Well, I wonder about things that readily root from the stem, like figs, currants, some perennial shrubs and of course tomatoes, etc. With things like that, y can just pin a branch to the ground with a rock and it will root into the ground within a few weeks/months without any need to wound it. I wonder specifically how the ground contact / moisture triggers the change, but either way their must either be an intermediate cell stage as @JustAnne4 suggests or perhaps the plant is able to sense the favorable rooting environment and new root cells are created directly. Maybe I’m missing something or other research explains it.
Really, I’m just happy that some things root so easily. I can just accept it as magic as long as it works.