105
EMFs and Environmental Stresses in Plants
and seedling growth, indicating the magnetically untreated seeds with the exposure time 60 min of
ultraviolet-C gave the highest seedling growth (Lazim and Nasur, 2017). A static MF of 200 mT
for 1 hour reduced the amount of hydrogen peroxide (36%) and activities of antioxidant enzymes
such as superoxide dismutase (38%), glutathione reductase (60%) and guaiacol peroxidase (66%) of
soybean (var. JS-335) plants that emerged from MF-treated seeds under ambient ultraviolet (280–
400 nm) stress compared to the control. The reduction in the hydrogen peroxide content (30%) and
antioxidant enzyme activities (40%) after MF treatment and ambient ultraviolet exclusion indicated
that solar ultraviolet components exert a signifcant stress on soybean plants. Similarly, the levels of
ultraviolet-absorbing compounds (14.6%–15%) were also decreased by exclusion of both ultraviolet
and MF treatment. The results indicate that the exclusion of solar ultraviolet components and MF
pre-treatment eliminates the need for defence against the ambient ultraviolet stress (Kataria et al.,
2017b).
Some experimental results have exhibited a protective response of the MF against high temperatures or heat stress. The effects of pre-sowing magnetic treatments (MF of 120 mT for 10 min
and 80 mT for 5 min) on the growth and yield of tomatoes (cv. Vyta) increased notably root length
(18%), fresh and dry root weight (48.2% and 80.7%), stem length (35.9%), fresh and dry stem weight
(39.6% and 75.4%), leaf area and foliole dry weight (39.3% and 26.7%), fruit number (21.3%), mean
fruit weight (25.5%) and fruit yield per plant (51.7%) and per area (50.8%) under high temperature
stress (34°C) and under feld conditions (De Souza et al., 2005). A weak sinusoidal and 50-Hz MF
of 100 μT alleviated the inhibitory effect of heat stress (40, 42 and 45°C for 40 min) on the growth of
cress seedlings (Lepidium sativum; 15%) only when applied previously, whereas the application of
MF alone and after heat stress did not produce any signifcant growth effects. It was also evident
that with a stronger stress (42°C and 45°C), the MF produced a more potent protective effect than at
40°C, indicating the protective effect of MF against high temperatures (Ruzic and Jerman, 2002).
These studies suggest that MF treatment ameliorates the adverse effects of drought, salinity, heavy
metal toxicity, ultraviolet light and high temperatures.
EFFECTS OF MFS ON BIOTIC STRESS
Biotic stress in plants is caused by living organisms, especially viruses, bacteria, fungi, nematodes,
insects, arachnids and weeds (Gull et al., 2019). These biotic stress agents cause various types of diseases, infections and damage to crop plants and ultimately affect the crop productivity. They depend
on the environment and thus vary from region to region, from one agroecology to another, from one
country to another country (Suzuki et al., 2014). Biotic stress plays a central role in regulating outbreaks of pests, pathogens, insects and weeds (McDonald et al., 2009; Peters et al., 2014; Ziska et al.,
2010). Plants respond to biotic stress through a defence system, and this mechanism is classifed as
an innate and systemic response. After infection, reactive oxygen species (ROS) are generated and
oxidative bursts limit pathogen spread (Atkinson et al., 2012). Several adaptive responses of plants
have shown the role of MF on plant defence response under biotic stress conditions (Table 9.2).
Magnetic treatment has been found to protect some plant species against fungi, bacteria, phytoplasma and virus. For example, exposure to 0.2-mT MF for 7 min 48 s, 11 min 42 s and 15 min
36 s on tomato seed infected by Fusarium sp. increased the rate of fowering (4.4%), fower number
(3.4%), the rate of fruiting (2.8%) and fruit number (11.%), while the combination of MF exposure
and seed soaking treatment enhanced fower number, the rate of fruiting and fruit numbers. 0.2-mT
MF for 7 min 48 s showed the highest rate of fowering and the largest number of tomatoes, while
0.2-mT MF for 11 min 36 s exhibited the most number of fowers (13.4%) and the highest rate of
fruiting (5.1%). However, soaking tomato seeds for 15 min before the 0.2-mT MF treatment gave a
better effect by increasing the rate of the plants to form fowers and fruits and increase the number
of fruits (Agustrina et al., 2018).
A static MF of 0.1, 0.5 and 1 mT decreased the growth of phytopathogenic microscopic fungal
colonies by 10%. At the same time, the number of developed conidia of Alternaria alternata and
EMFs and Environmental Stresses in Plants
and seedling growth, indicating the magnetically untreated seeds with the exposure time 60 min of
ultraviolet-C gave the highest seedling growth (Lazim and Nasur, 2017). A static MF of 200 mT
for 1 hour reduced the amount of hydrogen peroxide (36%) and activities of antioxidant enzymes
such as superoxide dismutase (38%), glutathione reductase (60%) and guaiacol peroxidase (66%) of
soybean (var. JS-335) plants that emerged from MF-treated seeds under ambient ultraviolet (280–
400 nm) stress compared to the control. The reduction in the hydrogen peroxide content (30%) and
antioxidant enzyme activities (40%) after MF treatment and ambient ultraviolet exclusion indicated
that solar ultraviolet components exert a signifcant stress on soybean plants. Similarly, the levels of
ultraviolet-absorbing compounds (14.6%–15%) were also decreased by exclusion of both ultraviolet
and MF treatment. The results indicate that the exclusion of solar ultraviolet components and MF
pre-treatment eliminates the need for defence against the ambient ultraviolet stress (Kataria et al.,
2017b).
Some experimental results have exhibited a protective response of the MF against high temperatures or heat stress. The effects of pre-sowing magnetic treatments (MF of 120 mT for 10 min
and 80 mT for 5 min) on the growth and yield of tomatoes (cv. Vyta) increased notably root length
(18%), fresh and dry root weight (48.2% and 80.7%), stem length (35.9%), fresh and dry stem weight
(39.6% and 75.4%), leaf area and foliole dry weight (39.3% and 26.7%), fruit number (21.3%), mean
fruit weight (25.5%) and fruit yield per plant (51.7%) and per area (50.8%) under high temperature
stress (34°C) and under feld conditions (De Souza et al., 2005). A weak sinusoidal and 50-Hz MF
of 100 μT alleviated the inhibitory effect of heat stress (40, 42 and 45°C for 40 min) on the growth of
cress seedlings (Lepidium sativum; 15%) only when applied previously, whereas the application of
MF alone and after heat stress did not produce any signifcant growth effects. It was also evident
that with a stronger stress (42°C and 45°C), the MF produced a more potent protective effect than at
40°C, indicating the protective effect of MF against high temperatures (Ruzic and Jerman, 2002).
These studies suggest that MF treatment ameliorates the adverse effects of drought, salinity, heavy
metal toxicity, ultraviolet light and high temperatures.
EFFECTS OF MFS ON BIOTIC STRESS
Biotic stress in plants is caused by living organisms, especially viruses, bacteria, fungi, nematodes,
insects, arachnids and weeds (Gull et al., 2019). These biotic stress agents cause various types of diseases, infections and damage to crop plants and ultimately affect the crop productivity. They depend
on the environment and thus vary from region to region, from one agroecology to another, from one
country to another country (Suzuki et al., 2014). Biotic stress plays a central role in regulating outbreaks of pests, pathogens, insects and weeds (McDonald et al., 2009; Peters et al., 2014; Ziska et al.,
2010). Plants respond to biotic stress through a defence system, and this mechanism is classifed as
an innate and systemic response. After infection, reactive oxygen species (ROS) are generated and
oxidative bursts limit pathogen spread (Atkinson et al., 2012). Several adaptive responses of plants
have shown the role of MF on plant defence response under biotic stress conditions (Table 9.2).
Magnetic treatment has been found to protect some plant species against fungi, bacteria, phytoplasma and virus. For example, exposure to 0.2-mT MF for 7 min 48 s, 11 min 42 s and 15 min
36 s on tomato seed infected by Fusarium sp. increased the rate of fowering (4.4%), fower number
(3.4%), the rate of fruiting (2.8%) and fruit number (11.%), while the combination of MF exposure
and seed soaking treatment enhanced fower number, the rate of fruiting and fruit numbers. 0.2-mT
MF for 7 min 48 s showed the highest rate of fowering and the largest number of tomatoes, while
0.2-mT MF for 11 min 36 s exhibited the most number of fowers (13.4%) and the highest rate of
fruiting (5.1%). However, soaking tomato seeds for 15 min before the 0.2-mT MF treatment gave a
better effect by increasing the rate of the plants to form fowers and fruits and increase the number
of fruits (Agustrina et al., 2018).
A static MF of 0.1, 0.5 and 1 mT decreased the growth of phytopathogenic microscopic fungal
colonies by 10%. At the same time, the number of developed conidia of Alternaria alternata and