The Effect on the Germination Vigour of Cucumber Seeds after Receiving Magnetic Field Treatment Pre-Sowing

Abstract

In the experiment, the impact of magnetisation on cucumber seeds is examined with the use of Bitter magnets with a constant magnetic field. The magnetisation process is performed in three magnetic fields: low—200 mT, medium—1 T, and high—9 T for 15 and 60 min. After germination, the biometric parameters are determined. The results of this research show that cucumber after pre-treatment in a magnetic field of 1 T for 60 min has a similar germination capacity and root length as the control sample. However, cucumber seeds magnetised in a 1 T field for 60 min have a significantly higher dry weight than the control sample (5.50 ± 0.32 mg vs. 3.01 ± 0.18 mg). The magnetisation in 9 T for both 15 and 60 min shows that these samples have a significantly lower germination capacity (86.8 ± 4.4% and 81.4 ± 7.3% vs. 91.8 a ± 3.2%) and root length (1.78 ± 0.02 cm and 4.42 ± 0.83 cm vs. 8.21 ± 0.34 cm) compared to the control sample. The cucumber seeds pre-treated at 9 T have a significantly greater dry weight than the control sample. Additionally, our research shows that some magnetic field intensities and magnetisation durations inhibit root growth and limit germination. These results are also important as they indicate which values of magnetic fields should be avoided.

1. Introduction

The world population is constantly increasing, which has caused an increase in world food demand. Therefore, the optimisation of food production, including yield size, is essential. One of the methods of increasing yield in modern, sustainable agriculture is the enhancement of germination rate and the improvement of vigour of seedlings. There are various methods of the pre-treatment of seeds to stimulate germination and seedlings growth, including thermal treatment [1], seed priming [2], seed coating [3], nonthermal plasma treatment [4], laser irradiation [5], or gamma irradiation [6]. One of promising techniques is the exposure of seeds to an electromagnetic field (EMF) or magnetic field (MF). The effect of MF or EMF on biological objects can relate to various phenomena such as the behaviour of magnetic particles, paramagnetic elements, and free radicals, the induction of currents in these objects, the change in the energy of intra-atomic and inter-atomic interactions, and the change in water component behaviour [7]. MFs affect plant photosynthetic function and enzyme activity [8]. Generally, scientific reports indicate positive results of treating seeds with an electromagnetic or magnetic field. Electromagnetic seed treatments can improve germination rate, growth, and plant yield. This effect is caused by the positive impact of the EMF on some biological processes such as the increase in enzymes activity and seed coat membrane integrity [9] or the change in lipid peroxidation [10]. It was proven that the magnetic field treatment of sunflower seeds improves the growth and yield of plants [11]. The positive effect of a stationary and homogeneous magnetic field in the range of 2.23–3.72 mT on the germination time of triticale (X Triticosecale Wittmack) seeds was reported [12]. The increase in germination rate and seedling length was observed after the pre-treatment of radish (Raphanus sativus L.) seeds with the use of a stationary magnetic field (8 mT and 20 mT) [13].

However, some negative effects of electromagnetic seed treatment were also reported in the literature. Khonsari and co-authors [14] used a weak magnetic field for the pre-treatment of Myrtus communis L. seeds and observed a reduction in the number and speed of germination when compared to the control [14]. The negative effects on the germination of P. elongata were caused by the exposure of dry seeds to a magnetic field [15]. The accumulation of reactive oxygen species in broad bean (Vicia faba L.) was also reported [16]. Ibrahim observed the negative effect of a 200 mT magnetic field on cucumber germination and seedlings vigour [17].

The research reports concerning the influence of magnetic fields on seeds concentrated mainly on germination rate. A significantly smaller number of reports focused on the growth of seedlings and yields. There is limited scientific reports describing the influence of magnetic fields on cucumber (Cucumis sativus L.) seeds, their germination, as well as the further growth of plants and yield. The cucumber is one of the most popular vegetables in the world. The global world production of cucumber in the year 2019 was about 87,805 million tonnes. Poland is one of the biggest producers of cucumber in the European Union with almost ten thousand hectares under cucumber cultivation in the year 2019. Only a few studies relating to the pre-sowing magnetic field treatment of cucumber seeds have been reported so far. The MF pre-treatment of cucumber seeds with 0.2 T and 0.45 T increased seed germination rate, seedling emergence rate, above-ground biomass, and leaf area [8]. The positive effect of magnetisation with a certain magnetic intensity on cucumber (Cucumis sativus L. var. Beit Alpha) seeds germination, seedlings biomass, and vigour was reported by Ibrahim [17]. The significant increase in percentage and speed of germination of cucumber seeds exposed to MF strengths from 50 to 250 mT for 1, 2, and 3 h was described by Bhardwaj and co-authors [18].

A static magnetic field is considered as generally safe for biological objects, including humans. A static magnetic field in the range from 0.2 T to 3 T is used in clinical MRI (Magnetic Resonance Imaging) scanners [19]. The exposure of patients to 8 T magnetic fields (infants aged 1 month or less to 4 T) has been approved by the FDA (Food and Drug Administration) [20]. It is very difficult to generate a pure, constant magnetic field, with no electric component or with a small electrical component of well-known intensity. This is possible when using Bitter magnets. The effects of the magnetic pre-treatment of seeds depend on several factors such as the field strength, duration of treatment, and field frequency (in the case of variable field).

The aim of this study was to investigate the effects of magnetic pre-treatment on the germination of cucumber seeds. Seeds were treated with the magnetic field of 200 mT, 1 T, and 9 T for 15 min and 60 min. The magnetic field was produced by a Bitter magnet. A vigour of cucumber seeds germination was evaluated based on the root and shoot length, dry weight of one shoot and one root, vigour index A, and vigour index B.

2. Materials and Methods

2.1. Magnetic Field Treatments

The magnetisation of the cucumber seeds was performed by using Bitter magnets with a constant magnetic field. The magnetic field was measured by using the Hall sensor (Lakeshore). This type of magnet generates a high magnetic field at room temperature. The Bitter magnet is constructed of circular conducting copper plates and insulating spacers put in the helical configuration, and not with coils of wire. This magnet is cooled by using demineralised water and not liquid helium as with superconducting magnets. Currently, Bitter magnets might generate one of the highest continuous magnetic fields on Earth and with high homogeneity in the magnetic field. The magnetisation process was performed in three magnetic fields: low—200 mT, medium—1 T–3 T, and high—9 T–14 T for 15 min and 60 min. The seeds magnetisation process was performed at the temperature of 20 °C and a homogeneous magnetic field. A slow increase in the magnetic field was used during the magnetisation process. This allows the reduction in the size of the eddy currents, which could lead to damage to the seeds structure (eddy currents generate heat). The seeds during magnetisation were put in a special container. This container was made of nonmagnetic materials (Teflon—diameter 25 mm and length 30 mm), which allowed the reduction in the influence of external factors on the grain magnetisation process.

2.2. Evaluation of Cucumber Seed Germination

The research was conducted in the laboratory of the Institute of Agroecology and Plant Production of the Wrocław University of Environmental and Life Sciences in 2022. Seed germination tests were conducted as a factorial experiment arranged in a complete randomised design (CRD) with four replications. Seeds after magnetic field treatment were sown according to the ISTA (International Seed Testing Association) methodology [21]. Glass Petri dishes of 12 cm in diameter were covered with sterile soft filter paper. Then, 100 cucumber seeds of the Spójnia HNO sp. z o.o. cultivar Śremski cv. were placed on the blotting paper. The seeds were not subjected to any additional processes.

After placing the seeds on the blotting paper, they were watered with distilled water and covered with the upper part of the dish. After cotyledons developed, the covers were removed from the dishes. The seeds were watered with distilled water according to the water requirements of the seedlings. Germination was carried out with access to light as recommended by the ISTA methodology. The first count was performed after 4 days and the final count after 8 days. The vigour of seeds and seedlings was also examined according to the ISTA by Perre’s growth test.

Seed germination capacity (GP) was calculated according to the formula:

$$GP=\frac{n}{N}\times 100$$

(1)

where n represents the number of newly germinating seeds, and N is the total number of seeds.

After determining the germination capacity, 30 seedlings were randomly selected for further studies for biometric measurements. The tests were performed for each variant in 4 repetitions.

After germination, biometric measurements were made—seedlings were measured and weighed. The number of germinated seedlings and dead seeds was determined. The length of the sub-leaf and root parts was measured with an accuracy of 1 mm. Then, the fresh weight of the aboveground parts and roots was weighed with an accuracy of 0.01 g on an Axis ATZ 1200 balance. In the fresh plant material, the dry matter content was determined with the dryer-weight method according to PN-A-75101-03:1990.

To comprehensively assess the effect of magnetic field and treatment time, seedling vigour indices A and B were introduced, which consider the number of germinated seeds and measurable seedling parameters. The calculation of the indices is given in

Table 1. Abbreviations and explanations used.

Abbr.	Explanation	Unit
GP	Germination capacity	%
RL	Root length	cm
SL	Shoot length	cm
DMS	Shoot dry weight	mg
DMR	Root dry weight	mg
Vigour A	Vigour Index A= Germination (%) × seedling length (root + shoot)
Vigour B	Vigour Index B = Germination (%) × seedling dry weight (root + shoot)

.

2.3. Statistical Analysis

The obtained results were subjected to analysis of variance and the differences between the means were evaluated by Tukey’s test, with NIRα = 0.05. The percentage number of germinated seeds was subjected to Bliss transformation.

3. Results

The germination process is crucial to the success of a crop, and the yield depends on fast growth and early harvesting. To speed up the germination process, special preparations are made to the field and seed. This research attempted to assess the effect of constant magnetic fields on the germination of cucumber seeds.

3.1. Germination Capacity

On average, for the experimental factors, the values of magnetic field induction (200 mT, 1 T, 9 T) for seeds stimulation did not cause a significant difference in the germination capacity of the seeds, as its average value in the experiment was 88.5 ± 6.1% (

Table 2. Effects of Bitter magnetic field and seed exposure time on germination, selected seedling parameters, and vigour index values A and B (mean values for factors and interaction).

Magnetic Field	Time (Min)	GP (%)	RL (cm)	SL (cm)	DMS (mg)	DMR (mg)	Vigour Index A	Vigour Index B	RL/SL
200 mT	15	85.9 ab ± 4.5	1.72 c ± 0.17	1.96 bc ± 0.41	21.2 ab ± 2.7	2.81 b ± 0.10	3.15 d ± 0.43	20.5 ab ± 1.2	0.90 a ± 0.14
	60	92.1 a ± 1.1	1.95 c ± 0.33	1.65 bc ± 0.10	15.9 c ± 1.1	2.05 b ± 0.40	3.31 d ± 0.38	16.5 bc± 1.3	1.18 a ± 0.17
1 T	15	82.9 b ± 8.9	2.54 c ± 0.31	1.94 bc ± 0.06	24.5 a ± 3.7	2.99 b ± 0.24	3.73 cd ± 0.67	22.7 a ± 3.2	1.30 a ± 0.11
	60	91.7 a ± 6.1	7.68 a ± 0.34	1.82 bc ± 0.17	15.1 c ± 0.0	5.50 a ± 0.32	8.72 b ± 0.73	18.9 abc ± 1.5	4.27 c ± 0.57
9 T	15	86.8 ab ± 4.4	1.78 c ± 0.02	2.15 b ± 0.06	17.0 bc ± 1.6	5.89 a ± 0.32	3.41 d ± 0.21	19.9 abc ± 2.7	0.83 a ± 0.03
	60	81.4 b ± 7.3	4.42 b ± 0.83	1.50 c ± 0.21	14.0 c ± 0.6	4.96 a ± 1.46	4.76 c ± 0.38	15.4 c ± 1.8	2.93 c ± 0.20
Control		91.8 a ± 3.2	8.21 a ± 0.34	4.06 a ± 0.36	15.3 c ± 1.1	3.01 a ± 0.18	11.26 a ± 0.59	16.9 bc ± 1.5	2.03 b ± 0.10
Magnetic Field	200 mT	89.9 ± 4.2	3.96 c ± 3.15	2.56 ± 1.16	17.5 ab ± 3.1	2.62 c ± 0.49	5.91 c ± 3.98	18.0 ab ± 2.2	1.37 a ± 0.52
	1 T	88.8 ± 7.3	6.14 a ± 2.69	2.61 ± 1.10	18.3 a ± 5.0	3.84 b ± 1.25	7.90 a ± 3.32	19.4 a ± 3.2	2.56 c ± 1.36
	9 T	86.7 ± 6.6	4.80 b± 2.80	2.57 ± 1.16	15.4 b ± 1.7	4.62 a ± 1.48	6.48 b ± 3.60	17.4 b ± 2.7	1.93 b ± 0.91
Time	0	91.8 a ± 3.2	8.21 a ± 0.34	4.06 a ± 0.36	15.3 b ± 1.1	3.01 b ± 0.18	11.26 a ± 0.59	16.9 b ± 1.5	2.03 b ± 0.09
	15	85.2 b ± 6.0	2.01 c ± 0.43	2.02 b ± 0.24	20.9 a ± 4.1	3.90 a ± 1.49	3.43 c ± 0.50	21.0 a ± 2.6	1.01 a ± 0.24
	60	88.4 ab ± 7.2	4.68 b ± 2.50	1.65 c ± 0.20	15.0 b ± 1.1	4.17 a ± 1.78	5.60 b ± 2.43	16.9 b ± 2.1	2.80 c ± 1.36
Mean		88.5 ± 6.1	4.97 ± 2.95	2.58 ± 1.11	17.0 ± 3.7	3.69 ± 1.40	6.76 ± 3.64	18.3 ± 2.8	3.5 ± 0.18
Significances
Magnetic Field × Time		*	***	*	**	***	***	*	***
Magnetic Field		NS	***	NS	**	***	***	***	***
Time		*	***	***	***	NS	***	*	***

GP, Germination capacity; RL, Root length; SL, Shoot length; DMS, Shoot dry weight; DMR, Root dry weight; Significance at: *** p  <  0.001, ** p  <  0.01, * p  <  0.05, NS—not significant, means marked with the same letter in columns do not significantly differ.

). The average time of seeds exposure to the magnetic field for 60 min had a similar effect on the value of this parameter as the absence of magnetisation treatment (control). The germination capacity of the seeds was modified by the interaction of magnetic field and magnetisation time. It was shown that, on average, about 92% germination capacity occurred in the combination of 200 mT and 1 T for 60 min and in the control (without magnetisation), while the lowest germination capacity was obtained by stimulating the seeds with the dose of 9 T for 60 min and in the combination of magnetisation with 1 T for 15 min.

It was shown that seed germination capacity was positively correlated with the vigour value A, the length of the aboveground part of seedling 1, and the rootlet, but negatively with the dry weight of the aboveground part (

Table 3. Correlation analysis of the studied features.

Specification	Magnetic Field	Time (Min)	GP (%)	RL (cm)	SL (cm)	DMS (mg)	DMR (mg)	Vigour Index A	Vigour Index B
Magnetic Field	1	0	0.164	−0.252	−0.015	0.073	−0.541 *	−0.174	−0.084
Time (Min)	0	1	−0.115	−0.276	−0.766 *	−0.24	0.302	−0.437 *	−0.178
GP (%)	0.164	−0.115	1	0.371 *	0.333 *	−0.351 *	−0.17	0.472 *	0.007
RL (cm)	−0.252	−0.276	0.371 *	1	0.742 *	−0.521 *	0.008	0.974 *	−0.410 *
SL (cm)	−0.015	−0.766 *	0.333 *	0.742 *	1	−0.268	−0.303	0.854 *	−0.289
DMS (mg)	0.073	−0.24	−0.351 *	−0.521 *	−0.268	1	−0.206	−0.478 *	0.841
DMR (mg)	−0.541 *	0.302	−0.17	0.008	−0.303	−0.206	1	−0.098	0.149
Vigour Index A	−0.174	−0.437 *	0.472 *	0.974 *	0.854 *	−0.478 *	−0.098	1	−0.363 *
Vigour Index B	−0.084	−0.178	0.007	−0.410 *	−0.289	0.841 *	0.149	−0.363 *	1

Significance at: * p  <  0.05.

).

3.2. Root Length

The length of the embryonic rootlet, at factor averages, was significantly dependent on the value of the magnetic field induction used for seeds stimulation (Table 2). The longest rootlets were obtained under the influence of the dose of 1 T and they were significantly longer compared to roots grown from seeds stimulated with the dose of 9 T and nonmagnetised seeds (control) by 21.8% and 35.5%, respectively.

In addition, the exposure time had a significant effect on the length of embryonic roots. Indeed, the longest roots were obtained in the control. Under the influence of magnetic field stimulation for 15 min and 60 min, significantly shorter roots were obtained in comparison with not stimulated seeds, by 75.5% and 43.0%, respectively.

Under the interaction of the studied factors (magnetic field × exposure time), the longest roots were obtained from nonmagnetised seeds. The lowest values were obtained after magnetising the seeds for 15 min, irrespective of the value of magnetic induction, and for 60 min, the lowest value of magnetic induction was obtained (200 mT).

In the experiment, it was shown that the increase in the length of the embryonic rootlet influenced the increase in the values of vigour A and length of the aboveground part of the seedling with a simultaneous decrease in its dry weight and the decrease in the value of vigour B (Table 3).

3.3. Shoot Length

The value of the studied trait was modified by the interaction of the magnetic field dose and exposure time (Table 2). The longest aboveground parts of seedlings were produced from nonmagnetically stimulated seeds (4.6 cm), which were 36% longer than the lowest value (1.5 cm) obtained under magnetic field stimulation at a dose of 9 T for 60 min.

In the experiment, it was proven that increasing the time of seed exposure to the magnetic field causes a decrease in the length of the aboveground part of the seedling. Stimulation of the seeds for 15 min resulted in a 50.5% reduction in the length of the aboveground part of the seedling, while increasing the duration of this treatment to 60 min resulted in a 59.4% reduction. The length of the aboveground part of the seedling was not modified by the value of magnetic induction.

It was recorded that prolonging the time of exposure of seeds to the magnetic field resulted in the decrease in the length of the aboveground part of the seedling, while with the increase in the value of this parameter, the length of the rootlet increased and the value of vigour A increased (Table 3).

3.4. The Root–Shoot Ratio

There was a significant correlation between the interaction of the studied factors (magnetic fields × time) on the proportion of rootlet length and aboveground part of the seedling (Table 2). Regardless of the magnetic field strength, the time of 15 min was less favourable compared to the control, but the application of 60 min of seed exposure in the magnetic fields of 1 T and 9 T was more favourable compared to the control and reached the highest value after the application of 1 T.

The analysis of the averages for the factors showed that the highest value for the RL/SL ratio was shaped by the magnetic field strength of 1 T, and the most favourable time for the tested seeds was 60 min.

3.5. Shoot Dry Weight

On average, for the experimental factors, the most favourable effect on the seedling weight was observed for the magnetic field stimulation at the dose of 1 T, which caused the increase in the dry weight of the seedling, as compared to 200 mT to 200 mT, on average by 4.4% (by 0.8 g), but the difference was not significant (Table 2). Increasing the dose of the magnetic field to 9 T caused a significant decrease in seedling weight by 15.8% (2.9 g) in relation to the dose of 1 T. The obtained value of the analysed feature under the influence of this dose of magnetic field was also lower than in the control by 12% (2.1 g), but this relation was not significant. The significantly highest dry weight of the above-ground part of the seedling was obtained from seeds exposed to a magnetic field for 15 min, while prolongation of the exposure time to 60 min resulted in a significant decrease in the weight of this part of the seedling by 28.2% (5.9 g).

The interaction of the examined factors (magnetic field × exposure time) revealed that the highest seedling aboveground mass could be obtained by magnetising the seeds for 15 min with a magnetic field of 1 T and a 200 mT induction value.

The dry weight of the above-ground part of the seedling was negatively correlated with root length, and with the A index of seedling vigour (Table 3).

3.6. Root Dry Weight

The dry weight of one seedling root was significantly modified by the duration of seed exposure to the magnetic field, as well as the interaction of these experimental factors (Table 2).

Magnetic field stimulation of the seeds caused the increase in the dry mass of the seedling root. On average, the highest dry weight was observed in roots grown from seeds stimulated with the magnetic field at the dose of 9 T, significantly higher than in unstimulated seeds and those treated with the magnetic field at the dose of 1 T, by 43.3% and 16.9%, respectively. It was also shown that the duration of magnetic field treatment had no significant effect on the value of this trait.

With the increase in seed exposure time in the magnetic field, an increase in root dry weight was shown. After magnetic stimulation of the seeds for 60 min, the root dry weight was 38.6% higher compared to the control.

At the interaction of the studied factors (magnetic field × exposure time), the highest value of the analysed trait was obtained under the influence of a magnetic field of 9 T at 15 min (5.89 mg) and 60 min (4.96 mg) and 1 T at 60 min (5.50 mg), and this value was higher compared to the lowest value obtained in the variant of 200 mT and exposure time of 60 min (2.05 mg), respectively, by 65.2%, 58.3%, and 61.4%.

A negative correlation was found between magnetic field strength and root dry weight (Table 3).

3.7. Vigour Index A

The value of the A seedling vigour index significantly depended on the dose of the magnetic field and the time of seed exposure to it, as well as on the interaction of factors (Table 2).

On average, the increase in the dose of the magnetic field from 200 mT to 1 T caused a significant increase in the value of index I of seedling vigour by 25.2%. The increase in the dose of the magnetic field to 9 T caused a decrease in the value of this parameter by 18.0% compared to the dose of 1 T.

The highest value of this parameter was achieved in the combination without magnetisation (11.26), while the magnetic field treatment of seeds caused a significant decrease in its value—smaller at longer exposure time.

In the evaluation of the effect of seed magnetisation on the value of this parameter, the most beneficial should consider the combination of 1 T for 60 min, when a value lower by 22.6% in comparison with the control was obtained, but it was higher by 63.9% in comparison with the combination with the lowest value of this feature (200 mT × 15 min).

There was a positive correlation between the A seedling vigour and germination capacity, length of the rootstock, and aboveground part of the seedling, and a negative correlation with exposure time and dry weight of the aboveground part of the seedling (Table 3).

3.8. Vigour Index B

The analysis of the average of the factors showed that an exposure time of 15 min was 19.5% more favourable compared to the control and an exposure time of 60 min (Table 2). The effect of magnetic field on the value of vigour B was found, indicating the most favourable value of 1 T. The effect of the interaction of the studied factors on the value of vigour B was demonstrated and the highest value of this parameter was obtained in the combination of 1 T magnetic field at 15 min (22.7). At magnetic field doses (200 mT, 1 T, 9 T), the decrease in vigour B value was observed with increasing seed exposure time.

Vigour index B was positively correlated with the dry weight of the aboveground part of the seedlings, but negatively with the length of the rootstock (Table 3).

3.9. Regression

Based on the regression analysis (

Table 4. Regression equation for the parameters studied under the influence of the Bitter magnetic field.

Dependents	Regression Equation (n = 72)	R2	F	p	Se
GP	Y = −0.151 T − 1.5 RL − 0.35 SL − 1.8 DMS − 0.72 DMR + 1.99 Vigour A + 1.62 Vigour B + 82 9	0.994	885.7	***	0.460
RL	Y = 0.08 T − 0.4 GP − 0.25 SL − 0.58 DMS − 0.23 DMR + 1.31 Vigour A + 0.54 Vigour B + 16.0	0.998	3333	***	0.114
SL	Y = −0.38 GP − 2.5 RL + 3.43 Vigour A + 6.11	0.978	519.4	***	0.164
DMS	Y = −0.43 GP − 0.41 DMR + 0.91 Vigour B + 22.2	0.997	3996	***	0.181
DMR	Y = −1.0 GP − 2.4 SL + 2.15 Vigour B + 20.2	0.983	687.5	***	0.161
Vigour A	Y = −0.06 T + 0.31 GP + 0.76 RL + 0.20 SL + 0.45 DMS + 0.18 DMR − 0.41 Vigour B − 15.2	0.999	5753	***	0.107
Vigour B	Y = −0.09 T + 0.52 GP + 0.34 RL + 1.07 DMS + 0.44 DMR − 0.45 Vigour A − 19.4	0.997	2417	***	0.138

Significance at: *** p  <  0.001.

), we can state, among other things, that the increase of 1 min in the exposure time of the seeds in the magnetic field causes an average decrease in germination capacity of 0.15%, an increase in average rootlet length of 0.08 mm, and a decrease in vigour values A and B. On the other hand, the increase in germination capacity by 1% causes a decrease in the above-ground length of the seedling and the radicle, as well as their dry weight, while it will cause increases in indices A and B.

4. Discussion

Previous studies have shown positive effects of magnetic and electromagnetic fields on germination, root length, dry matter, vigour, and yield [22,23,24]. Currently, however, most studies have reported the effect of very low magnetic fields close to the Earth’s magnetic field of around 5 µT [22] or slightly higher magnetic fields around 200 mT [22,23,24,25]. Currently, few results have been presented for magnetic and electromagnetic fields with much higher inductions of 1 T, 10 T, and 15 T [26,27,28]. Previous research results have indicated that high germination capacity and long root length lead to high dry matter (high amount of tissue in the plant). This may lead to a higher yield [29]. Xia et al. [30] treated the radish (Raphanus sativus L.) with the magnetic field of 20 mT for 10, 30, and 60 min, and proved a positive effect of MF on seed energy, seedlings’ length, and fresh weight, particularly for 60 min of exposure time. Afzal et al. [11] magnetised seeds of sunflower (Helianthus annuus L.) in magnetic fields of 50, 100, and 150 mT for 5, 10, and 15 min. They observed the increase in final germination, germination energy, root length, and shoot length. Podleśna et al. [31] reported the effect of pre-sowing magnetic field treatment on germination, above-ground parts, and roots of Faba Bean (Vicia faba L. spp. Minor). They used MFs of 30 and 85 mT for 15 s. Both MF doses had a positive effect on germination. Seven days after sowing, increases in root length (25.5% for 30 mT and 43.1% for 85 mT) and the stem length (28.1% for 30 mT and 52.3% for 85 mT) were observed.

However, our study shows that a low electromagnetic field with an induction of 200 mT and magnetisation times of 15 min and 60 min does not increase the germination capacity of the cucumber, and significantly decreases the root length and the amount of dry matter. Further results showed, however, that a higher electromagnetic field with an induction of 1 T and a time of 60 min allows a slight acceleration of germination capacity, does not affect root length but significantly increases the amount of dry matter (by 43%) compared to the control sample. This indicates that germination capacity and root length are not always correlated with the amount of dry matter. The significantly poorer results obtained for electromagnetic fields of 1 T induction and 15 min compared to the control sample indicate that cucumber seeds require a higher-energy dose and a longer magnetisation time. Further results obtained for electromagnetic fields of 9 T induction and magnetisation times of 15 min and 60 min show a significant reduction in germination rate and root length and a significant increase in dry weight by about 45% compared to the control sample. The above results indicate that there is not always a correlation between germination rate, root length, and dry matter. This finding is very important and requires further research to identify the dominant electromagnetic field factor that influences the increase in dry matter. The results presented by Paul et al. [28] suggest that the 9 T magnetic field does not affect the genome, because a change in the genome only occurs at fields above 15 T.

Because the magnetisation process was carried out for dry seeds and not for seedlings, this can indicate that the influence of electromagnetic field may relate more to physical properties, e.g., diamagnetism, paramagnetism, and ferromagnetism, which affect the acceleration of plant tissue growth processes (dry matter). Of course, one cannot exclude the influence of other factors on the dry matter growth process such as biological, chemical, biochemical processes, modification of cell structure, and directed movement of substances as a result of magnetic field [22].

5. Conclusions

Our research showed that the magnetic field of 1 T for 60 min and the magnetic field of 9 T for both 15 and 60 min resulted in a significant increase in the dry matter by about 49% compared to the control sample. It can be concluded that the increase in dry matter was not mainly dependent on the germination rate and root length (observed in 9 T magnetic field); other factors can be crucial. These factors can be the magnetic particles in the seed, the magnetic field intensity, and the magnetisation duration. The obtained results for the seeds magnetisation process indicated that the application of magnetic fields of 200 mT and 1 T and a magnetisation time of 15 min contributed to a significant increase in the dry mass of the aboveground part of the seedling and an increase in the vigour index B, while the field of 1 T and a seed exposure time of 60 min had a beneficial effect on root length and their dry mass. Irrespective of the intensity of the magnetic field, the 15 min magnetisation time was the most favourable for achieving the highest vigour index B values. It was shown that prolonging the time of exposure of seeds to the magnetic field resulted in the decrease in the length of the aboveground part of the seedling and in the value of vigour index B, while with the increase in the value of this trait, the length of the root and the value of vigour index A increased.