Flowering in many plants is induced by length of day and night.How do plants know when it is spring time or winter time?
Weelll...A good thing to google might be "phytochrome physiology". A very oversimplified explanation is that phytochrome is a pigment in plants that is sensitive to red light & it exists in 2 forms. It changes from one to the other in the dark. The form that is maintained by (red) light will gradually accumulate when the dark period decreases (spring) & at a certain level it will trigger flower bud development. Similar but opposite reaction for short-day (fall flowering) plants. These pigments control germination & other reactions in some plants as well. This stuff should be covered in to "plant physiology 101". My explanation is too basic & full of gaps to show the elegance of these mechanisms. E. & O.E.
