Charles Darwin and the plant root brain: Closing the gap in plant living systems theory
Peter Barlow
School of Biological Sciences, University of Bristol, Bristol BS8 1UG, UK
Charles Darwin was “always pleased to exalt plants in the scale of organised beings” and “felt an especial pleasure in showing how many and what admirably well adapted movements the tip of a root possesses.” (1) Indeed, Darwin went so far as to say that the root tip acts like a brain, located within the anterior end (sic) of the plant body, “receiving impressions from the sense organs and directing the root’s several movements.” (2) What clearly impressed Darwin was the ability of the root to perceive, often simultaneously, multiple vectorial stimuli – touch, moisture, light, gravity – and then make a “decision” about which “final purpose”, or bending response, to follow. In connection with these growth responses, Darwin had also said that “plants do not of course possess nerves or a central nervous system.” (2)

According to J.G. Miller’s “Living Systems Theory” (LST), developed over the last three decades mainly for human organisms and human societies, (3) there are sets of 20 subsystems which, within each level of organisation, from cellular to supranational, are functionally equivalent and govern each level’s activity. LST can be adapted, apparently with success, to plant organisms also. (4) About half of the LST subsystems concern the processing of information. Of interest in the present plant-neurobiological context is the subsystem “Channel and Net”. (5) In an earlier formulation of plant LST, (4) this subsystem was equated, at the cellular level of organisation, with cytoskeleton and endomembranes, and with the symplasm at the organ level. Now, in the light of recent discoveries from plant cell biology, these designations appear to be confirmed, reinforcing the idea that plants do possess a form of nervous system which, moreover, makes use of molecules and organelles similar to those found in animal systems. As a result, the systems-analytical approach to the constructional hierarchy of plant life converges upon that already recognised for animals, (3) hence providing a truly coherent LST for the two major living systems of Plants and Animals.

  1. Darwin C. 1880. The Power of Movements in Plants. London: John Murray
  2. Darwin C. 1876/1983. Autobiography. In G de Beer, ed; Charles Darwin and TH Huxley, Autobiographies. Oxford: Oxford University Press. p 8-88.
  3. Miller JG. 1978. Living Systems. New York: McGraw-Hill Publishing Co.
  4. Barlow PW. 1999. Living plant systems: How robust are they in the absence of gravity? Adv Space Res 23:1975-1986.
  5. Miller JL, Miller JG. 1995. Greater than the sum of its parts III. Information processing subsytems. Channel and net. Behav Sci 40:238-268.