patents and
citations excluded).  (b)~Schematic of a pile of seeds treated by cold
atmospheric plasma (CAP) with its 5 coupled properties: electrical,
chemical (RONS), radiative (UV), thermal (near-ambient) and
fluid-mechanical.}
\end{figure}

Cold plasmas are non-thermal discharges whose efficacy arises from the
co-action of five properties  (Figure~\ref{fig5}b):
\begin{itemize}
\item 
Electrical: transient fields, ionization fronts and pulsed currents
govern initiation and charge transfer
\item 
Chemical: cold plasmas generate reactive oxygen and nitrogen species
(RONS) both short-lived (OH, O, NO) and long-lived (H$_{2}$O$_{2}$,
O$_{3}$, $\mathrm{NO}_{2}^{-}/\mathrm{NO}_{3}^{-}$), with tunable lifetimes and fluxes
\item
Radiative: UV and VUV photons couple directly to DNA/protein targets or
water interfaces
\item 
Thermal: bulk gas remains near ambient, though local heating 
(10--50~\textdegree C above background) can be engineered or suppressed
\item 
Fluid-mechanical: ionic wind and microjets enhance mass transfer at
plasma--liquid and plasma--tissue boundaries. 
\end{itemize}
Depending on the source (DBD, jet, corona, glidarc) and feed gas, these
modalities combine to define the ``plasma cocktail'' at seed--water and
plant--air  interfaces~\cite{54,55,56}.

By 2025, plasma agriculture is organized around four application axes:
\begin{itemize}
\item 
Seed treatment exploits plasma-induced surface modification (enhanced
hydrophilicity, micro-etching) and low-dose RONS/UV to accelerate
germination kinetics and reduce microbial  load~\cite{57}. Direct
dry-seed exposure, post-imbibition treatment and immersion in
plasma-activated water (PAW) are distinguished  approaches~\cite{58}.
PAW chemistry is now routinely quantified by dose tracers
(H$_{2}$O$_{2}$, $\mathrm{NO}_{2}^{-}/\mathrm{NO}_{3}^{-}$, pH, conductivity),
providing reproducibility across  laboratories~\cite{59}.
\item 
Plant treatment applies CAP, afterglows and PAW under strict thermal
control to elicit signaling rather than damage. Contemporary work
demonstrates redox priming that activates antioxidant and defense
pathways and improves vigor in model and crop species (e.g.,
Ca$^{2+}$ transients in \textit{Arabidopsis} with PAW; tomato
seedlings under  CAP/PAW)~\cite{60,61,62}. Electrical inputs (kV, kHz,
W), flow, gap, exposure time and effluent temperature are
systematically coupled to PAW tracers, in line with international
plasma-agriculture roadmaps.
\item 
Media treatment focuses on irrigation water, soil and air. CAP and PAW
enable gentle disinfection, dose-controlled inputs and modulation of
microbial communities. Recent syntheses map PAW physico-chemistry and
antimicrobial action across  matrices~\cite{63}; field-adjacent studies
demonstrate impacts on irrigation water, soil properties and crop
stress  responses~\cite{64}.
\item 
Agri-food treatment uses CAP (DBD, plasma jets) and PAW to sanitize
produce, packaging and equipment while extending shelf life without
thermal stress. Efficiency scales with dose (voltage, frequency, gas,
flow/gap) and exposure time, primarily through RONS and  UV~\cite{65}.
``In-package'' plasma retains reactive species in sealed headspaces,
boosting microbial inactivation with limited quality  loss~\cite{66}.
On open lines, plasma jets reduce biofilms on food-contact surfaces
while PAW complements as a produce wash with minimal residues.
Industrial uptake by 2025 is contingent on validated protocols,
material compatibility and maintaining organoleptic  quality~\cite{67}.
\end{itemize}
In contemporary plasma agriculture, progress is defined by a
physics-based framework of explicit dosimetry: quantitative, traceable
dose metrics (such as RONS concentrations in PAW 
$(\mathrm{mol}{\cdot}\mathrm{L}^{-1})$, UV fluence
$(\mathrm{mJ}{\cdot}\mathrm{cm}^{-2})$, electrical or energy dose
$(\mathrm{J}{\cdot}\mathrm{cm}^{-2})$ and exposure time (min)) are
measured at the target. These are coupled with controlled source
parameters (voltage, frequency, power, feed gas, flow, gap and effluent
temperature) to establish reproducible dose--response relationships.
This approach contrasts sharply with 18th-century electroculture, where
no measurements of field strength, exposure time or chemical
by-products were attempted. To appreciate the extent of this
methodological shift, the following  Section~\ref{sec2} revisits the
early but pre-metrical program of Abb\'{e} Bertholon, one of the first
to propose the systematic use of atmospheric electricity in
agriculture.

\section{Reappraising the Abb\'{e} Bertholon's contribution to
agricultural electricity (1780s)}\label{sec2} 

\subsection{A brief scientific biography}\label{sec2.1} 
Pierre-Nicolas Bertholon de Saint-Lazare (1741--1800), a priest,
physicist and Enlightenment pedagogue, built his career in Montpellier
(France), where he taught experimental physics at the chair of the
\textit{\'{E}tats de Languedoc} and within the \textit{Royal Society of
Sciences}~\cite{68}. During the 1780s he emerged as a central figure of
experimental electricity in the city, notable for his focus on
applications rather than spectacle. Appointed in 1782 to the Society's
chair of physics, he combined public instruction with carefully staged
demonstrations, framing his program around three domains:
meteorological electricity, animal electricity and plant electricity,
each approached with an emphasis on practical  use~\cite{69}.

As part of this program, Bertholon designed the
\textit{electro-v\'{e}g\'{e}tom\`{e}tre}, a device intended to capture
and distribute ``atmospheric electricity'' to plants. He also promoted
``medical electricity'', devising therapeutic practices such as
positive and negative baths and even proposed a classificatory scheme
for diseases like ``electrical'' or  ``non-electrical''~\cite{31,70}.
His writings, first published in 1780, were widely circulated in both
French and translated editions, extending his influence beyond
Montpellier.

Bertholon also participated actively in civic and technical debates. He
advocated for the adoption of lightning rods in Languedoc and, by
analogy, suggested networks of pointed rods as earthquake prevention
devices, a proposal that drew attention as far as Germany 
(Wiedebourg)~\cite{69}. He engaged in the early aerostatic movement,
launching a hot-air balloon with Jean-Antoine Chaptal in Montpellier on
23 November 1783 and testing parachutes with Lenormand from the Babotte
Tower.

His intellectual interests extended further, encompassing geology,
volcanism and regional natural history, reflecting the broad culture of
inquiry encouraged by the Montpellier Society. In 1787, together with
Boyer, he co-edited the popular science journal \textit{La nature
consid\'{e}r\'{e}e sous ses diff\'{e}rents aspects}, underscoring his
role as a mediator between scientific institutions, laboratories and
wider  publics~\cite{71}.

\subsection{Bertholon's thesis: electricity as a stimulus to
vegetation}\label{sec2.2} 
In the late 18th century, as Leyden jars, electrometers and
electrostatic machines were establishing a first metrology of
electricity  (Section~\ref{sec1.1}), Pierre-Nicolas Bertholon advanced
a striking thesis: that atmospheric electricity was a constant
reservoir of electricity capable of stimulating the entire physiology
of plants. He argued that key functions (germination, sap circulation,
nutrition, secretion, growth, flowering, fruiting and transpiration)
could all be activated by this natural  resource~\cite{31}. Moreover,
artificial electricity generated by friction machines could, in his
view, produce equivalent effects. Electricity was thus conceived as a
subtle ``fluid'', often likened to fire, whose action might be
harnessed oriented and applied through engineered devices. Bertholon's
treatise was structured in three parts:
\begin{enumerate}[(1)]
\item 
To demonstrate the existence and influence of atmospheric electricity;
\item 
To catalogue its effects on plant functions (including germination, sap
flow, secretions, sensory qualities in the 18th-century sense and
``negative electricity'');
\item 
To operationalize these effects through dedicated instruments, most
notably the \textit{electro-v\'{e}g\'{e}tom\`{e}tre}, designed to
capture, conduct and distribute atmospheric electricity to crops.
\end{enumerate}
To substantiate this program, Bertholon assembled three types of
evidence. First, qualitative correlations: storms, rain, snow, hail and
fog were thought to deliver electrical fluid to plants. He noted that
``more electrical days'' coincided with faster germination, though
without controlling for cofactors such as temperature, humidity, light
or rainfall. Second, instrumented observations: he employed
electrometers, kites and electroscopes to register atmospheric charge
and compared these signals with stages of plant development. He
described precautions (stable weather, humidity, temperature) yet
acknowledged variability, preferring broad ``general results'' to
unstable numerical series. Third, mechanistic conjectures: electricity
was said to drive sap circulation and secretion through an ``electrical
affinity'' between molecules and vessels: an attempt, within the
conceptual vocabulary of his time, to articulate a theory of plant
interfaces.

From a historical perspective, the strength of Bertholon's work lies in
its unifying vision. He sought to connect atmospheric phenomena with
plant physiology and to design an agronomic technology of electricity.
His vocabulary drew on engineering concepts such as insulation, pointed
collectors, conductors and distribution networks and for his time this
represented a genuine methodological effort. The limits were equally
clear: no dosimetry of field strength, charge or energy was attempted,
the roles of different agents (electric fields, ozone, UV) were not
distinguished and much reasoning remained analogical rather than
quantitative. Even Bertholon conceded that his ``constant results''
were better understood as tendencies than as conclusive data.

Yet the legacy is not negligible. By framing electricity in agronomic
terms and articulating an operative vocabulary of capture, conduction
and distribution, Bertholon anticipated the logic of controlled
transfer that resonates with later traditions. In contemporary
cold-plasma agriculture, electrical parameters, physico-chemical
species and dose--response relations are explicitly integrated. Seen in
this continuum, Bertholon's program was not merely speculative
electroculture but an early, if limited, attempt to transform
atmospheric electricity into a measurable agronomic process.

\subsection{Bertholon's electroculture devices and operating
procedures}\label{sec2.3}
The first electroculture devices to be technically described and
illustrated appear in Bertholon's \textit{De l'\'{e}lectricit\'{e} des
v\'{e}g\'{e}taux} (1783). Because the original explanations, written in
18th-century French, are often obscure or misleading for modern
readers, this  section offers a reformulation in contemporary technical
language. The goal is not to modernize the science, but to clarify the
intended mechanisms, stabilize terminology and highlight the
operational logic of these instruments.

\subsubsection{Dry-route devices: the electro-v\'{e}g\'{e}tom\`{e}tre 
and the orchard discharge method}\label{sec2.3.1}
Bertholon's flagship instrument was the
\textit{electro-v\'{e}g\'{e}tom\`{e}tre}: an apparatus which, despite
its name, was not a measuring instrument: it recorded neither electric
field, nor electrical charge, nor current. It was a passive
collector--distributor of ``atmospheric electricity'', designed to
capture, conduct and spread charge over crops, with no readout and no
dosimetry. Bertholon designed two models of this device.

The first model  (Figure~\ref{fig6}a) which may be termed the
``\textit{single point, articulated arm}''. It consisted of a wooden
mast firmly anchored and protected against moisture. At the top, a
single iron point served as a collector. It was shielded from rain and
insulated from the electrical ground by a glass tube filled with
bituminous mastic. The captured charge descended via a conducting chain
to an insulated, articulated horizontal arm that could be aimed over
crop rows. The arm ended in a comb of points that release charge
gradually as bluish corona glows (\textit{aigrettes lumineuses}), which
Bertholon believed would stimulate vegetation.

\begin{figure}
\vspace*{1pt}
\includegraphics{fig06}
\vspace*{3pt}
\caption{\label{fig6}Bertholon's \'{e}lectro-v\'{e}g\'{e}tom\`{e}tre,
devised in the 1780s to channel ``atmospheric electricity'' toward
crops. Two variants are shown: (a)~Model I, with a single-point
collector and articulated arm distributing charge to pointed outlets;
and (b)~Model II, with a crown of points, a rotating extendable arm and
broader reach. Both relied on slow diffusion of charge through sharp
points, conceived as a gentle stimulus to vegetation and included a
neutralization device (Z) for safety, represented in inset of (b).
Adapted from~\cite{31}.}
\vspace*{5pt}
\end{figure}

The second model  (Figure~\ref{fig6}b) which may be termed the
``\textit{multi-point crown, rotating and extendable arm}''. It kept
the same logic while boosting collection and coverage. The mast head
received a resin-impregnated insert to improve insulation from the
ground and the single point was replaced by a cluster of sharp points
to enhance charge extraction. The transmission still used a vertical
chain that was connected to the horizontal arm. The arm could rotate 
360\textdegree\ and was length-adjustable, allowing one to sweep the
entire plot. Again, its tip carried diffusor  points.

For clarity,  Table~\ref{tab1} provides a comparative summary of the
two variants, detailing their structural components, operating
principles and distinctive features, in order to highlight both their
shared logic and their technical differences.

\begin{table}
\caption{\label{tab1}Comparison between the design and operation of
Bertholon's electro-vegetometer  (Figure~\ref{fig6}): variant I
(``single-point articulated arm'') and variant II (``multi-point crown,
rotating and extendable arm'')}
\fontsize{9}{12}\selectfont\tabcolsep3.5pt
\begin{tabular}{cll}
\thead
 & 
\multicolumn{1}{c}{\parbox[t]{5cm}{\centering  Model I\Lbreak
 Single-point, articulated arm}} & 
\multicolumn{1}{c}{\parbox[t]{5cm}{\centering Model II\Lbreak
Multi-point crown, rotating and extendable arm}}
\vspace*{4pt}\\
\endthead

{Purpose} & 
\multicolumn{2}{@{}c@{}}{\parbox[t]{10.3cm}{\raggedright Passive capture 
${\rightarrow}$ Insulated conduction 
${\rightarrow}$ Gentle diffusion over crops (no measurement)}} 
\vspace*{4pt}\\

{Mast/Base} & 
\parbox[t]{5cm}{\raggedright
Wooden mast (A--B): buried section fire-dried,  tarred, wrapped in
charcoal dust/cement,  then masonry footing; above-ground part
painted/bitumen-coated for weather resistance} & 
\parbox[t]{5cm}{\raggedright
Mast (A--B) with resin-saturated head cylinder (C) treated with
tar/pitch/turpentine to improve insulation from ground} 
\vspace*{4pt}\\ 

{Top insulation} &
\parbox[t]{5cm}{\raggedright
- Thick glass tube packed with bituminous mastic (D)\unskip\break
- Second glass insulator downstream (H)} &
\parbox[t]{5cm}{\raggedright
Insulated rotary interface via resin insert (D) and glass/mastic sleeve
(H)} \vspace*{4pt}\\ 

{\parbox[t]{3cm}{\centering
Collector (at mast head)}} & 
\parbox[t]{5cm}{\raggedright
Single pointed rod (E) mounted in D; protected by a tinplate funnel
(F)} &
\parbox[t]{5cm}{\raggedright
Multipoint collector (E) (sharp ``crown'') to maximize charge
capture}\vspace*{4pt}\\ 

{\parbox[t]{3cm}{\centering
Conduction path (vertical)}} & 
\parbox[t]{5cm}{\raggedright
Conducting chain (G) suspended from E, guided through H to prevent
leakage} & 
\parbox[t]{5cm}{\raggedright
Bent iron lever (C) carrying chain (G) to the arm interface} 
\vspace*{4pt}\\

{Regulation/buffer} & 
\parbox[t]{5cm}{\raggedright
Chain terminates at iron disk (K) acting as a small
``condenser/regulator'' to buffer atmospheric variations} & 
\parbox[t]{5cm}{\raggedright
No separate disk; regulation implicit (focus on mobility and reach)}
\vspace*{4pt}\\ 

{\parbox[t]{3cm}{\centering
Horizontal arm/distribution}} & 
\parbox[t]{5cm}{\raggedright
Articulated conductor arm (K--L--M--N) hinged at L and Q, supported on
insulating trestles (O, P) with stretched silk cords} & 
\parbox[t]{5cm}{\raggedright
Telescoping conductor arm (L--M) with its telescoping conductor (Q),
supported on insulating trestle (P) with stretched silk cords} 
\vspace*{5pt}\\

{\parbox[t]{3cm}{\centering
Terminal diffuser}} & 
\multicolumn{2}{@{}c@{}}{\parbox[t]{10.3cm}{\raggedright
Comb/cluster of sharp metal points at the arm tip
(N, R), releasing charge as non-disruptive corona over the crop
canopy/soil}}
\vspace*{4pt}\\ 

{\parbox[t]{3cm}{\centering
Mobility/coverage}} & 
\parbox[t]{5cm}{\raggedright
Arm swings on hinges (L, Q) to cover a sector (row/strip)} & 
\parbox[t]{5cm}{\raggedright
Full 360~\textdegree\ rotation via I--L--M and extend/retract (Q) to
sweep a full circle and vary reach} 
\vspace*{5pt}\\ 

{\parbox[t]{3cm}{\centering
Neutralization (on/off control)}} & 
\multicolumn{2}{@{}c@{}}{\parbox[t]{10.3cm}{\raggedright
Apply a chain (or vertical rod) between K and the
ground to break insulation and bleed charge. Also used to null effect
when ``excess'' of electricity is presumed}} 
\vspace*{5pt}\\ 

{\parbox[t]{3cm}{\centering
Operation (per Bertholon)}} & 
\multicolumn{2}{@{}c@{}}{\parbox[t]{10.3cm}{\raggedright
Use when the air is ``poor in electric fluid'';
distribute via N; ground at K when ``excess'' is observed}} 
\vspace*{5pt}\\ 

{Safety} & 
\multicolumn{2}{@{}c@{}}{\parbox[t]{10.3cm}{\raggedright
Sharp points release corona glows (no sparks).
``C-shaped exciter'' (copper/iron frame with glass handle ${+}$ trailing
ground chain) recommended to shunt charge during handling}} 
\vspace*{3pt}
\botline
\end{tabular}
\tabnote{The letters (A to Z) correspond to the
captions of the original figures. Both devices are passive
collectors--distributors (no field/charge/current measurement); the
terminal diffuser emits a charge in the form of a non-disruptive corona
above the crop.}
\end{table}

Both models included a ``C-shaped exciter'': a rudimentary grounding
tool designed for operator safety and represented in the inset of 
Figure~\ref{fig6}b. It consisted of a curved metallic rod with rounded
ends, one of which carried a chain trailing on the soil to provide an
earth connection. The user held the device by an insulated glass
handle. When brought near the electro-v\'{e}g\'{e}tom\`{e}tre, the
metallic arc collected excess atmospheric charge, which was harmlessly
discharged through the chain into the ground. In modern terms, it
functioned much like a primitive discharge wand still used in
high-voltage laboratories to neutralize charged equipment safely.

Bertholon imagined a second ``dry-route'' method to target wood-boring
insects hidden in branches, trunks or roots  (Figure~\ref{fig7}). He
proposed to discharge a Leyden jar directly through the affected wood
by positioning two iron wires on opposite sides and releasing the
stored charge across the gap. This brief high-voltage pulse would
result in a strong electric field forcing a transient current through
the tissue, with the aim of killing larvae inside. By shifting the
wires and repeating the operation, he imagined one could ``sweep'' the
branch until the pest was eliminated. For orchards, he extended the
design into a rudimentary electrical grid: trees were linked with bare
iron wires so that a single discharge could propagate through
successive spans, exposing multiple trunks at once. He even recommended
driving current through soil paths to target roots or applying
preventive shocks during the season when the infestation typically
began. As with the electro-v\'{e}g\'{e}tom\`{e}tre, this was not
measurement but mediation in intent: a scheme to channel atmospheric or
stored electricity into plant structures. No dosimetry of voltage,
current or energy was attempted, but the procedure illustrates
Bertholon's transition from abstract conjecture to technical
intervention: building circuits, defining contact points and
integrating electrical pulses into common agricultural practices.

\begin{figure}
\vspace*{1pt}
\includegraphics{fig07}
\vspace*{3pt}
\caption{\label{fig7}(a)~General view of a fruit orchard where trees
are interconnected by uninsulated iron wires forming a rectangular grid
(segments A--Q). A Leyden jar (not shown) is discharged across the
network, with its outer and inner coatings connected respectively to
the first and last wire, so that a single electrical pulse traverses
successive spans and penetrates branches, trunks or roots where boring
larvae are suspected. Repeated discharges allow the operator to
``sweep'' the orchard, while roots can be included by inserting opposed
wires directly into the soil. (b)~Close-up of one grid interval: two
wires bracket a trunk  section (B--C), so that a Leyden discharge is
forced through the wood, targeting larvae hidden in galleries.
Additional labeled spans (e.g., T--D--S) illustrate continuity of the
circuit to neighboring trees and plant parts. Adapted  from~\cite{31}.}
\vspace*{5pt}
\end{figure}

\subsubsection{Water-route devices: electrified irrigation and mobile
systems}\label{sec2.3.2} 
Bertholon also devised a second family of instruments based on
irrigation with ``electrified water'', this time powered by an
electrostatic machine rather than relying on the atmosphere. Two main
configurations were proposed  (Figure~\ref{fig8}).

\begin{figure}
\vspace*{1pt}
\includegraphics{fig08}
\vspace*{4pt}
\caption{\label{fig8}(Left) ``Artificial electrical watering''. An
electrostatic machine feeds a workstation on an insulating stool with
bucket and syringe-pump; the spray is charged before reaching the
canopy. The goal is practical (to integrate electricity into routine
watering). Insulation keeps body current negligible and directs it with
the jet into plants/soil. (Right) Mobile ``electric watering'' for
beds. A resin-insulated cart unwinds a wire from the machine, supported
on insulating posts. Holding the live cord, the operator pours from a
can, producing ``electric rain'' along the row. Designed for cadence
(assistant refills cans); insulation protects the operator; useful
current travels with the water. Adapted  from~\cite{31}.}
\vspace*{12pt}
\end{figure}

The first, intended for trees  (Figure~\ref{fig8}a), placed the
operator on an insulating stool holding a bucket and syringe pump. The
bucket was directly connected to the electrostatic machine, rendering
its contents conductive. Each spray of water was thus electrically
charged before reaching the canopy. Safety depended entirely on
insulation: as long as the operator remained isolated from the ground,
the body current was negligible, with visible sparks or tingling
confined to the water jet.

The second system was designed for vegetable beds 
(Figure~\ref{fig8}b). Here, an insulating resin cart carried a reel of
wire connected to the machine. As the cart advanced along the rows, the
operator, holding the live cord, poured from watering cans so that the
falling stream produced an ``electric rain''. The workflow was
organized for efficiency: a second gardener refilled cans continuously
while the cart advanced. Again, insulation ensured that the useful
current traveled with the water into the plants and soil, rather than
through the operator.

Both devices were described as inexpensive, adaptable and effective
when applied repeatedly over several days to seeds or growing plants.
Their operating principle was not metrological but practical: to embed
the action of electricity into everyday irrigation routines. The
comparative features of these two systems are summarized in 
Table~\ref{tab2}, which contrasts their design, workflow, safety
provisions and intended agronomic applications.

\begin{table}
\caption{\label{tab2}Comparison of Bertholon's devices for electrifying
irrigation water (Figure~\ref{fig8})}
\begin{tabular}{cll} 
\thead
Feature &
\multicolumn{1}{c}{Tree-by-tree irrigation} &
\multicolumn{1}{c}{Mobile cart for vegetable beds}\vspace*{2pt}\\
\endthead
Insulation of operator & 
\parbox[t]{4.5cm}{\raggedright
Operator stands on insulating stool (A), a board supported by glass
pillars} & 
\parbox[t]{5cm}{\raggedright
Operator stands on resin-molded insulating cart (A) drawn along garden
rows} \vspace*{4pt}\\

{Water source} & 
\parbox[t]{4.5cm}{\raggedright
Bucket (B) placed on the stool platform} & 
\parbox[t]{5cm}{\raggedright
Watering cans refilled continuously by a second gardener} 
\vspace*{4pt}\\ 

{Irrigation device} & 
\parbox[t]{4.5cm}{\raggedright
Syringe-pump (C) sprays water onto tree canopy (G)} & 
\parbox[t]{5cm}{\raggedright
Operator pours from watering can while holding live cord (G), producing
``electric rain'' over crops} 
\vspace*{4pt}\\ 

{Electrical connection} & 
\parbox[t]{4.5cm}{\raggedright
Electrostatic machine connected by chain (E) from conductor (D) to
workstation} & 
\parbox[t]{5cm}{\raggedright
Cart carries reel (D) with insulated axle, unwinding wire (C) connected
to machine conductor (H)} 
\vspace*{4pt}\\

Conduction to water &
\parbox[t]{4.5cm}{\raggedright
Tinplate plate (F) under operator's foot ensures bucket communicates
with charge} & 
\parbox[t]{5cm}{\raggedright
Wire passes through insulating supports (E) with glass rings (F);
additional supports can be added} 
\vspace*{4pt}\\ 

Mode of electrification & 
\parbox[t]{4.5cm}{\raggedright
Water in bucket becomes charged; sparks and tingling visible at jet or
on a metal plate} & 
\parbox[t]{5cm}{\raggedright
Watering can and operator at same potential; electrified water falls as
``electric rain'' onto crops} 
\vspace*{4pt}\\

Mobility/workflow & 
\parbox[t]{4.5cm}{\raggedright
Device carried tree to tree; simple and inexpensive} & 
\parbox[t]{5cm}{\raggedright
Cart advances row by row; workflow optimized with continuous supply of
full watering cans} 
\vspace*{4pt}\\

{Safety} & 
\parbox[t]{4.5cm}{\raggedright
Insulation of stool ensures current flows into water rather than
operator. Minor tingling only if grounding path provided} & 
\parbox[t]{5cm}{\raggedright
Operator insulated on resin cart; negligible current through body
unless contact with earth occurs. ``C-shaped exciter'' recommended for
safe approach/withdrawal} 
\vspace*{4pt}\\

{Agronomic use} & 
\parbox[t]{4.5cm}{\raggedright
Claimed effective when repeated daily over seedlings or growing
plants} & 
\parbox[t]{5cm}{\raggedright
Described as slightly slower than ordinary irrigation but with clear
agricultural benefits when repeated over several days}
\vspace*{2pt}
\botline
\end{tabular}
\xxtabnote{Tree-by-tree irrigation (Figure~\ref{fig8}a) used an
insulating stool, bucket and syringe-pump, while the mobile cart system
(Figure~\ref{fig8}b) adapted the principle to vegetable beds, with a
resin cart unwinding wire and electrifying watering cans. Both designs
aimed to embed electricity into routine watering practices; safety
relied on insulation from ground, with useful current carried by the
water jet into soil and plants.}
\end{table}

\subsection{Technical and methodological limitations}\label{sec2.4} 
By the late eighteenth century, Bertholon's program was limited above
all by instrumentation. Lane's spark electrometer (1767) and Henley's
quadrant (c.\ 1770) provided only coarse, qualitative indicators (spark
counts or angular deflections) that could at best approximate the
charge stored in a Leyden  jar~\cite{72,73}. They offered no means to
quantify the actual energy delivered to plant tissues or the flux of
charge at a biological target. Coulomb's torsion balance (1785), though
it established the first quantitative law of electrostatics, post-dated
Bertholon's writings and measured forces rather than energy deposition,
leaving no path toward calibrated protocols for agricultural 
electrification~\cite{74,75}.

The conceptual framework was equally incomplete. Several major agents
of electrical discharges remained unidentified: ozone, although its
pungent odor was remarked by van Marum in 1785, was not recognized as a
distinct chemical species until  1840~\cite{76}, while ultraviolet
radiation was discovered only in  1801~\cite{77,78}. Reactive oxygen
and nitrogen species (RONS), as well as electrohydrodynamic flows, were
entirely unknown. In this context, the functioning of Bertholon's
electro-v\'{e}g\'{e}tom\`{e}tre raises important retrospective
questions: was its terminal diffuser (a comb or cluster of sharp metal
points) capable of generating fields strong enough to act on
vegetation? Could it have produced a form of cold plasma, even if the
term was not yet available? In \textit{De l'\'{E}lectricit\'{e} des
V\'{e}g\'{e}taux} (pp.~399, 401), Bertholon himself reported luminous
and electrical \textit{aigrettes} visible at night on the multi-point
terminals of his device. Modern physics recognizes these bluish-violet
glows as corona discharges: localized plasmas produced when strong
fields at sharp tips accelerate electrons. Such discharges release
charge gradually, without sparks and generate species unknown in
Bertholon's time: ions, electrons, ozone and nitrogen 
oxides~\cite{31,79}. To Bertholon, however, they appeared as visible
manifestations of the ``electric fluid'' nourishing plants.

Experimental practice, too, fell well short of modern standards.
Bertholon relied on qualitative accounts of germination and growth,
with no systematic replication, randomization or formal control groups.
Trials were conducted in open air and thus remained fully exposed to
meteorological variability, including humidity, temperature, soil
conductivity, rainfall and illumination. Even the instruments available
to him, such as Henley's or de Saussure's electrometers, yielded only
relative indices rather than traceable measurements. The methodological
tools required to stabilize inference (i.e.\ randomized designs,
comparative statistics and variance analysis) would only appear in the
20th  century~\cite{80,81}.

Finally, the electrostatic machines themselves lacked regulation or
stability. Their output depended on crank speed, ambient humidity and
electrode condition. Accessories such as Leyden jars or pointed
conductors could channel or limit discharges but did not measure them.
Lane's discharger made it possible to fix a spark gap, yet it provided
no information about the actual dose delivered to plants. As a result,
pulse energy, repetition rate and source--plant geometry remained
uncontrolled, precluding the establishment of reproducible
dose--response curves.

In contrast, modern plasma agriculture defines ``dose'' through
explicit, quantitative parameters: electric field strength integrated
over time  $(\mathrm{V}{\cdot}\mathrm{m}^{-1}{\cdot}\mathrm{s})$,
surface charge density $(\mathrm{C}{\cdot}\mathrm{m}^{-2})$ and
specific or areal energy deposition
($\mathrm{J}{\cdot}\mathrm{kg}^{-1}$ or
$\mathrm{J}{\cdot}\mathrm{m}^{-2}$), all referenced in carefully
controlled source--target  geometries~\cite{54,56,82}. Today, the
respective contributions of fields, RONS, photons, localized heating
and electrohydrodynamic flows can be separated and quantified, enabling
reproducible mechanistic studies that were unattainable in Bertholon's
time.

\section{Modern physics of cold plasmas applied to
agriculture}\label{sec3} 
While Bertholon framed plant electrification through the metaphor of a
subtle ``electric fluid'', modern science grounds the discussion in
plasma physics. The shift from qualitative impressions (such as visible
aigrettes on metallic points) to quantitative descriptors of charge,
fields and species requires defining what a plasma is, the parameters
governing its behavior and the diagnostic methods that render it
measurable.

\subsection{Definition of cold plasma and key properties}\label{sec3.1}
Plasma is commonly known as the fourth state of matter, distinct from
solids, liquids and gases. It is characterized by macroscopic
quasi-neutrality  (i.e., approximately balanced positive-ion and
electron densities, as proposed in  Equation~(\ref{eq1})) and by
collective dynamics dominated by long-range Coulomb interactions. Two
fundamental parameters govern its electrostatic behavior: the Debye
length $\lambda_{\mathrm{D}}$  (Equation~(\ref{eq2})) and the electron
plasma frequency $\omega_{\mathrm{p}}$ (Equation~(\ref{eq3})), which
depend on the vacuum permittivity $\varepsilon_0$, the Boltzmann
constant $k_{\mathrm{B}}$, the elementary charge $e$, the electron
temperature  $T_{\mathrm{e}}$  and of the electron density 
$n_{\mathrm{e}}$~\cite{83}. A medium qualifies as a plasma when the
Debye length is much smaller than the system size $L$ 
(Equation~(\ref{eq4})), the number of particles in a Debye sphere 
$N_{\mathrm{D}}$ is  ${\gg}$1  (Equation~(\ref{eq5})) and collective
effects dominate over binary collisions
(Equation~(\ref{eq6}))~\cite{84}.
\begin{eqnarray}
n_{i} &\approx& n_{\mathrm{e}} \label{eq1}\Seqnsplit
\lambda _{\mathrm{D}} &=& \sqrt{\frac{\varepsilon
_{0}k_{\mathrm{B}}T_{\mathrm{e}}}{n_{\mathrm{e}}e^{2}}} 
\label{eq2}\Seqnsplit
\omega _{\mathrm{p}} &=&
\sqrt{\frac{n_{\mathrm{e}}e^{2}}{\varepsilon _{0}m_{\mathrm{e}}}} 
\label{eq3}\Seqnsplit
\lambda _{\mathrm{D}} &\ll& L \label{eq4}\Seqnsplit
N_{\mathrm{D}} &=&
\frac{4}{3}\uppi n_{\mathrm{e}}{\lambda }_{\mathrm{D}}^{3} 
\label{eq5}\Seqnsplit
N_{\mathrm{D}} &\gg& 1 \label{eq6}
\end{eqnarray}

Depending on density and temperature, plasmas range from strongly
collisional (when the mean free path is comparable to or smaller than
the system size) to weakly collisional, as in magnetospheric plasmas or
low-pressure RF discharges. In air at terrestrial pressure, electrons
of a few eV have a mean free path of approximately 0.1--1~$\rmmu$m.
Near boundaries, quasi-neutrality breaks down within space-charge
sheaths whose thickness is a  few $\lambda_{\mathrm{D}}$; these sheaths
control how current, energy and chemistry couple to 
surfaces~\cite{84,85}.

A cold atmospheric plasma (CAP; also non-thermal plasma, NTP) is a
non-equilibrium discharge in which the electron temperature  $T_{\mathrm{e}}$
(${\approx}$1--5~eV, i.e.,  11\,600--58\,000~K) greatly exceeds the gas
temperature  $T_{\mathrm{g}}$ (${\approx}$300--350~K). At atmospheric pressure,
strong collisionality leads to regimes dominated by electron--molecule
and ion--molecule collisions and to thin sheaths at electrode--gas or
gas--solid interfaces. Depending on configuration and excitation, one
observes streamer regimes (channeled micro-discharges  ${<}$10~ns,
reduced field E/N ${\approx}$100--300~Td) and dielectric-barrier
discharges (DBDs), which may be filamentary (E/N
${\approx}$150--200~Td)  or diffuse   (${<}$100~Td)~\cite{84}. The
reduced field E/N  $(1\;\mathrm{Td} =
10^{-21}~\mathrm{V}{\cdot}\mathrm{m}^{2})$ shapes the electron energy
distribution function (typically non-Maxwellian) and thus the
probabilities of excitation, ionization and dissociation through
energy-dependent cross  sections, directly influencing overall reaction
kinetics~\cite{86}.

CAPs couple multiple processes. The electric field drives charge
transport and interface polarization while the chemical component is
carried by reactive oxygen and nitrogen species (RONS). Those include
short-lived (e.g.,  O($\mbox{}^{3}$P)~$\upmu$s--ms,
$\mathrm{OH}^\bullet\approx\upmu\mathrm{s}$,
$\mbox{}^{1}\mathrm{O}_2\approx\mathrm{ms}$,
$\mathrm{NO}^\bullet\approx\upmu\mathrm{s}$) and long-lived (e.g.,
O$_{3}$~s--min, H$_{2}$O$_{2}$~s--h, 
$\mathrm{NO}_{2}^{-}$/$\mathrm{NO}_{3}^-$ stable in
aqueous  phase)~\cite{87,88}. These species are produced and
transported together with UV/visible emission from molecular bands
(e.g., N$_2$ second positive system, OH$^*$) and with electrochemical
gradients at plasma--gas, plasma--solid and plasma--liquid interfaces.
The energy chain can be summarized: source ${\rightarrow}$ electrons
${\rightarrow}$ elementary reactions ${\rightarrow}$ reactive species
${\rightarrow}$ interfacial  fluxes~\cite{89}.

Common atmospheric sources include DBDs (planar, coaxial or reactor
geometries) driven sinusoidally or in pulsed mode (kHz--MHz;
ns--$\upmu$s  pulses)~\cite{90} and atmospheric pressure
plasma jets (APPJ) operating in helium or argon with small O$_2$/H$_2$O
admixtures~\cite{91}. Control parameters (gap and geometry, dielectric
material and thickness, waveform, amplitude, frequency, duty cycle, gas
composition and flow, relative humidity) set E/N, the specific energy
deposition, discharge morphology (filamentary vs.\ diffuse, streamer
density) and the spectrum of species produced.

Metrological qualification is essential for reproducibility and
inter-comparison. Electrical diagnostics include recording $V(t)$ and
$I(t)$, estimating average power via Lissajous  figures and evaluating
energy per  pulse~\cite{92}. Temporal dynamics are resolved with ICCD
imaging (ns--$\upmu$s gates) to visualize streamer propagation and
discharge  morphology~\cite{93}. Gas temperature can be inferred from
rotational spectroscopy of  N$_2$ or OH bands and surface temperature
by infrared  thermography~\cite{94,95,96}. Physico-chemical analysis
uses optical emission spectroscopy to identify excited species and,
with kinetic modeling, to estimate effective electron energies. In the
aqueous phase, routine tracking includes  H$_{2}$O$_{2}$, 
$\mathrm{NO}_{2}^-$,  $\mathrm{NO}_{3}^-$, pH and conductivity, with
attention to their temporal  stability~\cite{87}.

Across applications, good practice entails arc suppression, monitoring
sheath evolution and controlling surface heating. Reporting conditions
in terms of specific energy (e.g.,  $\mathrm{J}{\cdot}\mathrm{cm}^{-3}$
of treated gas or activated liquid) and/or equivalent chemical
indicators enables robust links between process, dose and response,
independent of the particular agricultural use case.

\subsection{Technologies and laboratory protocols}\label{sec3.2} 
In agronomy, cold atmospheric plasma (CAP) is implemented through three
complementary routes that target different biological compartments:
seeds, seedlings, leaves/canopies, whole plants, fruits, soils and
waters. These are:
\begin{itemize}
\item
DDS (Direct Dry-Surface exposure): plasma applied directly to tissues
with no intentional free water at the interface.
\item 
DWS (Direct Wet-Surface exposure): plasma applied in the presence of a
thin aqueous film at the interface.
\item 
PAW (Plasma-Activated Water): water or nutrient solution treated ex
situ by plasma, then applied via soaking, spraying,
irrigation/fertigation, hydroponics or postharvest  rinsing~\cite{58}.
\end{itemize}
In practice, laboratories mainly rely on DBD and APPJ for DDS/DWS. DBD
panels or meshes are suitable for trays, awnings and fruit lines; APPJs
(He or Ar with traces of O$_{2}$/H$_{2}$O) offer directional diffusion
to localized tissues (wounds, grafts) and hard-to-reach geometries.
Corona arrays not only release charge but also generate a small
electrohydrodynamic (EHD) airflow, which disturbs the still boundary
layer of air on leaf surfaces and thereby improves the delivery of
plasma-generated species to plant tissues. For PAW generation and
process-water treatment, sliding arcs and DBD/pin-to-liquid jets are
commonly  employed~\cite{90,91,97}. The indicative operating ranges
include:
\begin{itemize}
\item 
DBD: 6--20~kV$_{pp}$,  5--50~kHz, gap 0.5--5~mm, exposure 0.5--60~s.
\item 
APPJ: 2--10~kV$_{pp}$, 10--200~kHz or RF, 
0.5--5~$\mathrm{L}{\cdot}\mathrm{min}^{-1}$  He/Ar with traces of
O$_{2}$/H$_{2}$O, nozzle-to-tissue distance of 5--30~mm.
\end{itemize}
The dose is expressed in units that are independent of the device and
related to the exposed entity. 
\begin{itemize}
\item 
For direct exposures (DDS/DWS), it can be expressed in specific energy
relative to the biological load, for example 
$\mathrm{J}{\cdot}\mathrm{m}^{-2}$ for leaves and 
$\mathrm{J}{\cdot}\mathrm{kg}^{-1}$  for seed lots, as well as
electrical operating conditions (waveform, pulse width and repetition
frequency, peak-to-peak voltage, energy per pulse and average power),
gas composition/flow rate, source-target distance, scan speed, exposure
time and effluent temperature. Where applicable, quantification of UV
fluence at the tissue level and emitted gas concentrations (O$_{3}$,
NO$_{2}$/NO) can further clarify the  regime~\cite{98,99}.
\item
For PAW, characterization generally includes the specific electrical
energy transmitted to the liquid $(\mathrm{J}{\cdot}\mathrm{L}^{-1})$,
the chemical state at the time of application (H$_{2}$O$_{2}$,
$\mathrm{NO}_{2}^-$/$\mathrm{NO}_{3}^-$, pH, conductivity) and the dose
applied ($\mathrm{mL}{\cdot}\mathrm{m}^{-2}$ or per plant, with contact
time)~\cite{87,100,101}. Where possible, a surface-normalized marker
load (e.g., $\upmu$mol H$_{2}$O$_{2}$ m$^{-2}$) is informative. In all
cases, noting the time between activation and use ($t_0$,  $t_0 +
\Delta t$) and reporting measurement uncertainties facilitates
comparison between devices and laboratories.
\end{itemize}

\subsection{Effects of cold plasma on seeds}\label{sec3.3}
CAP exerts three major, interdependent influences on seeds. First, they
alter the physico-chemistry of the seed coat, increasing surface
hydrophilicity and effective permeability. Second, they reduce
(sometimes nearly eliminate) microbial load and seed-borne pathogens.
Third, they trigger early physiological and molecular responses,
including hormonal adjustments, activation of antioxidant defenses and
transcriptional reprogramming. These processes are interlinked and
together help explain the consistent improvements in germination and
early growth reported across species. The following  sections detail
each of these three aspects in turn.

\subsubsection{Seed-coat modification and wettability}\label{sec3.3.1}
Microscopy studies (AFM/SEM) consistently show that cold atmospheric
plasma (CAP) alters the outer surface of seeds by roughening and
restructuring the coat through processes such as etching, ablation and
nano/micro-structuring. These changes directly improve the ability of
the seed to absorb water. In wheat and barley, for instance, 
Figure~\ref{fig9} shows that Ar--O$_{2}$ plasma treatments produced
visibly fissured, rougher surfaces that correlated with increased water
uptake, though the magnitude of this effect depended on the treatment 
protocol~\cite{102,103}. Glow discharge regimes produced strong etching
and nanostructuring, whereas afterglow exposures had little measurable 
effect~\cite{104}; extending the exposure time further enhanced surface
roughness~\cite{105}. Comparable modifications have been observed in
maize exposed to Ar/O$_{2}$ low-frequency glow  discharges~\cite{106}.
Surface chemistry is also transformed. Analyses using XPS and FTIR have
shown that plasma introduces oxygen-containing functional groups on the
seed surface, indicating oxidation. This chemical modification
increases surface energy and is stable over time, with no hydrophobic
recovery after  treatment~\cite{107,109}. One of the clearest
experimental signatures of these changes is the dramatic reduction in
water contact angle (WCA). In lentil, bean and wheat, RF air plasma
reduced WCA values from 127\textdegree, 98\textdegree\ and 
115\textdegree\ down to  20\textdegree,  53\textdegree\ and nearly 
0\textdegree\ (complete wetting), respectively 
(Figure~\ref{fig10})~\cite{110}. This sustained increase in
hydrophilicity accelerates imbibition, the crucial first step in
breaking dormancy and promoting uniform  germination~\cite{109,111}.

\begin{figure}
\includegraphics{fig09}
\vspace*{4pt}
\caption{\label{fig9}SEM images of wheat seed surfaces treated for 90 s
with (a)~control (no plasma),  (b)~Ar/O$_2$ plasma. Scale bar is
50~$\upmu$m. Reproduced from  Rahman et~al. \textit{Scientific Reports},
Springer Nature, 2018, licensed under CC BY  4.0~\cite{102}.}
\vspace*{6pt}
\end{figure}

\begin{figure}
\includegraphics{fig10}
\caption{\label{fig10}Water droplet deposited on a bean seed which is
(a)~untreated or  (b)~plasma-treated. Reproduced from Bormashenko 
et~al. Scientific Reports, Springer Nature, 2012, licensed under CC BY 
4.0~\cite{110}.}
\end{figure}

\subsubsection{Decontamination and pathogen control}\label{sec3.3.2}  
CAP treatments frequently achieve substantial reductions in surface
microbial loads for a wide variety of seeds (maize, wheat, 
sunflower,\,{\ldots})~\cite{112}. For instance,  
Figure~\ref{fig11}a demonstrates
effective fungal decontamination of sunflower seeds following a 5-min
plasma treatment achieved in ambient air. Similarly,
Figure~\ref{fig11}b indicates that 2--5 minutes of CAP exposure in
chickpea (\textit{Cicer arietinum}) lowered natural microbiota by 1--2
log units, with a 1-minute treatment proving optimal by both maximizing
germination (89.2\%) and reducing median germination time to 
2.7~days~\cite{113}. On hazelnuts, low-pressure SF$_{6}$ plasma achieved up
to a 5-log reduction of \textit{Aspergillus parasiticus}, as
highlighted in Figure~\ref{fig11}c~\cite{114}. However, complete
microbial inactivation remains uncommon and strongly species-dependent.
In sweet basil, DBD treatments applied for 10--15~minutes significantly
reduced \textit{Fusarium oxysporum} f.\ sp.\ \textit{basilici}
colony-forming units in a clear dose--response pattern, yet viable
colonies persisted within seed recesses, highlighting the limited
penetration of RONS and the resilience of certain propagules (e.g.,
chlamydospores). Extended treatment durations further decreased
germination capacity, particularly after 6 months of storage,
underscoring a trade-off between effective decontamination and seed 
viability~\cite{115}. At the community level, taxa such as
\textit{Alternaria} and \textit{Epicoccum} show comparatively high
tolerance and in buckwheat species, exposure beyond 90--120~s led
to sharp declines in germination, rendering treatments unsuitable for
sowing when doses are  miscalibrated~\cite{116}.

\begin{figure}
\includegraphics{fig11}
\vspace*{4pt}
\caption{\label{fig11}(a)~Photographs of sunflower seeds contaminated
by Rhizopus either untreated or plasma-treated for 5 min (T. Dufour,
LPP).  (b)~Influence of CAP treatment on the germination of Cicer
arietinum seeds (left axis) and on the survival of surface
micro-organisms (right axis). The bars show mean value ${\pm}$ SEM
germination (\%) ($n = 6$; $p<0.05$) Adapted  from~\cite{113}.
(c)~Reduction effect of air plasma and SF$_6$ plasma on A. parasiticus
contaminated hazelnuts for  15~min inoculation. Adapted 
from~\cite{114}.}
\vspace*{6pt}
\end{figure}

\subsubsection{Physiological and molecular responses}\label{sec3.3.3}
Mechanistically, plasma-generated RONS promote abscisic acid (ABA)
catabolism, enhance gibberellic acid (GA) signaling, interact with
nitric oxide (NO) and induce the expression of cell wall--weakening
genes in the endosperm and testa, thereby lowering barriers to dormancy
release. In \textit{Arabidopsis}, Grainge et~al., demonstrated that PAW
breaks dormancy through combined $\mathrm{NO}_{3}^{-}$, H$_{2}$O$_{2}$,
$\mbox{}^{\bullet}$NO and $\mbox{}^{\bullet}$OH signals, with distinct
responses observed in ABA/GA pathway mutants (e.g., \textit{cyp707a2},
\textit{nlp8}, \textit{prt6}), alongside activation of cell wall
remodeling  genes~\cite{117}. A companion study by the same group
showed that PAW also modulates very low- and low-fluence phytochrome
responses (VLFR/LFR; \textit{PHYA/PHYB}), thereby extending benefits to
photodormant  seeds~\cite{118}.

At the physiological level, one of the most consistent outcomes is the
up-regulation of antioxidant defenses. In oilseed rape seeds exposed to
drought, CAP improved germination parameters and also enhanced
post-germinative physiological responses. As reported in 
Figure~\ref{fig13}, the superoxide dismutase (SOD) and catalase (CAT)
activities were enhanced while lipid peroxidation (MDA) was reduced and
the accumulation of osmoprotectants was  enhanced~\cite{119}. In rice
under cold stress, argon DBD accelerated germination and seedling
growth, elevated SOD/CAT/peroxidase (POD) activity and triggered
transcriptomic shifts involving thousands of differentially expressed
genes, including suppression of \textit{NCED3} (ABA biosynthesis) and
induction of stress-tolerance  genes~\cite{120}. Similar trends were
reported in soybean, where CAP induced dose-dependent increases in SOD,
CAT and ascorbate peroxidase (APX), improving both germination indices
and  vigor~\cite{121}.

\begin{figure}
\includegraphics{fig12}
\vspace*{4pt}
\caption{\label{fig13}Effect of drought stress and cold plasma
treatment on 4 biomarkers of physiological state and stress response in
the case of oilseed rape seedlings.  (a)~SOD activity, (b)~CAT
activity,  (c)~MDA contents,  (d)~soluble sugar contents. In all
subfigures: WW: well watered; WW  ${+}$ CAP: well watered  ${+}$ plasma;
DS: drought stress; DS  ${+}$ Plasma: drought stress ${+}$ plasma. Error
bars indicate standard error  $(n = 3)$. Different lowercase letters
denote statistical differences between treatment groups at the 5\%
level according to Duncan's test. Adapted from~\cite{119}.}
\end{figure}

Overall, these effects often extend beyond germination. In wheat, PAW
enhanced early establishment by increasing photosynthetic pigments and
soluble protein content, suggesting a metabolic ``pre-priming'' effect
beyond simple microbial  decontamination~\cite{122}. In maize,
gliding-arc exposure modified hormone pools while simultaneously
stimulating seedling  establishment~\cite{123}.

\subsection{Effects of cold plasma on seedlings and
plants}\label{sec3.4} 
CAP (whether through DDS, DWS or PAW) can stimulate growth and stress
tolerance in multiple plant species, though outcomes remain strongly
dose- and context-dependent. Across species, CAP or PAW can increase
seedling biomass, leaf area and chlorophyll indices. For example, PAW
promoted tomato seedling growth and nutritional quality (polyphenols,
lycopene), while basil exposed to DBD showed elevated chlorophylls,
carotenoids and antioxidant activity with reduced ionic 
leakage~\cite{124,125}. Long-term benefits of PAW irrigation are
visible in tomato and pepper, where seedlings treated with PAW (with or
without seed priming) remained larger and more vigorous even 60 days
after sowing  (Figure~\ref{fig14}a for tomato plants, 
Figure~\ref{fig14}b for pepper  plants)~\cite{126}. In tomato, growth
stimulation was also shown to depend on exposure time: moderate PAW
treatments (15--30 min) maximized seedling development at 28 days,
while longer exposures became less effective 
(Figure~\ref{fig14}c)~\cite{124}. Similarly, lentil seedlings irrigated
with plasma-activated water (both tap and demineralized) displayed
stronger growth compared with controls at 18 days 
(Figure~\ref{fig14}d)~\cite{127}. 

\begin{figure}
\includegraphics{fig13}
\caption{\label{fig14}(a--b)~Long-term effect of PAW on tomato
seedlings with/without seed priming, observed on 60th day after sowing.
(b)~Same protocol as (a) for pepper plants. Reproduced from L.
Sivachandiran et~al., \textit{RSC Adv.}\ (2017). Licensed under CC BY 
3.0~\cite{126}. (c)~Effect of PAW on the growth of tomato seedlings for
different exposure times: 0, 15, 30 and 60 min (28 days old).
Reproduced from Adhikari  et~al. \textit{Scientific Reports}, Springer
Nature, licensed under CC  BY~\cite{124}. (d)~Lentil seedlings
irrigated either with tap water (TW), plasma-activated tap water
(PATW), demineralized water (DM) or plasma-activated demineralized
water (PADM). Observation on 18th day. Reproduced from Zhang et~al.,
\textit{RSC Adv.}\ (2017). Licensed under a Creative Commons
Attribution-NonCommercial 3.0 Unported Licence~\cite{127}.}
\end{figure}

Plasma also affects photosynthetic performance, particularly
photosystem II (PSII). Low doses improve photochemical parameters
($\Phi E_{0}$,  $\mathrm{ET}_{0}$/RC), while higher doses inhibit them.
For example, proso millet exposed to low discharge power showed
enhanced electron transport, but stronger discharges suppressed 
it~\cite{128}. Repeated PAW irrigation in barley improved chlorophyll
content and quantum yield, suggesting a potential for longer-term 
acclimation~\cite{129}.

Beyond growth promotion, CAP/PAW often upregulates antioxidant enzymes
(SOD, CAT, POX) and modulates secondary metabolism. In basil, plasma
increased antioxidant activity and peroxidase while stabilizing 
membranes~\cite{125}. In tomato, PAW stimulated salicylic and jasmonic
acid pathways and induced pathogenesis-related (PR) gene 
expression~\cite{130}. These responses highlight plasma's role as a
defense primer: tomato seedlings sprayed with PAW showed up to 61\%
reduced disease severity against Xanthomonas, despite no direct
antibacterial effect in vitro, clearly indicating host-defense 
activation~\cite{131}. Similar priming effects have been reported
against pests, e.g., increased spider mite mortality in PAW-treated 
tomato~\cite{132}.

The redox-active chemistry of PAW (H$_{2}$O$_{2}$,
$\mathrm{NO}_{2}^{-}$/$\mathrm{NO}_{3}^{-}$, mild acidification) has also been linked to
improved tolerance to salinity and drought. In hydroponic bok choy,
plasma-treated nutrient solutions enhanced growth and stress markers,
with intracellular RONS  implicated~\cite{133}. In barley, PAW
irrigation supported photosynthetic performance and antioxidant
adjustments under saline  stress~\cite{129}. At the root level, maize
showed accelerated endodermal lignification and finer branching under
arsenic exposure, suggesting plasma-induced anatomical
``fortification'' that may improve water and ion  uptake~\cite{134}.

Although the body of evidence supports plasma as a growth and
stress-priming tool, responses are highly species- and dose-specific.
Beneficial outcomes are typically observed at low exposures, while
excessive treatment can impair photosynthesis and growth. Moreover,
most studies remain limited to controlled environments, with little
information on field robustness, reproducibility across cultivars or
long-term yield effects. Clarifying these boundaries is essential
before practical deployment in agriculture.

\section{Conclusion and outlooks}\label{sec4}
This article has traced a continuous, if discontinuous, line from
18th-century ``electrizations'' to today's cold-plasma agronomy. The
pivot is metrology. Where Bertholon engineered pathways for an
indivisible ``electric fluid'' (capture ${\rightarrow}$ conduction
${\rightarrow}$ distribution) without access to dose or agents,
contemporary plasma agriculture defines sources, quantifies interfacial
transfers and measures dose under controlled conditions. Tunable
atmospheric DBDs and plasma jets, together with electrical ($V(t)/I(t)$,
Lissajous/Manley) and optical diagnostics (OES/absorption), have
transformed demonstration into experiment: dose--response curves can be
mapped, efficacy windows identified and results replicated across
laboratories.

Reappraised in this light, Bertholon's contribution is methodological
rather than evidentiary: he supplied an operative vocabulary and the
intuition that moderate electrical regimes might beneficially modulate
plant functions. Modern work explains when and why that intuition
holds. Cold plasmas co-generate fields, RONS, UV radiation, mild
heating and electrohydrodynamic flows; diagnostics separate and tune
these components. At seed and plant interfaces this yields a coherent
mechanistic picture: controlled redox priming and surface conditioning
(hydrophilization, micro-etching) accelerate imbibition and
germination, reduce surface bioburden, elevate antioxidant capacity
and, within defined windows, improve photosynthetic function and stress
tolerance. The same platform extends to media (irrigation water/PAW)
and the agri-food chain (product and equipment hygiene), provided
chemistry and exposure are tracked.

The rupture with historical electroculture is therefore threefold: the
nature of the electrical object (from a unitary essence to a
multi-physics process), the means of measurement and control (from
qualitative signs to chemical/energetic dosimetry) and the standards of
validation (from compelling trials to randomized, replicated designs
with device-independent reporting). These differences do not validate
18th-century claims; they render them intelligible and, where
appropriate, transferable.

Looking ahead, four priorities define an applied agenda. First, anchor
practice in traceable dosing for both CAP and PAW routes, reporting
source parameters, environmental conditions, seed-lot water status and
RONS markers. Second, scale up with eco-designed, air-fed sources and
low-energy PAW reactors, evaluating energy cost per agronomic gain.
Third, integrate plasma processes within agroecological itineraries,
sequencing disinfection with inoculation, pairing with coatings and
steering dose by field-relevant indicators. Fourth, ensure safe and
robust adoption through ozone/NOx and UV limits, arc protection,
effluent management and multicenter trials across species, varieties
and sites.

Seen across three centuries, the motif of an ``\'{e}lectricit\'{e}
vivifiante'' endures, but its status is transformed. It is no longer a
regulative idea grounded in atmospheric reservoirs; it is a mechanistic
toolbox (controlled redox signaling, interface engineering, gentle
sanitation) capable of delivering lower-input, traceable and
potentially more resilient crop systems. The historical bridge matters
not as ornament, but as orientation: it reminds us that a sound
intuition becomes technology only when it is instrumented, dosed and
shared.

\section*{Declaration of interests}
The author does not work for, advise, own shares in, or receive funds
from any organization that could benefit from this article, and has
declared no affiliations other than their research organization.

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