A food-for-thought question from a biochemist who doesn’t know much about water lilies specifically: your question assumes that it’s the opening/closing that requires energy, but another possible mechanism might be if the default, relaxed position was closed, and energy needed to be expended during the day to keep the flower open (or the inverse, where the open position is the default, relaxed position, but then at night, energy is continually expended to keep it closed). I suggest this based on how I know many of the molecular mechanisms of plants rely on turgidity (swollenness from water) to evoke structural changes.
It doesn’t change the question materially, it just involves looking at the question from different angles. I don’t know much about water lilies though, I didn’t even know that they close at night. I might report back here if I find anything interesting.
Okay, well this is actually super cool, thanks for driving my attention there. It seems that the word for this particular behaviour is "Nyctinasty
I think the short answer to your question appears to be “we don’t know”, because nyctinasty has been observed for millennia but there isn’t a clear, conclusive answer. In some plants that are open at night, it may be that they are pollinated by bats or nocturnal insects, but one of the open questions here is “does nocturnal nyctinasty happen via the same mechanism as diurnal nyctinasty?”. By that, I mean “does a nocturnal plant (like moonflower) use the same ‘muscles’ as a plant that’s open during day, like water lily?”.
I don’t recall it mentioning water lilies, but a book that you’d probably enjoy if you’re curious about this stuff is What a Plant Knows by Daniel Chamovitz. I remember there is some really interesting stuff in there about plant circadian rhythms, and the information is presented in an accessible and entertaining manner
A food-for-thought question from a biochemist who doesn’t know much about water lilies specifically: your question assumes that it’s the opening/closing that requires energy, but another possible mechanism might be if the default, relaxed position was closed, and energy needed to be expended during the day to keep the flower open (or the inverse, where the open position is the default, relaxed position, but then at night, energy is continually expended to keep it closed). I suggest this based on how I know many of the molecular mechanisms of plants rely on turgidity (swollenness from water) to evoke structural changes.
It doesn’t change the question materially, it just involves looking at the question from different angles. I don’t know much about water lilies though, I didn’t even know that they close at night. I might report back here if I find anything interesting.
Okay, well this is actually super cool, thanks for driving my attention there. It seems that the word for this particular behaviour is "Nyctinasty
I think the short answer to your question appears to be “we don’t know”, because nyctinasty has been observed for millennia but there isn’t a clear, conclusive answer. In some plants that are open at night, it may be that they are pollinated by bats or nocturnal insects, but one of the open questions here is “does nocturnal nyctinasty happen via the same mechanism as diurnal nyctinasty?”. By that, I mean “does a nocturnal plant (like moonflower) use the same ‘muscles’ as a plant that’s open during day, like water lily?”.
I don’t recall it mentioning water lilies, but a book that you’d probably enjoy if you’re curious about this stuff is What a Plant Knows by Daniel Chamovitz. I remember there is some really interesting stuff in there about plant circadian rhythms, and the information is presented in an accessible and entertaining manner