Air Atmospheric Dielectric Barrier Discharge Plasma Induced Germination and Growth Enhancement of Wheat Seed

Air atmospheric dielectric barrier discharge plasma (DBD) was attempted to pretreat wheat seed to improve its germination and growth in this study. The effects of the DBD plasma treatment on the wheat seed germination, seedling growth, osmotic-adjustment products, lipid peroxidation level, and antioxidant enzymes activity were investigated. The experimental results showed that the DBD plasma treatment with an appropriate time scale could promote the wheat seed germination and seedling growth. The germination potential, germination rate, germination index, and vigor index increased by 26.7, 9.1, 16.9, and 46.9% after 7 min’s DBD plasma treatment, respectively; the root length, shoot length, fresh weight, and dry weight of the seedlings also increased after the DBD plasma treatment. The osmotic-adjustment products, proline and soluble sugar contents, in the wheat seedlings were significantly enhanced after the DBD plasma treatment with an appropriate time scale, while the malondialdehyde content decreased. Moreover, the activities of superoxide dismutase and peroxidase also increased after the DBD plasma treatment. The DBD plasma treatment led to etching effect on the wheat seed coat, resulting in the improvement of its water absorption capacity.     

Effects of Oxygen (O2) Plasma Treatment in Promoting the Germination and Growth of Chili

In general, seed germination is improved by low-pressure plasma treatment using precursors such as air, nitrogen, O_2, and argon, etc. For the first time, low-pressure O₂ plasma was used to treat chili seeds in this study. When compared to untreated and vacuum-treated seeds, O₂ plasma treatment using the discharge power of 80 W for 60 s significantly improves chili seed germination and growth. The effect of vacuum on the germination and growth of chili seeds was also studied and shown to be negligible. The physical and chemical changes induced by O₂ plasma treatment were investigated to understand the plasma treatment to germination improvement. Combinatory etching and chemical modification aided imbibition and increased germination percentage in this O₂ plasma treatment on chili seeds. The success of this method has the potential to be scaled up to solve food security issues with seeds that would otherwise struggle to germinate.

     

Silicon Dioxide Coating of Titanium Dioxide Nanoparticles from Dielectric Barrier Discharge in a Gaseous Mixture of Silane and Nitrogen

The coating of titanium dioxide nanoparticles with silicon dioxide has been carried out by dielectric barrier discharge (DBD) plasma treatments to enhance the thermostability of Titania for applications at high temperature processes. During the first coating processing step, a closed film of silicon nitride was produced via plasma treatment in a gaseous mixture of silane and nitrogen, while atmospheric surface contaminations got mainly removed. In the second processing step, the DBD plasma treatment in oxygen or air was used to convert the silicon nitride mainly into silicon dioxide. Remaining carbon impurities at the interfaces between titanium dioxide and silicon nitride after the nitrogen/silane plasma treatment were subsequently removed simultaneously. Atomic force microscopy and X-ray photoelectron spectroscopy were employed to study the DBD plasma treatments of the TiO₂ nanoparticles.     

Influence of Discharge Atmosphere on the Ageing Behaviour of Plasma-Treated Polylactic Acid

The effect of a plasma treatment on polymers is not permanent, since the treated surfaces tend to recover to the untreated state (ageing process). This paper investigates the influence of discharge atmosphere on the ageing behaviour of plasma-treated PLA foils: these foils are plasma-treated with a DBD in 4 different atmospheres (air, nitrogen, argon and helium) and are subsequently stored in air. Results of contact angle and XPS measurements show that the discharge gas has a significant influence on the ageing behaviour of the PLA foils. This influence can be explained by the different cross-linking degree of the plasma-treated surfaces: helium and argon plasma-treated PLA films have a high cross-linking degree, which limits polymer chain mobility and as a result reduces the ageing process. In contrast, the ageing behaviour of air and nitrogen plasma-treated films is more pronounced due to their low cross-linking degree.     

Nitrate and Hydrogen Peroxide Generated in Water by Electrical Discharges Stimulate Wheat Seedling Growth

This paper reports the stimulation of wheat seedling growth by using plasma-treated water. A nanosecond pulsed generator in a gas bubble-in-liquid system with a point-to-plate electrode was employed to treat de-ionised (DI) water, producing mainly hydrogen peroxide (H₂O₂) in the water when argon gas was used, and nitrate (\({\text{NO}}_{3}^{ - }\)) when air was used. The H₂O₂ and \({\text{NO}}_{3}^{ - }\) generated, respectively, in argon and air plasma-treated water significantly increased the growth parameters such as biomass, leaf length, and the relative chlorophyll content of the wheat seedling. The total biomass of the seedlings grown in potting mix after 4 weeks was augmented by 61 and 87%, respectively, for argon plasma-treated water and air plasma-treated water compared with the control (untreated DI water). In hydroponics, the biomass of the seedling increased 27 and 38%, respectively, for the argon and the air after 2 weeks in comparison to the control. In potting mix, the shoots and roots of the seedlings responded differently to the treated water: the biomass of shoot increased 33% for air plasma-treated water compared with the argon, while that of root increased 17% for argon plasma-treated water compared with the air. A separate experiment in hydroponics with chemical solutions of H₂O₂ and \({\text{NO}}_{3}^{ - }\) matching with the concentrations of the H₂O₂ and \({\text{NO}}_{3}^{ - }\) generated in the plasma-treated water showed similar stimulation of wheat seedling growth.     

Biogenic Nanoparticle-Mediated Augmentation of Seed Germination,Growth, and Antioxidant Level of Eruca sativa Mill. Varieties

A study was undertaken to examine the influence of biogenic nanoparticles synthesized from Tridax procumbens on different parameters of seed germination, seedling growth, and various biochemical parameters in four Eruca sativa varieties having low percentage of germination. Seeds were treated with different concentrations (30 and 40 ppm) of biogenic nanoparticles, of which 30 ppm was found to be the most effective and was therefore used for subsequent studies. Initially, the effect of biogenic nanoparticles on germination percentage, speed of germination, coefficient of germination, mean germination time, shoot and root length, fresh and dry matter, and vigor index was studied. From the experiments performed and the results obtained, it was evident that the treatment with biogenic nanoparticles decreased the electrolyte leakage and level of malondialdehyde as compared to control. The treatment with biogenic nanoparticles enhanced the levels of proline and ascorbic acid and stimulated the antioxidant enzyme activities resulting in the reduced level of reactive oxygen species. These activities were found to be variety-dependent. The possible involvement of biogenic nanoparticles in the production of new pores in seed coat during their penetration, resulting in the influx of the nutrients inside the seed, is suggested. This accelerated seed germination is followed by rapid seedling growth. The present findings indicated that biogenic nanoparticles promote seed germination in E. sativa by overcoming the detrimental effects of reactive oxygen species (ROS) and improving the antioxidative defense system which finally result in increased seedling growth.     

A quantitative model for the surface restructuring of repeatedly plasma treated silicone rubber

Surface restructuring in ambient air of medical grade silicone rubber surfaces modified by repeated RF plasma treatments using various discharge gases including oxygen, argon, carbon dioxide and ammonia, was studied quantitatively. From advancing and receding water contact angle data, the fraction of the surface covered by mobile and immobile polar groups, and a characteristic time constant of the restructuring process were calculated. For argon plasma treated surfaces, the fraction of immobile polar groups increased with repeated plasma treatments, but remained relatively constant for samples repeatedly treated by an ammonia plasma. The use of an oxygen plasma only yielded incorporation of mobile polar groups but not of immobile polar groups. The increase in the restructuring time constants of argon and ammonia plasma treated silicone rubber with the number of plasma treatments suggested enhanced crosslinking of the silicone rubber by these plasmas. In contrast, when an oxygen plasma was repeatedly used, the restructuring time constant decreased suggesting chain cleavage by an oxygen plasma. Tentatively, the carbon dioxide plasma treatment of silicone rubber may initially (up to 3–4 repeated treatments) yield chain cleavage, while the occurrence of crosslinking is indicated after more repetitions.     

Magnetic Field Treatments Improves Sunflower Yield by Inducing Physiological and Biochemical Modulations in Seeds

Magnetic seed enhancement has been practicing as a promising tool to improve germination and seedling growth of low vigor seeds stored under suboptimal conditions, but there is still ambiguity regarding the prospects for magnetism in oilseeds. Present study elucidates the potential of magnetic seed stimulation to improve sunflower germination, growth and yield. Germination and emergence tests were performed to optimize the strength of the magnetic field to sunflower seed enhancement. The seeds were directly exposed to magnetic field strengths of 50, 100 and 150 millitesla (mT) for 5, 10 and 15 min (min) and then standard germination tests were performed. Secondly, the emergence potential of untreated seeds was compared with seed exposed to hydropriming, priming with 3% moringa leaf extract (MLE), priming with magnetically treated water (MTW) for 10 min and priming with 3% MLE solution prepared in magnetically treated water (MTW + MLE). Germination, emergence, seedling growth and seed biochemical properties were used to select the best treatment for field evaluation. The results of the study revealed that magnetic seed treatment with 100 mT for 10 min and seed priming with 3% MLE solution in magnetically treated water (MTW + MLE) significantly improved emergence, crop growth rate and sunflower yield.     

Seed Germination and Early Growth Responses to Seed Pre-treatment by Non-thermal Plasma in Hemp Cultivars (<Emphasis Type="Italic">Cannabis sativa</Emphasis> L.)

The two key questions addressed in this paper were whether different cultivars of hemp (Cannabis sativa L.) have the same reactions to non-thermal plasma seed pre-treatments and whether different plasma sources have different effects on the seeds. Seed germination and early growth of hemp in design of hierarchical analysis of variance was conducted. Differences in response among seeds of three hemp cultivars (‘Finola’, ‘Bialobrzeskie’, ‘Carmagnola’) to the non-thermal plasma pre-treatment generated by two apparatuses (gliding arc and downstream microwave devices) in four time expositions (0, 180, 300, 600 s) were found. The high importance was found in type of apparatus and time exposition. A positive/neutral effect was observed in all measured characteristics after gliding arc plasma pre-treatment. Gliding arc pre-treatment increased the length of seedlings, seedling accretion and weight of seedling in both cv. ‘Finola’ and cv. ‘Bialobrzeskie’ hemp. On the other hand, the downstream microwave apparatus had an inhibiting effect on all tested hemp cultivars. It was the first time when significant differences in response to non-thermal pre-treatment were found in taxonomically close plants. The results obtained in this study describes different effect of various plasma treatment on germination and early growth of hemp seeds. The direct pre-treatment of non-thermal plasma discharge in condition of atmospheric pressure was better. Results of our experiment show that the use of non-thermal plasma pre-treatment may increase survival of some hemp cultivars during seedlings establishment in a drier period and may be used in new agro-technical measures in unconventional agriculture.     

Surface modification of acrylate intraocular lenses with dielectric barrier discharge plasma at atmospheric pressure

Surface modification with dielectric barrier discharge (DBD) plasma was carried out at atmospheric pressure (argon as the discharge gas) to improve the biocompatibility of hydrophobic acrylate intraocular lens (IOL). Changes of the plasma-treated IOL surface in chemical composition, morphology and hydrophilicity were comprehensively evaluated by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and water contact angle (WCA) measurements. The surface biocompatibility of the untreated and plasma-treated IOLs was compared with the adhesion behavior of platelets, macrophages and lens epithelial cells (LECs) in vitro. After DBD plasma treatment, the hydrophilicity of the IOL surface was obviously improved. The changes in WCA with treatment extension may be attributed to both the introduction of oxygen or/and nitrogen-containing polar groups and the increase of surface roughness induced by plasma etching effect. The existence of low molecular weight oxidized material (LMWOM) was proved on the plasmatreated IOL which was caused by the chain scission effect of the plasma treatment. The plasma-treated IOLs resisted the adhesion of platelets and macrophages significantly. The LECs spreading and proliferation were postponed on the IOLs plasma-treated for more than 180 s, with a well maintained epithelial phenotype of LECs. The IOL biocompatibility was improved after the DBD plasma treatment. We speculate that slighter foreign-body reaction and later incidence of anterior capsule opacification (ACO) may be expected after implantation of the argon DBD plasma-treated IOL. Supported by the Zhejiang Natural Science Foundation of China (Grant No. 2004C23003)     

Hydrophilization of porous polyethylene films by cold plasma of different types

Porous PE films have been modified using high-frequency discharge plasma (in air) and dielectric surface barrier discharge plasma in static (in oxygen and nitrogen) and dynamic (in argon) regime. A noticeable increase in the hydrophilicity of samples and their adhesion to coatings has been established. Changes in chemical composition and morphology of the surface resulting from plasma treatment and subsequent aging have been studied. The treatment regime have been established under which sufficient hydrophilicity is reached and mechanical strength is preserved.     

Homogeneous Dielectric Barrier Discharge Reactor with Two L-Shaped Electrodes Operating at Atmospheric Pressure

Homogeneous non-thermal plasma at atmospheric pressure is highly effective for surface treatment of various polymeric substrates. We propose a dielectric barrier discharge (DBD) reactor consisting of two back-to-back L-shaped electrodes, driven by bipolar voltage pulses of opposite polarity. This structure and driving scheme allow the discharge to be initiated earlier inside the reactor than outside the reactor. The plasma formed inside the reactor is ejected through a slit and moves toward the substrate. As a result, an abundance of electrons is provided to the outside region of the reactor at its breakdown stage. These electrons play a role in suppressing the filamentary mode, and hence, homogeneous discharge in He and Ar can be achieved under an open air configuration. The discharge characteristics inside and outside the reactor are analyzed by using the discharge current and the temporal evolution of emission intensity, respectively. The importance of seed electrons available at the gas breakdown stage in achieving a homogeneous discharge is discussed together with the differences between the discharge characteristics of helium and argon gases.     

The Effects of Gas Composition on Active Species and Byproducts Formation in Gas–Water Gliding Arc Discharge

The effects of gas composition on hybrid gas–water gliding arc discharge plasma reactor have been studied. The voltage cycles are characterized by a moderate increase in the tension which is represented by a peak followed by an abrupt decrease and a current peak in the half period (10 ms). Emission spectrum measurements revealed that ^•OH hydroxyl radicals are present in the discharge with feeding any gas. The H₂O₂ concentrations reach 38.0, 15.0, 10.0, and 8.0 mg/l after 25 min plasma treatment with oxygen, argon, air, and nitrogen, respectively. O₃ was produced when oxygen and air are used, but not when nitrogen and argon. The O₃ concentration reached the highest value 1.0 mg/l after 25 min plasma treatment with oxygen feeding gas, but gradually decreased to 0.2 mg/l after that. With feeding nitrogenous gas, NO₂ ⁻ and NO₃ ⁻ byproducts were formed by the plasma chemical process.     

Emission characteristics of mixed gas plasmas in low-pressure glow discharges

Glow discharge optical emission spectrometry (GD-OES) with mixed plasma gases is reviewed. The major topic is the effect of type and content of gases added to an argon plasma on the emission characteristics as well as the excitation processes. Emphasis is placed on argon–helium, argon–oxygen, and argon–nitrogen mixed gas plasmas. Results for non-argon-matrix plasmas, such as neon–helium and nitrogen–helium mixtures, are also presented. Apart from the GD-OES, glow discharge mass spectrometry and furnace atomization plasma emission spectrometry with mixed plasma gases are also discussed.     

Study of allelopathic effects of Eucalyptus erythrocorys L. crude extracts against germination and seedling growth of weeds and wheat

Allelopathic materials inside a tree can produce positive or negative change in the survival, growth, reproduction and behaviour of other organisms if they escape into the environment. To assess these effects, this work was carried out to evaluate the allelopathic impact of Eucalyptus erythrocorys L. on seed germination and seedling growth of two weeds: Sinapis arvensis L. and Phalaris canariensis L.; on one cultivated crop: Triticum durum L. Aqueous; and on ethanolic leaf extracts of E. erythrocorys L. The study was effected using four concentrations (10, 20, 25 and 30 μL/mL) while distilled water was used as a control. The results showed that the E. erythrocorys L. crude extracts had an inhibitory effect on seed germination and seedling growth of both studied weeds and wheat. The inhibition rate was increased by the increase in extract concentration. Only ethanolic extracts of E. erythrocorys L. induced a significant inhibition of seed germination of durum wheat. The effect of E. erythrocorys L. crude extracts was more severe on weeds than on durum wheat. These results indicate that the seedling growth, especially radicle elongation, was the more sensitive indicator to evaluate the effects of extracts than was the seed germination.     

Non-thermal Plasma as a Priming Tool to Improve the Yield of Pea in Outdoor Conditions

Seed priming is a pre-treatment of seeds leading to the improvement of their germination, the plant growth, and the product yield. In this study we investigated the possibility of the use of non-thermal plasma operating in atmospheric pressure air for seed priming with the objective to improve the yield of pea seeds. Two priming ways were used: an indirect way by using plasma activated water (PAW) generated by the transient spark discharge with water electrospray or the glow discharge batch treatment and a direct exposure of seeds to the pulsed corona discharge. After treatment, the seeds were planted in the outdoor field for about 14 weeks until harvest. The direct plasma treatment resulted in two key results: the strong effectiveness of the pulsed corona plasma improving the yield, and the long-term effect of the plasma seed treatment. The results of the indirect treatment showed that the pea plants from the seeds primed using PAW gained some improved growth parameters, especially the number of seeds per pod and the total number of seeds per plant. The scanning electron microscopy analysis showed that PAW and direct treatment induced some morphology changes at the surface of the pea seeds. This study documents a long-term effect of non-thermal plasma seed priming and contributes to the plasma agriculture applications by suggesting the implementation of non-thermal plasma direct or indirect treatments into the field.

     

Ultraweak Photon Emission from the Seed Coat in Response to Temperature and Humidity—A Potential Mechanism for Environmental Signal Transduction in the Soil Seed Bank

Seeds beneath the soil sense the changing environment to time germination and seedling emergence with the optimum time of year for survival. Environmental signals first impact with the seed at the seed coat. To investigate whether seed coats have a role in environmental sensing we investigated their ultraweak photon emission (UPE) under the variable temperature, relative humidity and oxygen conditions they could experience in the soil seed bank. Using a custom‐built luminometer we measured UPE intensity and spectra (300–700 nm) from Phaseolus vulgaris seeds, seed coats and cotyledons. UPE was greatest from the internal surface of the seed coat. Seed coat UPE increased concomitantly with both increasing temperature and decreasing relative humidity. Emission was oxygen dependent and it was abolished by treatment with dinitrophenylhydrazine, demonstrating the key role of seed coat carbonyls in the phenomenon. We hypothesize that beneath the soil surface the attenuation of light (virtual darkness: low background noise) enables seeds to exploit UPE for transducing key environmental variables in the soil (temperature, humidity and oxygen) to inform them of seasonal and local temperature patterns. Overall, seed coats were found to have potential as effective transducers of key fluctuating environmental variables in the soil.     

Prospective Applications of Low Frequency Glow Discharge Plasmas on Enhanced Germination,Growth and Yield of Wheat

Medium pressure (~ 10 torr) low frequency (3–5 kHz) glow discharge (LFGD) plasmas were applied to treat wheat (Triticum aestivum) seeds to investigate the effects on water absorption, seed germination rate, seedling growth and yield. The LFGD plasmas were produced with air and air/O ₂. Optical emission spectroscopic diagnostic methods were revealed that the \({\text{N}}_{2} \left( {{\text{C}}^{3}\Pi _{\text{u}} - {\text{B}}^{3}\Pi _{\text{g}} } \right)\), \({\text{N}}_{2}^{ + } \left( {{\text{B}}^{2}\Sigma _{\text{u}}^{ + } - {\text{X}}^{2}\Sigma _{\text{g}}^{ + } } \right)\) and \({\text{N}}_{2} \left( {{\text{B}}^{3}\Pi _{\text{g}} - {\text{A}}^{3}\Sigma _{\text{u}}^{ + } } \right)\) produced with air, and O species were produced along with nitrogen species with air/O ₂ plasmas, respectively. The SEM images were revealed that the surface architectures and functionalities of the seeds were modified due to plasma treatments. Water absorption was found to increase with treatment time. 6 min treatment was provided 95–100% seed germination. The plants grown from treated seeds for 3 and 9 min duration by air/O ₂ plasma were showed the highest growth activity and dry matter accumulation. Total chlorophyll contents of the leaves, longest spikes and number of spikes/spikelet were also increased. The wheat yield was increased ~ 20% over control by 6 min treatment with air/O ₂ plasma. Overall results revealed that LFGD plasmas can significantly change seed surface architecture, water absorption, germination rate, seedling growth and yield of wheat.     

不同组分过渡金属氧化物催化剂对介质阻挡放电固氮的影响机制

为了促进介质阻挡放电(DBD)协同催化固氮效果, 制备了不同组分Mn/Co/W元素的单一型、 二元和三元复合型负载催化剂, 并将催化剂置入DBD气隙中进行等离子体协同催化固氮反应. 通过X射线衍射(XRD)、 扫描电子显微镜(SEM)和X射线能谱(EDS)表征了催化剂的性质, 并采用紫外分光光度法测定了液相中的总氮浓度. 结果表明, 填充催化剂实验组比未填充催化剂组的总氮浓度明显提升. 采用傅里叶变换红外光谱仪对有/无催化剂填充两种情况下DBD的气相产物进行了检测, 结果表明, 填充催化剂能促进空间内NO₂和N₂O₅的生成. 通过DBD气相链式反应和催化原理揭示了总氮浓度得以提升的原因, 是由于催化剂在等离子协同过程中提供了大量的氧空位, 使得NO _x 充分氧化. 多元复合型催化剂能在单一型的基础上, 通过金属元素价态的变换和能量的传递进一步促进固氮效果, 三元复合型催化剂Mn₃WCo/γ-Al₂O₃在电压为22 kV时的固氮最高总氮浓度为119.13 mg/L, 较未填充催化剂组的最大值提升了71.61%, 能耗降低了21.70%.     

Insights on Molecular Characteristics of Hydrochars by 13C-NMR and Off-Line TMAH-GC/MS and Assessment of Their Potential Use as Plant Growth Promoters

Hydrochar is a carbon-based material that can be used as soil amendment. Since the physical-chemical properties of hydrochar are mainly assigned to process parameters, we aimed at evaluating the organic fraction of different hydrochars through ¹³C-NMR and off-line TMAH-GC/MS. Four hydrochars produced with sugarcane bagasse, vinasse and sulfuric or phosphoric acids were analyzed to elucidate the main molecular features. Germination and initial growth of maize seedlings were assessed using hydrochar water-soluble fraction to evaluate their potential use as growth promoters. The hydrochars prepared with phosphoric acid showed larger amounts of bioavailable lignin-derived structures. Although no differences were shown about the percentage of maize seeds germination, the hydrochar produced with phosphoric acid promoted a better seedling growth. For this sample, the greatest relative percentage of benzene derivatives and phenolic compounds were associated to hormone-like effects, responsible for stimulating shoot and root elongation. The reactions parameters proved to be determinant for the organic composition of hydrochar, exerting a strict influence on molecular features and plant growth response.