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I've read that many plants have some sort of circadian rhythm where they perform a certain action on a cycle of about 24 hours, like the mimosa plant opening and closing its leaves. Obviously, this is done in order to synchronize with the sun, but many such plants continue to perform these actions even when left in constant darkness or light. It follows that this is the result of some sort of biochemical pathway, but whatever internal 'clock' is used is also independent of temperature.

How can these plants perform certain actions every 24 hours at different temperatures when the chemical reactions most biochemical pathways use are temperature dependent?

It would seem like the length of the cycle should vary widely according to the temperature as it affected the reactions involved, but instead it stays at a very constant length very close to 24 hours. How can this be?

(This is in my textbook, but unfortunately the book doesn't cite any studies. I would greatly appreciate it if anyone could help me find one to link to so I can improve the question. :)

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The short answer is that it is because the reaction chains dispensing time and enzymes doing those reactions have evolved to negate the impact of environmental factors.

The true answer is that the plant clocks do gradually lose sync with 24h cycle when put in stable lighting conditions and move to some more-less random characteristic frequency of their molecular clock which is quite likely dependent on environment (still it is obviously close to 24h) -- the sad truth is that every clock needs syncing to work properly.

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