I would be surprised by any organism that can sense its environment and doesn’t change behaviour at night. The difference is pretty extreme, whether its temperature, light or just all other beings changing what they’re doing. Even if you don’t notice yourself, you’ll probably be affected by second-order effects.
> Across the animal kingdom sleep satisfies most, though not necessarily all, of the following criteria: (1) decreased brain arousal and its behavioral correlate, decreased responsiveness to an animal’s surroundings, which distinguishes sleep from immobile wakefulness (also known as rest); (2) electrical changes in the brain’s activity patterns relative to the waking state; (3) behavioral quiescence, often accompanied by a preferred location and characteristic posture; (4) rapid reversibility, which distinguishes sleep from hibernation, anesthesia and coma; (5) homeostatic regulation, in which lost episodes of behavioral quiescence and low arousal are followed by compensatory (rebound) episodes [10].
And you don't think different criteria might apply to plants? I mean, look, we are just discovering how plants function as a society. They are immobile and 4 and 5 might be caused by the fact that an animal is mobile, at least for the most examples, but where not, it can at least react in some manner. Plants have a very very slow reaction time so to them 4 and 5 don't apply even in waking condition, I mean unless you consider several hours to be a reaction. Let's be frank: we don't know (yet).
What I don't appreciate is an outright dismissal "plants do not sleep".
We know plants have a diurnal cycle and react to sun/day and some visibly change between night and day. If we say that one of these states is less active, we may decide to call it dormant. Dormant comes from latin dormire, which is sleep. So... why not?
Animals have a sleep-wake cycle that is usually synchronized with the day-night (24 hour) cycle of the Earth. But this synchronization is not essential. All animals with nervous system have a sleep-wake cycle, even if they live underground or in the deep ocean, where the day-night cycle has no significant effect. So there must be an actual need for the sleep-wake cycle that is independent of the rotation of the Earth.
