Do Long-day plants require some darkness to flower?

Question

If a long day plant is given 24 hour lighting for a period of several months, with sufficient water and CO2 resources, can it still flower? Do plants require some darkness to induce flowering?

Answer 1

Yes, long-day plants definitely require some darkness to flower.

In fact, the whole "long-day" and "short-day" labels are misnomers.  Flowering in these plants depends on the length of darkness, not the length of light exposure.  Long-day and short-day plants could more accurately be called short-night and long-night plants, respectively, because the length of darkness is what triggers flowers to start growing.

Answer 2

Yes there are plants with different photoperiod requirements.

Some require 8-12 hours of sun while others may require a 16 hour photoperiod. The remainder of the time should be in darkness. For some plants however regardless of their light requirements, they must be placed in total darkness from 12 hours a day to 24 hours per day over multiple days to force

blooming. Some require darkness in addtion to exposure to natural gases given of by decaying fruits.