Effects of cold plasma treatment on alfalfa seed growth under simulated drought stress

The effect of different cold plasma treatments on the germination and seedling growth of alfalfa(Medicago sativa L.) seeds under simulated drought stress conditions was investigated.Polyethyleneglycol-6000(PEG 6000)with the mass fraction of 0%(purified water), 5%, 10%,and 15% were applied to simulate the drought environment. The alfalfa seeds were treated with15 different power levels ranged between 0–280 W for 15 s. The germination potential,germination rate, germination index, seedling root length, seedling height, and vigor index were investigated. Results indicated significant differences between treated with proper power and untreated alfalfa seeds. With the increase of treatment power, these indexes mentioned above almost presented bimodal curves. Under the different mass fractions of PEG 6000, results showed that the lower power led to increased germination, and the seedlings presented good adaptability to different drought conditions. Meanwhile, higher power levels resulted in a decreased germination rate. Seeds treated with 40 W resulted in higher germination potential,germination rate, seedling height, root length, and vigor index. Vigor indexes of the treated seeds under different PEG 6000 stresses increased by 38.68%, 43.91%, 74.34%, and 39.20%respectively compared to CK_(0-0), CK_(5-0), CK_(10-0), and CK_(15-0)(the control sample under 0%, 5%,10%, and 15% PEG 6000). Therefore, 40 W was regarded as the best treatment in this research.Although the trend indexes of alfalfa seeds treated with the same power were statistically the same under different PEG 6000 stresses, the cold plasma treatment had a significant effect on the adaptability of alfalfa seeds in different drought environments. Thus, this kind of treatment is worth implementing to promote seed growth under drought situations.     

Influence of low-vacuum helium cold plasma pre-treatment on the rooting and root growth of zoysiagrass (Zoysia Willd.) stolon cuttings

The influence of low-vacuum helium cold plasma treatment on the rooting percentage, root growth and physiochemical properties of zoysiagrass stolon cuttings was studied. Zoysiagrass stolon cuttings were pre-treated with 0, 100, 200, 300 and 400 W of cold plasma for 15 s. The cold plasma positively stimulated rooting and improved the root growth of the zoysiagrass stolon cuttings, and the 300 W treatment produced the best effect. The rooting percentage and root growth parameters, including the root length, total root surface area, total root volume, average root diameter, and root dry weight, significantly improved in response to the cold plasma treatment. In addition, the water uptake and relative conductivity of the stolon cuttings increased significantly in response to the cold plasma treatment. The results revealed that cold plasma-stimulated rooting and root growth appear to be a consequence of the improvement in permeability and water absorbing capacity of zoysiagrass stolon cuttings. The results of the present study will provide inspiration and support for the application of cold plasma in the vegetative propagation of plants.     

Effects of low-vacuum helium cold plasma treatment on seed germination,plant growth and yield of oilseed rape

The effects of low-vacuum helium cold plasma treatment on the seed germination,plant growth and yield of oilseed rape(Brassica napus L.cv.Zhongshuang 9) were investigated.Seeds were exposed to low-vacuum helium cold plasma ranging from 0–120 W for 15 s.Cold plasma increased the germination,plant growth and yield of oilseed rape,and the treatment of 100 W provided the best result.The germination rate,germination and vigor indices,and uniformity of emergence were improved by cold plasma treatment.Cold plasma raised the relative conductivity and water uptake,and reduced the apparent contact angle.The characteristics of plant growth,including plant height,stem diameter,dry weights of shoot and root at the seedling,bolting and flowering stages were increased by the cold plasma treatment.Yield components,including pod numbers per plant and 1000 seed weights were increased by the cold plasma treatment.Furthermore,the yield per plant increased by 28.20%.These results suggest that cold plasma treatment has the potential to improve the yield of oilseed rape through the enhancement of permeability,wettability and capacity of water uptake of the seeds,seed germination and plant growth.     

The impact of cold atmospheric pressure plasma jet on seed germination and seedlings growth of fenugreek(Trigonella foenum-graecum)

The effects of cold atmospheric-pressure plasma jet(CAPPJ) were investigated on germination and early seedling growth of fenugreek(Trigonella foenum-graecum L) seeds.A two-electrode argon CAPPJ system with and without an additional grounded electrode [accelerating grounded(AG) electrode] was used at different exposure times.After 16 h of observation,the germination rates increased by 4 and 7 times,without and with using an AG electrode,respectively,for 1 min of plasma exposure.An increase in shoot fresh weight was observed,especially at 10 min exposure time.A high dry weight of root and shoot at 1 min-AG exposure time was observed.The root:shoot ratio was lower in plasma-treated seedlings,compared with the control plants.The study found that the O-radical emission line(777.4 nm) enhanced 5 times,due to the presence of an AG electrode,which increased the axial electric field and led to the formation of more streamers.The three stated effects(O-radicals,enhancement of the electric field and streamers) could be the cause for the stimulation of seed germination and seedling growth parameters when using the CAPPJ.The scanning electron microscope images showed the etching of the seed surface layers,which was more pronounced when an AG electrode was applied.The results of the current study indicate that the germination rates increased due to the increase of O-radical concentration and the etching of the seed surfaces.     

Investigation of stimulated growth effect using pulsed cold atmospheric plasma treatment on Ganoderma lucidum

Cold atmospheric plasma (CAP) driven by pulsed high-voltage power has specific advantages in various fields, such as the growth promotion of edible fungi in plasma agriculture. Compared with other strains, Ganoderma lucidum has the significant advantage of high medicinal value, but the shortcomings of low yield, long growth cycle, and an uneven market quality. In this study, Ganoderma lucidum was treated with a CAP powered by a homemade pulsed high-voltage power supply. Three groups of Ganoderma lucidum were treated under different conditions. The stalk lengths and pileus areas of Ganoderma lucidum were recorded to evaluate growth status. Results showed that treatment frequency affected growth status considerably. Ganoderma lucidum was treated with 40 s plasma once a week and showed an improved growth status with a 33.63% increase in average stalk length and a 28% increase in the number of individuals whose pileus areas was greater than the average. Meanwhile, the growth speed was accelerated. However, treatment at an excessive frequency would damage and slow down the growth of Ganoderma lucidum.     

Effect of plasma treatment on the seed germination and seedling growth of radish (Raphanus sativus)

The effect on the germination and seedling growth of radish (Raphanus sativus) seeds were examined employing a dielectric barrier discharge (DBD) at atmospheric pressure and room temperature for various treatment time. DBD plasma using argon gas of flow rate 2 l m−1 was employed in this study. Radish seeds were treated with DBD plasma for 1–5 min, respectively. Germination characteristics, seedling growth parameters, the contact angle of the seed coat, water uptake capacity, mass loss, the temperature of the seeds, chlorophyll, and carotenoid contents of the seedlings were measured before and after the DBD plasma treatments. Plasma treatment of radish seeds significantly increased germination-related characters, including germination percentage, fresh and dry weight, vigor index, and total carotenoids contents. However, the cumulative production rate was found to be decreased. Results from the experiment indicate an acceleration in the water uptake of the radish seeds and make the seed surface hydrophilic by plasma treatment. Scanning electron microscopy analysis showed that etching effects on the seed coat occurred after the argon plasma treatments, which affected the wettability of the radish seed. The experimental findings showed that seeds being treated by DBD plasma for 2 and 3 min had a positive effect on the germination and seedling growth of radish.     

Non-thermal plasma modified growth and differentiation process of Capsicum annuum PP805 Godiva in in vitro conditions

With the aim of evaluating the possible impacts of cold plasma on the structure and growth pattern of Capsicum annuum,the current study was carried out.The seeds were exposed to an argon-derived plasma (0.84 W cm-2 surface power densities) for 0,1 or 2 minutes.Plasma treated seeds were grown in the Murashige and Skoog (MS) medium or MS medium supplemented with BA and IAA.The presence of purple stems was recorded in plasma-treated plants grown in the medium supplemented with hormones.The recorded morphological differences were dependent on the exposure time of plasma treatments and/or the presence of hormones in the culture media.Plasma treatment of 1 minute had an improving effect on the shoot and root lengths as well as total leaf area,whereas plasma treatment of 2 minutes had an adverse effect.In contrast to the 1 minute treatment,plasma treatment of 2 minutes significantly impaired growth and hence reduced the total biomass.Alterations in stem diameter and differences in tissue patterns (especially in the vascular system) occurred,and were mainly dependent on the plasma exposure time and/or the presence of hormones.This is a first report on the effects of cold plasma on plant growth in in vitro conditions.     

Influence of cold plasma treatment on insecticidal properties of wheat seeds against red flour beetles

For the long-term fortification of warehoused crops, the insecticidal impact of cold plasma treated wheat seeds against red flour beetles are studied. In this study, the gain weight loss, mortality and repellency tests of cold plasma treated seeds are investigated and statistical analysis is carried out by SPSS software. Cold plasma treatment is carried out at 800 V for 1 and 4 min. The results show that the minimum grain weight loss is observed in plasma treated seeds as compared to controlled seeds. It is also observed that the mortality rate is minimum in the controlled seed while maximum at 4 min plasma treatment. Similarly, the repellent effect has a very small variation as compared to the controlled seed for Tribolium Castaneum. Therefore, plasma treatment can be considered as a practical and effective method for seed protection against red floor beetles particularly during long-term storage by controlling the insecticidal effects.     

Characteristics of a radio-frequency cold atmospheric plasma jet produced with a hybrid cross-linear-field electrode configuration

Cold atmospheric plasma (CAP) jet has wide applications in various fields including advanced materials synthesis and modifications, biomedicine, environmental protection and energy saving, etc. Appropriate control on the volume, temperature and chemically reactive species concentrations of the CAP jet is of great importance in actual applications. In this paper, an radio-frequency atmospheric-pressure glow discharge (RF-APGD) plasma generator with a hybrid cross-linear-field electrode configuration is proposed. The experimental results show that, with the aid of the copper mesh located at the downstream of the traditional co-axial-type plasma generator with a cross-field electrode configuration, a linear field between the inner powered electrode of the traditional plasma generator and the copper mesh can be established. This liner- field can, to some extent, enhance the discharges at the upstream of the copper mesh, resulting in small increments (all less than 12.5%) of the species emission intensities, electron excitation temperatures and gas temperatures by keeping other parameters being unchanged. And due to the intrinsic transparent and conducting features of the grounded copper mesh to the gas flowing, electric current and heat flux of the plasma plumes, a plasma region with higher concentrations of chemically reactive species and larger plasma plume diameters is obtained at the downstream of the grounded copper mesh on the same level of the gas temperature and electron excitation temperature compared to those of the plasma free jet. In addition, the charged particle number densities at the same downstream axial location of the grounded copper mesh decrease significantly compared to those of the plasma free jet. This means that the copper mesh is also, to some extent, helpful for separating the chemically reactive neutral species from the charged particles inside a plasma environment. The preceding results indicate that the cross-linear-field electrode configuration of the plasma generator is an effective approach for tuning the characteristics of the RF-APGD plasma jet in order to obtain an appropriate combination of the plasma jet properties with higher chemically reactive species concentrations, especially relative higher number densities of neutral species, larger plasma volumes and lower gas temperatures.     

Effect of plasma absorption on dust lattice waves in hexagonal dust crystals

In the present paper, the effect of plasma absorption on lattice waves in 2D hexagonal dust crystals is investigated. The dispersion relations with the effect of plasma absorption are derived.It is found that the temperature effect(electron-to-ion temperature ratio τ) enhances the frequency of the dust lattice waves, while the spatial effect(dimensionless Debye shielding parameter k) weakens the frequency of the dust lattice waves. In addition, the system stabilities under the conditions of plasma absorption are studied. It is found that the temperature effect narrows the range of instability, while the spatial effect extends this range. And the range of instability is calculated, i.e. the system will always in the stable state regardless of the value of k when τ??3.5. However, the system will be unstable when τ?=?1 and k 4.1.     

A novel approach to regulate cell membrane permeability for ATP and NADH formation in Saccharomyces cerevisiae induced by air cold plasma

Air cold plasma has been used as a novel method for enhancing microbial fermentation.The aim of this work was to explore the effect of plasma on membrane permeability and the formation of ATP and NADH in Saccharomyces cerevisiae,so as to provide valuable information for largescale application of plasma in the fermentation industry.Suspensions of S.cerevisiae cells were exposed to air cold plasma for 0,1,2,3,4 and 5 min,and then subjected to various analyses prior to fermentation(0h) and at the 9 and 21 h stages of fermentation.Compared with nonexposed cells,cells exposed to plasma for 1 min exhibited a marked increase in cytoplasmic free Ca~(2+) concentration as a result of the significant increase in membrane potential prior to fermentation.At the same time,the ATP level in the cell suspension decreased by about 40%,resulting in a reduction of about 60%in NADH prior to culturing.However,the levels of ATP and NADH in the culture at the 9 and 21 h fermentation stages were different from the level at0 h.Taken together,the results indicated that exposure of S.cerevisiae to air cold plasma could increase its cytoplasmic free Ca~(2+) concentration by improving the cell membrane potential,consequently leading to changes in ATP and NADH levels.     

Ionization process and distinctive characteristic of atmospheric pressure cold plasma jet driven resonantly by microwave pulses

In the present study, a coaxial transmission line resonator is constructed, which is always capable of generating cold microwave plasma jet plumes in ambient air in spite of using argon, nitrogen, or even air, respectively. Although the different kinds of working gas induce the different discharge performance, their ionization processes all indicate that the ionization enhancement has taken place twice in each pulsed periods, and the electron densities measured by the method of microwave Rayleigh scattering are higher than the amplitude order of 10¹⁸ m⁻³. The tail region of plasma jets all contain a large number of active particles, like NO, O, emitted photons, etc, but without O3. The formation mechanism and the distinctive characteristics are attributed to the resonance excitation of the locally enhanced electric fields, the ionization wave propulsion, and the temporal and spatial distribution of different particles in the pulsed microwave plasma jets. The parameters of plasma jet could be modulated by adjusting microwave power, modulation pulse parameters (modulation frequency and duty ratio), gas type and its flow rate, according to the requirements of application scenarios.     

Rice plant growth and yield: foliar application of plasma activated water

Plasma activated water(PAW) was prepared for 10 min to be applied one to five times as a foliar spray to rice plants, to investigate plant growth, yield and the concentrations of total soluble protein and sugar in the rice grains produced. The results reveal that(1) the plant height, stem diameter, dry weight, chlorophyll and total carotene concentrations were improved by ～15%,～25%, ～24%, ～47% and ～45%, respectively, with respect to control,(2) defense mechanisms of the plants treated with PAW were improved,(3) concentrations of total soluble protein and sugar were enhanced in the rice grains of PAW treated plants and(4) yield was increased by ～14%.     

Measurement of cytoplasmic Ca2+ concentration in Saccharomyces cerevisiae induced by air cold plasma

In this study,a novel approach to measure the absolute cytoplasmic Ca2+ concentration ([Ca2+]cyt) using the Ca2+ indicator fluo-3 AM was established.The parameters associated with the probe fluo-3 AM were optimized to accurately determine fluorescence intensity from the Ca2+-bound probe.Using three optimized parameters (final concentration of 6 mM probe,incubation time of 135 min,loading probe before plasma treatment),the maximum fluorescence intensity (Fmax =527.8 a.u.) and the minimum fluorescence intensity (Fmin =63.8 a.u.) were obtained in a saturated Ca2+ solution or a solution of lacking Ca2+.Correspondingly,the maximum [Ca2+]cyt induced by cold plasma was 1232.5 nM.Therefore,the Ca2+ indicator fluo-3 AM was successfully applied to measure the absolute [Ca2+]cyt in Saccharomyces cerevisiae stimulated by cold plasma at atmospheric air pressure.     

Influences of the cold atmospheric plasma jet treatment on the properties of the demineralized dentin surfaces

Improvement of the bonding strength and durability between the dentin surface and the composite resin is a challenging job in dentistry. In this paper, a radio-frequency atmosphericpressure glow discharge(RF-APGD) plasma jet is employed for the treatment of the acid-etched dentin surfaces used for the composite restoration. The properties of the plasma treated dentin surfaces and the resin–dentin interfaces are analyzed using the x-ray photoemission spectroscopy, contact angle goniometer, scanning electron microscope and microtensile tester.The experimental results show that, due to the abundant chemically reactive species existing in the RF-APGD plasma jet under a stable and low energy input operating mode, the contact angle of the plasma-treated dentin surfaces decreases to a stable level with the increase of the atomic percentage of oxygen in the specimens; the formation of the long resin tags in the scattered clusters and the hybrid layers at the resin–dentin interfaces significantly improve the bonding strength and durability. These results indicate that the RF-APGD plasma jet is an effective tool for modifying the chemical properties of the dentin surfaces, and for improving the immediate bonding strength and the durability of the resin-dentin bonding in dentistry.     

Influences of the inner diameter of the solid shielding tube on the characteristics of the radio-frequency cold atmospheric plasma jet

Active control of the local environment of the cold atmospheric plasma (CAP) jet is of great importance in actual applications since the CAP operates in an open atmosphere with the inevitable entrainment of the surrounding cold air. In this paper, the solid shielding effects of the cylindrical quartz tubes with different inner diameters on the characteristics of the CAP jets driven by a radio-frequency (RF) power supply are studied experimentally. The experimental results show that the total length of the shielded plasma jet can be increased significantly by an appropriate combination of the quartz tube inner diameter and that of the plasma generator nozzle exit with other parameters being unchanged. This phenomenon may be qualitatively attributed to the loss of diffusion of the charged particles in the radial direction under different inner diameters of the quartz tubes. Compared with the plasma free jet, the plasma shielding jet is produced with optimized parameters including longer plasma jet length, higher concentrations of chemically reactive species, higher rotational, vibrational, and electron excitation temperatures when the inner diameters of the solid shielding tube and the generator nozzle exit are the same. A maximum plasma jet length of 52.0 cm is obtained in contrast to that of 5.0 cm of the plasma free jet in this study. The experimental results indicate that the solid shielding effect provides a new method for the active control of the local environment of the RF-CAP jet operating in an open atmosphere.     

Effect of Cold Plasma Treatment on Seed Germination and Growth of Wheat简

This study investigated the effect of cold helium plasma treatment on seed germina- tion, growth and yield of wheat. The effects of different power of cold plasma on the germination of treated wheat seeds were studied. We found that the treatment of 80 W could significantly improve seed germination potential （6.0%） and germination rate （6.7%） compared to the control group. Field experiments were carried out for wheat seeds treated with 80 W cold plasma. Com- pared with the control, plant height （20.3%）, root length （9.0%） and fresh weight （21.8%） were improved significantly at seedling stage. At booting stage, plant height, root length, fresh weight, stem diameter, leaf area and leaf thickness of the treated plant were respectively increased by 21.8%, 11.0%, 7.0%, 9.0%, 13.0% and 25.5%. At the same time, the chlorophyll content （9.8%）, nitrogen （10.0%） and moisture content （10.0%） were higher than those of the control, indicating that cold plasma treatment could promote the growth of wheat. The yield of treated wheat was 7.55 t-ha-1, 5.89% more than that of the control. Therefore, our results show that cold plasma has important application prospects for increasing wheat yield.     

Effect of inductively coupled plasma surface treatment on silica gel and mesoporous MCM-41 particles

Silica gel and MCM-41 synthesized mesoporous materials were treated with either oxygen (O2),hexamethyldisiloxane (HMDSO) and organic vapors like ethanol (EtOH),and acrylonitrile (AN) inductive plasma.The radiofrequency power for the modification was fixed to 120 W and 30 min,assuring a high degree of organic ionization energy in the plasma.The surface properties were studied by infrared spectroscopy (FTIR),scanning electron microscopy,x-ray photoelectron spectroscopy and dynamic light scattering technique was used for characterizing size distributions.When the silica and MCM-41 particles were modified by AN and HMDSO plasma gases,the surface morphology of the particles was changed,presenting another color,size or shape.In contrast,the treatments of oxygen and EtOH did not affect the surface morphology of both particles,but increased the oxygen content at the surface bigger than the AN and HMDSO plasma treatments.In this study,we investigated the influence of different plasma treatments on changes in morphology and the chemical composition of the modified particles which render them a possible new adsorbent for utilization in sorptive extraction techniques for polar compounds.     

Development of a portable cold air plasma jet device and observation of its photo ionization process

Photo ionization plays a critical role in the formation and propagation of atmospheric pressure plasma jet plumes. But in experiments, it is very difficult to observe the photo ionization due to its relative lower density of photo electrons. In the present study, we develop a portable cold air plasma jet device and observe the ionization wave in a dc spark air plasma jet. The discharge images acquired by an ICCD camera show that the ionization wave front performs as a quickly moving bright ball. Breakdown could take place at another side of the quartz plate or pork tissue layer(6 mm thick), which suggests that the ionization should be attributed to photo ionization.The laser schlieren images indicate there is propagation of a shock wave along with the plasma bullet. Based on the photo ionization theory and the photo-electric measurement, the direct photo ionization and multistage photo ionization are the main factors in charge of generating the cold air plasma jet. In addition, the plasma jet outside of the cathode nozzle is colder than 320 K and can be touched safely by a human. In view of the plasma jet including a large amount of active particles, such as NO, O, OH, emitted photons, etc, the proposed portable cold air plasma jet device could be qualified for plasma bio-medicine applications.