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Effect of Microwave Treated Water on the
Germination of Cajanus cajan Seeds
Cleve Hines, Kimoy Palmer, Tavia McLean, Max Wellington
Department of Biology, Chemistry, and Environmental sciences, Northern Caribbean University,
Mandeville, Manchester, Jamaica
Abstract— Microwaves are electromagnetic radiation with frequencies between 300 MHz to 300 GHz and wavelengths ranging from one
millimeter to one meter. Microwave radiation is common throughout the environment, it is present in the soil, and sunlight. Electronic
devices use microwave radiation to communicate, and humans employ microwave radiation for heating food and water for consumption.
The effect of microwave-treated water on the germination, growth, and development of Cajanus cajan seeds were investigated. The
investigation was carried out with water exposed to microwave radiation for one minute, three minutes and five minutes duration, as well as
flamed boiled water for one minute, three minutes and five minutes, there was a sample of water that was not exposed to any heat or
radiation, this was the control. The growth of the plants was studied for fourteen days. During the investigations, the other control variable
such as temperature, sunlight, humidity, and gases (CO2 O2 and N2) were managed so that every plant was getting the same amount. The
overall results showed that microwave treated water at three minutes and five minutes as-well as boiled water at five minutes showed
better growth rates and developmental rates as compared with normal water and water boiled under five minutes.
Index Terms— Microwave, Cajanus cajan, Growth, Germination, Conductivity, Density, Frequency, Radiation, Water
—————————— ——————————
1 INTRODUCTION
All life on earth is completely dependable on water, either
directly or indirectly. Studies have shown that ~70% of the cell
is composed of water. In other words, water is the staff of all
life on earth. Biochemical reactions occur within an aqueous
environment; water functions as a solvent for most polar
compounds and water also aid in transport and give cells its
shape. Water surface tension allows for some animals to walk
on water, allows for transport and capillary action, the surface
tension also gives water a relatively high boiling point. The
use of water is endless as related to life on earth.
The article “Effect of microwave-treated water on the
germination of Lens culinaris Seeds” was a written project
investigated by Jaffer, Dhansay and Panat (2015). The
researchers collected water samples and treated the samples at
30, 60, 90, 150, and 180-second intervals with 100w of
microwave radiation. Ten seeds were sowed in seven pots
each and watered every day for ten days. The results showed
that plants that were treated with water that was microwaved
for 120 seconds showed a significantly accelerated growth in
shoots. As with the root growth length, roots that were treated
with microwaved water of 120, 150 and 180 seconds showed
similar growth length. The other plants that were treated with
microwaved water below 90 seconds showed no significant
growth. So, the conclusion could be drawn that microwaved
treated water increases the growth rate of plants. [1]
The article “Long-Term Structural Modification of Water
under Microwave Irradiation: Low-Frequency Raman
Spectroscopic Measurements” was a written research
investigated by Yakunov, Biliy, and Naumenko (2017). The
researcher’s setup glass ampoules of 2, 5, and 10 mL and cover
the samples. One set of samples were heated conventionally,
another set of samples were heated with microwave radiation
of 3 GHz and another was placed in a refrigerator and another
left open at room temperature, both of which were used as a
control. Over a period of ten days, the samples were subjected
to heating conventionally and with a microwave and then
cooled back down to room temperature. The results showed a
significant difference at higher frequencies and the controls
showed a negative correlation while the samples tested
showed a positive correlation along with significant changes
in the structure of water. This leads them to conclude that
microwave radiation resulted in long-term structural changes
of water percolation cluster forming a network of hydrogen
bonds. It was also noted that recovery time of equilibrium
structure of the microwave action depended on the size of the
cluster, which takes longer to recover. Microwave action
changes the pH of water due to the formation of hydroxyl and
hydronium ions, these are later reacted back to form water. [2]
2 PROCEDURES
2.1 Sterilization
Forty Disposable clear 50 mL plastic cups were obtained,
washed twice with 50% soap mixed with 50% multi-clean
solution, followed by a single wash with tap water, then
sprayed with 95% ethanol, then finally 3-5 washes with DI
water and then air dried in a sterile area. Before and after each
task, the incubator, laboratory room and counters were
cleaned to remove unwanted microbial life. All other
equipment and materials were sterilized according to
manufacturer specification to remove microbes and other
materials.
2.2 Specimen preparation and selection
Cajanus cajan, commonly called ‘the Jamaican Gungo Peas’ are
obtained, 0.113 Kg of peas were submerged in approximately
1 L of tap water for under two minutes. The peas that floated
were discarded; immature peas, dried up peas, deformed and
damaged peas were also removed.
Peas that were dark in colour, sank to the bottom of the
container and the hydrated peas were selected for sowing. The
selected peas were washed with a 10-15% sodium
hypochlorite solution for five minutes.
The stock supply of water used for the experiment was a 20L
bottle of drinking water purchased at the Supermarket. Cups
used were labelled accordingly: Normal, 1-minute, 3 minutes,
5 minutes Boiled and microwaved separately.
2.3 Procedure for data collection
The cups were lined with a clean (stylized) paper towel, after
which the seeds were inserted approximately half distance in
the container towards the side. Each cup had eight to ten seeds
after the seeds were inserted, the cups were sprayed with
approximately five to ten millimetres of treated water and
covered. Every day, the cups containing the seeds were
sprayed with treated water, the root lengths and shoot lengths
were observed and recorded. After three weeks of
observations, the dry mass of the leaves was taken. The
nitrogen, phosphorus, and potassium content of the leaves
were analysed using Micro Kjeldahl digestion, followed by
spectrophotometric determination using Nessler reagent
(SIRI).
Water samples were analysed for the total bacterial count,
density, pH levels, CO2, temperature, conductivity (uS), and
total dissolved ions (ppm).
Figures 1.
Diagram illustrating sowed Cajanus cajan seeds.
3 Results
Table 1. Shows the Root Growth Rate
Table 2. Shows the Shoot Length Growth Rate
Table 3. Shows the Water Content of Each Leaf
Table 4. Shows the Nutrient Content of the Leaves
Table 5. Shows the Chemical and Physical Properties of each water Samples
4 DISCUSSIONS
When someone thinks of Microwave radiation, they
immediately associate it with being a carcinogen. However,
microwave radiation is used throughout the everyday lives of
humans, nonetheless, concentrated doses can lead to health
issues in many organisms. [5] Microwave radiation causes polar
molecules such as water to spin rapidly, however, the
molecules in the air aren’t directly heated because there are
not a lot of polar air molecules present. [2]
Figure 6. Graph Showing Water Content of Leaves
The dry mass percentage gives an idea of the water content
of the leaves. Qualitative analysis of figure 5 & 6 shows that
plants treated with water microwaved for three minutes
showed the best overall health.[3] Table 3 shows the NPK
content of the dried leaves. NPK level is a good indicator of
the nutrient content and health of the plant.[3][4] Plants treated
with microwaved water for three minutes showed the highest
shoot and root health appearance. The leaves were, thicker,
greener, larger and highly hydrated. The plants treated with
normal water showed overall the highest growth in the first
week, however, after six-day, the growth rate started to
decrease almost by half each day. The leaves were very thin,
small and poorly hydrated, it was also noted that the plant
was easily dehydrated. As with figure 6. The plants treated
with boiled water did not show health appearance when
compared to the ones treated with microwave water, however,
after one week, the plants treated with five minutes boiled
water, had similar appearance to that of the plants treated
with microwave water, while the plant treated with normal
water continued to decrease in overall healthy appearance.
The health of each plant can be associated with the dry weight
which gives an idea of the water and nutritional content.[3][4][6]
1 min 3 minutes 5 minutes
Figure 3. Shows Comparison among Plants treated with
Microwaved Water
Normal 1 minutes 3 minutes 5 minutes
Figure 4. Shows Plants That Were Not Treated with
Microwave Treated Water but boiled and normal water
instead.
Figure 5. Shows the Growth Rate per Day
Table 6. Above Shows the ANOVA: Two-Factor Without
Replication
Based on the ANOVA statistical analysis of Table 6, the F-
calculated was allotted greater than the F-critical, thus, the p-
value was very small and as such the H0 was rejected, and it
can be concluded that there is a significant difference in the
average among the data sets.
Figure 7. Shows the Growth Rate of the Shoot System
The ANOVA statistical analysis of Table 7 shows that the F-
calculated was a lot greater than the F-critical, thus, the p-
value was very small and as such the H0 was rejected, and it
can be concluded that there is a significant difference in the
average among the data sets.
Table 7. Above Shows the ANOVA: Two-Factor Without
Replication
The ANOVA statistical analysis of Table 7 shows that the F-
calculated was a lot greater than the F-critical, thus, the p-
value was very small and as such the H0 was rejected, and it
can be concluded that there is a significant difference in the
average among the data sets.
Figure 8. Shows the Density of each Water Sample
Density is the mass per unit volume. When water samples are
exposed to electromagnetic radiation, it may result in long-
term changes in the vibrational density states. According to
(Yakunov, Biliy & Naumenko, 2017) the greater the volume,
the greater retention time of structural changes of water. These
changes in the chemical composition of water can lead to
changes in the structure of the percolating cluster formed
because of the network of hydrogen bonding. Depending on
the cluster sizes, water may take a longer while recover, than
the chemical composition of water.[2] Moreover, plants would
require less energy for water absorption, this may explain the
reason why the weight of the leaves that were treated with
microwave treated water for three, and five minutes were
greater than the others.
Figure 9. Shows the pH value of Each Water Sample
When water is heated the equilibrium changes and carbonic
acid decomposes into carbon dioxide gas and defuses out of
the water causing the pH to increase.
CO2 + H2O <-> H2CO3 Due to the water reaching boiling
point under normal atmospheric pressure at a faster rate as
compared to microwaving, excessive amounts of carbon
dioxide and Sulphur dioxide diffuses out of the water causing
it to be a more basic due to the presence of carbonates and
sulphates that remain. Heating leads to the destruction of
percolating cluster and perturbation introduced by
microwaves and conventional boiling which affects the
structure of water. Bernal-Fowler rules describes the structural
organization of water molecules and autoproteolytic property
of water 2H2O -> OH- + H3O+. Absorbing Microwave
radiation cause a change in the equilibrium concentration of
ion defects, it also affects the autoproteolytic property of water
by reorienting of the interacting polar molecules and a change
in the activation energy.[2]
Figure 10. Shows the Conductivity of each Water Sample
The Conductivity gives an idea of the number of dissolved
ions in solution. Since the volume of water decreases, the
concentration of ions increases. In addition, these changes
observed can be mainly attributed to the species transfers,
either between gaseous (atmospheric gases) and liquid (water)
phases for nitrate, or between vessels walls and water, for
fluoride, chloride and sulphate. These anions are important in
the growth and development of plants. Chloride anions are
utilized by plants to split water during photosynthesis, plants
also use (Cl-) anions to chemically balance the potassium (K+)
cation concentration that increases in the guard cells during
the opening and closing of the stomata. Chloride also
functions in photosynthesis, specifically in the water splitting
system.[3] Fluoride (F-) anions, toxic effects depends on the
cation to which it is attached, however, fluoride is not readily
available to plants; it strongly inhibits photosynthesis and
other biochemical reactions, so fluoride can be harmful to
sensitive plants.[3] Sulphates (SO4) anions are naturally
abundant in nature because it is soluble in water. Plants utilize
sulphates to build organic molecules such as proteins and
hormones which are important in the plant biochemistry.[3]
Overall, the conductivity results showed that upon heating
whether by flame or microwave, anion concentration
decreases. This may be due to the anions combining with
other cations in the solution or at the water-air junction where
it may combine with other molecules present in the air.
Figure 11. Shows the Total Dissolve Solutes
The carbonate concentration will be higher depending on the
concentration of carbon dioxide and the pH values.
Microorganisms produce carbon dioxide, and sulphurous
compounds that may increase the pH value of the water, and
over-time these metabolic byproduct compounds will react
with the dissolved solutes. Upon heating, these solutes would
precipitate out of solution.
Figure 13. Shows the Total Bacterial Count of Each Water
Sample
Microwave water is super-heated, yet it does not reach its
boiling since it is heated from the side of the container. So, the
centre of the water is a lot cooler than the sides, thus, bacteria
can survive microwave treated water, while for boiled water,
it is heated uniformly, thus, all the bacteria present in the
sample will experience similar heat.
5. CONCLUSION
The H0 was rejected because the overall results showed that
microwave treated water at three minutes and five minutes as-
well as boiled water at five minutes showed better growth
rates and developmental rates as compared with normal water
and water boiled under five minutes.
ACKNOWLEDGMENT
PhD. Max Wellington, my research adviser of the Department
of Chemistry, Biology & Environmental Sciences, Northern
Caribbean University
Dr. Maureen Wilson of Sugar Industry Research Institute
Jamaica
REFERENCES
[1] Jaffer, P., Dhansay, B., and Panat, O. (2015) Effect of microwave-
treated water on the germination of Lens culinaris Seeds”. Weekly
Science Research Journal 3, 1-4.
[2] Yakunov, A., Biliy, M., and Naumenko, A. (2017) Long-Term
Structural Modification of Water under Microwave Irradiation: Low-
Frequency Raman Spectroscopic Measurements. Advances in Optical
Technologies 2017, 1-5.
[3] Reginald H. Garrett Charles M. Grisham 5th Ed Biochemistry 2012
[4] Ugulin, T., Bakonyi, T., Berčič, R. and Urbanek Krajnc, A. (2015)
Variations in leaf total protein, phenolic and thiol contents amongst
old varieties of mulberry from the Gorizia region. Agricultura 12, 1-5.
[5] Pall, M. Journal of Chemical Neuroanatomy 2016, 75 1-7
[6] Vaieretti, M.; Diaz, S.; Vile, D.; Garnier, E. Annals of Botany 2007, 99,
955-958