more info around transduction pathways.
http://aob.oxfordjournals.org/content/92/1/1.full.pdf+html Aspects of Plants Intelligence
PLANT MEMORY AND INFORMATION
RETRIEVAL
In nervous systems, new connections (dendrites) between
nerve cells may form the basis of memory (Kandel, 2001)
and loss of the dendrite coincides with loss of memory.
What is required for memory is an ability to access past
experience so that new responses incorporate relevant
information from the past. Many different forms of plant
memory can be envisaged, all of which modify signal
transduction, from the current chemistry and enzymology of
membranes (Gilroy and Trewavas, 2001) or wall charac-
teristics (Trewavas, 1999), to prior expression of particular
genes. It is also clear that the history of stimulation modiÆes
subsequent transduction (Ingolis and Murray, 2002) and, in
plants, intepretation through [Ca2+]
is likewise modiÆed by
previous signalling, ensuring another form of memory is
present (Trewavas, 1999). All these forms of memory can be
recognized by the ability to interact with, and modify, the
transduction pathways to new signals. The only requirement
is merely that the memory can be accessed and can inØuence
the response to the current signal. A more complex form of
memory requires information storage of previous signalling,
with the ability to retrieve the information at a much later
time. Both forms occur in plants.