I have observed something about the onions in my pantry. Occasionally, one or two of the onions will develop what appears to be layers of black mildew sandwiched between the onion layers. Invariably, these onions are found to be breaking dormancy, putting out leaves in the pantry. Other onions, that are still dormant, are sound, with no mildew. It seems to be a pretty quick reaction: the last onion that I found putting out leaves appeared at first glance to be sound, but then I found one patch of mildew, one layer in. So it would appear that the onions react to getting mildew by starting to grow – presumably, in an effort to get in one last reproductive attempt before they die; or perhaps, active growth is necessary for mounting an immune response. Could such an effort succeed, I wonder?
Anyway, we are so seldom able to see plants reacting, I find this a fascinating observation.