When we talk about photoperiods in hydroponics we are talking about the triggering of vegetative or flowering growth by changing the duration of the plants light cycle or photoperiod.
Photoperiods -- The duration of an organism's daily exposure to light, considered especially with regard to the effect of the exposure on growth and development.Veg-Phase -- Vegetative growth of a plant by division of cells, without sexual reproduction.
Flower-Phase -- Flowering growth of a plant.
Photoperiods in detail:
Flowering plants or angiosperms are the most widespread group of land plants. flowering plants use the pigment phytochrome to sense seasonal changes in day length, which they take as signals to flower. Broadly, flowering plants can be classified as long day plants, short day plants, or day neutral plants.Long day plants require a certain amount of daylight to initiate flowering (this was initially thought) it is now known that it is actually the night length that will influence the flowering, so a long day plant needs a short night which in turn will mean it has a long day. These plants flower in the spring or summer. Conversely, short day plants will flower when the length of daylight falls below a certain amount. Short day plants need the night to be longer and therefore the days are short, they will flower in late summer, autumn or winter. Day neutral plants do not initiate flowering based on photoperiodism i.e. they can flower regardless of the night length; some may use temperature (vernalization) instead.
A long day plant is a plant that requires less than a certain number of hours of night in each 24 hour period to induce flowering. Long day plants typically flower in the late spring or early summer.
A short day plant is a plant that cannot flower under the long days of summer. Short day plants typically flower in the fall of the year. These plants require a certain number of hours of darkness in each 24 hour period (a short daylength) before floral development can begin. Plants use the phytochrome system to sense day length or photoperiod.
A short day plant (long night) will not flower if a flash of light is used on the plant during the night. This does not occur from natural light such as lightning, fire flies, etc.
Last Updated: May 03, 2008
