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Study of effects of electromagnetic fields on seeds germination, seedlings ontogeny, changes in protein content and catalase enzyme in Valeriana Officinalis L.

Introduction

Electromagnetic fields (EMFs) affect biological systems as the kind of abiotic stress. The development of modern technologies has applied EMFs widely because of their positive or negative effects on living systems including plants [16,22]. EMFs increase percentage of germination in Cucumis sativus L. seeds [27] however they decrease speed of germination in Vicia sativa L. [16], stimulate plantlets development and increase fresh weight, growth [1], and chlorophyll a, b and total chlorophyll amount [3], change antioxidant enzyme such as superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, catalase and glutathione reductase []13,24] and anti tensional proteins activity [23]. Electromagnetic fields elongate G1 in the various plants species and G1 and G2 in lentil and flax, inhibit primary root growth in the early stages of germination and decrease proliferation of root meristem cells compare to control [8]. Weak magnetic fields decrease genome activity before proliferation [6], change plant ontogeny [12], configuration of epicotyl of Triticum aestivum L. and Pisum sativum L. and mutation in Arabidopsis thaliana L. and Crepis capillaries L. [21]. EMFs decrease the number of the grains in the spike and the spike weight [11], chromosomal aberrations including fragments, bridge and lagging chromosomes in the pollen mother cells of wheat [28]. High electromagnetic field causes increasing the amount of plastoglobules and changes the structure and export products of Golgi apparatus [23] and configuration and size of hypodermal cells [4]. EMFs affect rhizogenesis through impairment of biochemical process [24], delay the senescence process [18], change protein synthesis such as Calmodulin-[N.sub.6], cmbp and pin [22], increase the mitotic index and mitotic abnormalities in root meristematic cells [22], enhance lipid peroxidation and hydrogen peroxide content [25], enhance seedlings survival and increase crop capacity [4], and heat-shock response [19] and maintain cell membrane integrity [10].

Valeriana officinalis L. is a highly variable species of the Valerian family (Valerianaceae) that has a lot of medicinal properties. The roots and rhizomes of Valerian extract are traditionally used to treat sedative, anxiety, epilepsy, insomnia, hysteria, fatigue and menstrual cramps [5]. In this research, we have investigated the effects of electromagnetic fields on seeds germination, seedlings ontogeny, protein content changes and catalase activity in V. officinalis L. Considering the fact that this plant is very useful in medicinal purposes and Valerian seeds have low germination ability, the goal of this study was to determine that how electromagnetic fields with low intensities affect the germination and growth of Valerian and determine a relationship between low frequency electromagnetic fields and catalase activity.

Material and Methods

Seeds preparation and treatment:

V. officicnalis L. seeds var. Hungary were supplied by Pakan bazr institute, which guarantees high seeds quality and homogeneity. The healthy uniform seeds were selected and divided into wet and dry seeds groups. In the case of wet treatment, the seeds were soaked in distilled water for 30 minutes. Then wet and dry seeds were separately sterilized. They were washed with dish washing liquid for 5 to 6 min, then were transferred to laminar air flow, they were sterilized in benomyl solution (0/2 g in 50 ml) for 10 min and merck ethanol for 30 s. After each level, seeds were rinsed with distilled water and placed on solid MS (Murashig and Skoog, 1962) basal medium containing 3 % sucrose and 0/7 % agar. Petri dishes containing wet and dry seeds were separately divided into three groups: control, 1mT and 2mT treatments. Three replicates were used in the experiment with 12 seeds in each one. Treatment groups were separately exposed to 1mT and 2mTduring 3 days for 30 min in each day. Control seeds were kept under similar condition but without any EMFs intensity. To generate EMFs, a handmade cylindrical-shaped coil was used that had made of a polyethylene tube with 12 cm diameter and 50cm length. The coil was connected to a 220V AC power supply (ED-345BM, China), teslameter (516 62, LEYBOLD, Germany) and ampermeter to generate electrical current of 60 HZ and showing electromagnetic field strengths and current intensities, respectively. EMF intensities were measured by a B-probe type of Hall Sound. Petri dishes containing seeds were placed in the middle part of coil and then treated by 1 and 2 mT electromagnetic field strengths. Then they were maintained in incubator under a photoperiod of 16h day/8h dark at 23[degrees]C and 4000 lux. Speed and percentage of germination of Valerian seeds were determined from 3th to 11th day after treatment. Root length, number of lateral roots, petiole length, fresh and dry weight and leaf area were considered on 40th day. After 2 months, seedlings were transferred to pots containing peat and perlite and kept in green house under a photoperiod of 16h day/ 8h dark at 23[degrees] C and 4000 lux. After a month, aerial parts was harvested for protein content and catalase activity assays.

Preparing of protein extraction:

Fresh leaf of each treated and control samples (0.15 mg) was ground in 5 ml of 100 M phosphate buffer (pH 7) under ice-cold condition and then was centrifuged at 12000 rpm at 4[degrees]C for 45 min, separately. The supernatant was used for assaying of protein content and catalase activity.

Protein content assay:

The protein content of the supernatant was determined by Bradford's method with bovine serum albumin (BSA) as reference standard. 90 [micro]l phosphate buffer and 5 ml Bradford's reagent was added to 10 [micro]l protein extraction and after 5 min, the absorbance was measured at 595 nm. The protein concentration was expressed as mg [ml.sup.-1].

Catalase assay (CAT, EC 1.11.1.6):

Reaction mixture (3 ml) contained 50mM potassium phosphate buffer (pH 7), 20 mM Hydrogen peroxide and 100 [micro]l enzyme extraction. CAT activity was determined as the rate of disappearance of [H.sub.2][O.sub.2] at 240 nm, according to Pereira (2002). The activity of catalase was expressed as |mol-1min-1mg protein.

Statistical analysis:

The experimental design is completely randomized. All of the experiments were carried out three replicates and all of the data were expressed as the mean [+ or -] SE. Means were compared using the post hoc Tukey's test at P<0/05, level of significance to detect differences between treated and control seedlings by SPSS 16 software.

Results:

Seeds germination:

Electromagnetic fields increased the speed and percentage of seeds germination in Valerian especially in the higher electromagnetic field intensities. The percentage of wet treated seeds germination increased compare to dry condition in 3, 5 and 7 day. There was a significant difference between wet control and treated seeds with 2mT at P<0.05. Percentage of seeds germination increased in dry treated seeds with 2mT compare to wet ones but there was no significant difference. The speed of germination of dry treated seeds was more than control but it was completely converse in the wet condition (Table 1).

Petiole length and leaf area:

Electromagnetic fields increased the petiole length and the leaf area of Valerian seedlings. The dry treated seeds with 2mT had longer petiole length compare to control and the group of wet treated samples but the wet treated seeds with 1mT had longer petiole length compare to the other wet ones. There was a significant difference between them, the other treatments and controls. The leaf area of dry treated seeds with 2mT significantly increased compare to wet ones, control and the other treated samples. There was an increase in leaf area of wet seeds but it was not significant (Table 2).

Root length and number of lateral roots:

The results showed an increase in the root length for most of electromagnetic fields treatment. Wet treated seeds had the longest roots compare to dry ones. There was a significant difference between them, control and dry samples. The dry treated seeds with 1mT had the shortest roots compare to the other groups. There was a significant difference between this one and the group of dry treated seeds with 2mT. Electromagnetic fields increased the number of lateral roots in Valerian. The dry treated seeds with 2mT had more number of lateral roots compare to the others. There was a significant difference between them and dry and wet treated seeds with 2mT (Table 2).

Fresh and dry weight:

Electromagnetic fields increased dry and wet weight of Valerian seedlings. The dry treated seeds with 1mT had the freshest weight. The wet control and the wet treated seeds with 1mT had the shortest roots compare to the others. There was a significant difference between this one, wet treated seeds with 1mT and wet control. The highest and the lowest of dry weight were observed in the dry treated seeds with 1mT and the wet treated seeds with 2mT, respectively. There was not any significant difference between them, controls and the other treatment groups (Table 2).

Protein content:

Electromagnetic fields decreased protein content in Valerian. Wet samples and treated seeds with 2mT had more protein content than dry samples and treated seeds with 1mT. Dry control and wet treated seeds with 1mT had the most and the least protein content, respectively (Table 3).

Catalase activity:

Electromagnetic fields increased catalase activity in Valerian. Dry treated seeds had the most catalase activity compare to the other groups and control. Dry treated seeds with 1mT and wet treated seeds with 1mT had the most and the least catalase activity compare to the others (Table 3).

Discussion:

Effect of electromagnetic fields on seeds germination:

According to the results, electromagnetic fields enhanced percentage of seeds germination. The treated Valerian seeds with 2mT increased germination compare to controls and 1mT. Wet condition caused to increase germination percentage compare to dry one, which confirmed the conclusion of other studies in which the germination of Arachis hypogaea L. and tomato seeds Lycopersicum esculentum were increased [2,17]. Florez et al. [7] reported the positive effects of magnetic field treatments on germination rate and growth. Garcia and Arza [9] found that stationary magnetic fields cause an increase in water absorption in lettuce seeds. The electromagnetic fields probably affect germination genes in Valerian and accelerate the speed and percentage of germination. Expression of germination genes was enhanced by increasing the electromagnetic field intensity. Wet condition increases water absorption by cellulose, pectin and starches of the seeds. Water absorption increases gibberellins activity and then induces hydrolytic enzymes. Electromagnetic fields probably accelerate this process especially in the group of treated seeds with 2mT field intensities. In this case, the genes of cellulose, protease and pectinase synthesis can be active and so increase the germination percentage [15].

Effect of electromagnetic fields on seedlings ontogeny:

The results showed that the effect of electromagnetic fields on Valerian growth in terms of root, petiole and number of lateral roots was more than control. Wet condition increased growth and development of roots however dry condition increased growth of leaf and petiole. Vashisth & Nagarajan [26] observed an increase in the total length of Helianthus annuus L. by magnetic field. Electromagnetic fields probably affect the plant growth regulators like auxin and cytokinin and can be effective on the plant growth and development. Electromagnetic fields probably increase auxin rate and are effective on genes activity which produce growth proteins in nucleus and so increase the protein production and lead to growth. Also they can increase the ATPase pumps activity in cell wall and peroxides so they can extend the cell wall integrity and lead to cells growth. They can be effective on genes regulators like cytokinin and increase mitosis divisions in shoot and root meristems [15].

Effect of electromagnetic fields on dry and fresh weight:

Treated seeds had more fresh and dry weight compare to control. Electromagnetic fields probably increase mineral elements absorption, water absorption and enzymes activity so they lead to increase plants biomass. On the other hand, they probably affect mRNA, gene expression and cell division and lead to increase growth, fresh and dry weight. Florez et al. [7] indicated that electromagnetic fields increased enzymes activity and protein contents and led to enhance biomass of plants. Yinan et al. [27] demonstrated that biomass of the Cucumis sativus L. increased by electromagnetic fields. Radhakrishnan & Kumari [20] reported an increase in the fresh and dry weight and mineral accumulation by pulsed magnetic field.

Effect of electromagnetic fields on protein content and catalase activity:

Our results showed that electromagnetic fields decreased protein content and increased catalase activity especially in dry condition. In the early stages of seedlings ontogeny because of higher levels of growth and germination genes activity, electromagnetic fields have more effects on the genes and cause to stop or decrease their activity in the other stages of Valerian ontogeny and lead to decrease protein content in Valerian seedlings. These results agree with the conclusion of other studies. Radhakrishnan & Kumari [20] reported that pulsed magnetic field increased protein content and catalase activity. Electromagnetic fields tension especially in dry condition increased catalase activity. Plants begin to enhance oxidative enzymes activity like catalase against electromagnetic fields tension and free radicales which has protective role against electromagnetic fields and detoxification of [H.sub.2][O.sub.2]. These results agree with Kursevich and Travkin [14] and Atak et al. [3] that found magnetic field treatment increase catalase and peroxidase activity.

Higher levels of catalase, peroxidase, and superoxide dismutase and glutathione reductase in MF-treated seedlings cause to delay senescence. Catalase stops [H.sub.2][O.sub.2] accumulation in cells and protects plants against ROS [18].

References

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[2.] Arbabian, S., 1998. Effect of biological-environmental factors on vegetative and generative growth of three varieties of Arachis hypogaea L., PhD thesis, Islamic Azad Univ., Science and Research Branch, Tehran, Iran.

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[27.] Yinan, Y., L. Yuan, Y. Yongqing and L. Chunyan, 2005. Effect of seed pretreatment by magnetic field on the sensitivity of cucumber (Cucumis sativus) seedlings to ultraviolet-B radiation. Environmental and Experimental Botany, 54: 286-294.

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(1) Sara Farzpourmachiani, (2) Ahmad Majd, (2) Sedigheh Arbabian, (3) Davoud Dorranian, (4) Mehrdad Hashemi

(1) Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran.

(2) Department of Biology, Faculty of Biological Sciences, North-Tehran Branch, Islamic Azad University, Tehran, Iran.

(3) Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Iran. "Department of genetics, Tehran medical Branch, Islamic Azad University, Tehran, Iran.

(4) Sara Farzpourmachiani, Ahmad Majd, Sedigheh Arbabian, Davoud Dorranian, Mehrdad Hashemi; Study of effects of electromagnetic fields on seeds germination, seedlings ontogeny, changes in protein content and catalase enzyme in Valeriana officinalis L.

Corresponding Author

Sara Farzpourmachiani, Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran.

Tel.: +9888893199; fax: +9888893199.

E-mail: sfarzpourmachiani@yahoo.com
Table 1: The effect of low frequency electromagnetic fields on
seeds germination in V. officinalis L.

condition     EMF            3th day                 5th day
            intensity
              (mT)

wet            0       4.32 [+ or -] 0.96b    17.59 [+ or -] 4.03 b
               1       3.7 [+ or -] 0.63 b    19.44 [+ or -] 2.78 b
               2          0 [+ or -] 0 a      16.98 [+ or -] 1.65 ab
dry            0       1.25 [+ or -] 0.33 a     5.55 [+ or -] 0 a
               1       0.92 [+ or -] 0.03 a   11.11 [+ or -] 1.5 ab
               2       0.81 [+ or -] 0.36 a   19.44 [+ or -] 2.78 b

condition          7th day                  9th day

wet         21.28 [+ or -] 3.7 ab    23.14 [+ or -] 4.03 a
             24.2 [+ or -] 2.64 b    24.99 [+ or -] 4.81 a
            16.98 [+ or -] 1.65 ab   34.12 [+ or -] 4.54 a
dry          5.55 [+ or -] 1.32 a      8.33 [+ or -] 0 a
            16.66 [+ or -] 4.16 ab   25.75 [+ or -] 5.81 a
            27.77 [+ or -] 5.55 b    33.33 [+ or -] 9.62 a

Data are the means  [+ or -]  SE (n=10). Different letters in the
column indicate significant difference at P<0.05 level applying post
hoc Tukey's test.

Table 2: The effect of low frequency electromagnetic fields on
seedlings growth, fresh and dry weight in Valeriana officinalis L.

Condition    EMF        Petiole length               Leaf
           intensity         (cm)                 area (cm2)
             (mT)

Wet           0        0.29 [+ or -] 0.1    40.14 [+ or -] 12.21 **
              1       0.53 [+ or -] 0.04    54.67 [+ or -] 21.05 **
              2       0.36 [+ or -] 0.06    53.86 [+ or -] 7.38 **
Dry           0       0.14 [+ or -] 0.02    59.88 [+ or -] 8.14 **
              1       0.46 [+ or -] 0.11    52.8 [+ or -] 10.29 **
              2        0.86 [+ or -] 0.1    179.09 [+ or -] 25.5 **

Condition      Root length               Number of
                   (cm)                lateral roots

Wet         0.81 [+ or -] 0.09     0.53 [+ or -] 0.12 **
           0.99 [+ or -] 0.08 *     0.53 [+ or -] 0.13
           0.98 [+ or -] 0.11 *    0.69 [+ or -] 0.16 *
Dry        0.39 [+ or -] 0.09 *   0.05 [+ or -] 0.006 ***
           0.3 [+ or -] 0.16 *      0.88 [+ or -] 0.01
            0.74 [+ or -] 0.17    1.88 [+ or -] 0.11 ***

Condition       Fresh weight              Dry weight
                    (gr)                     (gr)

Wet        0.008 [+ or -] 0.003 *   0.0007 [+ or -] 0.0002
             0.01 [+ or -] 0 *      0.0023 [+ or -] 0.0003
            0.019 [+ or -] 0.002    0.0015 [+ or -] 0.0008
Dry         0.034 [+ or -] 0.013    0.0023 [+ or -] 0.0003
            0.05 [+ or -] 0.01 *    0.0056 [+ or -] 0.0016
            0.031 [+ or -] 0.004    0.0046 [+ or -] 0.0012

Means  [+ or -]  Standard Error.

* Significant differences: P<0.05

** Significant differences: P<0.01

*** Significant differences: P<0.001

Table 3: The effect of electromagnetic fields on
protein content and catalase activity in
Valeriana officinalis L.

Protein conetent          Catalase activity
(mg[ml.sup.-1])          ([mu]mo [min.sup.1]
                         [mg.sup.1] protein)

1.32 [+ or -] 0.014 *   0.016 [+ or -] 0.006 *
0.99 [+ or -] 0.04 *    0.02 [+ or -] 0.008 *
1.05 [+ or -] 0.024 *    0.2 [+ or -] 0.011 *
1.35 [+ or -] 0.008 *    0.3 [+ or -] 0.05 *
0.82 [+ or -] 0.026 *    0.35 [+ or -] 0.07 *
0.94 [+ or -] 0.02 *     0.22 [+ or -] 0.08 *

Data are presented as the means [+ or -] SE with n = 10.
Bars with different letters are significantly different at
P [less than or equal to] 0.05, according to post hoc
Tukey's test.
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Title Annotation:Original Article
Author:Farzpourmachiani, Sara; Majd, Ahmad; Arbabian, Sedigheh; Dorranian, Davoud; Hashemi, Mehrdad
Publication:Advances in Environmental Biology
Article Type:Report
Date:Sep 1, 2013
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