E. Rajasekhar, M. Nagaraju*, S. Raisa Reshma and R. Jeevan Kumar. ABSTRACT. is study investigated the influence of static electromagnetic fields on.
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Effect of Different Static Electromagnetic Fields on Germination Speed of Mung Beans (Vigna radiata var. radiata) E. Rajasekhar, M. Nagaraju*, S. Raisa Reshma and R. Jeevan Kumar
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Effect of Different Static Electromagnetic Fields on Germination Speed of Mung Beans (Vigna radiata var. radiata) E. Rajasekhar, M. Nagaraju*, S. Raisa Reshma and R. Jeevan Kumar ABSTRACT is study investigated the influence of static electromagnetic fields on speed of seed germination of mung beans (green beans), measured as the number of germinated seeds aer 24 h of incubation. Prior to germination, seeds were exposed to different types of electromagnetic fields (EMF), namely Helmholtz, north pole and south pole, and different field strengths of 5, 10, 30 and 60 millitesla (mT) at exposures of 15, 30, 45 and 60 min. Results indicated that speed of germination improved following exposure to south pole EMF compared to the control and the other two field types. Upon increasing field strength up to 10 mT, speed of germination improved, but decreased at higher field strengths. Increasing exposure period up to 45 min also led to improved speed of germination. e highest speed of germination was observed using a south pole EMF at 10 mT and an exposure period of 45 min. INTRODUCTION
Seed germination is already known to be affected by both electric and magnetic fields from Earth itself, without the application of an external electromagnetic radiation. Perhaps the most remarkable fact in this area is that electro-stimulation plays an important role in optimizing crops in terms of the maximization of yield, promotion of plant growth and protection against exogenous agents that cause plant disease (Pittman and Ormrod, 1971; Cerdonio et al., 1979; McKenzie and Pittman, 1980; Oomori, 1992; Maeda, 1993). Biostimulation can be accomplished by applying different techniques such as electromagnetic or magnetic stimulation, as well as lasers, UV radiation, gamma rays, ultrasound and ionized radiation. e main advantage of using electromagnetic stimulation methods over traditional chemical processes is the absence of toxic residues. Previous studies have shown positive effects of electromagnetic treatments on seed germination of tomato (Solanum lycopersicum L. var. lycopersicum) (De Souza et al., 2006), rice (Oryza sativa L.) (Carbonell et al., 2000), barley (Hordeum vulgare L.) (Lynikiene and Pozeliene, 2003) and lettuce (Lactuca sativa L.) (Reina et al., 2001). However, only a few studies have been performed to evaluate the influence of electromagnetic fields on mung bean [Vigna radiata (L.) R. Wilczek var. radiata] seed germination (Sharma et al., 2010; Singh et al., 2011). Mung beans are commonly used in China, ailand, Japan, Korea, Philippines, Pakistan, India and all over Southeast Asia to produce different E. Rajasekhar and R. Jeevan Kumar, Molecular Biophysical Laboratories, Department of Physics, S.K. University, Anantapur-515055, A.P., India; M. Nagaraju and S. Raisa Reshma, Department of Microbiology, National P.G. College, Nandyal-518502, A.P., India. *Corresponding author (E-mail: raju8875 @yahoo.co.in). Received 18 May 2011.
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foodstuffs such as bean sprouts, green bean soup, jellies, transparent/cellophane noodles and several desserts and snacks. is study attempted to determine the effects of static electromagnetic fields on mung bean seed germination. e aim was to investigate whether germination speed can be improved by subjecting seeds to different types of electromagnetic fields (Helmholtz, north pole and south pole), field strengths (5, 10, 30 and 60 mT) and exposure periods (15, 30, 45 and 60 min). MATERIALS AND METHODS To establish the required electromagnetic fields, a locally designed magnetic field generator (Sahebjamei et al., 2007) and a 220VAC power supply equipped with a variable transformer as well as a single-phase full-wave rectifier were used. e maximum power was 1 kW and the passing current 50A DC. is system was designed to generate electromagnetic fields (EMF) in the range of 0.5 μT to 75 mT. It consisted of two coils, each with 3000 turns of 3 mm copper wire, on a U-shaped laminated iron core (to prevent eddy current losses). Using two vertical connectors, the arms of the U-shaped iron core were terminated in four circular iron plates covered with a layer of nickel (each 23 mm thick, 260 nm in diameter). e germination experiment was conducted as a completely randomized design with three replications, each treatment consisting of 25 seeds per replicate. Germination tests were performed according to International Seed Testing Association guidelines (ISTA, 2004). Each filter paper with seeds was rolled and placed in a vessel containing distilled water. Four hours aer soaking, individual rolls were subjected to the different electromagnetic treatments. Moistened rolls containing seeds were placed between the two pairs of Helmholtz coils and exposed to EMF of 5, 10, 30 or 60 mT for 15, 30, 45 or 60 min. e same procedure was followed for the other two types of electromagnetic fields, north pole and south pole. Finally, all vessels containing rolls with seeds were moistened and placed in a germinator at 23 °C. Germination was considered to have taken place once the tip of the radicle (1–2 mm) emerged from the seed coat (Moon and Chung, 2000). Speed of germination was measured as percentage germination that was recorded aer 24 h of incubation. In this study, unexposed seeds were treated as control. RESULTS In general, results indicated that germination speed of mung beans as a function of EMF, and at different exposure periods, was higher under a south pole EMF compared to all other treatments and the control. For every EMF tested, increasing the exposure period at a particular field strength led to an increase in germination speed, followed by a decline as the exposure period was further increased (Table 1). For instance, for Helmholtz, at field strength of 10 mT, germination was 67 and 75% aer 15 and 30 min of exposure, respectively, compared to a control value of 40%. However, increasing the exposure period to 45 min led to a decline in germination to 42% and a further decline to 33%, lower than that of the control, when exposure was increased to 60 min.
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Similar trends were also observed for seeds exposed to north and south pole EMF (Table 1). Additionally, irrespective of EMF used, speed of germination tended to be lowest at the highest tested field strength (60 mT). Overall, speed of germination was more stimulated aer exposure to the south pole EMF compared to the untreated control and the other two field types. Also, at all south pole field strengths and exposure periods, speed of germination values were higher than the untreated control. In contrast, for the north pole EMF, most results were lower than those of the control (Table 1). Exposure period, field type and strength all had a significant effect on speed of germination results, as indicated by analysis of variance (data not shown). Figures 1, 2 and 3 show the effects of each pair of factors averaged over the third factor. Increasing exposure periods up to 45 min under Helmholtz and
Table 1. Speed of germination of mung bean seeds, measured as germination percentage 24 h aer incubation, as influenced by electromagnetic field type, field strength and exposure period. Electromagnetic field type Field strength
Exposure period
Helmholtz
(mT)
(min)
North pole
South pole
0
0
40 ± 0.42†
40 ± 0.42
40 ± 0.42
5
0
40 ± 0.42
40 ± 0.42
40 ± 0.42
5
15
50 ± 0.12
42 ± 0.25
53 ± 0.25
5
30
58 ± 0.18
67 ± 0.48
67 ± 0.29
5
45
67 ± 0.11
33 ± 0.28
67 ± 0.38
5
60
25 ± 0.09
25 ± 0.39
58 ± 0.23
10
0
40 ± 0.42
40 ± 0.42
40 ± 0.42
10
15
67 ± 0.11
58 ± 0.56
61 ± 0.19
10
30
75 ± 0.15
33 ± 0.48
64 ± 0.16
10
45
42 ± 0.56
25 ± 0.11
83 ± 0.36
10
60
33 ± 0.47
25 ± 0.55
75 ± 0.58
30
0
40 ± 0.42
40 ± 0.42
40 ± 0.42
30
15
67 ± 0.23
42 ± 0.33
50 ± 0.12
30
30
50 ± 0.29
33 ± 0.14
58 ± 0.47
30
45
25 ± 0.31
25 ± 0.19
73 ± 0.24
30
60
17 ± 0.33
25 ± 0.28
58 ± 0.38
60
0
40 ± 0.42
40 ± 0.42
40 ± 0.42
-------------------- Germination (%) --------------------
60
15
42 ± 0.27
42 ± 0.31
45 ± 0.82
60
30
67 ± 0.29
58 ± 0.67
52 ± 0.39
60
45
27 ± 0.39
17 ± 0.19
67 ± 0.29
60
60
8 ± 0.09
17 ± 0.18
50 ± 0.44
† Mean ± SD.
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south pole EMF led to higher speed of germination, with the highest value observed for the south pole EMF aer 45 min of exposure (Fig. 1), followed by a subsequent decline at 60 min. Field strength of 10 mT resulted in the highest speed of germination under Helmholtz and south pole EMF, compared to the control, but higher field strengths had a negative effect on speed of germination (Fig. 2). With one exception at 5 mT, exposure to north pole EMF led to reductions in germination speed compared to the control. Increasing exposure period up to 45 min led to increased germination speed at all field strengths, followed by a decline at 60 min, especially for the 60 mT treatment, which was lower than the control (Fig. 3). DISCUSSION ere is an increasing interest in developing new techniques to improve the speed of seed germination. Research on EMF effects on seeds is most oen concerned with their impact on germination (Hirota et al., 1999; Pietruszewski, 1999a; Bovelli and Bennici, 2000). Studies have shown that an optimal external electromagnetic field could enhance the activation of seed germination (Oomeri, 1992; Maeda, 1993), but the mechanisms of these actions are poorly understood (Morar et al., 1988; Xiyao et al., 1988). Probably, electric and/or Figure 1. Speed of germination of mung bean seeds, measured as germination percentage 24 h aer incubation, as influenced by electromagnetic field type (north pole, Helmholtz and south pole) and exposure period (15, 30, 45 and 60 min). Each mean is the average of all tested field strengths (5, 10, 30 and 60 mT). e horizontal line is the mean germination speed of the control treatment.
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Figure 2. Speed of germination of mung bean seeds, measured as germination percentage 24 h aer incubation, as influenced by electromagnetic field type (north pole, Helmholtz and south pole) and field strength (5, 10, 30 and 60 mT). Each mean is the average of all tested exposure periods (15, 30, 45 and 60 min). e horizontal line is the mean germination speed of the control treatment.
Figure 3. Speed of germination of mung bean seeds, measured as germination percentage 24 h aer incubation, as influenced by field strength (5, 10, 30 and 60 mT) and exposure period (15, 30, 45 and 60 min). Each mean is the average of all tested electromagnetic field types (north pole, Helmholtz and south pole). e horizontal line is the mean germination speed of the control treatment.
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magnetic treatments enhance seed vigor by influencing the biochemical processes that involve free radicals and by stimulating the activity of proteins and enzymes (Kurinobu and Okazaki, 1995; Phirke et al., 1996). Additionally, exposure to magnetic fields has been shown to influence the structure of cell membranes, increasing their permeability and ion transport, which then affects various metabolic pathways (Labels, 1993), increases enzyme activity (Aksyonov et al., 2000) and increases water uptake rates (Garcia and Arza, 2001). In this study, results showed that the germination speed of EMF treated seeds, measured as percentage germination aer 24 h of incubation, was 1.7 (north pole), 1.9 (Helmholtz), and 2.1 (south pole) times higher compared to those of the control (Table 1). In addition, germination speed increased by increasing the exposure period up to a point, followed by a decline with longer exposure periods. Similar results were observed by other researchers. According to Odhiambo et al. (2009), Rose coco (Phaseolus vulgaris L.) seeds subjected to different EMF had increased germination aer up to 4.5 hours of exposure, but germination declined aer longer exposure periods. Studies conducted by Rochalska (2002) on germination and growth of wheat, (Triticum aestivum L.), triticale (× Triticosecale spp.), maize (Zea mays L.), and soybean [Glycine max (L.) Merr.] also indicated that the magnetic field can be used as a method of seed vigor improvement. Likewise, favorable effects of EMF on the germination and emergence of seeds were shown for cereals (Pietruszewski, 1999b), legumes (Podlesny et al., 2003) and some vegetables (Prokop et al., 2002). Our results showed that speed of germination of seeds subjected to a north pole EMF was lower than the control. Similarly, percentage germination of Rose coco bean seeds declined when they were subjected to a north pole EMF (Odhiambo et al., 2009). Increasing the field strength at the same EMF first increased, then decreased germination speed, with the highest results observed at 10 mT for Helmholtz and south pole, and 5 mT for north pole. It may be assumed that under this condition the cell water potential forces act in the same direction on germinated seeds (Das and Bhattacharya, 2006). e stimulatory effect of the application of different magnetic doses is in agreement with reports by researchers such as Flórez et al. (2007) who observed an increased rate of initial growth and early sprouting of rice and maize seeds exposed to 125 and 250 mT stationary magnetic fields. Similarly, a suitable EMF treatment (10 mT) did speed up seedling development and increased biomass accumulation of maize (Shabrangi and Majd, 2009), wheat and barley (Martinez et al., 2000 and 2002), onion (Allium cepa L.), rice (Alexander and Doijode, 1995) and bean (Odhiambo et al., 2009). e decline in germination speed that was associated with higher exposure periods was also reported by Balouchi and Modarres Sanavy (2009), who found that Medicago radiata L. root length was improved by exposures of 10 rather than 30 min, at a field strength of 80 μT. In conclusion, results of the present investigation clearly indicated that subjecting mung bean seeds to a south pole EMF for 45 min and at field strength of 10 mT resulted in the greatest enhancement of speed of germination, and therefore was the best treatment combination. In contrast, negative effects were
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observed at higher field strengths and for longer exposure periods. Treatment interactions with biological processes involved in germination may alter these requirements as well as affect physiological and chemical processes. erefore, more research is needed to study EMF effects on seed germination beyond 24 h and investigate the effects of potential energy from EMF on cellular and physiological functions. ACKNOWLEDGMENT We wish to thank Dr. S. Imthiyaz Ahamed, Principal, National P.G. College, Nandyal, for providing lab facilities and encouraging us throughout this study. REFERENCES Aksyonov, S.I., A. Buchylev, T.Y. Grunina, S.N. Goryachev and V.B. Turovetsky. 2000. Physicochemical mechanisms of efficiency of treatment by weak ELF-EMF (extremely low frequency and electromagnetic fields) of wheat seeds at different stages of germination. Proc. 22nd Annu. Meeting Eur. Bioelectromagnetics Assoc. June 11–16, Munich, Germany. Alexander, M.P. and S.D. Doijode. 1995. Electromagnetic field, a novel tool to increase germination and seedling vigour of conserved onion (Allium cepa L.) and rice (Oryza sativa L.) seeds with low viability. Plant Genet. Resour. Newsl. 104:1–5. Shabrangi, A. and A. Majd. 2009. Comparing effects of electromagnetic fields (60 Hz) on seed germination and seedling development in monocotyledons and dicotyledons. Prog. Electromagnetics Res. Symp. Proc. Moscow, Russia. August, 18–21. Balouchi, H.R. and S.A.M. Modarres Sanavy. 2009. Electromagnetic field impact on annual medics and dodder seed germination. Int. Agrophysics. 23:111–115. Bovelli, R. and A. Bennici. 2000. Stimulation of germination callus growth and shoot regeneration of Nicotiana tabacum L. by pulsing electromagnetic fields (PEMF). Adv. Hortic. Sci. 14:3–6. Carbonell, M.V., E. Mrtinez and J.M. Amaya. 2000. Stimulation of germination in rice (Oryza sativa L.) by a static magnetic field. J. Electromagnetic Biol. Med. 19(1):121–128. Cerdonio, M., S. Morante-Mazzoncini and M. Vincentini-Missoni. 1979. Polar growth response of Pisum arvense L. seeds to weak magnetic fields. Can. J. Plant Sci. 59:883–885. Das, R. and R. Bhattacharya. 2006. Impact of electromagnetic field on seed germination. Int. Union Radio Sci. Retrieved from http://www.ursi.org/Proceedings/ProcGA05/ pdf/KP.14(0983).pdf. De Souza, A., D. Garci, L. Sueiro, F. Gilart, E. Porras and L. Licea. 2006. Pre-sowing magnetic treatments of tomato seeds increase the growth and yield of plants. Bioelectromagnetics. 27(4):247–257. Flórez, M., M.V. Carbonell and E. Martinez. 2007. Exposure of maize seeds to stationary magnetic fields: effects on germination and early growth. Environ. Exp. Bot. 59:68–75. Garcia, F. and L.I. Arza. 2001. Influence of stationary magnetic field on water relations in lettuce seeds. Part I: eoretical considerations. Bioelectromagnetics. 22(8):589–595. Hirota, N., J. Nagagawa and K. Kitazawa. 1999. Effects of magnetic field on the germination of plants. J. Appl. Phys. 85(8):5717–5719. ISTA. 2004. International rules for seed testing. Int. Seed Test. Assoc., Zurich, Switzerland. Kurinobu, S. and Y. Okazaki. 1995. Dielectric constant and conductivity of one seed in germination process. Proc. Annu. Conf. Record, Inst. Electr. Electronics Eng./Industry Appl. Soc. December 8–10. Orlando, FL, USA.
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Labels, M.M. 1993. A possible explanation for the effect of magnetic fields on biological systems. Nature. 211, 969. Lynikiene, S. and A. Pozeliene. 2003. Effect of electrical field on barley seed germination stimulation. Agric. Eng. Int.: CIGR-J. Sci. Res. Dev., August. Maeda, H. 1993. Do living things feel the magnetism (in Japanese)? Kodansha Press, Tokyo, Japan. Martinez, E., M.V. Carbonell and J.M. Amaya. 2000. A static magnetic field of 125 mT stimulates the initial growth stages of barley (Hordeum vulgare L.). Electro-and Magnentobiology. 19(3):271–277. Martinez, E., M.V. Carbonell and M. Flórez. 2002. Magnetic biostimulation of initial growth stages of wheat (Triticum aestivum L.). Electromagnetic Biol. Med. 21(1):43–53. McKenzie, H and U.J. Pittman. 1980. Inheritance of magnetotropism in common wheat. Can. J. Plant Sci. 60:87–90. Moon, J. and H. Chung. 2000. Acceleration of germination of tomato seeds by applying AC electric and magnetic fields. J. Electrostatics. 48:103–114. Morar, R., A. Iuga, L. Dascalescu, V. Neamtu and I. Munteanu. 1988. Separation and biostimulation of soybeans using high-intensity electric fields. Proc. Int. Conf. Modern Electrostatics, October 21–25. Beijing, China. Odhiambo, J.O., F.G. Ndiritu and I.N. Wagara. 2009. Effects of static electromagnetic fields at 24 hours incubation on the germination of rose coco beans (Phaseolus vulgaris L.). Romanian J. Biophysics. 19(2):135–147. Oomori, U. 1992. Bioelectromagnetics and its applications (in Japanese). Fuji Techno System Press. Tokyo, Japan. Phirke, P.S., A.B. Kubde and S.P. Umbakar. 1996. e influence of magnetic field on plant growth. Seed Sci. Technol. 24:375–392. Pietruszewski, S. 1999a. Influence of pre-sowing magnetic biostimulation on germination and yield of wheat. Int. Agrophysics. 13:241–244. Pietruszewski, S. 1999b. Magnetic treatment of spring wheat seeds (in Polish). Rozprawy Naukowe, Univ. Agric. Press. Lublin, Poland. Pittman, U.J. and D.P. Ormrod. 1971. Biomagnetic response in germinating malting barley. Can. J. Plant Sci. 51:64–65. Podlesny, J., W. Lenartowicz and M. Sowinski. 2003. e effect of pre-sowing treatment of seed by magnetic biostimulation on morphological features and yield of white lupine (in Polish). Appl. Prob. Post Agric. Sci. 495:399–406. Prokop, M., S. Pietruszewski and V. Kornarzynski. 2002. Preliminary investigation of magnetic and electric field influences on germination, crops, and mechanical features of radish and skall radish roots (in Polish). Acta Agrophysica. 62:83–93. Reina, F.G., L.A. Pascua and I.A. Fundora. 2001. Influence of a stationary magnetic field on water relations in lettuce seeds. Part II: Experimental results. Bioelectromagnetics. 22:596–602. Rochalska, M. 2002. Magnetic field as a method of seeds vigour estimation (in Polish). Acta Agrophysica. 62:103–111. Sahebjamei, H., P. Abdolmaleki and F. Ghanati. 2007. Effects of magnetic field on the antioxidant enzyme activities of suspension-cultured tobacco cells. Bioelectromagnetics. 28:42–47. Sharma, V.P., H.P. Singh, D.R. Batish and R.K. Kohli. 2010. Cell phone radiations affect early growth of Vigna radiata (mung bean) through biochemical alterations. Z. Naturforsch. 65c:66–72.
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Singh, H.P., V.P. Sharma, D.R. Batish and R.K. Kohli. 2011. Cell phone electromagnetic field radiations affect rhizogenesis through impairment of biochemical processes. Environ. Monit. Assess., DOI10.1007/s10661-001-2080-0. Xiyao, B., M. Ancheng, M. Jingrun, L. Xiaoling, Y. Li and W. Qingzhao. 1988. Physiological and biochemical experiments in electrostatic treated seeds. Proc. Int. Conf. Modern Electrostatics, October 21–25. Beijing, China.
