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Variation of flowering time is found in the natural
populations of many plant
species. If
colonizing populations
face heterogeneous and unpredictable assemblages of pollinators,
herbivores, and resources, then individual
variation in flowering
phenology may have strong but reproductive consequences.
A major environmental
factor that determines flowering time is
photoperiod , integrating
circadian clock and
light signal. The photoperiod or
day length is the length of the light period, which changes across
the year differently with geographical latitude. The response to
photoperiod, circadian clock and light signals is determined by
specific plant genes that act as
positive and negative regulators
of floral initiation, and
otherwise exert control over various aspects of plant
development.
In an annual plant, the
flowering time is directly related to availability of water its
fitness.
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