Here is one interesting text about flowering hormone- florigen.
https://www.scq.ubc.ca/florigen-the-hidden-hormone/
According to the text, if I had a well-developed photoperiod plant outside and grafted a small twig of autoflower on it, the whole plant would start to bloom along with the autoflower. Regardless of the length of the day. Useful for long-flowering sativa. If that’s really the case.
Edit
Hmmm
But that somehow doesn’t fit me with the fact that one plant can both bloom and not bloom at the same time.
But still, an interesting text