Cell movement seems to be impacted by electricity in humans. Perhaps the same is true for plants, and can be part of the explanation behind this?
(Easier to digest version of the link, but in Swedish: https://www.chalmers.se/aktuellt/nyheter/mc2-sa-kan-elektric...)
Your paper references a highly controlled field on a chip.
Those metal rods are plugged into earth. They don't do anything particular in regards of electronic fields.