Plantifreeze?

I have noticed quite a few plants react to a touch of frost. Snowdrops, for instance, lie down: only standing back to attention after the temperature rises.
The effect of a bit of a chill on certain Rhododendrons I only noticed comparatively recently, could be because it only affects this particular one quite so noticeably.
For the record the two shots were taken a mere 5 hrs apart,
09:30-14:30 all bar a couple of minutes either side of the 1/2 past the hour mark.