Aspasia Efthimiadou1, Nikolaos Katsenios2, Anestis Karkanis3, Panayiota Papastylianou2, Vassilios Triantafyllidis4, Ilias Travlos2, Dimitrios J Bilalis2. 1. Open University of Cyprus, P.O. Box 24801, 1304 Nicosia, Cyprus. 2. Laboratory of Crop Production, Agricultural University of Athens, Iera Odos 75, 11855 Athens, Greece. 3. Department of Agriculture Crop Production and Rural Environment, University of Thessaly, Fytokou Street, N. Ionia, 38466 Magnisia, Greece. 4. Department of Business Administration of Food and Agricultural Enterprises, University of Patras, Seferi Street 2, 30100 Agrinio, Greece.
Abstract
The use of magnetic field as a presowing treatment has been adopted by researchers as a new environmental friendly technique. The aim of this study was to determine the effect of magnetic field exposure on tomato seeds covering a range of parameters such as transplanting percentage, plant height, shoot diameter, number of leaves per plant, fresh weight, dry weight, number of flowers, yield, and lycopene content. Pulsed electromagnetic field was used for 0, 5, 10, and 15 minutes as a presowing treatment of tomato seeds in a field experiment for two years. Papimi device (amplitude on the order of 12.5 mT) has been used. The use of pulsed electromagnetic field as a presowing treatment was found to enhance plant growth in tomato plants at certain duration of exposure. Magnetic field treatments and especially the exposure of 10 and 15 minutes gave the best results in all measurements, except plant height and lycopene content. Yield per plant was higher in magnetic field treatments, compared to control. MF-15 treatment yield was 80.93% higher than control treatment. Lycopene content was higher in magnetic field treatments, although values showed no statistically significant differences.
The use of magnetic field as a presowing treatment has been adopted by researchers as a new environmental friendly technique. The aim of this study was to determine the effect of magnetic field exposure on tomato seeds coverinpan>g a range of parameters such as transplantinpan>g percentage, plant height, shoot diameter, number of leaves per plant, fresh weight, dry weight, number of flowers, yield, and lycopene content. Pulsed electromagnetic field was used for 0, 5, 10, and 15 minutes as a presowing treatment of tomato seeds in a field experiment for two years. Papimi device (amplitude on the order of 12.5 mT) has been used. The use of pulsed electromagnetic field as a presowing treatment was found to enhance plant growth in tomato plants at certain duration of exposure. Magnetic field treatments and especially the exposure of 10 and 15 minutes gave the best results in all measurements, except plant height and lycopene content. Yield per plant was higher in magnetic field treatments, compared to control. MF-15 treatment yield was 80.93% higher than control treatment. Lycopene content was higher in magnetic field treatments, although values showed no statistically significant differences.
Magnetic and electromagnetic treatments are being used in agriculture, as a noninvasive technique, to improve the germination of seeds and increase crops and yields [1]. Researchers consider that the prospect of using cheap magnetic energy to improve the properties of soil and plant growth and development may be of great practical importance [2]. Magnetic field has been found to improve food reserve utilization and help for better absorption and assimilation of nutrients by plants [3] and photosynthetic activities [4].The choice of the investigated plants is based mainly on the importance they have. It has been found that the percent germination rates of the treated tomato seeds were accelerated about 1.1 to 2.8 times compared with that of the untreated seed, while an inpan>hibitory effect onpan> germinpan>ationpan> was shown inpan> the case of the electric field more than 12 kV/cm and the exposure time more than 60 seconpan>ds [5]. Recently, it has been reported that treated tomato seeds with magnetic field by 100 gauss for 15 minutes with magnetically treated irrigated water improved vegetative growth, increased total phosphorus content of tomato leaves and total yield, and reduced pH value in soil extraction [6]. In the vegetative stage, the treatments led to a significant increase in leaf area, leaf dry weight, and specific leaf area per plant. Also, the leaf, stem, and root relative growth rates of plants derived from magnetically treated seeds were greater than those shown by the control plants. In the generative stage, leaf area per plant and relative growth rates of fruits from plants from magnetically exposed seeds were greater than those of the control plant fruits [7]. Our study examines the enhancement of magnetic field in agronomic characteristics for two years and explains how it leads to higher yield. Moreover, it uses a different type of magnetic field, to confirm the positive effect on tomato plants.Magnetic field dose (strength and exposure duration) has been found to have strong effect on plant properties. In a recent research on garden pea seeds, of the various combinpan>ationpan>s of field strengths and exposure time, 60 mT and 180 mT for 5 minpan> treatments yielded the better results [8]. Moreover, radish seeds were exposed to full wave rectified sinusoidal MF of different magnetic field doses and, among various combinations, 80 mT for the 5–10 min and 110 mT for the 2.5 min exposure yielded superior results [9].Krylov and Tarakanova [10] reported that the seeds of corn and wheat with their embryonic roots oriented towards the south magnetic pole sprouted earlier than the seeds facing towards north magnetic pole. Another important enhancement of magnetic field is the improved root length, a characteristic that suggests that magnetically treated seeds can be used in practical agriculture where better root growth will enable extraction of moisture from deeper soil layers [11]. The new approach of several researchers is to provide more complete investigation of the effects of magnetic field in plants. Even more studies are directed to investigate quality characteristics, plant physiology measurements, enzyme activity, and yield production [12]. Researchers are investigating more widely the positive effects of magnetic fields spreading their findings to plant pathology. In plants derived from seeds exposed to magnetic fields, a significant delay in the appearance of first symptoms of geminivirus and early blight and a reduced infection rate of early blight were observed [7]. Pulsed electromagnetic fields showed could replace hormones in vegetative propagation of oregano, stimulating rooting process in stem cuttings [13]. Enhancements of plant characteristics with economic impact on producer's income could be the future of modern, organic, and sustainable agriculture [14]. Furthermore, the adoption of organic cultural system could reduce energy inputs [15].The main aim of agriculture remains the yield, so the encouraging results in such measurements boost the interest of researchers to continue further. Harichand et al. [16] reported that the magnetic field treatment at 10 mT for 40 h boosted up pea height, mass, and crop yield. Lycopene is the red pigment and a major carotenoid in tomato fruit. It is a potent natural antioxidant and the focus of many breeding programs [17].The aim of this study was to determine the effect of magnetic field exposure onn class="Species">tomato seeds, coverinpan>g a complete range of agronpan>omic characteristics such as transplantinpan>g percenpan>tage, plant height, shoot diameter, number of leaves per plant, fresh weight, dry weight, number of flowers, yield, and n class="Chemical">lycopene content, as an environmental friendly method.
2. Materials and Methods
A field experiment was established at the Agricultural University of Athens (Greece), in summer 2011 and summer 2012. A n class="Species">tomato (Solanumly copersicum) hybrid (NOXANA) was used. The durationpan> of exposure to magnetic field was 0, 5, 10, and 15 minpan>utes.
n class="Species">Tomato seeds were treated by Papimi electromagnetic field genpan>erator for 5, 10, or 15 minpan>utes before plantinpan>g. Seeds that were not treated have beenpan> used as conpan>trol. Papimi device is a pulsed EMF genpan>erator (Figure 4). (Papimi model 600, Pulse Dynpan>amics, Athenpan>s, Greece. Manufacturer characteristics: 35–80 J/pulse enpan>ergy, 1 × 10−6 s wave durationpan>, 35–80 × 106 W wave power, amplitude onpan> the order of 12.5 mT, rise time 0.1 ms, fall time 10 ms, and repetitive frequenpan>cy of 3 Hz.) The same device has beenpan> used inpan> agricultural studies [13].
Figure 4
PAPIMI device and external loop.
The tomato seedlinpan>gs have been transplanted to their finpan>al positionpan> inpan> the field after beinpan>g germinpan>ated inpan> pots filled with peat as substrate, 15 days after sowinpan>g. Fifteen days after transplantinpan>g, the measurement of successfully transplanted tomatoes has been conducted. Destructive measurements took place 100 days after transplanting (DAT). Plants were watered every day during the morning. Shoot fresh weight was measured by a precision balance and then the samples were oven-dried at 70°C for three days in order to measure the dry weight in grams per plant. Lycopene content has been measured using high performance liquid chromatography (HPLC) method as described by Hyman et al. [17].The experiment followed a completely randomized design, with 4 main treatments (control, MF-5, MF-10, and n class="Disease">MF-15) and 4 replicationpan>s for each treatmenpan>t. Every treatmenpan>t was composed of 20 plants. The mainpan> factors for the statistical analysis were three (treatmenpan>t, year, and replicationpan>). The experimenpan>tal data were analyzed usinpan>g the software Statistica [18], accordinpan>g to the completely randomized design. Values were compared by onpan>e-way analysis of variance (ANOVA) and mean differenpan>ces were determinpan>ed usinpan>g the least significant differenpan>ce (LSD) test, at the 5% level of significance.
3. Results
The use of pulsed electromagnetic field as a presowing treatment was found to enhance tomato plants inpan> certainpan> durationpan> of exposure. The exposure of 10 and 15 minpan>utes gave the best results inpan> all measurements, except plant height and the number of leaves. The analysis of variance (ANOVA) showed that year was a nonpan>significant factor, time was a significant factor, and there was no inpan>teractionpan> between year and time of exposure (Table 1). In many measurements, the exposure of 5 minpan>utes had a negative effect onpan> tomato plant, where values were similar to or lower than the control. The highest response was reached at 15 min, the longest exposure tested. This means that a longer duration may give better results, a probability that must be further investigated.Pulsed electromagnetic field exposure of 10 and 15 minutes improved the percentage of successfully transplanted tomato plants (Figure 1). The highest percentage of successfully transplanted tomato plants has been recorded at MF-10 treatment (98.41), followed by MF-15 treatment (98.0). Both treatments gave values with statistically significant differences compared to MF-5 and control. In this measurement control (94.01) was statistically significant and higher than the treatment of MF-5 (80.70), for significant level of 0.05.
Figure 1
Pulsed electromagnetic field effect on percentage of successful transplanted seedlings. Seeds have been exposed for 0, 5, 10, and 15 minutes in magnetic field. Means followed by the same letter for treatments are not significantly different according to the LSD 5% test. Control: untreated seeds; MF-5, MF-10, and MF-15: seeds treated with pulsed electromagnetic field for 5 min, 10 min, and 15 min, respectively.
Plant growth characteristics gave statistically significant differences in all measurements (Table 2, Figures 2 and 5). The highest values in plant height were measured in control treatment (144.4) with statistically significant differences, followed by n class="Disease">MF-15 (138.1) treatmenpan>t. n class="Disease">MF-15 value was higher with statistically significant differences from MF-10 (132.4). MF-5 treatment (104.8) gave the lowest values with statistically significant differences.
Table 2
Mean values of main plant characteristics and quality measurements.
Plant height (cm)
Shoot diameter (mm)
Number of leaves per plant
Fresh weight (g)
Number of flowers in the second week
Lycopene content (μg/100 g fresh weight)
Control
144.4a
15.5b
34.5d
842.9d
14.6c
6083a
MF-5
104.8d
16.1b
31.6c
834.3c
15.2b
6130a
MF-10
132.4c
16.3ab
47.3b
964.0b
15.0bc
6122a
MF-15
138.1b
17.0a
50.8a
968.7a
16.3a
6214a
Control: untreated seeds; MF-5, M F-10, and MF-15: seeds treated with pulsed electromagnetic field for 5 min, 10 min, and 15 min, respectively.
a,b,c,dMeans followed by the same letter for treatments are not significantly different according to the least significant difference (LSD) test.
Figure 2
Pulsed electromagnetic field effect on dry weight per plant. Seeds have been exposed for 0, 5, 10, and 15 minutes in magnetic field. Means followed by the same letter for treatments are not significantly different according to the LSD 5% test. Control: untreated seeds; MF-5, MF-10, and MF-15: seeds treated with pulsed electromagnetic field for 5 min, 10 min, and 15 min, respectively.
Figure 5
Showing the comparative effect of pulsed electromagnetic field treatment on the main agronomic plant characteristics. Control: untreated seeds; MF-5, MF-10, and MF-15: seeds treated with pulsed electromagnetic field for 5 min, 10 min, and 15 min, respectively.
Shoot diameter showed statistically significant differences among treatments. The highest values of shoot diameter were measured inn class="Disease">MF-15 treatmenpan>t (17.0) where the value was statistically significant and higher than conpan>trol (15.5) and MF-5 (16.1) treatmenpan>t, inpan> both years. MF-10 treatmenpan>t gave the lowest values with statistically significant differenpan>ces, onpan>ly with n class="Disease">MF-15 treatment.
Number of leaves per plant was statistically significant and higher for n class="Disease">MF-15 (50.8), compared to all other treatmenpan>ts. MF-10 treatmenpan>t (47.3) gave higher values with statistically significant differenpan>ces from MF-5 (31.6) and conpan>trol (34.5). MF-5 gave the lowest values with statistically significant differenpan>ces.
Fresh weight was significantly higher for n class="Disease">MF-15 (968.7), compared to all other treatmenpan>ts. MF-10 treatmenpan>t (964.0) gave higher values with statistically significant differenpan>ces from MF-5 (834.3) and conpan>trol (842.9). MF-5 gave the lowest values with statistically significant differenpan>ces. Dry weight (g) was founpan>d higher inpan> MF-10 (254.7) and n class="Disease">MF-15 (254.3) treatments with statistically significant differences, compared to MF-5 (224.7) and control (224.8).
The number of flowers per plant in the second week was found higher inn class="Disease">MF-15 treatmenpan>t (16.3) with statistically significant differenpan>ces. The differenpan>ces betweenpan> the other two magnetic field treatmenpan>ts (MF-10, MF-5) were not statistically significant. Conpan>trol (14.6) treatmenpan>t had no statistically significant differenpan>ces compared with MF-10 treatmenpan>t.
The presowing application of magnetic field had positive effects on yield parameters (Figure 3). In yield per plant measurement, MF-15 treatment (2448.8) gave the highest value, followed by MF-10 (2082.6), MF-5 (1845.6), and conpan>trol (1353.5). All differences between treatments were statistically significant. Lycopene content measurements showed no statistically significant differences between treatments, although magnetic field treatments gave higher values than control. Plants derived from seeds treated for 15 minutes with magnetic field gave the highest value of lycopene content.
Figure 3
Pulsed electromagnetic field effect on yield per plant. Seeds have been exposed for 0, 5, 10, and 15 minutes in magnetic field. Means followed by the same letter for treatments are not significantly different according to the LSD 5% test. Control: untreated seeds; MF-5, MF-10, and MF-15: seeds treated with pulsed electromagnetic field for 5 min, 10 min, and 15 min, respectively.
4. Discussion
The results obtained in this experiment showed a positive impact of pulsed electromagnetic field, in certain time of exposure and inn class="Species">tomato cultivationpan>. Magnetic field has been found to enhance the success inpan> transplantinpan>g, the plant growth, and the finpan>al yield. There are also inpan>dicationpan>s that magnetic field could improve quality characteristics such as n class="Chemical">lycopene content.
Moon and Chung [5] found that the percent germination rates of the tomato seed treated with AC electric and magnetic fields were accelerated about 1.1–2.8 times compared with that of the untreated seeds. Presowinpan>g treatment with magnetic field inpan> wheat seeds resulted in higher yields and gluten content [19]. In our measurements, the treatment of MF-5 gave lower percentage of successful transplanting compared to control, while MF-10 and MF-15 gave higher percentage. Inhibition of magnetic field has been found in garden pea mean emergence time, where electromagnetically treated seeds showed negative response as compared to untreated seeds [8].Bondarenko et al. [20] used a device for magnetic field treatment in field experiments in Russia and found that in vegetable seeds the germination percentage was higher and the plant growth in early stages was higher too. Magnetic field treatment has been found to improve transpiration rate, photosynthetic rate, stomatal conductance, root growth, shoot growth, and N, P, K, Ca, and n class="Chemical">Mg percentage accumulationpan> inpan> early stages of cottonpan> [21]. The inpan>crease inpan> germinpan>ationpan> when seeds were magnetically treated could be explainpan>ed by better availability and absorptionpan> of nutrients. Pulsed electromagnetic fields have been found to promote germinpan>ationpan> and improve early growth characteristics of cottonpan> seedlinpan>gs [22]. In pea, the inpan>vestigationpan> of optimal magnetic field doses showed that low magnetic field strength for the lonpan>ger time of exposure and high magnetic field strength for shorter durationpan> were found to be the most effective inpan> enhancinpan>g the growth and yield inpan> the pea cultivar [23].
Recently, the productivity of tomato plants usinpan>g magnetic stimulated seeds or irrigationpan> with magnetized water was investigated. The results showed that the stimulated seeds gave better results compared to the control treatments, that is, gave taller and heavier plants. Growth characteristics such as fresh weight were higher in plants grown with magnetic treatments than those grown without magnetic treatment [6]. A very important yield enhancement has been recorded in tomato plants derived from magnetic field treated seeds. The yield in cultivar Monza was 28–51% higher in early stages [24]. In a similar experiment, tomato seeds were exposed to full-wave rectified sinusoidal nonuniform magnetic fields (MFs) induced by an electromagnet at 100 mT (rms) for 10 min and at 170 mT (rms) for 3 min. The leaf, stem, and root relative growth rates of plants derived from magnetically treated seeds were greater than those shown by the control plants. At fruit maturity stage, all magnetic treatments increased significantly the mean fruit weight, the fruit yield per plant, the fruit yield per area, and the equatorial diameter of fruits in comparison with the controls [7]. In pea cultivar it has been found that the magnetic field presowing seed treatment can be used practically to enhance the growth and yield [23].Lycopene conpan>tent values were higher inpan> magnetic field treatments, although without statistically significant differences. Higher time of exposure, for example, 25 minpan>utes, can be used for further evaluationpan>. Lycopene as a carotenoid pigment is a very important quality characteristic for tomatoes. In date palm it has been found that pigments content (chlorophyll a, chlorophyll b, carotenoids, and total pigments) was significantly increased under static magnetic field, while the highest measurements were recorded at 100 mT, after 360 min of exposure [25]. Chlorophyll a and carotenoids were more affected than chlorophyll b in date palm seedlings.
5. Conclusion
These results indicate that the application of magnetic field inn class="Species">tomato seeds can be an ecofrienpan>dly practice that improves plant characteristics inpan> all stages, from germinpan>ationpan> to finpan>al yields. Magnetic field treatmenpan>t, inpan> certainpan> times of exposure, improved shoot diameter, number of leaves per plant, fresh and dry weight, number of flowers, and yield per plant. These studies provide a holistic approach of an agricultural cultivationpan> that can lead to the comprehenpan>sionpan> of the exact mechanism of magnetic field effect onpan> plant tissues and lead to the appropriate applicationpan> of the magnetic fields. The determinpan>ationpan> of the optimal durationpan> of exposure, the type of magnetic field used, and the effect of magnetic field onpan> quality characteristics are some major factors that deserve further inpan>vestigationpan>.
(a)
Percentage of successfully transplanted tomatoes (%)
Plant height (cm)
Shoot diameter (mm)
Number of leaves per plant
Fresh weight (g)
Year
1.31ns
0.008ns
8.90ns
10.02ns
10.91ns
Time
365.22∗∗∗
1869.73∗∗∗
2.49ns
693.80∗∗∗
1899.14∗∗∗
Year ∗ time
0.90ns
0.04ns
2.87ns
0.50ns
0.50ns
(b)
Dry weight (g)
Number of flowers in the second week
Yield (g per plant)
Lycopene content (μg/100 g fresh weight)
Year
0.03ns
11.79ns
6.20ns
0.34ns
Time
133.17∗∗∗
6.33∗∗∗
3924.19∗∗∗
0.34ns
Year ∗ time
0.22ns
0.43ns
0.84ns
0.10ns
Significance at 0.05, 0.01, and 0.001; ns: not significant.
Authors: Sonja Michèle Schmidtpott; Saliba Danho; Vijay Kumar; Thorsten Seidel; Wolfgang Schöllhorn; Karl-Josef Dietz Journal: Int J Environ Res Public Health Date: 2022-04-23 Impact factor: 4.614
Authors: M Graça Dias; Grethe Iren A Borge; Kristina Kljak; Anamarija I Mandić; Paula Mapelli-Brahm; Begoña Olmedilla-Alonso; Adela M Pintea; Francisco Ravasco; Vesna Tumbas Šaponjac; Jolanta Sereikaitė; Liliana Vargas-Murga; Jelena J Vulić; Antonio J Meléndez-Martínez Journal: Foods Date: 2021-04-21
Figure 4
Figure 1
Figure 2
Figure 5
Figure 3