How do plants sense it's warm out (cf. winter temp weirdness)?

In this freaky warm weather recently in the East Coast I’ve noticed little sort of buds on plant and bushes and trees, and read about “you get one shot to bloom” sort of thing.

Not only now, but in general: how do these organisms “register” heat within/as part of a complicated biological system?

(Also, BTW, and I think I asked in a different thread also: is a tree a plant, technically?)

Thats a great question, I was wondering the same thing about seed germination which is related to your question I think.

There is some commentary and references here.

In part, at least:

On a basic level.
Chemical reactions will vary with temperature. Some chemicals will change state quite dramatically in a few degrees. Plants have fluid delivery pathways. Fluids will move easier at higher temperatures. Combinations of these things will trigger other things.

One thing that can happen is the sudden availability of fluid water available to the plant. This doesn’t have to really “register” with a sensory process, or sense organ. When water is frozen, the plant can’t grow, when spring thaw arrives and the ice an snow melts, the plant can, and it does.

I’d heard, anecdotally, possibly in the New York Time’s Science Times, that buds form in late summer and are hidden by leaves, what we see in Autumn and winter may look big, but they’re not ready to open until Spring. Then again, as above, lots of liquid water may force buds to soften. The water has to go somewhere, and may swell buds.

Many plants (but not all) rely on photoperiod. The number of hours of sunlight causes changes that set off the blooming process. So maybe, even if plants have to soften their buds, they won’t be totally “fooled” by this warm winter and go into full bloom.

Thanks to all.

I just noticed the nice name/topic combination!

I was just in Boston to visit family for Christmas. We went for a walk on the Boston Common and got a nice picture of us under a blooming cherry tree.

I’ll reiterate that at least some plants have their blooming cycle dependent on insolation and not temperature, something that is vastly better correlated with predicting the future temperature than the current temperature in many locations. It really just is a matter of evolution as to whether only plants that developed sensitivity to seasonal light changes survived more often enough for it to make a difference; just one warm spell in January in the wrong time might kill off (or force into useless energy expenditures that lower overall fitness) a lot of temperature-sensitive plants in the area and cause those relying on light to be able to take over, but that’s probably going to be fairly localized as well as rare for a plant to have developed that capability genetically when the temperature acts as a very good automatic regulator of cellular activity.

A couple comments. First my daughter (a biology major) told me that when a tree blooms significantly earlier (or later) than all the others, it probably evolved further south (or north) of where it is growing. This is a limitation on the insolation strategy. Second, I have read that some trees require a minimum amount of sub-freezing weather before a warm spell can cause their buds to open. Clearly plants do not necessarily all use the same strategy.

Even if it is more difficult to evolve a mechanism to integrate insolation ab initio (I don’t know if that’s true), once it has evolved, adjusting the mechanism quantitatively to optimize to local conditions will be fast. If transplanted to a different climate, I don’t see any obvious reason that an insolation detector would be expected to adapt more slowly than a temperature detector.