The critical photoperiod is limit of
the photoperiod for the
occurrence of biological response.
This limit be a maximum or
minimum, according to the
of the biological response
to the studied plant.

determine the critical photoperiod
to flowering, 24 groups
plants of the same can betaken
and the experiment can be
done: group is submitted to
different photoperiod, the first to
1 hour of exposure to light, the
to 2 hours, the to 3 hours,
and on, until the last is
exposed to 24 . It is observed
later beyond a specific duration
light exposure plants present do not
present flowering the remaining
submitted to shorter photoperiod
present opposite . The duration
of the exposure that separates
these groups is the critical
.