The plants were grown in pots with forked bases, which could be filled with either dry or damp soil. As expected, roots proved very sensitive to the presence of moisture, and readily grew towards it. Then Dr Gagliano added a twist. Some forks were surrounded by plastic pipes full of water, creating watery noises but remaining inaccessible to the roots. When the alternative was a tube full of dry soil, those noises proved just as enticing to the growing roots as water itself.
Fascinated, Dr Gagliano and her colleagues placed small speakers at the bases of some tubes and played either a recorded sound of water, white noise, or nothing. Intriguingly, the plants seemed able to tell that they were being duped. Even when the alternative was parched soil, almost all chose to grow away from the speaker. They could only be persuaded to grow towards a speaker when forced to choose between two, in which case they chose the one playing watery noises. Dr Gagliano suspects—but cannot yet prove—that the small magnets found in the speakers are responsible for such discerning behaviour. A few older papers have suggested that plants can detect magnetic fields.