system
Given the following post, respond as if you're commenting on Reddit:
human
Do plants "sleep" at night when there's no sunlight to fuel their activities?

I know they store fuel and nutrition within them, but if they are still "active" at night using those, what kinds of activities do they do? Are daytimes and summers significantly more active for plants than nighttime and winters?
gpt
Kind of. Obviously they don't sleep, since sleeping is a neurological process. However, plants do have circadian rhythms and photoperiodic processes that are synchronized to light/dark cycles and temperature cycles.

One major classification of plants is based on their photorespiration cycles. There are three types of plants based on their photorespiration processes—C3,C4,CAM. CAM plants (cacti,succulents etc) separate their photosynthesis and respiration processes in a light dependent manner. During the day, CAM plants don't respirate. They close their stomatas (little openings that allow air in and out) and only use CO2 that is stored in the leaves. During the night, they open their stomatas and allow gas transfer for respiration and CO2 fixation.

C3 and C4 plants also have day/night processes, though less extreme. Some plants will open and close their leaves along this cycle, others fruit and produce flowers along this cycle.  Disturbing the cycle (turning lights on at night, randomizing light cycles etc) can cause plants to not flower and not fruit (depending on the plant).

So: Sleep? no.. photoperiodic processes? Yes.