Plant intelligence dux: a comprehensive rebuttal of Kingsland and Taiz

Again, in quoting MacDougal (1908 p175) by Kingsland and Taiz, “In no instance does the activity of the plant involve choice or decision (spoiler alert; they do. Nick 2023), or anything except the most generalised form of consciousness”. This most generalised consciousness is downgraded by Taiz and Kingsland “to responding to stimuli” with no justification. What Macdougal did say is written in the New York Times (1909) article discussing Frances (son of Charles) Darwin’s statement in 1908 that plants retain a faint trace of consciousness of the kind in mankind. MacDougal (1909 p75) wrote “If the proposal of Woodbridge be accepted, that the coupling up of two forms of perceptions gives rise to consciousness then this faculty may be shared by some plants of which the narcissus, or Chinese lily is an example. The orientation by daffodil blossom depends both on the force of gravity and the direction of illumination”. Integration of signals is indicative of a conscious reaction albeit at a low level. Kingsland and Taiz (2024) have put their own (fake?) words into his mouth.

Moreover, in their article, Kingsland and Taiz state that dead people cannot rebut statements made on their behalf, but they ignore that when discussing McDougal and others now dead, including Barlow, who died 7 years ago. They claim that supposed anthropomorphic statements have sometimes been made by us. Not recognising that what is actually anthropomorphic is frankly in the eye of the beholder and not fact, just opinion. The narrowness of conservative attitudes and claims is invariably defeated by advancing knowledge (Minorsky 2024). It is claimed by Kingsland and Taiz (2024) that plant neurobiology has contributed nothing that could not be dealt with by ordinary technology; Minorsky (2024) exposes the falsity of that view.

When I use such names of such “luminaries”, it is because such people were usually the first to suggest important aspects which changed perspectives on plant and cell intelligence. It is a scientific courtesy to indicate the contribution of each of these since they were the first in their field to do so. But also in my long experience in science, such scientists have usually spent some considerable time thinking through the consequences of what they have found and putting them down on paper. Every plant scientist needs to understand their insights in order to help them understand such concepts and design better experiments. This is not confirmation bias but simply good scholarship.

Kingsland and Taiz profess ignorance of what Darwin actually said about intelligence. The most extensive discussion on intelligence by Darwin comes from his experiments and observations on earthworms. He was the first published source on biological intelligence so far as I could find some 25 years ago. Darwin’s interest in earthworm behaviour started in the 1830s, and he involved both relatives, friends and his son in making the observations (Darwin 1881 and Darwin letters (https://www.darwinproject.ac.uk) (University of Cambridge)). Darwin (1881) noted the typical behaviour of earthworms was to drag leaves (as eventual food) into their burrow and asked himself at the beginning as to what is the most efficient way of getting differently shaped leaves, into the ground when randomly distributed on the surface. If they were pointed, then he considered that the efficient way would be to pull the leaf into the burrow, point-first for leaves of that shape because he would do it that way. He records that about 80–85% of worms drag leaves into their burrows by the pointed part of the leaf. Experiments using differently shaped, triangular-like bits of paper confirmed that conclusion. Descriptions then followed using different types of leaf that came from plants that were not native to England with similar conclusions on leaves of pointed shape. Completely round leaves (lime tree, for example) with a tiny point led only to slight, point-based differences in the removal to the earthworm burrow. How then do worms determine the shape in the first place? He describes how they touch the leaf all around (they do not have eyes) and must clearly remember the shape so they can drag it point first into the burrow. Darwin concludes that worms have some degree of intelligence, it is not chance behaviour.

George Romanes, who Darwin first noticed at Cambridge in 1871, became Darwin’s close associate in 1874. In discussion (Darwin 1881), Romanes pointed out that intelligence can only be safely inferred when we see that an individual profits from its own experience. “Now if worms try to drag leaves into the burrow first in one way or another until they at last succeed, they profit at least in each particular instance by experience” was Darwin’s response (Darwin 1881. p.40). Trial and error.

Darwin handed over a lot of material he had accumulated on intelligence to Romanes who included them in his book “Animal Intelligence” (1883). Romanes included a definition of intelligence (Romanes 1883. p17) of “Intentional adaptability of means to ends”. Darwin’s contributions are indicated throughout the book, and they give some further understanding of Darwin’s understanding of intelligence. In my view, Romanes had a better grasp of biological intelligence than Darwin.

“Intelligence is based on how efficient a species becomes at doing the things they need to survive”, is a statement I have used twice and is, in my view, an accurate summary of Darwin’s understanding of intelligence. It is irrelevant to me whether Darwin actually wrote those exact words. If the statement accurately fits the observations (something we do all the time as indicated earlier), then they are Darwin’s written opinions briefly summarised, so they are refenced to Darwin. “Efficient” covers profiting from experience in the recovery of food for survival. The more efficient, the more gain of food: with plants the physical resources of the environment are the equivalent of “food”. The more efficient, gain more, with a similar outlay of energy.

On rereading Darwin’s book for this article, I realised that he did mention plants which I had forgotten. In discussing intelligence Darwin says, “We see how difficult it is to judge whether intelligence comes into play, for even plants might sometimes be thought to be thus directed: for instance, when displaced leaves redirect their upper surfaces towards the light by extremely complicated movement and by the shortest course” (Darwin 1881 p38). This is an adaptive response. Von Hartmann (1875) concerning the self-same plant response concludes “If one sees how many means are here to attain the same end, one will be almost tempted to believe that here dwells a secret intelligence which chooses the most appropriate means for the attainment of the end”. The ability of the leaves of many species to perform this task can improve the probability of survival and is therefore adaptive but only in relevant wild circumstances.

The refence to her is the oft-repeated statement “a goal for the future would be to determine the extent of knowledge the cell has of itself and how it uses that knowledge in a ‘thoughtful’ manner when challenged” (McClintock 1984). McClintock spent considerable time in thinking because she introduced transposons when the dogma was that the genome was inviolate. Dogmatic voices tried to see her observations destroyed (Keller 1983. p8-10). Is this familiar? She was even described as mad. Such attitudes are common amongst those who fail to see the value of freedom of thought. Keller (1983) spent a lot of time recording conversations with McClintock who indicated the importance of holding on to an idea despite the difficulties “don’t throw it away many good ideas have gone that way”.

Kingsland and Taiz (2024) state that I sometimes modify McClintock’s statement in two ways. One is the insertion of the word “organism” replacing the word “cell”. That is because I read Keller’s book throughout before writing; Kingsland and Taiz have not. I quote from Keller page 200, “Organism” is for her a code word, not simply a plant or animal. She regards cells as organisms and organisms as cells. Note her commitment to the “oneness” of nature (Keller 1983 p.201).

.Another transgression that I made according to Kingsland and Taiz (2024) is my removal of apostrophes around the word thoughtful. Dennis Bray quotes McClintock’s statement with the apostrophes around the word thoughtful but his interpretation is the same as mine. The title of his book “Wetware a computer in every living cell (2009)” identifies what Keller’s statement means to him and to me. Bray has given me numerous insights into cell function with valuable articles published in Nature and elsewhere. Others concur in understanding. “The cell is like a table in which decision makers debate a question and respond collectively to the information put to them” (Levy et al. 2010). The negative attitude of Kingsland and Taiz has given me nothing and does not progress understanding; it is in fact the reverse. The only reason for the apostrophes is that she recognised that thoughtful was not a common word to use about cells.

Barbra McClintock’s “ Knowledge the cell has of itself” and “thoughtful cell” counter the dogma associated with the modern synthesis of evolution that is fast collapsing under its own contradictions (Ball 2023; Noble 2008; Noble and Noble 2023; Schapiro 2011). Her information indicated that the cell is master of the genome and not as commonly assumed the reverse (Trewavas 2014, chapter 21; Schapiro, 2011). Ball (2023) makes this conclusion very clear too. In McClintock’s view, the cell, not the gene, is the basic element of life. “There’s no such thing as a central dogma into which everything will fit-any mechanism you can think of you will find- even if it is the most bizarre form of thinking behaviour” (Keller 1983. p179).

Went and Thimann wrote (1937 p151) “In tropic responses plants exhibit a kind of intelligence; their movement is of subsequent advantage to them”. “This sensitivity, not otherwise noticeable in plants, explain why it is in this regard to tropistic responses, the parallelism between plants and animals has been so much stressed” (Went and Thimann 1937). Kingsland and Taiz (2024) omit the second sentence and claim that “the context does not mean they thought plants had a kind of intelligence”. That is wrong. Thimann was a chemist and F. Went disappeared into ecology after this publication. The key words here are “advantage”, that is benefit, profit as indicated by Romanes (1883) in his definition of intelligence. Secondly, is the parallelism between plants and animals in movement. Tropic responses are adaptive responses: Romanes definition is as applicable to plants as it is to animals.

Darwin’s earth worm experiments on intelligence and Romanes definition are routinely included in university lectures and particularly in lectures on soil. Only in wild or even agricultural field circumstances will gravitropism be an advantage; it has no benefit in laboratory experiments. I have always reproduced the Went and Thimann statement above because it is the first time that plant physiologists identified a kind of intelligence in plants.

Von Sachs was for some 60 years a lonely voice concerning a role for purpose in plant development and behaviour. Sachs (1887) p601) said “All those adaptations in the organism are purposeful which contribute to its maintenance and insure its existence”. What upset von Sachs was not the imagined ramblings of Kingsland and Taiz but the following: “Concerning the point, I should wish to anticipate viz the use of the word purpose which many fanatics of the theory of descent would if possible, banish from the language”. “To the purpose means therefore the same as capable of existence” (1887, p10). Purposeful behaviour has the same meaning as intentional behaviour forming part of Romanes (1883) definition of intelligence. Purpose describes goal-directed behaviour. But the use of purpose was condemned by the Modern Synthesis of Evolution that insisted incorrectly that mutations were randomly distributed through the genome. It is now known they are not randomly distributed in bacteria, plants and animals (Martincorena et al. 2012; Zamai 2020: Grey-Monroe et al. 2022). The recovery of purpose, that is, goal direction, in plants is to be found in Russell (1946). He carefully skirts the problems of the dogma of the Modern Synthesis of Evolution.

The Modern Synthesis of Evolution is fast disappearing as it is known that cells control their own genomes (Schapiro 2011). The genome is just another cell organ or organelle. Such purposeful behaviour is now described as teleonomic, and von Sachs had the foresight to appreciate that (Gilroy and Trewavas 2023). If further information on teleonomy is required, then the 15 papers on teleonomy (Biological Journal of the Linnean Society 139: pp341-587) are required reading. Gilroy and Trewavas (2023) on plant teleonomy illustrate how Darwin’s self-admitted error of underestimating environmental influences obviously and particularly on plant evolution, resuscitates purpose and directiveness in plant development and evolution through environmental change.

What is meant by teleonomy or goal-directed behaviour? It can be said that a seed germinates and makes a new plant, or more accurately that a seed germinates to make a new plant. A flower opens to attract pollinators; a fruit ripens to attract predators that will spread its seed. These statements indicate purpose; Von Sachs would have approved.

Bose is considered justifiably the father of plant electrophysiology with 7–8 books, numerous papers and thousands of experiments on numerous plants. In the preface to his “Nervous mechanism of Plants” (1926), he states “I next tried to find whether ordinary plants, meaning those regarded as insensitive, exhibit characteristic electric responses already known in sensitive plants. I was able to show that every plant is excitable and responds to a stimulus by electric responses of galvanometric negativity the response being abolished at the death of a plant”. In page 157 onwards, he demonstrates that the pulvinus operates electrically under asymmetric light stimulation; this is the tissue that Darwin and von Hartmann referred to earlier in reference to intelligence.

I published several of his results in Calvo et al. (2016) illustrating fatigue and were able to demonstrate a similar fatigue in intracellular calcium during repetitive wind signalling (Knight et al. 1992). What Bose was detecting is undoubtedly interpreted through elevations of cytosolic calcium.

He was much and incorrectly maligned by proponents of the Modern synthesis. I read through the translation by Packard and isolated what he said of value to plant behaviour. I have published the list twice in Trewavas (2014, 2023). Gilroy and Trewavas (2023) explain his use in understanding plant evolution.

The suppression of uncomfortable ideas may be common in religion or in politics, but it is not the path to knowledge and there is no place for it in the endeavour of science.—Carl Sagan (1981)

I have used this quote from Carl Sagan, husband of Lynn Margulis, and a noted astrophysicist. I am not an astrophysicist but this quote from a television programme in 1980 (Cosmos; Heaven and Hell) summarises my reaction to Alpi et al. (2007). Negative attitudes do not contribute to the path of knowledge, and this group that organised Alpi et al. (2007) seems incapable of constructive criticism but only condemnation.

Much is made by Kingsland and Taiz (2024) of the 36 scientists who signed up to a letter sent around by David Robinson and finally published as Alpi et al. (2007). That claim was that plant neurobiology was of no use and as Minorsky (2024) puts it, an attempt to strangle it at birth. But a counterbalancing statement was not offered as it should have been. The contribution by Alpi et al. (2007) was constructed in my view as an alarmist statement as though plant biology would collapse if people did not sign up. An alternative point of view was not solicited as good scientists would have done.

In 2005/2006, I was contacted by a German scientist, a future signatory of Alpi et al. (2007), asking me to do something about plant neurobiology. The correspondent said I was one of his heroes (reference to a furore that occurred on publication of Trewavas (1981)) and that the zoological members of his department were laughing about neurobiology in plants. He had hoped that molecular biology would raise their appreciation of plant biology, but this was being diminished by plant neurobiology. I suspect that this is the fundamental reason for Alpi et al. (2007). I refused because I have always believed in open debate.

We do not know the following about the Alpi et al. (2007) petition. The immediate group and outsiders totalled 36 out of how many plant biologists solicited? We have not been told how many contacted but did not sign. The signatories who signed up from outside the immediate group around Taiz and Robinson seemed to have accepted the Robinson statement on trust, suggesting previous contact, friends and similarity of a particular research area played a strong part in those that did sign. Or at least there is no indication that those who signed attempted to investigate the truth of the Robinson claims. That is a serious mistake because there was good justification for rejecting Robinson’s statement whose information seemed to have been acquired second hand.

The original Robinson letter stated that proponents of neurobiology had suggested that higher plants have nerves, synapses, the equivalent of a brain localised somewhere in the root and an intelligence. That was misleading. Darwin was responsible for the statement of the root tip acting not as a brain but “like the brain” of a lower animal. As regards nerves and synapses, there was no mention in Alpi et al. (2007) of JC Bose’s enormous compendium of thousands of experiments and demonstrations of nerve and synapse in Mimosa and related sensitive plants and other species too. I suspect that no one in the list of 36 was in any way aware of Bose’s contribution. His publications were in the 1920s. You would have to be in plant electrophysiologist to even have heard of Bose. But his nerves and synapses are functional activities; they behave like nerves and synapses, but the refined and highly differentiated anatomical in animals is not present, and it would not be expected to be so.

To quote Bose, “Experiments are described showing that the response of the isolated plant-nerve is indistinguishable from that of the animal nerve throughout a long series of parallel variation of conditions”. “In the case of responsive plants that exhibit visible movement (like Mimosa or Dionaea) are not unique but occur under similar circumstances even in ordinary apparently insensitive plants and are characteristic of all plant organs” (Bose 1926. p44, p45 and following; Bose 1907, p 15).

I wrote to most of those who signed asking for their reasons. Only four replied; two said it was a spat that would fade quickly, and two others said that they thought it was another version of The Secret Life of Plants (Tompkins and Bird 1973) indicating no clarity of understanding.

Despite intelligence being mentioned in the original letter by Robinson, it is not discussed at all in Alpi et al. (2007). It is not surprising that plant scientists do not read the intelligence literature. I assume like others they considered intelligence, incorrectly, to be the equivalent of human intelligence and IQ. This initial group of 36 in my view signed up for something they had no clear understanding of at all and may have been misled by the compilers of it. It was a false prospectus driven not by the desire to improve scientific knowledge but to condemn. This group of 36 quickly evaporated. Most were evidently not committed and did not join any subsequent venture. It was down to five or six for the arguments about consciousness and is now down to one in this article. Hardly a vote of confidence or perhaps an appreciation that Alpi et al. (2007) got it wrong.

Disputes in plant science should be about clarifying thought, the dispassionate exchange of ideas and information. I have indicated that debates should be based on reasonable guidelines, and I have indicated some of these. I do think there was an editorial failure in TIPS not to insist on immediate countervailing views so that assessment could be more easily made. But I have put in some guides to a debate which would be helpful if notice is taken of them. The intention behind my introduction in Trewavas (2003) was to upgrade the status of plants indicating that they, like all life, are intelligent. That view has surely had an impact and as an idea is now much more widely spread. The value to me personally is that it drove me to understand better the nature of plant life in the wilderness and taken me into different avenues of understanding which are presently being written up.