Charles Darwin and the Plant Root Apex: Closing a Gap in Living Systems Theory as Applied to Plants - Communication in Plants: Neuronal Aspects of Plant Life - page 48

reception of his book The origin of species , he might well have kept any
ideas about plants possessing brains strictly to himself.
One attribute of a brain, as the term is commonly understood, is that
it is an organ with a definite structure and location which gathers or
collects information, which was originally in the form of vibrations (heat,
light, sound, chemical, mechanical, . . .) in the ambient environment and
somehow transforms them into an output or response. Interestingly, the
execution of these responses is by means of another vibrating system -
the circumnutating root (Darwin 1880). Any change in the direction of
thestimulustemporarilyoverridesthenutationalprocessuntiltheusual
orientation of the plant organ is regained. Maybe this was how Darwin
understood the situation. However, the absence of obvious nervous tissue
wouldhavebeenaseriousprobleminhisfurtherpursuitofthematter.But
the situation has changed in recent years, as other chapters in this topic
will show. With the discovery within plants of many of the components
of animal-type nervous systems (Baluška et al. 2004), the question is how
this new knowledge can be conceptualised, and whether any paradigm
will emerge which acknowledges some sort of plant nervous system; and
moreover, whether this nervous system will have features which can be
generalised to all eukaryotic organisms.
In recognising the possession, by the root apex, of a brain-like function,
alacunaisfilledinapplyingMiller'scomprehensivelivingsystemstheory
to plants. Consequently, there is now scope for analysing the information-
processing subsystems and linking them with the other two major types
of subsystems that process matter and energy (Barlow 1999). This task can
be done at the various levels of organisation that characterise all biological
constructions.
The subsystems are not static artefacts of theory, but represent inherently
dynamic processes by which biological constructions act. They apply not
only to large constructions such as social communities, but also to smaller
microcosms such as cells. Indeed, the subsystems fulfil the role of the 'coor-
dinative conditions' which the physicist and systems analyst Lancelot Law
Whyte had seen as providing a key to understanding biology in general:
“Until the coordinating conditions have been identified no theory of phylo-
genesis, of ontogenesis, or of their relations, can be regarded as definitive.
Moreover [they] hold the clue to the relation of physical laws and to the
unity of the organism” (Whyte 1965, p. 67). For Whyte, these conditions
express “the biological spatio-temporal coordination, the rules of order-
ing which must be satisfied . . . by the internal parts and processes of any
organism capable of developing and surviving in some environment. The
coordinating conditions are the expression of geometrical, 3D, or perhaps
kinematic rules determining the necessary 3D or spatio-temporal network
of the atoms, ions, molecules, organelles, etc. in a viable organism. They . . .