Abstract
The scientific literature describing the effects of weak magnetic fields on living systems contains a plethora of contradictory reports, few successful independent replication studies and a dearth of plausible biophysical interaction mechanisms. Most such investigations have been unsystematic, devoid of testable theoretical predictions and, ultimately, unconvincing. A recent study, of magnetic responses in the model plant Arabidopsis thaliana, however, stands out; it has a clear hypothesis—that seedling growth is magnetically sensitive as a result of photoinduced radical-pair reactions in cryptochrome photoreceptors—tested by measuring several cryptochrome-dependent responses, all of which proved to be enhanced in a magnetic field of intensity 500 μT. The potential importance of this study in the debate on putative effects of extremely low-frequency electromagnetic fields on human health prompted us to subject it to the ‘gold standard’ of independent replication. With experimental conditions chosen to match those of the original study, we have measured hypocotyl lengths and anthocyanin accumulation for Arabidopsis seedlings grown in a 500 μT magnetic field, with simultaneous control experiments at 50 μT. Additionally, we have determined hypocotyl lengths of plants grown in 50 μT, 1 mT and approximately 100 mT magnetic fields (with zero-field controls), measured gene (CHS, HY5 and GST) expression levels, investigated blue-light intensity effects and explored the influence of sucrose in the growth medium. In no case were consistent, statistically significant magnetic field responses detected.
Highlights
Exposure to the extremely low-frequency (ELF; 50/60 Hz) electromagnetic fields associated with electrical power distribution is unavoidable in modern industrial societies and has led to concerns about adverse effects on human health (Crumpton & Collins 2004; Crumpton 2005)
All three effects of the 500 mT field—a 12–37 per cent reduction in hypocotyl lengths, a 28–45 per cent increase in anthocyanin production and a reduction in Cry2 levels—are consistent with a magnetic fieldinduced increase in the sensitivity of the seedlings to blue light. This was interpreted by Ahmad et al in terms of a flavin–tryptophan radical pair formed by photoinduced electron transfer within a cryptochrome photoreceptor (Giovani et al 2003)
We report here our attempts to subject the Arabidopsis study to the ‘gold standard’ (Crumpton 2005) of independent replication
Summary
Exposure to the extremely low-frequency (ELF; 50/60 Hz) electromagnetic fields associated with electrical power distribution is unavoidable in modern industrial societies and has led to concerns about adverse effects on human health (Crumpton & Collins 2004; Crumpton 2005). All three effects of the 500 mT field—a 12–37 per cent reduction in hypocotyl lengths, a 28–45 per cent increase in anthocyanin production and a reduction in Cry levels—are consistent with a magnetic fieldinduced increase in the sensitivity of the seedlings to blue light This was interpreted by Ahmad et al in terms of a flavin–tryptophan radical pair formed by photoinduced electron transfer within a cryptochrome photoreceptor (Giovani et al 2003). For which magnetic responses have no apparent function and which presumably lack a highly evolved, specialized magnetoreceptor, are sensitive to external magnetic fields conceivably other cryptochromecontaining species may be too In this context, it may be noted that cryptochromes are key components in the regulation of the mammalian circadian clock and that disruption of circadian timing has been linked to susceptibility to cancer (Reddy et al 2005). Hypocotyl lengths of plants grown in 0 mT, 1000 mT and approximately 100 mT magnetic fields have been recorded, gene (CHS, HY5 and GST ) expression levels measured, bluelight intensity effects investigated and the influence of sucrose in the growth medium explored
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