Plants

Static magnetic fields with flux density below and above the Earth’s magnetic field can influence plants, especially in terms of germination, growth, and development. The Earth’s magnetic field also presumably played a role in the evolution of plants ^[1]. Plants contain cryptochromes (receptors for blue light) that are involved in the regulation of growth and development ^[2]. These are influenced by the Earth’s magnetic field, whereby the effect does not necessarily have to be light-dependent ^[3] and can also take place during darkness ^[4].

Germination and growth

A positive influence on germination rate, germination speed, and plant growth was described after pre-treatment of seeds with static and low-frequency magnetic fields for various types of cultivated plants but predominantly at magnetic flux densities above the limit values valid for humans (i.e. in the range of several millitesla). With regard to the influence on plant growth, the results are not consistent. Some studies describe growth-promoting and others growth-inhibiting effects of low-frequency electric and magnetic fields. The agronomic applications of magnetic fields on seeds and plants are summarised in a review paper ^[5]. Another review describes applications to help plants better withstand various environmental stress factors. In both cases, they are compilations of observations ^[6]. The mechanisms of action (possibly mediated by light receptors, reactive oxygen species, and other messenger substances) are being investigated.

Influence of high-voltage power lines

The influence of power lines on plant growth under field conditions has been investigated in only a few studies. In a five-year field study on winter wheat and maize ^[7], a yield reduction of about 7% was found at magnetic flux densities of a few microtesla, with the losses attributed to years of increased drought stress. The detectability of the field effect in comparison with the much stronger influencing factors of climate and precipitation was at the limit of statistical significance.

In China, beans were exposed to electric fields of 2 and 10 kV/m. Especially during germination and in the growth phase, a growth-promoting effect of the fields was shown; this was more pronounced at 2 kV/kg than at 10 kV/m ^[8].

Overall, it is possible, and above the limit values even quite likely, that low-frequency and especially static electric and magnetic fields can influence the growth of plants. Below the limit values under normal outdoor conditions, no adverse effects on plants are to be expected – even in the immediate vicinity of power lines.

References

[1] Maffei ME (2014) Magnetic field effects on plant growth, development, and evolution. Fron. Plant Sci. 5 (445): 1 - 1.

[2] Chaves I, Pokorný R, Byrdin M, Hoang N, Ritz T, Brettel K, Essen LO, van der Horst GT, Batschauer A, Ahmad M (2011) The cryptochromes: blue light photoreceptors in plants and animals. Annu. Rev. Plan.t Biol. 62: 335 - 364.

[3] Agliassa C, Narayana R, Christie JM, Maffei ME (2018). Geomagnetic field impacts on cryptochrome and phytochrome signaling. J Photochem Photobiol B 185: 32-40.

[4] Pooam M, Arthaut LD, Burdick D, Link J, Martino CF, Ahmad M (2019). Magnetic sensitivity mediated by the Arabidopsis blue-light receptor cryptochrome occurs during flavin reoxidation in the dark. Planta 249(2): 319-332.

[5] Sarraf M, Kataria S, Taimourya H, Santos LO, Menegatti RD, Jain M, Ihtisham M, Liu S (2020) Magnetic field (mf) applications in plants: An overview. Plants (Basel, Switzerland) 9(9).

[6] Radhakrishnan R (2019) Magnetic field regulates plant functions, growth and enhances tolerance against environmental stresses. Physiol Mol Biol Plants 25(5): 1107-1119.

[7] Soja G, Kunsch B, Gerzabek M, Reichenauer T, Soja AM, Rippar G, Bolhar- Nordenkampf HR (2003) Growth and yield of winter wheat (Triticum aestivum L.) and corn (Zea mays L.) near a high voltage transmission line. Bioelectromagnetics. 24(2): 91 - 102.

[8] Li X, Liu X, Wan B, Li X, Li M, Zhu H, Hua H (2019). Effects of continuous exposure to power frequency electric fields on soybean Glycine max. J Environ Radioact 204: 35-41.5.