VOL. 11, NO. 23, DECEMBER 2016 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences © 2006-2016 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com 13740 THE EFFECTS OF STATIC ELECTRIC FIELD ON GERMINATION AND GROWTH OF MUNGBEAN SEEDS (Vigna radiata L.) IN VEGETATIVE PHASE Siti N. Khotimah 1 , Dzikri R. Romadhon 2 and Sparisoma Viridi 1 1 Nuclear Physics and Biophysics Research Division, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Indonesia 2 Master Programs in Physics Teaching, Institut Teknologi Bandung, Indonesia E-Mail: nurul@fi.itb.ac.id ABSTRACT The food made of mungbean seeds (Vigna radiata L.) and bean sprouts can be found everyday in many Asian countries. This study discusses the germination and growth of mungbean seeds at early stage and the influence of static electric field to them. The germination percentage of mungbean seeds increased almost linearly in the first 8 hours and reached its maximum value at about 30 hours. This germination percentage had a germination rate about 0.12/h from the percentage of the number of seeds that have not germinated. This study used some variations of relatively low static electric field and short exposing time on wet seeds to investigate their influences in germination percentage. The field of 2.4 kV/m with exposing time of 2.5 hours appeared to increase the germination percentage in comparison to control so that its effect on early growth of mungbean seeds in vegetative phase was studied. The experimental results indicate that the bean sprouts grown from the treated seeds had heavier in fresh weight, longer roots, stems and leaves in comparison to the control. Keywords: static electric field, mungbean seeds, germination, vegetative phase. INTRODUCTION When the seeds and seedlings were exposed to an electromagnetic field, they may respond differently to the process of germination and growth. Many studies have examined the effects of magnetic fields and electric fields separately. It has been reported that the exposures of magnetic fields on a wide variety of seeds (mungbean, maize, pea, tomato, chickpea) increased the germination or early growth [1-5]. The exposures of AC electric field on tomato seeds also accelerated the germination [4]. It was reported that the germination of the preliminary soaked seeds increased by about 10 % compared to the non- soaked seeds [6]. Besides the exposure on seeds, it was also studied when the seedlings were exposed to electromagnetic fields. The exposures of high static electric field (25 kV/m) continuously for 5 days on mungbean seedlings increased the growth [7]. In more recent study, Sedighi et al (2013) reported that there was an optimum value of the electric field intensity and exposing time for the growth of corns so that the rate of growth decreased after passing this value [8]. In many tropical countries, mungbean is one of the food sources of high vegetable protein in daily life. Mungbean seeds are cooked to be used as bread sandwich and porridge. Bean sprouts are consumed for other foodstuffs. In order to study the process of germination and growth, seeds of mungbean are exposed to static electric fields. In this study, wet mungbean seeds were exposed to low static electric fields up to 2.5 hours, the germination percentage and the fresh weights in vegetative phase were measured to be compared to control. EXPERIMENTAL METHODS Dry seeds of Vigna radiata were initially soaked in tap water for two hours. Then, the seeds were drained and placed between two plastic so that they were distributed in one layer. Seeds were then sandwiched between two parallel metal plates with diameter of 15 cm and the distance between the plates is 0.5 cm. The static electric field is generated between the plates by connecting the plates to the DC power supply [9]. The electric field is the ratio of the difference voltage between the plates, which was measured using a voltmeter, and the distance between the plates. Then the seeds were put on a glass dish containing a little water so that the seeds in wet conditions with partly seeds soaked in water. The water was renewed every 12 hours. Seeds having radicules more than 2 mm are said to be germinated. The germinated seeds were counted every 2 hours for the first 34 hours. The germination percentage was calculated for control and treated seeds [10]. To investigate the effects of electric field and exposing time on germination percentage, static electric fields of 0 (control), 0.8, 1.2, 1.6, 2.0, and 2.4 kV/m were used with exposing time of 0.5, 1.0, 1.5, 2.0 and 2.5 hours. To study further the effects on the growth in vegetative phase, a combination of static electric field and exposing time which gave a maximum positive effect than control was then used. For the growth in vegetative phase, the seedlings were rinsed every 4 hours and kept in a dark- damp place to grow to be bean sprouts. The fresh-weight of the bean sprout and the length of roots, stems, and leaves were measured at 110 hours or 108 hours after soaking in tap water.