Is consciousness to be found in quantum processes in microtubules?

[Michael 345]

consciousness

Surely consciousness is a CONCEPT and as such not suitable for detection

You may ask a person (as I was required to do frequently) if a person was " aware of your surroundings" and a few like questions to guage the person's level of being conscious

Consciousness goes one level higher, in such, the person is not only aware (perhaps just as important alert to their surroundings) and is conscious and alert of being conscious and alert along with being a independent entity able to act independently, not merely subject to forces outside of theirself

I would contend once a entity gains the ability of being conscious and alert add a few more neurones to the processing unit and CONSCIOUSNESS will arise

 

[Write4U]

Surely consciousness is a CONCEPT and as such not suitable for detection

It is an emergent sophistication in sensory reception and awareness of meaning, evolved from the fundamental need for "life-sustaining energy " and "fight or flight" survival mechanisms.

This sensory awareness begins very early in the cytoplasm of even single-celled organisms like the paramecium.

Watch these Amoebas, microtubular pseudopods, hunt Parameciums that are trying to escape via their microtubular ciliary propulsion.

and this perfect example of microtubule catastrophe, causing the loss of cytoplasm and the resulting death of this organism.

 

[exchemist]

No, I haven't. Billvon and now you are missing the point.

......[snip].............

How can billvon be missing his own point?

 

[Write4U]

How can billvon be missing his own point?

Because it isn't relevant to the phenomenon we are discussing.

But perhaps you misunderstand billvon and you are the one missing the relevance. Maybe billvon can confirm your understanding of the point he was making.

 

[Write4U]

In regard to ORCH OR this may be of interest.

What is quantum coherence?

Quantum coherence refers to the ability of a quantum state to maintain its entanglement and superposition in the face of interactions and the effects of thermalization . Mar 18, 2021

It is indispensable for quantum technologies — be they in sensing, transduction or computing — permitting them, in principle, to outperform their classical counterparts. To realize the promise of these technologies, one key challenge is to identify quantum states within systems that are quantum coherent.
https://www.nature.com/articles/s41567-021-01211-5

 

[Write4U]

Perhaps it is time to restate the basic conceptualization of ORCH OR

Orchestrated reduction of quantum coherence in brain microtubules: A model for consciousness
StuartHameroff/RogerPenrose

Abstract

Features of consciousness difficult to understand in terms of conventional neuroscience have evoked application of quantum theory, which describes the fundamental behavior of matter and energy. In this paper we propose that aspects of quantum theory (e.g. quantum coherence) and of a newly proposed physical phenomenon of quantum wave function “self-collapse” (objective reduction: OR - Penrose, 1994) are essential for consciousness, and occur in cytoskeletal microtubules and other structures within each of the brain's neurons. The particular characteristics of microtubules suitable for quantum effects include their crystal-like lattice structure, hollow inner core, organization of cell function and capacity for information processing.

We envisage that conformational states of microtubule subunits (tubulins) are coupled to internal quantum events, and cooperatively interact (compute) with other tubulins. We further assume that macroscopic coherent superposition of quantum-coupled tubulin conformational states occurs throughout significant brain volumes and provides the global binding essential to consciousness. We equate the emergence of the microtubule quantum coherence with pre-conscious processing which grows (for up to 500 ms) until the mass-energy difference among the separated states of tubulins reaches a threshold related to quantum gravity.

According to the arguments for OR put forth in Penrose (1994), superpositioned states each have their own space-time geometries. When the degree of coherent mass-energy difference leads to sufficient separation of space-time geometry, the system must choose and decay (reduce, collapse) to a single universe state. In this way, a transient superposition of slightly differing space-time geometries persists until an abrupt quantum → classical reduction occurs.

Unlike the random, “subjective reduction” (SR, or R) of standard quantum theory caused by observation or environmental entanglement, the OR we propose in microtubules is a self-collapse and it results in particular patterns of microtubule-tubulin conformational states that regulate neuronal activities including synaptic functions.

Possibilities and probabilities for post-reduction tubulin states are influenced by factors including attachments of microtubule-associated proteins (MAPs) acting as “nodes” which tune and “orchestrate” the quantum oscillations. We thus term the self-tuning OR process in microtubules “orchestrated objective reduction” (“Orch OR”), and calculate an estimate for the number of tubulins (and neurons) whose coherence for relevant time periods (e.g. 500 ms) will elicit Orch OR.

In providing a connection among (1) pre-conscious to conscious transition, (2) fundamental space-time notions, (3) non-computability, and (4) binding of various (time scale and spatial) reductions into an instantaneous event (“conscious now”), we believe Orch OR in brain microtubules is the most specific and plausible model for consciousness yet proposed.

https://www.sciencedirect.com/science/article/abs/pii/0378475496804769

 

[exchemist]

Perhaps it is time to restate the basic conceptualization of ORCH OR

Orchestrated reduction of quantum coherence in brain microtubules: A model for consciousness
StuartHameroff/RogerPenrose

Abstract

https://www.sciencedirect.com/science/article/abs/pii/0378475496804769

That paper is 25 years old and the ideas involved have gone nowhere since, as post 5 pointed out.

 

[Write4U]

That paper is 25 years old and the ideas involved have gone nowhere since, as post 5 pointed out.

Well yes, your post # 5 itself is 4 years old and all the objection mentioned in that post have been addressed and resolved. If you had read some of my posts you would be familiar with the current state of critical reviews.

Most objections have been proven premature and some valid objections due to flawed maths have been addressed and corrected.

There are no outstanding objections. There are still a number of unresolved questions, but there is currently no danger of an outstanding argument that would be fatal to ORCH OR or any of the similarly based competing hypotheses. ORCH OR is not the only proposition that uses terms like Orchestration, or Integration, or Global Workspace, all requiring a form of Reduction.

The contestants are Giulio Tononi’s integrated information theory (IIT) and Stanislas Dehaene’s global workspace theory (GWT). The competition was dreamed up at the Allen Institute for Brain Science, in Seattle, and is being paid for by the Templeton World Charity Foundation.

The practical side of things is being led by Lucia Melloni of the Max Planck Institute for Empirical Aesthetics, in Frankfurt.

https://www.economist.com/the-world...theories-of-consciousness-are-put-to-the-test

The Role of Predictions in Consciousness - Lucia Melloni

 

[exchemist]

Well yes, your post # 5 itself is 4 years old and all the objection mentioned in that post have been addressed and resolved. If you had read some of my posts you would be familiar with the current state of critical reviews.

Most objections have been proven premature and some valid objections due to flawed maths have been addressed and corrected.

Well I've just checked and here is the current version of the same link I posted in post 5 four years ago: https://en.wikipedia.org/wiki/Quantum_mind

The text I quoted four years ago has not been changed. So it is false to say the objection have been overcome. They haven't. Orch-OR is just as much a dead end now as it was then - in fact more so, since more time has elapsed.

 

[Write4U]

Well I've just checked and here is the current version of the same link I posted in post 5 four years ago: https://en.wikipedia.org/wiki/Quantum_mind

The text I quoted four years ago has not been changed. So it is false to say the objection have been overcome. They haven't. Orch-OR is just as much a dead end now as it was then - in fact more so, since more time has elapsed.

Well, the text of the bible hasn't changed in 3000 years and it is still wrong.

A repost of a recent article re; ORCH OR

‘Orch OR’ is the most complete, and most easily falsifiable theory of consciousness
Stuart Hameroff
Pages 74-76 | Received 02 Sep 2020, Published online: 24 Nov 2020

ABSTRACT

The ‘Orch OR’ theory attributes consciousness to quantum computations in microtubules inside brain neurons. Quantum computers process information as superpositions of multiple possibilities (quantum bits or qubits) which, in Orch OR, are alternative collective dipole oscillations orchestrated (‘Orch’) by microtubules.

These orchestrated oscillations entangle, compute, and terminate (‘collapse of the wavefunction’) by Penrose objective reduction (‘OR’), resulting in sequences of Orch OR moments with orchestrated conscious experience (metaphorically more like music than computation). Each Orch OR event selects microtubule states which govern neuronal functions. Orch OR has broad explanatory power, and is easily falsifiable.

https://www.tandfonline.com/doi/full/10.1080/17588928.2020.1839037

And this lecture at the Qualcomm Institute. January 10, 2020
Roth Auditorium - Sanford Consortium for Regenerative Medicine La Jolla, CA

An intimate lecture with renowned mathematical physicist Sir Roger Penrose and anesthesiologist Dr. Stuart Hameroff, followed by a conversation with The Science Network co-founder Roger Bingham.

Co-organized by The Penrose Institute and the UC San Diego Institute for Neural Computation, with the support of Intheon, Neocortex Ventures, and the Data Science Alliance.

Sir Roger Penrose and Dr. Stuart Hameroff discuss one of the leading theories of consciousness recently selected by the Templeton Foundation for study. Is the brain a sophisticated computer or an intuitive thinking device?

Following on from their conference in Tucson which pitted Integrated Information Theory (IIT) against Orchestrated Objective Reduction (Orch-OR), Sir Roger Penrose OM and Stuart Hameroff discuss the current state of theories that might explain human consciousness.

Sir Roger Penrose describe examples of ‘non-computability’ in human consciousness, thoughts and actions such as the way we evaluate particular chess positions which cast doubt on ‘Turing’ computation as a complete explanation of brain function. As a source of non-computability, Roger discuss his ‘objective reduction’ (‘OR’) self-collapse of the quantum wavefunction which is a potential resolution for the ‘measurement problem’ in quantum mechanics, and a mechanism for non-computable physics.

Dr. Stuart Hameroff reviews neuronal and biophysical aspects of Orch OR, in which ‘orchestrated’ quantum vibrations occur among entangled brain microtubules and evolve toward Orch OR threshold and consciousness. The nature, feasibility, decoherence times and evidence for quantum vibrations in microtubules, their role and correlation with consciousness, effects upon them of anesthetic gases and psychedelic drug molecules will be discussed, along with Orch OR criticisms and predictions of microtubule quantum vibrations as therapeutic targets for mental and cognitive disorders.

Biography: Sir Roger Penrose OM FRS, Emeritus Professor at the Mathematical Institute of the University of Oxford, Emeritus Fellow at Wadham College, and winner of the Wolf Prize in Physics, has made profound contributions across a broad range of scientific disciplines. His work encompasses geometry, black hole singularities, the unification of quantum mechanics and gravity, the structure of space-time, and the origin of our Universe. His geometric creations inspired the works of Escher, and the Penrose steps have been featured in several movies. His tilings adorn many public buildings, including the Oxford Mathematics Institute, and will soon decorate the San Francisco Transbay Terminal. The five-fold symmetry, initially thought impossible or a mathematical curiosity, has now been found in nature. In 1989 Penrose wrote The Emperor’s New Mind which challenged the premise that consciousness is computation and proposes we need new physics to understand it.

Biography: Stuart Hameroff MD is an anesthesiologist at the University of Arizona in Tucson. In the mid 1990s Hameroff teamed with famed British physicist Sir Roger Penrose to develop a quantum theory of consciousness (‘orchestrated objective reduction’, ‘Orch OR’) based on microtubule quantum computing. Highly controversial and harshly criticized, Orch OR is now supported by evidence, e.g. that anesthetics act in quantum channels in microtubules, and that microtubules have multi-scalar resonances, e.g. in megahertz. He and anesthesiology colleagues performed and published the first clinical trial of transcranial ultrasound (‘TUS’) on mental states in human volunteers, showing mood enhancement from brief, low intensity TUS. Beginning in 1994 Hameroff was the lead in starting an interdisciplinary, international conference series ‘Toward a Science of Consciousness’ held in even-numbered years in Tucson, and odd-numbered years elsewhere around the world.

Biography: Roger Bingham is the Cofounder and Director of The Science Network (http://thesciencenetwork.org/) and a member of the Computational Neurobiology Laboratory at the Salk Institute and the Institute for Neural Computation, UC San Diego. He is the co-author of The Origin of Minds: Evolution, Uniqueness, and the New Science of the Self, and the creator and host of Emmy award-winning PBS science programs on evolutionary psychology and cognitive neuroscience, including the critically acclaimed series The Human Quest. He is the Founding Director of the Collaboratory, a Center within INC, which is developing a Science In Society program of public and student engagement to explore and bridge the chasm between the creators and consumers of science and technology.

Be prepared for some mindblowing propositions by a Nobel prize laureate.

 

[Write4U]

Trying to stay current.

Signal transmission through elements of the cytoskeleton form an optimized information network in eukaryotic cells

• B. R. Frieden &
• R. A. Gatenby

Scientific Reports volume 9, Article number: 6110 (2019)

Abstract

Multiple prior empirical and theoretical studies have demonstrated wire-like flow of electrons and ions along elements of the cytoskeleton but this has never been linked to a biological function. Here we propose that eukaryotes use this mode of signal transmission to convey spatial and temporal environmental information from the cell membrane to the nucleus.

The cell membrane, as the interface between intra- and extra-cellular environments, is the site at which much external information is received. Prior studies have demonstrated that transmembrane ion gradients permit information acquisition when an environmental signal interacts with specialized protein gates in membrane ion channels and producing specific ions to flow into or out of the cell along concentration gradients.

The resulting localized change in cytoplasmic ion concentrations and charge density can alter location and enzymatic function of peripheral membrane proteins. This allows the cell to process the information and rapidly deploy a local response.

Here we investigate transmission of information received and processed in and around the cell membrane by elements of the cytoskeleton to the nucleus to alter gene expression.

We demonstrate signal transmission by ion flow along the cytoskeleton is highly optimized. In particular, microtubules, with diameters of about 30 nm, carry coarse-grained Shannon information to the centrosome adjacent to the nucleus with minimum loss of input source information.

And, microfilaments, with diameters of about 4 nm, transmit maximum Fisher (fine-grained) information to protein complexes in the nuclear membrane. These previously unrecognized information dynamics allow continuous integration of spatial and temporal environmental signals with inherited information in the genome.

Here we address the question of how environmental information that is transmitted through the cell membrane through ion fluxes is communicated internally to other components of the cell. We expect that many environmental perturbations (e.g. a localized mechanical deformation by a small environmental object) may only elicit and require a local response.

However, some signals received at the membrane, because of their content, amplitude, or spatiotemporal frequency, may require a global (or ‘coordinated’) cellular response including increased energy production in the mitochondria7,8 and changes in gene expression9 or translation within the nucleus and endoplasmic reticulum10.

Signal transmission through elements of the cytoskeleton form an optimized information network in eukaryotic cells - Scientific Reports
Multiple prior empirical and theoretical studies have demonstrated wire-like flow of electrons and ions along elements of the cytoskeleton but this has never been linked to a biological function. Here we propose that eukaryotes use this mode of signal transmission to convey spatial and temporal...

www.nature.com

And we have the rudimentary beginnings of a generalized conscious response system. In the brain, this may well be the model for the evolution of self-aware consciousness.

​

 

[Write4U]

And a little reminder of what the microtubule population in the cytoplasm and cytoskeleton of each individual cell in the body looks like.

Credit
THOMAS DEERINCK, NCMIR / SCIENCE PHOTO LIBRARY

Caption

Cell microtubules. Fluorescent light micrograph of a culture cell showing its nucleus (blue) and microtubules (green). Microtubules form part of the cytoskeleton, the internal structural units of a cell that assist in transporting material around the cell, and maintaining its shape. Microtubules are composed of polymers of the proteins alpha and beta tubulin. They are involved in transporting organelles around the cell, notably in mitosis (cell division), and they form the scaffold of cilia and flagella. The other main components of the cytoskeleton are actin and intermediate filaments (neither seen). Magnification: x600 when printed 10cm high

https://www.sciencephoto.com/media/214761/view/cell-microtubules-light-micrograph

Now imagine 1oo trillion cells connected by 1000 trillion synapses in brain alone constantly processing and transporting electrochemical information.

One can see that the resulting network is unmatched by any other physically connective structures.

If consciousness emerges from somewhere at all, the microtubule network is the ONLY qualifying candidate, IMO.

 

[origin]

If consciousness emerges from somewhere at all, the microtubule network is the ONLY qualifying candidate, IMO.

Your opinion is not worth much.

 

[Write4U]

Your opinion is not worth much.

And this, your opinion isn't worth anything at all.

Obviously, you are completely ignorant about this subject and have no clue as to what I am talking about. Try to inform yourself before you make a "contribution" to this conversation.

If you cannot refrain from ad hominem , it's better you don't post at all and soil this informative thread with your NON-SENSE, ok?

 

[James R]

If consciousness emerges from somewhere at all, the microtubule network is the ONLY qualifying candidate, IMO.

Of course it isn't!

You haven't ruled out the possibility that consciousness emerges as a result of connections between neurons, way above the size scale of anything that's happening in microtubules.

 

[Write4U]

Of course it isn't!

You haven't ruled out the possibility that consciousness emerges as a result of connections between neurons, way above the size scale of anything that's happening in microtubules.

Without microtubules there isn't any connection. Synapses are the terminal ends of microtubule bundles inside axions and dendrites!

Dynamic microtubules at the synapse
Erik W. Dent1,*
Author information Copyright and License information Disclaimer

Abstract

Microtubules (MTs) are a fundamental cytoskeletal component that give neurons structure and are the primary polymer system for long distance transport of cargo throughout the cytoplasm. Although neurons are highly polarized and their structure is often maintained throughout the life of an organism, MTs can remain dynamic in axons and dendrites, undergoing bouts of polymerization and depolymerization, referred to as dynamic instability.

Furthermore, MTs can be nucleated outside of the centrosome or MT organizing center (MTOC) that is located in the cell body, allowing dynamic formation and branching of MT polymers throughout the neuron. Together, these recent findings point to a much more dynamic landscape of microtubules in developing and mature neurons than was previously appreciated. Here we will focus on recent studies that show MT dynamics are playing a role at the synapse, both post-synaptically in dendrites and pre-synaptically in axons.

more....
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7423735/

All cellular connections at all scales are provided by microtubules. Doesn't anybody read any of the quoted science?

What you are asking is if an electrical network can have an electric field without copper wiring inside the cable transporting the electricity. Can it?

Do dendrites connect to synapses?

Stanford study reveals growing neurons gain an edge by making connections

A normal Purkinje brain cell (top) and a Purkinje cell with a GluD2 gene mutation (bottom) that affects the ability to make early synaptic connections with neighbors. (Image credit: Andrew Shuster)

In a first of its kind study, researchers led by Stanford biologist Liqun Luo used genetic experiments and computer models to shed light on two important steps of brain development in young mice: the growth of branching extensions on the bodies of neurons, called dendrites, and the connections that dendrites make with other neurons. Like biological antennas, dendrites receive incoming signals from other neurons via connections called synapses. Luo’s team found that the dendrites of growing neurons compete with one another to form connections with their partners, and the presence of successful connections increases the odds of dendrite growth.

Like biological antennas, dendrites receive incoming signals from other neurons via connections called synapses. Mar 11, 2021

“How does the brain get wired up? How do neural circuits form? These are big, unanswered questions,” Luo said.

https://news.stanford.edu/2021/03/11/growing-neurons-gain-edge-making-connections/

Dendrites In Vitro and In Vivo Contain Microtubules of Opposite Polarity and Axon Formation Correlates with Uniform Plus-End-Out Microtubule Orientation
Kah Wai Yau,1,* Philipp Schätzle,1,* Elena Tortosa,1 Stéphane Pagès,2 Anthony Holtmaat,2 Lukas C. Kapitein,

1 and Casper C. Hoogenraad

1

Abstract

In cultured vertebrate neurons, axons have a uniform arrangement of microtubules with plus-ends distal to the cell body (plus-end-out), whereas dendrites contain mixed polarity orientations with both plus-end-out and minus-end-out oriented microtubules.

........

Interestingly, at early stages of neuronal development in nonpolarized cells, newly formed neurites already contained microtubules of opposite polarity, suggesting that the establishment of uniform plus-end-out microtubules occurs during axon formation. We propose a model in which the selective formation of uniform plus-end-out microtubules in the axon is a critical process underlying neuronal polarization.

The brain’s wiring

That’s because how neurons grow is a chicken-and-egg problem, explained Luo. Do dendrites have to exist before synapses can form? Or is the formation of synaptic connections vital for dendritic growth?

According to one idea, called the synaptotrophic hypothesis, synapses stabilize dendrites and make them more likely to grow further, while dendrites without synapses are more likely to recede. Luo said that, as far as he knew, this theory has never been tested in a developing mammalian brain before. So, he decided his lab would be the first to do so.

Luo’s lab specializes in exploring how neural circuits form during development, and how they’re organized to perform specific functions. For more than two decades his lab has investigated these questions, oftentimes using Purkinje cells, principal neurons in the cerebellum that influence motor and cognitive functions.

“Purkinje cells are my first love because they were the first mammalian neurons I studied, while I was still a postdoc,” Luo said. “They look like beautiful trees and there are many genetic tools to study them.”

........
SIGNIFICANCE STATEMENT

Live-cell imaging was used to systematically analyze microtubule organization in primary cultures of rat hippocampal neurons, dentate granule cells in mouse organotypic slices, and layer 2/3 pyramidal neuron in somatosensory cortex of living mice. In vitro and in vivo, all microtubules have a plus-end-out orientation in axons, whereas microtubules in dendrites have mixed orientations.

Interestingly, newly formed neurites of nonpolarized neurons already contain mixed microtubules, and the specific organization of uniform plus-end-out microtubules only occurs during axon formation. Based on these findings, the authors propose a model in which the selective formation of uniform plus-end-out microtubules in the axon is a critical process underlying neuronal polarization.

Keywords: cytoskeleton, dendrites, development, microtubule dynamics, neuron, polarity

Much more........this is a formal paper.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4728718/#

 

[Write4U]

More on synaptic connection:

A conceptual view at microtubule plus end dynamics in neuronal axons
Author panel; AndréVoelzmanna, InesHahna, Simon P.Pearceab, NataliaSánchez-Sorianoc, AndreasProkopa

Highlights
. Axons are the cable-like extensions of neurons which wire the brain.
. Axon formation and maintenance requires ordered microtubule (MT) bundles.
. We discuss the mechanisms that regulate the de/polymerisation of axonal MTs.
. We discuss the model of local homeostasis to explain the maintenance of MT bundles.

Fig. 1. Life stages of axons. Images show one neuron during its various life stages, with the cell body on the left and axon on the right; MTs are shown as green interrupted lines, actin in magenta and muscles as pink round shapes. The different life stages are indicated in the headings, and the various biological processes associated with those stages are annotated in each figure. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

1. Introduction

Axons are the slender, up-to-a-metre long processes of neurons which form the cables that wire the nervous system. These delicate structures often need to survive for a lifetime, i.e. many decades in humans. Parallel polar, predominantly plus end out oriented, bundles of microtubules (MTs) run all along axons to form their structural backbones and highways for life-sustaining transport (Baas and Lin, 2011). These MT bundles are so densely packed,with MTs being separated by less than 100 nm, that they can only be reliably resolved through electron microscopy (Mikhaylova et al., 2015).

MTs are important at every life stage and for virtually all morphogenetic changes of axons (Penazzi et al., 2016, Prokop, 2013) (Fig. 1). Alterations in MT properties are often linked to developmental and/or intellectual brain disorders, and the precocious decay of MT bundles is seen as an important cause for axon degeneration (Adalbert and Coleman, 2012, Neumann and Hilliard, 2014). MTs are therefore viewed as attractive targets for drug therapies (Baas and Ahmad, 2013, Benitez-King et al., 2004, Eira et al., 2016).

more.......
https://www.sciencedirect.com/science/article/pii/S0361923016301885#fig0015

 

[Write4U]

continued from thread "Is mass a number"

My search led me to this astounding video.

This video may be revelatory of interpretation of natural fractals and how this might affect consciousness.

 

[Write4U]

Do plants have a form of consciousness?
If microtubules are associated with sensory data processes, they should affect the behavior of plants. Plants have microtubules in their cytoskeleton and cytoplasm

And behold they do!

 

[Write4U]

In furtherance of plant sentience.
Plant Physiology

The Role of Microtubules in Guard Cell Function[URL='https://www.ncbi.nlm.nih.gov/pmc/articles/PMC61019/#FN1']1[/URL]
ABSTRACT

Guard cells are able to sense a multitude of environmental signals and appropriately adjust the stomatal pore to regulate gas exchange in and out of the leaf. The role of the microtubule cytoskeleton during these stomatal movements has been debated. To help resolve this debate, in vivo stomatal aperture assays with different microtubule inhibitors were performed. We observed that guard cells expressing the microtubule-binding green fluorescent fusion protein (green fluorescent protein::microtubule binding domain) fail to open for all major environmental triggers of stomatal opening.

Furthermore, guard cells treated with the anti-microtubule drugs, propyzamide, oryzalin, and trifluralin also failed to open under the same environmental conditions. The inhibitory conditions caused by green fluorescent protein::microtubule binding domain and these anti-microtubule drugs could be reversed using the proton pump activator, fusicoccin.

Therefore, we conclude that microtubules are involved in an upstream event prior to the ionic fluxes leading to stomatal opening. In a mechanistic manner, evidence is presented to implicate a microtubule-associated protein in this putative microtubule-based signal transduction event.

Guard cells regulate gas exchange in and out of the leaf by precisely controlling the size of their stomatal aperture. These dynamic changes in aperture size (i.e. stomatal movements) occur in response to environmental and endogenous stimuli that may involve auxins, light, CO2, and humidity (for review, see

Assmann, 1993).

In a specific manner, blue and red light induce stomatal opening by activating a plasma membrane H+ ATPase (

Shimazaki et al., 1986; Serrano et al., 1988). Activation of the proton pump leads to an influx of K+, due to an opening of the voltage-gated K+ channels and consequently, water enters the cell via osmosis. This increase in turgor pressure causes the opening of the stomatal aperture. Although these general physiological events are well documented, the precise signaling events required for proton pump activation are less understood.

The molecular intricacies of stomatal opening are widely under investigation; however, how guard cells transduce the signal from perception to stomatal opening remains unclear.

One area of interest involves the role of microtubules. These proteinaceous, dynamic polymers (

Mitchison and Kirschner, 1984) have been implicated in guard cell development (Palevitz and Hepler, 1974; Palevitz, 1982; Apostolakos and Galatis, 1998, 1999).

Like other diffusely growing plant cells, microtubules in the cortex of developing guard cells guide the deposition of cellulose microfibrils (

Giddings and Staehelin, 1991).

However, unlike other plant cells, the cortical microtubules in guard cells remain well organized after differentiation is complete. This suggests that microtubules have an additional role in guard cells beyond cellular morphogenesis.

Some possibilities include an involvement in the opening or closing of the stomata and/or the transduction of the signal from perception to proton pump activation.

In other eukaryotes, microtubules have been implicated in cell signaling (

Leiber et al., 1993; Bershadsky et al., 1996), but little direct evidence exists for their involvement in signal transduction in plants.

Nonetheless, plant microtubules are likely regulated by calcium (

Fisher et al., 1996; O'Brien et al., 1997), a ubiquitous cell-signaling molecule in plants (Poovaiah and Reddy, 1987; Gilroy et al., 1993). Calcium also regulates stomatal opening and closure (Blatt, 1999), therefore, an interplay between calcium, microtubules, and stomatal movements is possible.

more.....
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC61019/#

The uncanny ability of microtubules to detect and control cellular responses and activities in flora as well as in fauna makes the microtubule network in cytoskeleton, cytoplasm, and neural network a prime candidate for consideration as a form of cellular proto-sentience in all eukaryotic organisms.