Plants do need that period of darkness for their metabolism to work properly. They are not designed to create food non-stop, and it will do them harm in the long term to put them in this sort of situation. So, yes, plants need their darkness just as much as they need their light.

Is darkness important for plants?

Periods of darkness are required for plants as it affects their metabolism. It also gives them time to stop producing food (photosynthesis) and use the huge amount of energy they've stored through the day to grow.

Do plants need total darkness at night?

Plants, shrubs and trees use sunlight for photosynthesis during the daytime, but at night they need darkness to regenerate a key compound - phytochrome. Nighttime lighting can reduce vegetation's ability to properly create this compound.