the seasonal day-length responses that cause altered physiological states such as flowering or non-flowering, diapause or development; the photoperiod is usually taken as the time between lights-on and lights-out in an artificial LD cycle (though many photoperiodic responses are in reality to changes in night length) – see critical photoperiod .

An organismâ€(tm)s response to the length of day and night within a 24-hour period (photoperiod); in many plants, this phenomenon determines when flowering occurs.

The reaction of plants to periods of daily exposure to light.

Response of plants to increasing ( long-day plants) or decreasing ( short-day plants) daylengths, in terms of flowering, bulbing, tillering, etc.

the length of light in a light/dark cycle

fo-toe-PER-ee-o-diz-um A plant's ability to measure seasonal changes by the length of day and night. 583

The ability of certain plants to sense the relative amounts of light and dark in a 24-hour period; controls the onset of þowering in many plants.

seasonal response by organisms to change in length of the daylight period.

The effect of day and night length on plant flowering. Some plants are long day, requiring14 - 16 hours of sunlight per day to flower. Others are short day requiring only 8 - 9 hours. Others are day neutral and unaffected by day length. Photoperiosim also effects the breeding cycles of farm livestock

Describes the alternating periods of light and darkness which African Violets and other plants need for peak flowering. In addition to receiving plenty of indirect light, particularly in the red range of the spectrum, African Violets need at least six hours of darkness each day. Red light is absorbed by the phytochrome pigment in the leaves which activates the production of florigen, the hormone which regulates flowering. While the production of this hormone is stimulated by light, exposure to light actually destroys florigen. Thus, an African Violet must have sufficient light to produce florigen, while having enough darkness to use it in the production of flowers. Also see Florescence.

responses of plants to the relative lengths of light and dark cycles.

(1) Mechanism possessed by some organisms to use photoperiod to sense seasonal time. (2) Response by organisms to changes in the duration of day and night.

The response of plants to length of day and night based on the number of hours of light and darkness they receive. An example of a photoperiod response is budding or producing flowers.

Response of an organism to the relative duration of dark and light periods. In plants, photoperiodism may affect flower or seed development, vegetative growth, formation of bulbs and tubers, leaf shape, character and extent of branching, abscission (dropping of vegetative growth, i.e., protective seed sheath) and leaf fall, root development, dormancy, and death.

Photoperiodicity is the physiological reaction of organisms to the length of day or night. It occurs in plants.