photoperiodism


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Related to photoperiodism: vernalization

photoperiodism

 [fo″to-pēr´e-o-dizm]
the physiologic and behavioral reactions brought about in organisms by changes in the duration of daylight and darkness.

pho·to·per·i·od·ism

(fō-tō-pēr'ē-ō-dizm),
The periodic (seasonal or diurnal) activities, behavior, or changes in plants or animals brought about by the action of light.

photoperiodism

/pho·to·pe·ri·od·ism/ (fo″to-pēr´e-ah-dizm) the physiologic and behavioral reactions brought about in organisms by changes in the duration of daylight and darkness.

photoperiodism

(fō′tō-pîr′ē-ə-dĭz′əm)
n.
An organism's response or ability to respond to changes in photoperiod.

photoperiodism

the response observed in an organism to the relative length of light and dark periods. While all organisms can be affected by PHOTOPERIODS (See also BIOLOGICAL CLOCK the term is most commonly used in connection with higher plants, particularly their flowering. The regulation of flowering is rather complex and difficult to generalize about, but it is possible to divide plants into three categories: LONG-DAY PLANTS, SHORT-DAY PLANTS and DAY-NEUTRAL PLANTS (the latter being unaffected by photoperiod).

Plants appear to detect the photoperiod with the pigment PHYTOCHROME which can exist in two forms in the leaves, P660 in red light and P725 in far-red light. If there is more P660 than P725 in a short-day plant, or P725 than P660 in a long-day plant, then flowering is induced as a vegetative apical MERISTEM is changed to a flowering one.

Phytochromes are also present in the seed coat, the correct balance of P660 and P725 stimulating enzyme activation and hence GERMINATION. See also FLORIGEN.

photoperiodism

the physiological and behavioral reactions brought about in organisms by changes in the duration of daylight and darkness, e.g. in reproductive activity, shedding of hair. Birds respond to longer daylight hours by increased sexual activity. Use is made of the phenomenon by using artificial light to stimulate egg production.
References in periodicals archive ?
In the "Evolution of Photoperiodism Under Domestication" section, photoperiodic adaptation to latitude is discussed, and it is pointed out that when strains adapted to the season of one area are grown in an unsuitable latitude they may fail to develop seeds.
They are growing their winter fur based on photoperiodism, not temperature.
Deciphering time measurement: the role of circadian 'clock' genes and formal experimentation in insect photoperiodism.
Interactions between photoperiodism and temperature with respect to the control of dormancy in the adult stage of Pterostichus oblongopunctatus F.
Photoperiodism (discovered in 1918) shows that flowering in plants is controlled by changes in day length.
Every year based on photoperiodism an instinctive desire to breed in whitetail deer gets triggered.
The author explains the radiation flux in the free atmosphere and biosphere and concentrates on such processes as photosynthesis and photoperiodism.
These responses, which are associated with the seasons of the year, involve physiological processes known as photoperiodism (Koukkari and Robert, 2006).
Photoperiodism is the reaction of plants to changing lengths of darkness.
Garner and Allard called this phenomenon photoperiodism and went on to work with other plants.
This photoperiodism, as it is technically known, is used by professional growers for a wide variety of plants to force them to perform at a time of the year when they would not naturally do so.