| Plants depend crucially on timekeeping. The Circadian Clock is essential for coordinating metabolism, growth, and reproduction, vernalization, etc. Most plants can be considered either short-day or long-day flowering, where highly-sensitive response to the delta in day-length is tracked to coordinate flowering. Nearly all plants anticipate events like sun-rise and sun-set with precision to coordinate (expensive!) photosynthetic expression, open/close stomata, alter xylem and phloem, etc. Applying this to longer time-scales should not be terribly surprising for such sophisticated time-keepers. Here's some information about in-vitro induction of flowering, induced with the sorts of chemicals you might expect (e.g. cytokinin promoting, auxin repressing): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5603696/ As for the particular regulatory network that accomplishes this, it's very difficult to study an event that occurs so seldom. Even annual breeding cycles can make detailed genetic investigations take decades. What we can infer from homology is that there's likely some kind of feedback and balance of hormones that 'count' the time. There is nothing "in the DNA" that tracks time, but the genes that DNA encodes can provide this clock function. |