180 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 28, NO. 1, FEBRUARY 2000

Effect of Glow Discharge Air Plasma on Grain CropsSeed

A. E. Dubinov, E. M. Lazarenko, and V. D. Selemir

Abstract—Oat and barley seeds have been exposed to both con-tinuous and pulsed glow discharge plasmas in air to investigate theeffects on germination and sprout growth. Statistical analysis wasused to evaluate the effect of plasma exposure on the percentagegermination and length of sprout growth. A stimulating effect ofplasma exposure was found together with a strong dependence onwhether continuous or pulsed discharges were used.

Index Terms—Air plasma, germination, glow discharge, seed.

I. INTRODUCTION

T HERE are many publications in Russian and foreign liter-ature devoted to the issue of crop stimulation using phys-

ical factors (ionizing radiation, laser, high-power light radiation,electromagnetic fields, etc.). The main task of these investiga-tions is to search for methods to improve the sowing quality ofseeds that can create prerequisites for larger crops when otherconditions are equal.

The main criteria of the quality of sowing material in the fieldof plant cultivation is the ability of the seeds to grow and pro-duce healthy plants, which is expressed in percentage germi-nation and percentage infected with different diseases. Exper-iments can be conducted to determine laboratory germination(ability of the seeds to germinate in laboratory conditions) andfield germination (ability of the seeds to germinate in the soilin field conditions). Seed germination is unsatisfactory whenfewer than 95 of 100 seeds germinate, i.e., germination is lessthan 95%.

In particular, it is shown in [1] and [2] that spring wheat seedsthat are characterized as having unsatisfactory germination (lessthan 95%) have better laboratory germination under the effectof physical factors (ionizing, laser, and plasma). Intensity of theinitial germination is improved at the expense of accumulationof germ mass, in comparison with test seeds, and an increase ofroot length and mass are observed. Under the influence of allphysical factors used, field germination increases from 4% to22.5% depending on weather conditions.

As a rule, small doses of physical effects are used for stimu-lation of seeds before sowing. This promotes the fullest demon-stration of potential possibilities of the plant. But it is necessaryto take into account the fact that the same physical factor withthe same intensity level could or could not cause so called stress,i.e., a general reaction of the organism to an unfavorable influ-

Manuscript received April 28, 1999; revised August 30, 1999.The authors are with the Russian Federal Nuclear Center, Nizhni Novgorod,

Sarov 607190, Russia.Publisher Item Identifier S 0093-3813(00)01479-X.

ence. When a stress reaction occurs in plant tissue, the hormoneconcentration increases, reducing metabolism and slowing thegrowing processes. That is why it is very important to find theoptimum dose to obtain the desired physical effect, namely, im-proving the quality of the sowing material.

The authors started the investigations to determine whetherapplication of an air glow discharge plasma prior to sowingcould stimulate crop seeds. The goal of this research is to ob-tain information about the influence of low-temperature gas-dis-charge plasma on the intensity of the initial growth of graincrops seed characterized by low sowing indexes and also on thedynamics of sprout growth.

II. M ATERIAL AND EXPERIMENTAL METHODS

Air-dried oat seeds (Avena Savita) of the “Komes” brandand barley seeds (Hordeum Rulgare) of the “Zazersky 85”brand with initial germination of 75% were taken as subjects ofinquiry. The device, based on a direct current glow dischargechamber described in [3] and presented in Fig. 1, was used forthe plasma effect investigation.

The chamber consists of a glass tube with an internal diameterof 150 mm and a length of 3 m with steel electrodes on bothends.

A thin seed layer was exposed to the plasma effect in twodifferent regimes:Regime 1 air pressure torr, discharge current

mA, exposure time min, andcontinuous discharge;

Regime 2 air pressure torr, discharge currentmA, exposure time min, pulsed

discharge with pulse repetition rateHz, and pulse duration of≈150–200 ms;barley seeds were exposed to plasma only inthis regime.

In both regimes, the plasma gas temperature during theprocess did not exceed room temperature by more than 5C,and its luminescence brightness did not exceed natural roomillumination. That is why it is possible to assert that the physicalbasis of the effect was bombardment of the seed surface withlow-energy ions (∼0.1 eV) and electrons (∼3 eV).

The interval between exposure of the seeds and planting wasseven days. The seeds were germinated in optimum conditions.The experiments were performed in fivefold and fourfold rep-etitions. From each repetition, we have planted 40 seeds. Theintensity of seed growth and sprout length on the eleventh dayafter planting were used as indexes for estimation of the physi-ological state of the plants.

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DUBINOV et al.: EFFECT OF GLOW DISCHARGE AIR PLASMA ON GRAIN CROPS SEED 181

Fig. 1. External view of experimental setup.

TABLE I

III. RESULTS AND DISCUSSION

It is known that there is a range of maximum seed sensitivityfor presowing stimulation, depending on the initial sowing qual-ities of the seeds and the conditions of their formation. In [4], itwas determined that the largest effect from presowing stimula-tion is obtained in the case when initial germination lies within70%–90% for grain crops seed. This was taken into account inour experiments due to the fact that the quality of seed grain isone of the serious problems of plant cultivation.

In our experiments, it was determined that oat seeds of the“Komes” brand exposed to the plasma, germinated six days be-fore the reference seeds. Moreover, the quantity of germinatedseeds exposed to regime 1 in the experiments was 27% higherthan the reference seeds at the fifth day. Up to the eleventhday, the length of reference and exposed sprouts was almost thesame.

The results obtained from the experiments were statisticallyanalyzed with the single-factor dispersion analysis method andare presented in Tables I and II. The analysis results for the in-

182 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 28, NO. 1, FEBRUARY 2000

TABLE II

tensity of seed germination are presented in Table I. It showsthat at the 99% significance level, a zero hypothesis is rejectedand the difference between the exposed germinated oat seeds forthe experiments in regime 1 and the reference seeds is signifi-cant and the result adequacy rather high. The percentage of oc-casional errors is not high (>24%), and the influence of plasmaexposure on the resulting sign is high (∼76%). Analyzing theresults obtained using regime 2, the zero hypothesis is also re-jected. The difference between the exposed seeds and the refer-ence seeds is significant at the 95% significance level, but thestimulating effect is more weakly expressed.

Table II presents the analysis results on the resulting sign“length of sprout.” Analysis has shown that the zero hypothesisis not rejected, and there is no significant difference in sproutlength between the exposed seeds and the reference seeds on theeleventh day. Dispersion analysis did not reveal any plasma ef-fect on either resulting signs for barley seeds exposed in regime2.

A well-known physiological factor [5] could easily explainthe smoothing of quantitative differences. This is the case whenfull or partial smoothing of quantitative differences starts beforethe end of one ontogenesis stage and the beginning of the nextquantitative ontogenesis stage. The difference here appears ac-cording to the criteria that arecharacteristic for the new stage.

Differences in the biological effect between regimes 1 and2 could be explained, apparently, by that fact that a contin-uous exposure to the plasma (regime 1) intensifies biochem-ical processes in the seed (breathing, membrane penetrability,etc.) more effectively. It is possible that presowing processing

causes chemical reactions with unsaturated hydrocarbon, andprotective substances are formed. Moreover, since the penetra-tion depth of charged plasma particles is only several tens ofangstroms, there is a possibility of a surface disinfectant ef-fect. It is also possible that the process of exposing the seeds tovacuum has some influence on the increase of germs growth.We have studied this process and kept seeds in a vacuum of∼0.1 Torr for 4 min. The change of germs growth was small.Moreover, the difference in results between regimes 1 and 2 in-dicates that the role of vacuum is rather small. All these factorsprobably influence the appearance of the stimulating effect.

IV. CONCLUSION

Based on these experimental investigations, it is possible toconclude the following.

1) With the proper conditions of exposure, plasma condi-tioning of seeds provides a stimulating effect and couldbe used for presowing seed stimulation.

2) Exposure of seeds to a continuous plasma dischargeis more effective than exposure to a pulsed plasmadischarge.

In the future, the authors plan to increase the scale of investi-gation both in the laboratory and under field conditions.

REFERENCES

[1] V. I. Kostin and V. I. Yermokhin, “Improvement of sowing quality ofspring wheat seed in the result of their processing with physical fac-tors,” in Abstract 1st All-Union Meeting (Application of Physical andChemical Mutagenesis in Agriculture), Kishinev, Russia, 1987, p. 13.

DUBINOV et al.: EFFECT OF GLOW DISCHARGE AIR PLASMA ON GRAIN CROPS SEED 183

[2] Z. N. Bychkova, V. I. Levin, and V. S. Khlebny, “Metabolism changein seeds at physical factors effect,” inAbstract 1st All-Union Meeting(Application of Physical and Chemical Mutagenesis in Agriculture),Kishinev, Russia, 1987, p. 40.

[3] S. V. Bulychev, A. E. Dubinov, and V. S. Zhdanovet al., “A gas-dis-charge chamber with a discharge initiatied by an auxialiary dischargealong the surface of a ferroelectric ceramic,”Instrum. Experiment. Tech.,vol. 42, no. 3, pp. 394–397, 1999.

[4] V. V. Orlov, “Efficiency of pre-sowing irradiation of crop seed dependingon their sowing qualities,” inProc. Colloquium Experimental Mutagen-esis of Plants, vol. 2, Baku, Elm, 1974, p. 54.

[5] R. R. Riza-Zade, “On regularities of display of pre-sowing seeds irradi-ation effect,” inProc. Colloquium Experimental Mutagenesis of Plants,Baku, Elm, 1974, p. 53.

A. E. Dubinov was born in 1958 in Arzamas-16,Russia. He graduated from Moscow Engineer andPhysical Institute in 1988. He received the Ph.D.degree in physical and mathematical sciences fromthe Russia Federal Nuclear Centre in 1997.

At present, he is Vice-Head of the Division ofHigh-Energy Density Physics and Directed Radia-tion Fluxes of the Russian Federal Nuclear Center.His field of scientific interest includes relativisticmicrowave electronics, accelerators, plasmas, gasdischarges, and nonlinear phenomena.

E. M. Lazarenko was born in Arzamas-16, Russia,in 1957. She graduated from Mordovian State Uni-versity in 1986.

She is a Senior Scientist with the Russian FederalNuclear Center. Her field of scientific interest in-cludes radiobiology and experimental mutagenesis.

V. D. Selemir was born in Chernovtsy, the Ukraine,in 1948. He graduated from Kharkov State Universityin 1972.

At present, he is Head of the Division of High-En-ergy Density Physics and Directed Radiation Fluxesat the Russian Federal Nuclear Center. His field ofscientific interest includes high-current electronics,accelerators, plasma, and high-energy densityphysics.