Interesting. It seems this phase of the germination process occurs at a relatively low moisture level. I wonder, too, if the ethanol somehow interacts with ethylene receptors, as they're important in cellular signalling in plants.
Alternatively, we could just be looking at an artefact of solvent-induced swelling that happens to mimic the initial phase of germination. It kind of raises the question - what's the maximum tolerable ethanol concentration for germinating seedlings of any given species of plant? And also, is there a level that's more beneficial than water alone?
Maybe vodka will prove to be of benefit in rue cultivation