Agriculture Reference
In-Depth Information
a plant nervous system, the corresponding plant subsystems can be more
confidently identified; and if so, whether they are concordant with those
analysed by Miller and Miller (1995) for animal/human systems. Table 3.2
summarises the present position for the various levels of plant organisation.
Of the information-processing subsystems listed in Table 3.1, s14, timer,
is not directly relevant in the present context as it deals with the timing of
processes in relation to innate or external cues. At the levels of the cell and
organ, subsystems s16 and s17, associater and memory, respectively, may
have correspondences with the fast electrical signals that can be propa-
gated along plant organs. The remaining subsystems are those which either
transmit information in the form of an auxin flow (especially s13, chan-
nel and net, at the organ and organism levels), or are concerned with the
transduction of external information into the body of the plant and its con-
version into internal information for eventual transduction as an output
response.
In whatever form information is perceived by the plant, it is internalised
andprocessedinsuchawaythatitcanbeultimatelydirectedtowardsmove-
ment or reproduction. The movement of plant organs involves tropisms
(nastic movements are excluded for the moment owing to their autonomous
nature), the informational inputs for which are mainly gravity, illuminance
andmoisture.Auxinisthekeymediatorofthesegrowthevents.
Although plant life can be decomposed into a series of hierarchical levels,
these are more than merely classificatory conveniences but are systems of
dynamic interactions. Thus, the states of the lower organisational levels
provide conditions for the emergence of larger-scale organisations such as
the group or community, and in particular for the physical movements of
the latter whereby they - individuals, groups, communities - are able to
occupy new environments by means of propagules adapted and dispersed
for this purpose (seeds, abscinded plant parts, etc.). Finally, the communal
movement of plants aids in the construction of a green energy receptor and
transducer - and maybe something more (Miller and Miller 1982) - which
coversthesurfaceoftheEarth.Insomeunfathomableway,thislivingskin
may even fulfil the role of a subsystem within some much higher level of
organisation and thereby participates in the ongoing creative evolution of
organic living systems.
3.6
Conclusions and Future Prospects
Was Charles Darwin prescient in his use of the word brain in connection
with his studies of the activities of the plant root apex and the implications
that might flow therefrom? We shall never know. Given his unease over the
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