Effect Of Corona Discharge Treatment On Strength

Types of Plasmas used for Water Activation

Discuss about the Effect Of Corona Discharge Treatment On Strength.

Preparation of Plasma-activated water involves exposure to plasma that is non-thermal, which is produced by a direct current corona positive discharge in a momentary spark system. The water activation process is conducted in an atmosphere of different gases which are; argon, air, carbon dioxide and nitrogen. Water treatment by gas expulsion plasma leads to solutions that are acidic and have an extensive antibiotic activity. Different sources of plasma can be used in water activation and this includes low-frequency discharge, direct current, pulsed coronas, and pressure plasma jets of the atmosphere, radio-frequency discharge, microwave discharge, and dielectric barrier discharge (Oehmigen et al 2010). Plasma-activated water causes great bacterial membrane damages and can easily diffuse in the extracellular matrix; it also establishes good anti-biofilm activities. For this reason, plasma-activated water efficiently inactivates a variety of microbes such as Escherichia coli, Hafnia alvei, Candida albicans, Saccharomyces cerevisiae, and Staphylococcus aureus. More studies show that presence of some metal ions such as zinc and copper in the plasma-activated water, which is because of plasma treatment cause bacterial inactivation. The role of the metal ions in inactivating bacteria differ among the plasma-activated waters from various working gases, however, the acidification of the solution triggered by the reactive species present in the plasma is important (Ekezie 2017).

There are various types of plasma used in water activation; however, the atmospheric pressure plasmas are the ones that are used mostly. They comprise the corona discharge, dielectric barrier discharge, and the arc discharge.

At atmospheric pressures the corona discharges appear in strong electric fields that are uneven, the sharp-edged electrodes of high voltage produce uneven fields. Once the field present in the remaining space is insignificant, the corona emission is ignited. At the negative corona, electrons are discharged at the cathode accelerating in the electric field ionizing the gas its atoms collide with creating more electrons and eventually an avalanche is created. Photoionization in the volume of the gas and electron discharge at the cathode is the secondary processes. Negative corona forms an even glow at the sharp electrode edges. The electrons that are instigating the avalanches at the positive corona are because of gas photoionization that is around the anode of high voltage. The photons are discharged in an active area of the vicinity of the anode, the electrons avalanches then spread to the anode, and the positive corona’s plasma has numerous continuously moving filaments. The advantage of the corona emission is the simplicity of the direct current electrodes of high voltage (Brzezinski et al. 2009).

The Corona Discharge

At atmospheric pressure, the Arc emissions are the direct current electric emissions that are self-sustained with huge electric currents, normally greater than 1A and might go up to 100,000A and have comparatively low voltages (10-100V).  The increased frequencies of collision of the plasma species cause the pressure of the atmosphere arcs to be in thermal symmetry at temperatures of 6000C to 12000C. Ions produced at the ion cathode are accelerated in the voltage and are imparted to the surface of the cathode with great energies. This process results in the cathode being heated up causing stimulation of thermal electron discharge, which withstands the great emission currents. The technology of pulsed atmospheric arc develops the stability of the arc at low currents of electricity and capitalizes on the emission volume, for this reasons it is economically essential for application in industries (Machala et al 2009).

The dielectric barrier emission occurs between the two electrodes that are usually divided by a dielectric. Because of the pressure of the dielectric obstacle, the plasma source functions only with high-pulsed voltages or with sine wave. The operating range of frequency is not affected by discharge’s physical principles. The characteristic frequencies of the normally used solid-state supplies of high voltage are 0.05 – 500 kHz (Neretti 2017). The power of the emission of the dielectric barrier is higher than the power of the corona discharge; however, it is smaller when compared to the arc emission. The emission normally entails several micro-discharges; however, there are cases when even discharges are produced (Jiang 2014).

Non-thermal plasma has illustrated its significance in the fields of food science, medicine, and plasma-supported polymerization as well as in other fields. Non-equilibrium (non-thermal) plasma is gas that is ionized that has been created by electrical emissions. The Non-thermal plasma (NTP) has the following features; the producing energy, which helps the electrons and presence of, limited transmission of momentum among the heavy particles and the electrons (Bruggeman 2009). This causes the electrons to show very high temperatures, on the other hand, the ion’s temperatures are about the ambient temperature, and the energy distribution of the electrons is usually near the thermal distribution. The conditions stated above determine the functioning and characteristics of the non-equilibrium plasma (Taghioskoui 2011). The chemical and ionization process brought by non-thermal plasma is connected to the electron energy. The impact of other particles and these electrons bring about the creation of an electromagnetic radiation, charged particles, and reactive radicles, which range mostly from infrared to visible spectral area (Burlica 2006). Therefore, non-thermal plasma has the possibility of initiating various unique chemical responses in fast, simple, cost-effective, and environmentally friendly ways. The NTP also promotes precise modifications of nearly all surfaces without damaging them thermally, including many of the resistive materials.

The Arc Discharge

The influence of NTP on electrical, morphological, and structural properties of a conductive polymer polypyrrole in nanostructured and in the globular state when dispersed in purified water

The transient spark technique is normally applied; as it is inexpensive, simple and can be used for sample treatment purposes in other liquids that, in comparison with the gases, generate an extensive range of species that are reactive. The samples to be used should be characterized before and after alterations by energy dispersive Fourier transform infrared spectroscopy, X-ray spectroscopy, scanning electron microscopy and Raman spectroscopy. The measurement of polymer polypyrrole’s electrical conductivity after different alteration steps together with its ZP (zeta potential) characterization is essential (Ehlbeck 2010).

The samples of PPy-NT and PPy-G and are prepared and treated a suspension of water by non-thermal plasma for different time intervals ranging from 1 to 60 minutes.

Source: (Ajo 2018)

Structure of non-thermal plasma apparatus; experimental arrangement used for the adjustment of the PPy and NTP generation in purified water. There is the use of the discharge in a positive system of a momentary spark at atmospheric pressure (Ajo 2018).

Morphology of set and treated samples of PPy is characterized. SEM pictures of PPy-NT and PPy-G without and after 50 min of treatment with plasma are presented. Both polymer structures show a similar shape before and after the process of treatment, there is also no polymer-cutting or cross-linking. Therefore, the plasma process does not alter the morphological properties of the polymer forms; this shows the non-distractive property of the NTP treatment.

Morphology of PPy viewed under a scanning electron microscope; (a) as-prepared PPy-G; (b) PPy-G after 50 min of plasma treatment; (c) as-prepared PPy-NT and (d) after 50 min of plasma treatment (Galá? 2017).

The dependence of composition of elements (chlorine and oxygen) on the period of plasma treatment for PPy-NT and PPy-G are evaluated by Raman spectra and FTIR.

The conductivity dependences on plasma treatment period applied on PPy-NT and PPy-G in the suspension of water indicate that the conductivity is intensely decreased in the first few minutes of treatment irrespective of the structure of PPy. The sequence of both PPy-NT and PPy-G electrical conductivity habits is agreeable among Raman characteristic, FTIR, and EDX.

Studies show that the effect of the presence of NTP on physical, structural, and morphological properties of the nanostructured and globular conductive polymer polypyrrole in purified water is characterized by EDX, Raman spectroscopy, FTIR, measurement of zeta-potential and conductivity as well as SEM.

Dielectric Barrier Discharge

Production of PPy-G is by dissolution of the pyrrole monomer (2ml) in purified water (600ml) then cooled by the thermostat to about 5oC and then followed by the iron (III) chloride hexahydrate (8.12g) drop-wise addition that is dissolved in purified water (69ml). The black gel that is filtered is dried in vacuum for one week at 40oC; this is then ground into uniform black powder.

PPy-NT is prepared by use of methyl orange; the pyrrole monomer (2ml) is dissolved in a solution of 600mM of 2.5mM methyl orange. The solution’s temperature is lowered to 5oC and stirred for even spreading. There was the dissolving of Iron (III) chloride hexahydrate (8.12g) in purified water followed by drop-wise addition to the reaction solution. After about one day, the black precipitate formed is filtered and Soxhlet extraction method by use of acetone is employed in cleaning the precipitate for one week. The resultant PPy nanotubes are dried in vacuum (40oC) for about one week; it is then ground into fine black powder

The non-thermal plasma is made by a non-commercial open-air device, by use of the electrical emission between the plate electrode and the point electrode, emitted at the suspension surface (Lu 2017). The suspension surface is connected electrically to the power source’s negative pole, by a submerged platinum wire sealed with glass through steadying the ballast impedance including the parallel linking of a capacitor (250PF) and resistor (10 MΩ). NTP is used in the modification of both PPy-NT and PPy-G that are usually suspended in purified water. There has been a consideration that Non-thermal plasma is an effective way of decontaminating food products. This is evidenced by the numerous studies that relay that plasma-activated water has a wide range of inactivating microorganisms.

Decontamination of microorganisms via gas plasma is usually accomplished under an active discharge that is the targets that are contaminated are treated by use of the discharge of plasma. The production of Glidarc in the air that is humid is a technique that is simple and it inactivates microorganisms under direct discharge as well as functions at atmospheric pressure. The major species that are in the glidarc plume of plasma, primarily NO and OH, are the precursors in water of HNO3, HNO2, and H2O2. It is also shown that planktonic H.alvei may be destroyed via contact with water that is activated through gliding electrical discharges, without exposure of the cells to the plume of the plasma (Naïtali et al 2010). The ability of plasma-activated water in inactivating microbial organisms is tested on four organisms which are; Saccharomyces cerevisiae (yeast) and bacteria which are, H. alvei (a Gram-negative microbe) and Staphylococcus epidermidis, Leuconostoc mesenteroides, (Gram-positive bacterias). The testing is also based on microbes adhering to a solid as well as those that are in a planktonic nature.

Influence of NTP on Electrical, Morphological, and Structural Properties of a Conductive Polymer Polypyrrole

The non-thermal plasma of the sliding arc type functioning at the atmospheric pressure together with plasma gas, which is the humid air, is the technique that is involved in the production of the decontaminating solution. A glass treatment reactor, which is about 95mm tall with an internal diameter of 65mm, is circulated with a water jacket that prevents thermal influence. Disinfected distilled water (about 20ml) is treated for about 5 minutes (this varies depending on the amount of water to be treated) and then used immediately as plasma-activated water (Pavlovich et al 2014).

Staphylococcus epidermidis, Leuconostoc mesenteroides, Saccharomyces cerevisiae (yeast), and H. alvei are the microbial models used for the study. These microbes are cultured and then harvested by centrifugation; they are then washed and suspended in NaCl. Concentrated suspensions, which are useful for inactivation of planktonic cells is prepared, diluted solutions essential for microbial adhesion, are also prepared (Kamgang?Youbi 2009).

Planktonic cells are inactivated by placing the concentrated suspensions of microbes in contact with plasma-activated water. For every time of treatment, the concentrated microbial solution is diluted in plasma-activated water of the quenching solution to stop inactivation, after the serial dilution process in NaCl and neutralization process which takes about 5minutes, the microbes that are not destroyed are planted on TS Agar for new strains or on MRS Agar for Leuc. Mesenteroides. In the case of adherent cells, the substrates that are contaminated are covered with plasma-activated water (10ml) and for every time of treatment there is a removal of the solid substrate from the decontaminating solution and then placed in a quenching solution to stop the inactivation (Lazovi? 2010).

Studies show that yeast and bacterial cells can be successfully inactivated by plasma-activated water both in their adherent and planktonic state. Plasma-activated water can kill Gram-negative bacteria (H. alvei) in its planktonic state; however, even in presence of exopolymers, plasma-activated water can inactivate both planktonic and adherent cells of Gram-negative and Gram-positive bacteria and also yeast. Using the plasma-activated water, the microbes are destroyed even without the exposure to the plume of the plasma. In this case, the products to be disinfected do need require subjection to the discharge, and this limits any alterations initiated by the treatment process and increases the variety of prospective applications. Plasma-activated water does not destroy solid substrates and does not oxidize stainless steel; therefore, glidarc can be used in the disinfection of surfaces and equipment. It is important to take into consideration the production of by-products that are toxic (Naïtali et al 2012). The efficiency of the disinfection process by plasma-activated water depends on various factors which are; water hardness, the existence of organic soils, temperature and biotic aspects such as the inherent resistance of microbes towards harmful agents and the microbe’s physiological nature as well as the microbe’s sessile or planktonic state. Other parameters that affect the disinfection process are; the population of the microorganisms and the tolerance of the microbes.

Morphology of PPy

The inactivation process of the adherent bacterial organisms by plasma-activated is less efficient than that of bacteria that are planktonic; this is because the sessile cells are more resistant. The resistance, however, does not depend on whether the bacterium is Gram-negative or Gram-positive; this has been observed concerning the disinfection of food by use of a uniform atmospheric glow discharge. S. cerevisiae (yeast), which is an adherent microbe and the most tolerant to plasma-activated water, is efficiently inactivated by the plasma-activated water process (Joshi 2017).

In the field of plasma healthcare and biomedicine, non-thermal plasma has been used in cancer treatment, NTP sterilizes medical equipment, non-thermal plasma does not oxidize stainless steel, and therefore, it is efficient for sterilizing medical equipment. Disinfects and decontaminates, medical surfaces, healthcare rooms and various sections within the healthcare can be decontaminated and made devoid of infectious micro-organisms such as E. coli by the use of non-thermal plasma. Non-thermal plasma can be used as a drug-delivery and therapeutic technique, it is essential in healing skin diseases and wounds by destroying microbes that cause the diseases and inactivating microbes that worsen the situation, non-thermal plasma is also essential in cosmetics (Park et al 2017).

In the field of polymer science, the non-thermal polymerase is essential in the development of inorganic/organic nanostructures and modifying their practical properties. To be specific plasma-aided polymerization and the process of deposition of thin coatings on different surfaces in addition to the Nano crystallization process and the purposeful adjustment of these surfaces’ properties has been of great interest in the field of science. The advancement in NTP has made it applicable in other different fields such as photovoltaic and microelectronics (Oldham 2009).

Non-thermal plasma has been of great use in the field of agriculture, it is a significant alternative to the traditional process of sanitization applied in agriculture, for instance, the of vegetables and fruits (Ma, R ET AL 2015). Plasma-activated water, which is as a result of non-thermal plasma activation of purified water, is reported to be able to inhibit the activities of S. aureus that is inoculated to strawberries. Soaking in PAW is also essential in fresh-keeping of the agricultural products against the microbial attack such as the A. bisporus (Ziuzina 2016).

In the food industry, plasma-activated water, which is formed via non-thermal plasma activation of distilled water, inhibits a wide range of microorganisms including Escherichia coli, Candida albicans, Saccharomyces cerevisiae and Hafnia alvei, it is therefore used in decontaminating processed and fresh foods. This PAW inactivates microbes with minimal adverse effects on the surroundings; it also does not have the requirements of storage and transportation of possibly hazardous chemical such as the chloride-based products, which have raised concerns on public health, and the danger of carcinogenic organic compounds, which are chlorinated. This makes plasma-activated water a great medium for sterilization of various food substances within the food industry as it has no side effects and it is very simple. Non-thermal plasma has also been essential in the sterilization of equipment within the food industry, as it has no effect on stainless steel (Pavlovich 2014).

1. aureus inhibition

The colonies are counted to evaluate the microbial effects of plasma-activated water stored at varied temperature rates for different days (Paniagua-Martínez et al 2018). The bactericidal capability of plasma-activated water increases with the decreasing temperature, that is with −80 > −20 > 4 > 25 (°C) acquired in a descending manner for inhibition of bacteria. Prior to storage, the fresh PAW causes inactivation of S aureus (log reduction of about 5). The growth of bacteria at -80oC and 25oC reduces to 3.7 and 1.8 respectively, after a single day of storage (Scholtz et al 2015). Plasma-activated water that is stored at −80 °C maintained a greater antibacterial activity than other temperatures, resulting in a log decrease of 3~4 for S. aureus; at the other temperatures total growth of bacteria is reduced by PAW at 1.8, 2.2, 2.9 logs in comparison to the untreated control, and this decreases to approximately 1log after storing for 30 days. This shows that losing of bactericidal activity in plasma-activated water (−80) is reduced when matched with that of the other temperatures this indicates that PAW (−80) maintains an effective bactericidal activity. Therefore, storage of PWA at −18 °C is more efficient in retaining the existing bactericidal activity and chlorine concentration in comparison to storage at 25 °C. Inactivation rate of S. aureus treated with plasma-activated water kept at different temperatures for 30 days

Different lowercase letters for the same time of storage specify important differences (p < 0.05). Different capital letters for the same temperature of storage but at different times show substantial differences (p < 0.05) (Kroupitski et al 2009).

 The SEM study, verifies further the bactericidal capability of PAW (−80) which is stronger compared to the bactericidal ability of other temperatures. The bacteria undergo a conversion from having smooth surfaces to having surfaces with rupture, distortion, and shrinkage of the external layer once treated with PAW. The level of destruction depends on storage temperature, and it is more severe for −80 °C than 25 °C temperatures, these results are steadfast with the reduction in bacterial number, this indicates the strength of plasma-water kept at −80 °C over the PWA stored at other temperatures.

Optical Emission Spectra (OES) Detection of Main Excited ROS (reactive oxygen species) in PAW

The OES is used in investigating the major agitated active species produced in PAW.  OES data show that agitated atomic nitrogen and oxygen are generated in water by the plasma. The atomic oxygen produced is chemically sensitive and can cause destruction to biological molecules; due to the increased activity by chemical reactions, the atomic oxygen is converted to different species of reactive oxygen such as H2O2, O3 and OH. The metabolites of NO are nitrates, nitrites, nitrosamines, and S-nitrosothiols, they are also the mediators of the associated cytotoxic outcomes, which are, the inhibition process of mitochondrial DNA destruction causing gene mutation, alteration of protein and function loss, apoptosis and necrosis (Chen et al 2017).

The physicochemical factors of PAW show major dissimilarities at all temperatures of storage when compared with the controlling set (PAW-0). Solution ORP and pH are acquired in the process of storage. After activation by plasma for about 20 min, the pH of PAW decreases from 6.8 to 2.3, and the ORP rises from 250mV to about 540 mV, however, there is no major difference in pH between the different storage temperatures at the same time (M. J. Traylor et al 2011). 

ORP is the significant aspect that influences microbial inhibition; high levels of ORP can destroy the inner and outer membranes of the microbes. Data in the above tables show ORP for samples of PAW kept at different conditions for 30 days, respectively. As for varying temperatures, fluctuations follow a related trend; they slightly decrease in the initial seven days of storage by15.6%, 13.3%, 17.1%, and 17.5%, respectively, and are reduced by 15.6%, 13.3%, 10.0%, and 6.2%, respectively, from 7th to the 30th day. The synergetic outcome of the ROS and acidic pH provides a guarantee of comparatively good germicidal value; also, the high ORP shows a solution has high strength of oxidation (Luke 2014).

H2O2 is one of the antimicrobial properties of plasma-activated water, the antimicrobial influences of H2O2 (hydrogen peroxide) in PAW have been assessed.  About 3 mM H2O2 gives a 2-log decrease in the formation of the bacterial colony, and 10 μM acidified H2O2 brings a reduction of about 0.4-log. The concentrations of H2O2 in PAW kept at −80 °C is about 20 μM and doesn’t vary significantly within the 30 days of storage, however, in the other PAW samples kept at other temperatures, the concentration reduces from 24.4 μM to 6.0 μM after the 30 days, this shows that H2O2 present in PAW reacts with several substances depending on the temperature conditions. H2O2 is a strong oxidizer, particularly in acidic conditions; therefore, loss of H2O2 plays a significant role in various disinfection efficiencies (Joslin et al 2016).

RNS (Reactive nitrogen species) such as peroxynitrites, nitrates, and nitrites have purifying mechanisms in plasma-activated water. Concentrations of NO3− have a related tendency in PAW samples for all temperature conditions and decrease with the time of storage. NO2−, concentrations remain constant within the storage time (30 days) in PAW (−80) about 1.2 μM; the nitrite levels present in PAW, varies, they decrease from 1.2 μM to 0.1 μM, 1.2 μM to 0.4 μM, and 1.2 μM to 0.6 μM at 25 °C, 4 °C, and −20 °C, respectively in the 30 days of storage, the nitrite levels, on the other hand, decreases with increasing temperature.  The reaction of the post-discharge between nitrite ions and hydrogen peroxide happening in water after the plasma treatment enables the establishment of peroxynitrites. The chemistry of Peroxynitrites participates significantly in antimicrobial PAW properties (Kojtari et al 2013). The amounts of NO3− in the samples of PAW decreases greatly after storage, while the H2O2 and NO2− amounts decrease quicker after storage at the other temperatures in comparison to −80 °C. This shows that PAW (−80) is efficient in keeping bactericidal activity, H2O2, and NO2−. Indicating that PAW (−80) is more favorable to keep NO2−, H2O2, and consequently, bactericidal activity.

A concentration of (A) nitrate and (B) nitrite in PAW stored at different temperatures and times (Traylor et al 2011).

Presence of NO is detected in PAW but is nearly absent in the control agent (PAW-0). There is the generation of NO radical in the solutions treated by plasma. The amount of NO radical is not the essential aspect that affects the decontamination capability of PAWs kept at varying temperatures. However, possible antibacterial effects of NO have been identified, exogenous NO is able to induce production of ROS, and this has resulted to oxidative destruction to proteins in the process of germination, causing Penicillium expansum inhibition. After the storage of PAW, the RNOs cause nitrosative and oxidative destruction, by inhibiting the functioning of the enzymes, inducing peroxidation of lipids and altering DNA and this indicates the NO’s antibacterial properties (Lukes 2012).

The PAW’s (−80) bactericidal ability remains constant during storage and that of PAW (25), PAW (4), PAW (−20) showed a declining tendency with the increasing time of storage. The inhibitory activity of PAW change with the time of storage and this depends on various germicidal aspects which are; NO3−, H2O2, and ORP. ORP is the significant aspect of the killing of the microbes, as it can destroy the inner and outer membranes of E. coli, this leads to inhibition of E. coli. H2O2 is the significant essential in purification, nitrate is a secondary product, and it is accountable for the biological outcomes of PAW after activation by plasma. H2O2, ORP, and the mixture of these two with nitrates have been projected to be the leading aspects in PAW (- 20), PAW (4), and PAW (25) affecting the killing of the microbes over the storage time ( Tian et al 2015).

Results show that bactericidal activity could be conserved at −80 °C during the storage of PAW. Subsequently, −80 °C has the possibility to retain freshness and product purification in melted plasma-activated water. When the physicochemical properties of the PAW (−80) are compared to those of the other samples of PAW stored at other different temperatures, there are major changes. This is essential to the users of PAW, as the samples of PAW can be kept at −80 °C until they are required; this prevents loss of elements during storage.  The plasma-activated water can be used as the normal water since it has less adverse effects on the environment as well as on the humans (Shen et al 2016).

PAW has various advantages and this includes: Increased agricultural production- the antimicrobial characteristics of PAW inhibits the activities of S. aureus that is inoculated to strawberries, PAW has also been found to inhibit the infectious activities of Xanthomonas vesicatoria in tomatoes (Park et al 2017). Improved food processing- PAW inhibits a wide range of microorganisms including Escherichia coli, Candida albicans, Saccharomyces cerevisiae and Hafnia alvei; it is therefore used in decontaminating processed and fresh foods (Pavlovich 2014). Improved safety and quality medical care- NTP sterilizes medical equipment, non-thermal plasma does not oxidize stainless steel, and therefore, it is efficient for sterilizing medical equipment, it is also found to be useful in cancer treatment (Park et al 2017).

There are gaps in the PAW process this involves; some applications of the PAW in Agriculture have not been investigated in detail, for instance, in the case of testing the antimicrobial characteristics of PAW in in-vivo trials in; Candidatus Phytoplasma asteris infected in shoots of micro-propagated periwinkles and Xanthomonas vesicatoria infected in the tomato plants (Ziuzina and Misra 2016). It has been shown that scientists are still conducting further experiments on various plants to be certain of the application of PAW in agriculture.

The Medical application (in drug-delivery and therapeutic techniques) of PAW is not clearly indicated, this raises various safety concerns if it is reliable to be applied in health centers for quality and safe healthcare (Park et al 2017). Another gap is the application of PAW in polymer- science (development of inorganic/organic nanostructures and modifying their practical properties), this application requires further research to ensure the scientific application of PAW is effective in the field.

Conclusion

Plasma-activated water is prepared by non-thermal plasma activation; water is treated by gas expulsion plasma leading to an acidic solution, which is the plasma-activated water. The plasma-activated water formed has extensive antimicrobial activities, as it is able to inhibit varieties of microorganisms such as Candida albicans, Staphylococcus aureus, Hafnia alvei, and Escherichia coli. This antibiotic characteristic is gained through plasma activation of water, which induces the formation of peroxides, nitrites, and nitrates as well as changing the pH of the water. This has enabled PAW to gain application in various fields such as in agriculture, (for instance, the use of PAW for treating plant affected by various bacterial organisms such as Xanthomonas vesicatoria in tomato plants). The procedure involves soaking tomato roots into PAW, SDW for 10 minutes as well as into the inducer of plant resistance these tomatoes are then inoculated by spraying Xanthomonas vesicatoria on their leaves.

On the other hand, the micro-propagated periwinkle shoots are strayed with Candidatus Phytoplasma asteris and 1ml of PAW is added to the agar’s surface present in the tubes of micro-propagation. The results obtained indicate that there are no phytotoxic effects on micro-propagated periwinkles and on the tomato leaves by the PAW. There is a reduction in the number of leaf spots caused by Xanthomonas vesicatoria when treated with PAW (Ziuzina and Misra 2016).

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