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Minds of small things  ·  Article

Root tip as brain-like sensing organ

His chapter summary also calls the root tip highly sensitive2. The idea matters because it places sensing in one small region of a plant organ and sets plant movement beside animal movement1.

Earliest held
1880, Darwin, C.
Most discussed in
The Power of Movement in Plants, 1880
In the library
10 passages in 4 works
Rewritten
2026-10-03
18501875190019251950197520002025Darwin, C., 18801Darwin, C., 18802James, W., 18903James, W., 18904Bose, J. C., 19065Bose, J. C., 19066Bose, J. C., 19267Bose, J. C., 19268
01

Darwin's summary

It says the radicle first protrudes and circumnutates, and that its tip is highly sensitive2. The same list names localised sensitiveness and the resemblance between the movements of plants and animals. It ends with the brain statement1. The held passages give only these headings. They do not give the experiments behind them, so this article cannot report what Darwin measured on the root tip.

02

A sensitive tip in James

James (1890) writes about the human body, not roots. He says that when a part of a limb is touched, we move the limb so that the touching object glides to the place where sensibility is greatest4. From this, he says, lines of habitual passage arise from all points of a member to its sensitive tip3. The held passages do not link James to Darwin or to plants. The shared phrase, sensitive tip, is a point of comparison only.

03

Bose on tips and thresholds

Bose (1906) lists, in his table of contents, negative heliotropic curvature induced by stimulation of the tips of root and shoot5. The same list names localised sensitiveness to light and transmission of excitatory effect6. Only headings survive in the held text, so the measurements are not available here. Bose (1926) reports that excitation in certain sensitive plants occurs under a current too feeble for the human tongue tip to detect7. For Biophytum he gives a figure as low as 0.5 micro-ampere8. These passages concern stems and leaves, not root tips.

SourcesEach quotation was checked word for word against the passage it opens.
  1. Localised sensitiveness — Resemblance between the movements of plants and animals—The tip of the radicle acts like a brain.Darwin, C., 1880 · The Power of Movement in Plants · open at passage 1074
  2. The radicle first protrudes and circumnutates—Its tip highly sensitive—Emergence of the hypocotyl or of the epicoty] from the grcundDarwin, C., 1880 · The Power of Movement in Plants · open at passage 11
  3. There thus arise lines of habitual passage from all points of a member to its sensitive tip.James, W., 1890 · The Principles of Psychology, Vols. 1-2 · open at passage 2043
  4. to move the member so that the touching object glides along it to the place where sensibility is greatest.James, W., 1890 · The Principles of Psychology, Vols. 1-2 · open at passage 2043
  5. Negative heliotropic curvature induced by stimulation of the tips of root and shootBose, J. C., 1906 · Plant Response as a Means of Physiological Investigation · open at passage 1388
  6. Localised sensitiveness to light and transmission of excitatory effectBose, J. C., 1906 · Plant Response as a Means of Physiological Investigation · open at passage 1388
  7. Excitation in certain sensitive plants is found to occur under a current so feeble that it cannot even be detected by the very sensitive tip of the human tongue.Bose, J. C., 1926 · The Nervous Mechanism of Plants · open at passage 96
  8. in Biophytum it may be as little as 0-5 micro-ampere, an intensity of current which cannot be detected even by the highly sensitive tip of the human tongue.Bose, J. C., 1926 · The Nervous Mechanism of Plants · open at passage 90
Linked ideas
Circumnutationpart of / contains
Darwin's account places the radicle's circumnutation and its sensitive tip together in the same chapter summary.
Tropismrelated to
Darwin and Bose both discuss movements excited by light and gravitation, and Bose describes tip stimulation producing curvature.
Bose describes excitatory impulses transmitted from a stimulated plant region and polar excitation by weak current.
Darwin's comparison of a root tip to a brain is an early case of crediting plants with animal-like control.
The brain comparison treats a plant organ as directing behaviour, which bears on what counts as mind-like.
Darwin and Bose both describe tip-localised light sensitivity with excitation transmitted to the bending region, a specific mechanism inside the broader tropic-response topic.
Where it is discussedPassages matching tip of the radicle acts like a brain, radicle tip sensitive, sensitive tip, localised sensitiveness
1880The Power of Movement in Plants · Darwin, C.5
1906Plant Response as a Means of Physiological Investigation · Bose, J. C.2
1926The Nervous Mechanism of Plants · Bose, J. C.2
1890The Principles of Psychology, Vols. 1-2 · James, W.1