best way to change light cycle

Nocturn3 said:

Plants only measure darkness, so if you need to make adjustments to your timings, make the days longer/shorter to compensate, whilst always maintaining 12 hours of darkness.

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HOHO said:

may i ask your source of info?...meaning you've tried this or read somewhere or...it sounds logical..

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Researchers have figured out through a lot of experimentation, that plants are actually measuring the duration of darkness (or night), rather than duration of light (or day). They use a chemical called phytochrome which functions as a chemical clock or stopwatch. Phytochrome has two chemical forms - phytochrome far-red (Pfr) and phytochrome red (Pr). Phytochrome is usually, but not always, located in the leaves, so the leaves are responsible for doing most of the work of measuring photoperiod.
Phytochrome is a photoreceptor pigment that absorbs light energy. Pr absorbs red light energy (wavelength = 666 nm) and is chemically converted into Pfr. Pfr absorbs far-red light (wavelength = 730nm) and is converted into Pr. Since the sun produces both red and far-red light, there is constant two-way conversion between Pr and Pfr - an equilibrium develops. During light hours, conversion of one form to the other occurs rapidly - within milliseconds. Of the two, Pfr is the more biologically active form; it triggers plant responses to day length information. These reactions both require light energy. So, during darkness neither of these active reactions can occur.
During the night however, Pfr very slowly and passively degrades to Pr in a process called dark reversion. On a summer morning there is typically a high Pr : Pfr ratio. By detecting morning levels of Pr and Pfr, the plant is essentially measuring how much time has passed during the night. When the level of Pfr reaches a critical point, physiological responses such as flowering or root growth might be triggered.
As the days lengthen and nights shorten (as in the spring), the amount of Pfr remaining in the morning increases from one day to the next and indicates to the plant what time of year it is. A second biochemical signal is then dispatched to communicate this day-lengthening information to various plant tissues to initiate floral development or seed production etc. The reverse situation occurs in the fall of the year - the amount of Pfr remaining in the morning decreases from one day to the next and indicates to the plant that days are shortening. Some plants, and some plant tissues, have adapted to respond to one or both seasonally important situations. So...in order to detect the time of year, plants must be able to tell the time of day, measure duration of night and compare it to the duration of night yesterday. Pretty complex, eh?
A short burst of light during an otherwise dark night disrupts the effect of the dark period because the flood of light converts Pr to Pfr to normal equilibrium levels within seconds, and the slow degradation from Pfr to Pr has to start all over again. The plant clock 'resets' when this occurs and night won't be detected until the next uninterrupted dark phase.

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Nocturn3 said:

Plants only measure darkness, so if you need to make adjustments to your timings, make the days longer/shorter to compensate, whilst always maintaining 12 hours of darkness.

Click to expand...