Acceleration of germination of tomato seed by applying AC electric and magnetic "elds

Transcription

1 Journal of Electrostatics 48 (2000) 103}114 Acceleration of germination of tomato seed by applying AC electric and magnetic "elds Jae-Duk Moon *, Hwa-Sook Chung Department of Electrical Engineering, College of Engineering, Kyungpook National University, 1370 Sankyuk-Dong, Buk-Ku, Taegu , South Korea Department of Biology Education, College of Engineering, Kyungpook National University, 1370 Sankyuk-Dong, Buk-Ku, Taegu , South Korea Received 2 April 1999; received in revised form 23 July 1999; accepted 9 August 1999 Abstract The e!ects of di!erent intensities and exposure time of AC electric "eld and AC magnetic "eld on tomato seed have been investigated to determine the optimal conditions for accelerating germination. The percent germination rates of the treated sample seed were compared with those of the untreated seed germinated under normal conditions. The seeds were treated with AC electric "elds ranging from 4 to 12 kv/cm and AC magnetic #ux densities ranging from 3 to 1000 G, and were exposed to three time periods ranging from 15 to 60 s with corresponding equal rest time periods. It is found that the percent germination rates of the treated tomato seed were accelerated about 1.1}2.8 times compared with that of the untreated seed. However, an inhibitory e!ect on germination was shown in the case of the electric "eld more than 12 kv/cm and the exposure time more than 60 s Elsevier Science B.V. All rights reserved. Keywords: Electric "eld exposure; Magnetic "eld exposure; Seed germination 1. Introduction All plants on earth live under an electric and magnetic "eld because the earth is a magnet [1}6] and there is an electric "eld between clouds and the earth [3]. It has been reported that external electric and magnetic "elds in#uence both the activation of ions and the polarization of dipoles in living cells [7}9]. Investigations into * Corresponding author. Tel.: # ; fax:# address: [email protected] (J.-D. Moon) /00/$- see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S ( 9 9 )

2 104 J.-D. Moon, H.-S. Chung / Journal of Electrostatics 48 (2000) 103}114 electromagnetic e!ects on plants have already been carried out in Russia [5,7] with some remarkable results [1}4,8}11]. The optimal external electromagnetic "eld could accelerate the activation of seed germination [3,6]. But the mechanism of these actions is still poorly understood [12,13]. Electric and/or magnetic treatments are assumed to enhance seed vigor by in#uencing the biochemical processes that involve free radicals and by stimulating the activity of proteins and enzymes [8,14}17]. Field tests report greater than 10% increase in the "eld of maize and wheat, after submitting the seeds to carefully controlled electric "elds [15,16]. These e!ects were mainly attributed to the "eld-induced intensi"cation of the biological processes in seeds. The crop increase could also be related to the sterilizing e!ect of high-voltage application. The authors aimed to analyse this aspect of electric and magnetic "eld, and exposure time using tomato seeds as an experimental system. In preliminary studies, other seeds, such as rice, soya bean, and red pepper were checked, but their enhanced accelerations of the percent germination rates were low compared with tomato seed. In this paper the e!ects of AC electric "eld, AC magnetic "eld and exposure times on tomato seed germination have been carried out experimentally to investigate the potential of acceleration of seed germination by the "eld intensity and exposure time. The percent germination rates of treated tomato seeds were analysed and compared with those of the untreated seeds. 2. Experimental setups and methods Fig. 1 illustrates the experimental set up including the treatment cells for the electric "eld and the magnetic "eld exposures. The seeds were inserted into the parallel plate type cell box [epoxy box, 1 mm wall thickness, 5.5 dielectric constant] for exposure to AC electric "eld, E (Fig. 1a), and AC magnetic "eld, B (Fig. 1b). Copper tapes, used as electrodes, were attached to the two outer sides of the cell and all the edges of the electrodes were covered with insulating glue to prevent the occurrence of unwanted surface discharges. The size of the cell was 2.5 cm in width and 6.5 cm in height, and the gap between the parallel electrodes was 0.50 cm, where the seed samples were inserted. An AC high-voltage transformer was used for the electric "eld treatment. Various 60 Hz AC electric "elds ranging from 4 to 12 kv/cm with "ve steps were applied to treat the seed. The applied electric "elds, E, were calculated from voltages measured by a digital voltmeter, VM1 (Fluke 73) and a high-voltage probe (Keithley 1000 : 1), assuming that the cell is a parallel plate system. Fig. 1b illustrates the experimental set up for the magnetic "eld treatment. The magnetic "eld treating system consists of a rectangular-type iron core (3 kva capacity) and coils (6000 turns) for various magnetic "eld inductions. An adjustable air gap spacing of 60 mm was set in the center of the upper part of the core, where the treatment cell (epoxy box, 1 mm wall thickness) was inserted. The magnetic #ux density, B, in the cell was varied from 3 to 1000 G with six steps by changing the applied AC current in the induction coil as measured by VM3 (Fluke 73) across R. The inductance and the resistance of the magnetic "eld induction coil set were measured by an LCR meter (Ando Electric,

3 J.-D. Moon, H.-S. Chung / Journal of Electrostatics 48 (2000) 103} Fig. 1. Schematic diagram of experimental set up. AG-4311B) to be 970 mh and 14 Ω, respectively. Six capacitors of 60 μf connected in series with the induction coil of the core were used for power factor compensation. The magnetic #ux density in the gap spacing of the treatment cell was measured by a gaussmeter (Walker Scienti"c, Inc., MG-5D). The seed samples were exposed thrice to the electric "eld and the magnetic "eld with correspondingly equal rest periods following each "eld treatment time. Tomato seeds (Lycopersicun esculentum L.) were selected as the sample seeds which were distributed by an agricultural agent. Before the experiment, the uncovered seeds were stored for a month in an incubator at 43C, 50% RH to equilibrate to an identical seed moisture condition. Fifty seeds were inserted in the cell and treated by the electric "eld and the magnetic "eld for various time periods with corresponding rest time. The

4 106 J.-D. Moon, H.-S. Chung / Journal of Electrostatics 48 (2000) 103}114 treated and untreated seeds were then germinated under an identical condition of the water-bedded petri dish in a temperature- and relative humidity-controlled incubation room (203C, 75% RH). It was considered to be germinated when a root tip of Fig. 2. Percent germination of tomato seed as a function of the incubation time, for each constant electric "eld treatment, showing exposure time as a parameter.

5 J.-D. Moon, H.-S. Chung / Journal of Electrostatics 48 (2000) 103} mm length had emerged from the seed. Three replication experiments at the same conditions were performed. The percent germination rates in the "gures in this paper meant the normalised mean values of the three replicated data. The data of three replicated measurements showed a little di!erence from each experiment, but 10% as maximum di!ered from each experiment for electric and magnetic "elds. And the #uctuation ranges of each point on the "gures were not indicated to avoid the complications of the "gures. 3. Experimental results and discussion Fig. 2 shows the germination characteristics of the tomato seed samples as a function of the incubation time for the various periods of exposure time and electric "eld Fig. 3. Percent germination of tomato seed as a function of the incubation time, for each "xed exposure time, showing electric "eld treatment as a parameter.

6 108 J.-D. Moon, H.-S. Chung / Journal of Electrostatics 48 (2000) 103}114 Fig. 4. Percent germination of tomato seed for various applied electric "eld intensities and exposure time periods at each "xed incubation time.

7 J.-D. Moon, H.-S. Chung / Journal of Electrostatics 48 (2000) 103} intensities applied. The percent germination began to increase gradually in 4 days but rapidly elevated after 5}7 days and then saturated after 7 days, and most seeds were germinated. As shown in Figs. 2a and b, when lower "elds of 4 and 6 kv/cm were applied, enhancement of the maximum percent germination rate was obtained at an exposure time of 30 s; however, at 15 s the percent germination was low. In the case of higher "elds of 8 and 10 kv/cm and longer treatment time of 30 and 45 s, the enhanced percent germination responses were obtained. When the very high "eld of 12 kv/cm was applied with a shorter exposure time of 15 s, the highest germination enhancement was obtained. However, electric "eld intensity higher than 14 kv/cm and exposure time longer than 90 s, indicated an inhibitory e!ect upon the germination of the seed, and those were discarded from the data. Fig. 3 shows the germination characteristics of the seed as a function of incubation times for the various electric "eld intensities applied at "xed exposure time periods. The seeds exposed for short time periods of 15 and 30 s and relatively higher electric "elds showed better germination than the seeds exposed to the relatively lower electric "elds. Figs. 3c and d show the percent germination with relatively higher exposure times of 45 and 60 s. A higher electric "eld treatment, however, produced a higher percent germination in the early growing stage, but decreased the percent germination in the late stage. It is believed that the strong impact of the higher electric "eld intensity on the seed inhibits the biological processes and stimulates the seed germination activity [13], and there are optimal conditions for the "eld and exposure time. Fig. 4 illustrates the germination characteristics of the seed for various applied electric "eld intensities and exposure times at each "xed incubation time periods of 5, 6 and 7 days. Even though there are #uctuations in Fig. 4a, the percent germination of the seeds show the increased values of 1.2}2.8 times in 5 days incubation when the electric "elds of 4}12 kv/cm were applied. But some show less values of percent germination, compared with the untreated seeds. The increased germination Fig. 5. Magnetic #ux density characteristics of the treatment cell as a function of the induction coil current.

8 110 J.-D. Moon, H.-S. Chung / Journal of Electrostatics 48 (2000) 103}114 characteristics for the applied "elds of 4}12 kv/cm are also shown at 6 and 7 days incubation, and, the increased percent values are about 1.1}1.8 and 1.1}1.3 times at 6 and 7 days incubation, respectively, as shown in Figs. 4b and c. Fig. 5 shows the measured magnetic #ux density in the treatment cell as a function of the applied AC current. The applied AC currents required to provide speci"ed magnetic #ux densities for seed treatment were determined from Fig. 5. Fig. 6 shows the germination characteristics as a function of the incubation time for indicated treatment values of magnetic #ux density and exposure time. There was a gradual increase for 5 days and then a rapid increase during 6}7 days until saturation and more than 98.7% of the seeds were germinated. In the lower magnetic "eld treatments of 3 and 10 G, the percent germinations increased slowly, yet once the seeds began to germinate, their percent germination rates rapidly Fig. 6. Percent germination of tomato seed as a function of the incubation time, for each "xed exposure time, showing magnetic "eld treatment as a parameter.

9 J.-D. Moon, H.-S. Chung / Journal of Electrostatics 48 (2000) 103} Fig. 7. Percent germination of tomato seed as a function of the incubation time, for each constant magnetic "eld treatment, showing treatment time as a parameter.

10 112 J.-D. Moon, H.-S. Chung / Journal of Electrostatics 48 (2000) 103}114 Fig. 8. Percent germination of tomato seed for various applied magnetic #ux densities and exposure time periods at each "xed incubation time.

11 J.-D. Moon, H.-S. Chung / Journal of Electrostatics 48 (2000) 103} increased and saturated. When the seeds were treated with the higher magnetic "elds of 300 G and 1 kg, the percent germination rate became much higher, but #uctuated. Fig. 7 shows the germination characteristics as a function of the incubation time for "xed values of magnetic #ux density and exposure time. Di!erent characteristics were indicated with increased exposure time for each "xed magnetic #ux density. The percent germination values of the magnetically treated seeds, at the beginning of the incubation time, were high even when the low magnetic #ux densities, lower than 100 G, were applied. And then the percent germinations were rapidly increased and saturated with an increase of the incubation time. However, they did not show an inhibitory e!ect on the germination when the magnetic "eld and the exposure time were high and long enough at 1 kg and 60 s. Fig. 8 illustrates the germination characteristics of the seed for various applied magnetic #ux densities and exposure times at each "xed incubation time periods of 5, 6 and 7 days. They show large #uctuations in Fig. 8, but the percent germination of the seeds are shown to have the increased values of 1.1}3.5 times in 5 days incubation as shown in Fig. 8a when the magnetic #ux densities of 3}1000 G were applied. Similar enhanced germination characteristics are also shown at 6 and 7 days incubation but the enhanced percent values are 1.1}1.6 and 1.1}1.3 times at 6 and 7 days incubation, respectively, as shown in Figs. 8b and c. As a result of electric "eld and magnetic "eld treatments with a proper exposure time, higher germination percents were obtained. In addition, the saturation points of germination can be achieved more than one day earlier compared with those of the untreated seeds. 4. Conclusion The e!ects of di!erent intensities and exposure time of AC electric "elds and AC magnetic "elds on tomato seed germination have been investigated as a potential means to accelerate the germination of the seed. The following conclusions have been obtained: 1. The tomato seed treatment by AC electric "eld and AC magnetic "eld for short time periods accelerated the percent germination. In comparison with the untreated seed, the percent germination rates were enhanced by 1.1}2.8 times, using AC electric and magnetic "elds, and the saturation points of germination can be achieved one day earlier. 2. The higher percent germination rate enhancement were obtained at the electric "eld ranges of 4}12 kv/cm and magnetic "eld ranges of 3}100 G for the exposure times of 30}45 s. However, with the electric "eld higher than 12 kv/cm and the exposure time longer than 60 s, the germination of the tomato seed began to show an inhibitory e!ect.

12 114 J.-D. Moon, H.-S. Chung / Journal of Electrostatics 48 (2000) 103}114 Acknowledgements The authors express their appreciation to KOSEF (Korea Science and Engineering Foundation, ) for their "nancial support of this work. References [1] Y. Watanabe, T. Yamashita, Creation of seed, Japan Industry News Paper, 1987 (in Japanese). [2] H. Maeda, Do the Living Things Feel the Magnetics, Kodansha, Tokyo, 1993 (in Japanese). [3] U. Oomori, Bioelectromagnetics and its Applications, Fuji Technosystem Ltd., 1992, Ch , pp. 340}346 (in Japanese). [4] H. Takahashi, Electricity and Life, Institute Publication Center, Tokyo, 1986 (in Japanese). [5] A. Bertholon, UG ber ElektrizitaK t in Berziehung auf die P#anzen, Leipzig, [6] S.O. Nelson, E.R. Walker, J. Agric. Eng. 42 (1961) 688. [7] J.S. Townsend, The di!usion and mobility of ions in magnetic "eld, Proc. Roy. Soc. A&B (1912) 571}577. [8] L.E. Murr, Plant growth response in electrostatic "eld, Nature 207 (1965) 1177}1178. [9] C.C. Johnson, A.W. Guy, Nonionizing electrostatic wave e!ects in biological materials and system, Proc. IEEE 60 (6) (1972) 692}718. [10] G.H. Sidaway, G.F. Asprey, In#uence of electrostatic "elds on seeds germination, Nature 211 (1966) 303. [11] F.W. Wheaton, W.G. Lovely, C.W. Bockhop, E!ects of static and 60 Hz electric "elds on germination rate of corn & soybeans, Trans. ASAE 14 (1971) 339}342. [12] R. Morar, A. Iuga, L. Dascalescu, V. Neamtu, I. Munteanu, Separation and biostimulation of soybeans using high-intensity electric "elds, Proceedings of the International Conference on Modern Electrostatics, Beijing, China, 1988, pp. 158}160. [13] B. Xiyao, M. Ancheng, M. Jingrun, L. Xiaoling, Y. Li, W. Qingzhao, Physiological and biochemical experiments in electrostatic treated seeds, Proceedings of the International Conference on Modern Electrostatics, Beijing, China, 1988, pp. 161}165. [14] Y. Jia-Ming, E!ects of high-voltage electrostatic "eld on growth in plants, Proceedings of the International Conference on Modern Electrostatics, Beijing, China, 1988, pp. 140}143. [15] R. Morar, A. Iuga, L. Dascalescu, I. Munteanu, Electric "eld in#uence on the biological processes of seeds, Proceedings of the International Symposium on High-Voltage Engineering, Yokohama, Japan, 1993, p [16] R. Morar, R. Munteanu, E. Simion, I. Muteanu, L. Dascalescu, Electrostatic treatment of bean seeds, IEEE-IA 35 (1) (1999) 208}212. [17] S. Kurinobu, Y. Okazaki, Dielectric constant and conductivity of one seed in germination process, Annual Conference Record of IEEE/IAS, 1995, pp. 1329}1334.