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A dose of radio waves seems to encourage plant seedlings to grow slightly faster, a find that, if confirmed, could have applications from farming to medicine.

Margaret Ahmad at Sorbonne University in Paris, France, and her colleagues exposed thale cress seedlings (Arabidopsis thaliana) to weak pulses of radio frequency (RF) radiation at 7 megahertz, a frequency normally used by amateur radio operators.

The team found that this altered the activity of a type of light sensor in the plants called a cryptochrome. The expression of several genes regulated by the cryptochrome also changed, and the seedlings grew slightly faster.

This is the first time anyone has found a biological receptor sensitive to radio waves, says Ahmad. 鈥淲hat we showed is that we can manipulate the 鈥榗hemistry鈥� of the cryptochrome receptor in living plants by a remote radio frequency signal.鈥�

Cryptochromes are proteins found across biology in insects, birds and mammals, including humans. They have a wide range of functions, from regulating plant growth rates and biological clocks to helping birds navigate. They are thought to sense weak magnetic fields in many species, through a quantum mechanism in which the field alters the rate at which the protein is activated by light.

Ahmad, who discovered cryptochromes in the 1980s, wondered if these receptors might also be sensitive to radio waves. Extremely weak RF radiation is known to disrupt magnetosensing in birds, insects and rodents, but the mechanism is unknown.

The team predicted that if the quantum cryptochrome theory is correct, RF radiation should also interfere with the sensor, blocking the effect of Earth鈥檚 magnetic field. This is indeed what they found, with the seedlings responding in the same way as a control group placed in a null magnetic field.

The result strengthens the idea that human-made electromagnetic noise, or 鈥渆lectrosmog鈥�, can have biological effects. The signals used by Ahmad鈥檚 team were about 10 times higher than the radiation emitted by radio transmissions or electrical appliances in a home. But she points out that the behaviour of birds and insects can be affected by far lower intensities.

Alfonso Balmori, a biologist in Valladolid, Spain, who has reviewed the potential ecological impacts of RF radiation, says this adds to growing evidence for biological effects that aren鈥檛 currently considered in health and safety standards for telecommunications networks. There鈥檚 still lots we don鈥檛 know, he says, 鈥渟o we should always apply the precautionary principle鈥�.

David Keays at the Research Institute of Molecular Pathology in Vienna, Austria, says the effect is potentially very interesting, but needs to be replicated by an independent team.

He argues that any effect on wildlife is likely to be small. Birds use several different methods to orientate themselves, he says, including visual cues, so can probably work around any electromagnetic noise. 鈥淢y suspicion is that climate change and light pollution have a much larger impact,鈥� says Keays. He also emphasises that the research in no way supports conspiracy theories relating to 5G cell phone networks spreading the coronavirus.

Cryptochrome reactions produce potentially toxic chemicals called reactive oxygen species. These can be harmful at high levels, but at smaller doses, they activate cellular repair and stress response mechanisms.

Ahmad suspects that organisms would soon adapt to any low-level, continuous RF radiation found in the environment. But she believes short, tailored pulses of radio waves could prove useful. Farmers might use radio masts to trigger defence responses in crops, making them more robust against drought or pests, she says. In medicine, she says RF pulses might help to trigger repair mechanisms in specific tissues. 鈥淭he potential for therapy is very real,鈥� she says.

Keays, however, says he doesn鈥檛 think the effects could ever be large enough to be useful.