22nd International Symposium on Plasma Chemistry
July 5-10, 2015; Antwerp, Belgium
Stimulation of wheat seedling growth by plasma-treated water
M. Maniruzzaman1, H.I. Hussain2, X. Wang1, A.J. Sinclair3, D.M. Cahill2 and X.J. Dai1
1
2
Institute for Frontier Materials, Deakin University, Geelong, VIC, Australia
School of Life and Environmental Science, Deakin University, Geelong, VIC, Australia
3
School of Medicine, Deakin University, Geelong, VIC, Australia
Abstract: We report plasma treated water significantly increased the fresh weight, leaf
length and relative chlorophyll content of the wheat seedlings compared with the control.
Plasma treatment produced various reactive oxygen and nitrogen species e.g. hydrogen
peroxide, nitrite and nitrate, which are important for plant growth, development and
pathogen control. Separate experiments showed that plant growth was enhanced to a
similar extent when pure solutions of nitrate and hydrogen peroxide were included in
untreated water. Plasma treated water has potential as a fertilizer for plant growth.
Keywords: plasma-treated water, nitrate, hydrogen peroxide, wheat, and seedling growth
1. Introduction
Non-thermal plasma in, and in contact with, liquid has
wide applications in e.g. waste water treatment and
bacterial inactivation in aqueous solutions. However, its
potential in agriculture, has largely been unexplored.
Nitrate and hydrogen peroxide are the most stable species
in plasma-treated water [1]. Nitrate is the most important
form of nitrogen for plants. Nitrogen is one of the
essential nutrients as it is a constituent of amino acids,
proteins, nucleotides, chlorophyll and numerous other
metabolites and cellular components. It is a principal
limiting element in plant growth and development. On the
other hand, hydrogen peroxide is widely generated in
plants and mediates various physiological and
biochemical processes. As a signalling molecule, it can
activate proteins/genes related to plant growth and
development. It can induce hypersensitive response (a
programmed cell death) at the site of pathogen infections
[2]. Accumulation of hydrogen peroxide can reinforce cell
walls through lignification. Therefore, reactive oxygen
and nitrogen species generated in plasma-treated water
could have a significant impact on plant growth,
development and disease control. An initial study
examining the effects of three types of plasma found
improved growth [3]. Here, we report a systematic study
of the effect of plasma-treated water on wheat seedling
growth and the key species in plasma-treated water
responsible for this growth.
2. Material and methods
A nanosecond pulsed atmospheric pressure plasma
system was used to treat milli-Q water. A schematic of
the experimental setup is shown in Fig. 1. Plasma
parameters were: 90% pulse width = 10 ns, peak to peak
voltage =18 kV (channel 1 = +9 kV and channel 2 = -9
kV), frequency= 4.7 kHz. The top spiral electrode made
of copper wire covered by glass was connected to channel
1 and placed 2 mm above the water surface. The bottom
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electrode made of stainless steel mesh was connected to
channel 2 and placed inside the water. A Pyrex glass
beaker containing 500ml water was used as the reaction
chamber. Argon gas (5litre/min) flowed through the
showerhead and top electrode to the water.
Fig. 1. Apparatus for plasma treatment of water.
The viable wheat seeds (Naracoorte, South Australia)
were selected and surface sterilised by 80% ethanol and
then imbibed in water for 2 hour. After imbibition, the
seeds were placed into Petri dishes with two layer of filter
paper moistened with control and plasma-treated water.
The Petri dishes were covered with aluminium foil and
placed into a growth cabinet. After germination, the
seedlings were transferred to a soil-free plant growth
system [4]. The controlled condition (21°C, 14h light
(300 μmol/m2/s)) was maintained throughout the seedling
growth.
3. Results and discussion
The plasma-treated water was characterised by
measuring pH, conductivity and the concentration of
nitrate and hydrogen peroxide. The pH of milli-Q water
decreased from7 to 4.5 and conductivity increased from 0
up to 40 μS/m after 20 minutes of treatment (data not
shown). The nitrate and hydrogen peroxide concentrations
1
increased up to 27 and 59 ppm respectively after 20
minute treatment as shown in Fig. 2.
Fig. 2. Nitrate and hydrogen peroxide concentration in
plasma-treated milli-Q water. Data shown is the mean of
3 experiments.
Wheat was grown in control (milli-Q water) and
plasma-treated milli-Q water (10 and 20 minutes). A
representative picture of 12 day old wheat seedlings is
shown in Fig. 3.
Fig. 3. A representative picture of wheat seedlings in
control and plasma-treated water (10 and 20 min).
The fresh weight, leaf length, root length and the
relative chlorophyll content of the seedling were recorded
at 7 and 14 days of growth. The fresh weight and leaf
length were increased by 68% and 38% respectively in
plasma-treated water (20 min) compared with the control
at 14 days of growth, as shown in Fig. 4. The relative
chlorophyll content increased by 14 % (20 min) but the
root length did not show any significant changes (data not
shown). To understand which species in plasma-treated
water might have been responsible for the seedling
growth, wheat was also grown in nitrate, hydrogen
peroxide and nitrate + hydrogen peroxide solutions
matched with the concentrations found in plasma-treated
water. It was found that both these species were important
for the seedling growth and that they worked
synergistically.
Fig. 4. Wheat growth parameters. (A) Fresh weight and
(B) leaf length. Different letters indicates statistical
significance according to student t-test (p<0.05). Sample
size, n=18. Error bars show standard error.
4. Summary
A nano-second pulsed atmospheric pressure plasma
changed the chemical composition of water. The plasmatreated water stimulated wheat seedling growth. Nitrate
and hydrogen peroxide working synergistically appeared
to be responsible
5. References
[1] P. Bruggeman and C. Leys, J. Phys. D: Appl. Phys.42,
053001 (2009).
[2] D. B. Graves, J. Phys. D: Appl. Phys. 45, 263001
(2012).
[3] D. P. Park, K. Davis, S. Gilani, C. Alonzo, D.
Dobrynin, G. Friedman, A. Fridman, A. Rabinovich, G.
Fridman, Current Applied Physics, 13, S19-S29 (2013).
[4] T. Gunning and D. M. Cahill, J. Phytopathol, 157,
497-501 (2009)
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