What happens biologically to a short-day facultative plant that is a few weeks into its short day (flowering) photo period and is suddenly given a 24 hour period of light? Does anything change biologically after one day of long day (vegetative light) or will it take several days?

If there is any biological change that is of concern what can one do to try and alleviate any negative affects?

https://en.wikipedia.org/wiki/Photoperiodism -

  • $\begingroup$ Please clarify - which plant are you speaking of, and are you saying it is already flowering - decided to answer anyway. $\endgroup$
    – Bamboo
    Commented May 30, 2016 at 12:40
  • $\begingroup$ Yes in this example the plant is already a few weeks into flowering photo period. I am curios in regards to the entire class of short-day facultative plants. $\endgroup$
    – BryanK
    Commented May 30, 2016 at 15:25

1 Answer 1


There is nothing you can do to alleviate the effects of (presumably) gro lights being left on for a 24 hour period. It's not likely to have a particularly dramatic effect on a short day facultative plant, other than to possibly delay flowering - it may mean the plant has to go through an extra period of darkness at nights for a longer time, in other words, the process of flower induction may need to start all over again. Or, as it was just one night, you might get away with it and they'll flower when you expected them to. The biggest interruption in the flowering process of a short day plant is a few minutes light in the middle of a period of darkness over successive nights, but either way, it's not possible to offset that 24 hour period of light in any way. I'm afraid you'll just have to wait and see, but in the meantime, maintain the growing routine with regard to lighting.


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