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Photoperiodism, the light - dark influence on plants that "turns on" plant switches (or switches) plant seeds to germinate or plants to blossom. It can also be used to "turn off" plant for opposite effect. This switch can be fliked on and off indefinitely and plant remembers the last position of the switch.
In 1920, they wanted the tobacco plant to flower and only when the daylight period was short and the night long would they flower. Temperature and water changes would not trigger tobacco plant flowering. Google pictures of flowering tobacco plants if you want to see a flower variety surprise.
Now two categories of "short day" and "long day" plant types for study that would make a plant flower. A few plants apparently will not respond to the length of day changes. Next, they find it is the length of night and not the time of daylight that made the plants flower. Next, white light has all the spectrum of light but the red light spectrum was the key light. Even a flashing sign can effect the cycle of plants.
They have commericial or home type growth chambers to buy if you want to experiment. This is still a wide open field. Man, animals, migration or hibernation of birds and mammals is connected with light and dark day cycle.
In simulator, midnight time lights on timer of a few minutes to an hour can. awaken or turn off plant cycles.
Simple experiment.
Wrap green tomato in aluminum foil. Nine days later unwrap your pink tomato.
Wrap green tomato in aluminum foil with round coin sized in foil. Nine days later unwrap a pink and red polka-dot tomato.
After centuries we find the importance of the first Creative Day . Genesis 1:3-5
3 And God said: “Let there be light.” Then there was light.+ 4 After that God saw that the light was good, and God began to divide the light from the darkness. 5 God called the light Day, but the darkness he called Night.+ And there was evening and there was morning, a first day.
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