It may seem like we’ve digressed from the topic of this section, Adaptations to
Climate. But let’s briefly discuss how photoperiodism affects a plant’s ability
to survive in a particular environment.First of
all, let’s think about the role flowers play in the life of a plant. We said in Week
1 that they are reproductive structures and are responsible for producing seeds. Now
let’s think about why the timing of flowering might be important to a plant. Here are
a few possibilities:
- Timing must be such that other plants of the same species
are flowering at the same time, to encourage cross-pollination.
- The plant should flower when its pollinators, such as bees,
are active.
- The plant should flower early enough in the season for
seeds to ripen before the cold weather sets in.
It’s easy to see that, as they say, timing is
everything. Photoperiodism is a way that plants can "tell time," and ensure that
flowering occurs on schedule. (It is also a factor in other plant responses such as
dormancy; we’ll look at this in the next section.) This awareness, or measurement, of
day length is also common in the animal kingdom. For example, the mating season for many
animals such as deer is in the fall. That way, the gestation period lasts through the
winter, and the young are born in the spring—and they have all summer to mature
before the cold weather returns. Scientists believe that this timing is in response to
photoperiod—rather than being based on weather conditions or other environmental
factors. Photoperiodism also influences the timing of animal migrations, and even seasonal
changes in fur color by animals such as arctic hares and foxes.
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