part of photoperiodism vegetative to reproductive phase transition of meristem photoperiodism, flowering photoperiodic control of inflorescence development response to day length, flowering photoperiodic control of flowering time A change from the vegetative to the reproductive phase as a result of detection of, or exposure to, a period of light or dark of a given length. The length of the period of light or dark required to initiate the change is set relative to a particular duration known as the 'critical day length'. The critical day length varies between species. GO:0048573 response to photoperiod, flowering biological_process response to night length, flowering