Dear 100 Hour Board,
Do trees sleep? Do they need to sleep? Like, if I were to make a greenhouse with grow lights and grow a tree 24/7 without ever turning off the lights, would the tree suffer from some kind of exhaustion they way humans would?
Not much is known on the subject, but one study indicated that, apparently, trees do have a day-night rhythm.
I don't think anything is known about the way trees experience their lives, so it would be hard to know if they suffer from "exhaustion the way humans would". We can't deprive trees of sleep in the first place, and, even if we could, we wouldn't be able to talk to them and ask them how it was.
Trees/plants do not sleep. They have no central nervous system to shut down or rest. As Sheebs stated, they do have circadian rhythm but most plants can adapt to changes in sunlight patterns pretty quickly. One study even showed them using sunlight to learn when caterpillars usually came to eat, and they began to adjust their chemistry to defend themselves at that time of day. When the sun goes down plants largely stop photosynthesizing. They turn their energy instead to using and transporting the glucose they produced throughout the day during photosynthesis (a.k.a growing.)
Plants do have preferences for how much sun they get, but sturdy plants can adjust their patterns to the conditions they're given. For however long it can, a plant will find a way to balance photosynthesis and growth simultaneously. If a plant gets too much sun it is the heat energy that does them in, not the abundance of light/photosynthesizing. The heat causes them to use too much of their available water to keep cool.
Keep in mind, the various processes of plants are rarely "on" or "off". They just change how much of something they're doing, or how much they prioritize it.
Whether plants experience things like animals at all is still debated and, from my observation, largely a conversation about semantics. Can we call what plants do the same thing we call what we do? When plants remember, respond, defend themselves, "rest" photosynthesis etc., it can be traced back to their chemistry. These human-like experiences are the product of pre-loaded chemicals, ready to react with whatever chemical signature they come in contact with. But isn't that kind of what we do? I think in a lot of ways it is the same. Respecting the fact that they don't have nerves or a concept of "good" or "bad" with which to enjoy comfort or dislike pain. They just react.
I'll let you simmer on that, keeping in mind that plants are living organisms which evolve with the same pattern we do. They were also created by the same God, who created all things spiritually before he created them physically. I think the biggest difference is really agency but I think I've digressed enough.