22nd International Symposium on Plasma Chemistry
July 5-10, 2015; Antwerp, Belgium
Non-equilibrium plasmas in agriculture
J. Han1, B. Peethambaran2, R. Balsamo3, A. Fridman1, A. Rabinovich1, V. Miller1 and G. Fridman1
1
A.J. Drexel Plasma Institute, 200 Federal Street Suite 500, US-08103 Camden, NJ, U.S.A.
2
University of the Sciences, 600 S 43rd Street, US-19104 Philadelphia, PA, U.S.A.
3
Villanova University, 800 East Lancaster Avenue, US-19085 Villanova, PA, U.S.A.
Abstract: Reduction of water uptake by plants together with the enhancement of plant
development and growth is one of the major agricultural challenges of the modern society
both in the third world and in the developed countries. Preliminary investigation, reported
here, shows that this challenge can be met by cold non-equilibrium air plasma (NEAP)
treatment of water without any additional chemicals. In particular, it was shown that
application of NEAP water permitted using half as much water for germination and growth
of A. thaliana; in addition, the plants grew larger and produced more flowers. The goal of
the ongoing project is to ascertain how reactive species generated by NEAP treatment
reduce water uptake by plants in conjunction with enhanced plant growth.
Keywords: non-thermal plasma, agriculture, germination, drought control
In a five-week pilot study using A. thaliana, seedlings
used half as much plasma acid water as compared to
untreated water (Fig. 1). In addition, the plants grew
larger (Fig. 2) and produced more flowers. Soil treated
with plasma acid water had higher levels of measured
nitrates (Fig. 3), a possible contributor to enhanced plant
growth. However this does not explain the reduced water
uptake. The alterations in water chemistry as a result of
plasma treatment seem to alter the water requirement to
produce better observable growth, i.e., the physiology of
plants.
Figure 3. Nitrate levels in soil of control plants and plants
treated with plasma acid water at week 5.
Figure 1. Water consumption of plants watered with
control or plasma acid water over 5 weeks.
Figure 2. Photo of plant growth with control treatment
and plasma water treatment.
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An understanding of the fundamental correlation
between the chemical species present in water treated with
plasma and how they regulate gene expression to influence
cellular functions in plants could provide the knowledge
required to improve yield while conserving resources.
Non-thermal atmospheric pressure air plasma is able to
generate high concentration of reactive oxygen and
reactive nitrogen species as well as charged species and
ultraviolet radiation that all have been shown to effectively
and efficiently inactivate pathogens. Recent developments
in nanosecond and sub-nanosecond pulsed electronics
made it possible to provide uniform soft treatments
leading to promising results in pathogen remediation,
including even direct plasma treatment of wounds to
reduce or eliminate bacterial load in the wound of a live
patient. Plasma was shown to effectively inactivate
bacteria, fungi, and viruses in air streams [1-3], on various
surfaces [4, 5] including chicken meat [6], in liquid [7-11],
including conductive liquids [12], and on skin and in
wounds [13].
The key issue with using nanosecond pulsed dielectric
barrier discharge is the volume of water we are able to
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treat with it which seems to be of the order of miligrams
per minute. For industrial applications water flow rates
need to be on the order of grams per second and thus a
scale-up of this technology is needed. For this, we have
developed a gliding arc Plasmatron system with a set of
replaceable electrodes of different lengths and diameters
(see Fig 4). The Plasmatron consists of two cylindrical
electrodes that face each other, separated by a 2 mm gap.
Compressed gas at a rate of 100–200 litters per minute is
supplied between the two electrodes through the gap by
small jets to form a swirl flow. This swirl flow keeps the
electric discharge from attaching to a single point on the
electrodes.
Figure 4. Laboratory Gliding Arc Plasmatron with
Changeable Electrodes.
The overall schematic of the spectroscopic
measurements of the system is given in Fig. 5. It consists
of gliding arc Plasmatron that is powered by a high
voltage power supply and an optical (UV) spectrometer to
analyse the light emission from the discharge. One
electrode is connected to a current limited high voltage
power supply and the other electrode is grounded. The
power supply delivers a maximum of 1.5 kV with a
maximum power of 12 kW. A high voltage probe and a
current probe are connected to the high voltage lead on the
Plasmatron. They in turn are connected to a Tektronix
DPO 3014 oscilloscope to monitor the power delivered to
the Plasmatron. A 10 cm in diameter, 25 cm focal length
quartz lens located 25 cm from the exhaust of the
Plasmatron collects the axially emitted light from the
discharge and concentrates it at the focal length into a
1 meter long, UV-grade fiber optic cable, which in turn is
connected to an optical spectrometer. The spectrometer is
the THORLABS Model CCS200 spectrometer. It has a
600 lines/mm grating and fix slit. The spectral resolution
is about 2 nm with a wavelength range of 200 to 1000 nm.
Conclusion
We report on increase in drought resistance, increase in
germination rate, and increase in yield in A. thaliana
plants, following treatment by gliding arc plasma-treated
water. The mechanisms of the observed phenomena are
likely related to the production of the short-lived
peroxinitrate radical and will be discussed during
presentation.
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Figure 5. Schematic of the laboratory Plasmatron system.
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