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Plant neurobiology: an integrated view of plant signaling

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Abstract

Plant neurobiology is a newly focused field of plant biology research that aims to understand how plants process the information they obtain from their environment to develop, prosper and reproduce optimally. The behavior plants exhibit is coordinated across the whole organism by some form of integrated signaling, communication and response system. This system includes long-distance electrical signals, vesicle-mediated transport of auxin in specialized vascular tissues, and production of chemicals known to be neuronal in animals. Here we review how plant neurobiology is being directed toward discovering the mechanisms of signaling in whole plants, as well as among plants and their neighbors.

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... We begin in the next section by reviewing the current empirical evidence concerning plant cognition. After this, we introduce the reader to the emerging field of Plant Neurobiology (Brenner et al., 2006). The idea here is that if we can understand how sensorimotor integration takes place within plant vascular structures, we will be a step closer to understand what it is like to be a plant (Calvo, 2017). ...
... Plant neurobiology (PN) studies plant signaling with the aim of providing an explanation of how plants, qua informationprocessing systems, perceive, and act in an integrated and purposeful manner Brenner et al., 2006;Calvo, 2016). The rationale that underlies this scientific endeavor is that intelligent behavior requires information to be integrated with an eye to coordinating physiological needs among the different plant structures. ...
... As the reader may have guessed, the very idea of plant neurobiology is not free from controversy. Since the term was first coined in 2006 (Brenner et al., 2006), different authors have reacted against it. For instance, Alpi et al. (2007, see also Struik et al., 2008) argued that the concept is based on vague analogies, and adds nothing to our current understanding of plant physiology, ecology, and metabolism. ...
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Unlike animal behavior, behavior in plants is traditionally assumed to be completely determined either genetically or environmentally. Under this assumption, plants are usually considered to be noncognitive organisms. This view nonetheless clashes with a growing body of empirical research that shows that many sophisticated cognitive capabilities traditionally assumed to be exclusive to animals are exhibited by plants too. Yet, if plants can be considered cognitive, even in a minimal sense, can they also be considered conscious? Some authors defend that the quest for plant consciousness is worth pursuing, under the premise that sentience can play a role in facilitating plant's sophisticated behavior. The goal of this article is not to provide a positive argument for plant cognition and consciousness, but to invite a constructive, empirically informed debate about it. After reviewing the empirical literature concerning plant cognition, we introduce the reader to the emerging field of plant neurobiology. Research on plant electrical and chemical signaling can help shed light into the biological bases for plant sentience. To conclude, we shall present a series of approaches to scientifically investigate plant consciousness. In sum, we invite the reader to consider the idea that if consciousness boils down to some form of biological adaptation, we should not exclude a priori the possibility that plants have evolved their own phenomenal experience of the world. Cognitive Biology > Evolutionary Roots of Cognition Philosophy > Consciousness Neuroscience > Cognition A climbing bean (Phaseolus vulgaris) with needle electrodes inserted into its main stem aimed to reveal the underpinnings at work as it responds to the environment. At the Minimal Intelligence Laboratory, we seek to correlate the behavior of plants and phytoneural activity in order to study plant cognition and sentience.
... Calvo (2016) pinpoints plant signaling and plant neurobiology as precursors of the philosophy of plant neurobiology, a new field of research emerging at the intersection of the philosophy of cognitive science and plant neurobiology. Brenner et al. (2006) were one of the first to posit the fundamentals of plant neurobiology, a field of research that aims to understand how plants process the information they obtain from their environment to develop, prosper and reproduce optimally. The informational network within plants is focused on systemic signals, which include intercellularly transported macromolecules that regulate development and/or defense pathways, including transcriptional activators, RNA molecules, peptide hormones, and phytohormones (Brenner et al. 2006, p. 413). 2 Gagliano (2017) has recently shown that we might even try to posit basic consciousness if we take into account proposed associative learning in plants, which could then open a new interface to exploring the concept of emergence of consciousness, a part of, maybe, an information-centered all-inclusive theory of consciousness. ...
... We still do not know whether such problems can be solved in an easier way, i.e., reduced to problems that have a polynomial increase (the P vs. NP problem), 9 but it is interesting to note that even though modern computers cannot do it efficiently, swarm intelligence seems good at it. 10 Sheldrake (2020, p. 53) sees mycelial networks as swarms of hyphal tips and "patterns of collective behavior", but also emphasizes how mycelium quickly outgrows the analogy because all the hyphal tips in a network are connected to one another. Fungi are a decentralized organism, and there is no such thing as a head or a brain, which is why it seems difficult to put it in one of the predefined drawers containing abstract concepts related to life, cognition, and intelligence. ...
... The P vs. NP question asks whether such difficult problems can be also solved quickly, and the modern intuition seems that the answer is a negative one. 10 Many algorithms have been inspired by biological swarm activity, especially regarding ant and bee foraging, and belong to a class of evolutionary algorithms that provide good approximate solutions to hard computational problems. See Bonabeu, Dorigo & Theraulaz 1999 for an overview. ...
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Recent mycological research has brought to light several interesting characteristics of fungi. In this paper, the goal is to highlight philosophically interesting phenomena spanning the world of fungi. We will examine how mycelium networks can form a certain neural network of possible computation and contrast them with computationalist and connectionist theories in logic and philosophy of mind. We will analyze how various fungi as able to solve hard computational problems and revisit the notion of swarm intelligence to be able to expand our notion of intelligence overall. Next, we will inspect the mind-controlling mechanism of various species of fungi such as Ophiocordyceps and see which metaphysical and cognitive consequences altering the behavior of other animal species might have. All of these issues bring to light the need to incorporate fungi phenomena into cognitive studies and philosophy in general.
... Most importantly, plants naturally lack Htt homologs, and transgenic plants expressing Htt or mHtt would avoid any endogenous Htt's effects, which will simplify the interpretation of polyQ effects compared to any HD animal models. Furthermore, recent molecular, biochemical and physiological studies have shown that plant root apices possess sensing functions, such as receiving, integrating and responding to signals from their environment, and that root hairs share several morphological and biochemical features with neurons, such as a single tubularshaped cell, long extension tip growth, high energy demand, cell polarity, action potential, and environmental sensing capacity [7,8]. Therefore, roots and root hairs might be more susceptible to polyQ-induced toxicity than other organs/cells to exhibit phenotypic changes. ...
... Root hairs and neurons have been reported to share similar morphological and biochemical features [7,8], and both the axon extension and root hair tip growth processes are tightly associated with tubular endoplasmic reticulum (ER) remodeling in the direction of cell elongation [8,[24][25][26]. During the subculture and propagation of transgenic plants, we paid special attention to root growth. ...
... In addition, neuronal loss is a common pathological hallmark of HD and many other NDDs [1,2]. Root hairs and neuronal cells share some strikingly similar characteristics, such as polarity, long extension outgrowth, high energy demand, and environmental sensing capacity [7,8]. Observation of restricted root hair outgrowth in Htt ex1 Q63 roots and partially restricted in Htt ex1 Q42 roots means that root hairs might also respond to toxic polyQ repeats similar to neuronal cells. ...
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Pathophysiology associated with Huntington’s disease (HD) has been studied extensively in various cell and animal models since the 1993 discovery of the mutant huntingtin (mHtt) with abnormally expanded polyglutamine (polyQ) tracts as the causative factor. However, the sequence of early pathophysiological events leading to HD still remains elusive. To gain new insights into the polyQ-induced early pathogenic events, we expressed Htt exon1 (Htt ex1 ) with a normal (21), or an extended (42 or 63) number of polyQ in tobacco plants, which lack an Htt ortholog to avoid any associated effects from endogenous Htt . Here, we show that transgenic plants accumulated Htt ex1 proteins with corresponding polyQ tracts, and that mHtt ex1 induced protein aggregation and affected plant growth, especially root and root hair development, in a polyQ length-dependent manner. Quantitative proteomic analysis of young roots from severely affected Htt ex1 Q63 and unaffected Htt ex1 Q21 plants showed that the most impaired protein by polyQ63 is a GTP cyclohydrolase I (GTPCH) along with many its related one-carbon (C 1 ) metabolic pathway enzymes. GTPCH is a key enzyme involved in folate biosynthesis in plants and tetrahydrobiopterin (BH 4 ) biosynthesis in mammals. Validating studies in 4-week-old R6/2 HD mice expressing a mHtt ex1 showed reduced levels of GTPCH and dihydrofolate reductase (DHFR, a key folate utilization/alternate BH 4 biosynthesis enzyme), and impaired C 1 and BH 4 metabolisms. Our findings from mHtt ex1 plants and mice reveal impaired expressions of GTPCH and DHFR and contribute to a better understanding of mHtt-altered C 1 metabolism and C 1 interconnected BH 4 metabolism leading to the pathogenesis of HD.
... Most importantly, plants naturally lack Htt homologs, and transgenic plants expressing Htt or mHtt would avoid any endogenous Htt's effects, which will simplify the interpretation of polyQ effects compared to any HD animal models. Furthermore, recent molecular, biochemical and physiological studies have shown that plant root apices possess sensing functions, such as receiving, integrating and responding to signals from their environment, and that root hairs share several morphological and biochemical features with neurons, such as a single tubularshaped cell, long extension tip growth, high energy demand, cell polarity, action potential, and environmental sensing capacity [7,8]. Therefore, roots and root hairs might be more susceptible to polyQ-induced toxicity than other organs/cells to exhibit phenotypic changes. ...
... Root hairs and neurons have been reported to share similar morphological and biochemical features [7,8], and both the axon extension and root hair tip growth processes are tightly associated with tubular endoplasmic reticulum (ER) remodeling in the direction of cell elongation [8,[24][25][26]. During the subculture and propagation of transgenic plants, we paid special attention to root growth. ...
... In addition, neuronal loss is a common pathological hallmark of HD and many other NDDs [1,2]. Root hairs and neuronal cells share some strikingly similar characteristics, such as polarity, long extension outgrowth, high energy demand, and environmental sensing capacity [7,8]. Observation of restricted root hair outgrowth in Htt ex1 Q63 roots and partially restricted in Htt ex1 Q42 roots means that root hairs might also respond to toxic polyQ repeats similar to neuronal cells. ...
Article
Full-text available
Pathophysiology associated with Huntington’s disease (HD) has been studied extensively in various cell and animal models since the 1993 discovery of the mutant huntingtin (mHtt) with abnormally expanded polyglutamine (polyQ) tracts as the causative factor. However, the sequence of early pathophysiological events leading to HD still remains elusive. To gain new insights into the early polyQ-induced pathogenic events, we expressed Htt exon1 (Httex1) with a normal (21), or an extended (42 or 63) number of polyQ in tobacco plants. Here, we show that transgenic plants accumulated Httex1 proteins with corresponding polyQ tracts, and mHttex1 induced protein aggregation and affected plant growth, especially root and root hair development, in a polyQ length-dependent manner. Quantitative proteomic analysis of young roots from severely affected Httex1Q63 and unaffected Httex1Q21 plants showed that the most reduced protein by polyQ63 is a GTP cyclohydrolase I (GTPCH) along with many of its related one-carbon (C1) metabolic pathway enzymes. GTPCH is a key enzyme involved in folate biosynthesis in plants and tetrahydrobiopterin (BH4) biosynthesis in mammals. Validating studies in 4-week-old R6/2 HD mice expressing a mHttex1 showed reduced levels of GTPCH and dihydrofolate reductase (DHFR, a key folate utilization/alternate BH4 biosynthesis enzyme), and impaired C1 and BH4 metabolism. Our findings from mHttex1 plants and mice reveal impaired expressions of GTPCH and DHFR and may contribute to a better understanding of mHtt-altered C1 and BH4 metabolism, and their roles in the pathogenesis of HD.
... Under the entry for "nervous system", Encyclopaedia Britannica states that [i]n animals, in addition to chemical regulation via the endocrine system (which plants have), there is another integrative system called the nervous system. 1 Most dictionaries and textbooks maintain that only animals have nervous systems. Although plants do not have a nervous system according to this phylogenetic definition, a growing body of botany research from the past 25 years shows that many plants transmit electrical signals to and from different parts of their bodies to respond to environmental stimuli. 2 Several scientists from different fields have spoken about plant neurobiology and the nervous systems of plants, [3][4][5] but this new viewpoint is not free of controversy and has been criticized by others. 6,7 One could consider this controversy to be an ontological debate about whether some entities belong to one category or another, not affecting physiological plant and animal research, but this debate is not harmless to scientific knowledge -it is significant in evolutionary biology because a phylogenetic definition does not allow for considering processes of convergence evolution, which is necessary when discussing the evolution of living beings. ...
... 115,116 The nerve-like cellular makeup of plants mentioned in the previous section does not reach the same degree of complexity as animal nerves, but research findings have led some scientists to propose that plants have simple nervous systems and that plant neurobiology exists. 4,41 However, these proposals have been openly rejected by some in the scientific community, 6,7 who argue that concepts of neuroscience cannot be applied to plants because certain definitions cannot be fulfilled. We think that the emergence of this debate puts the spotlight on the definitions used in neuroscience, specifically on the definition of a nervous system. ...
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Most textbook definitions recognize only animals as having nervous systems. However, for the past couple decades, botanists have been meticulously studying long-distance signaling systems in plants, and some researchers have stated that plants have a simple nervous system. Thus, an academic conflict has emerged between those who defend and those who deny the existence of a nervous system in plants. This article analyses that debate, and we propose an alternative to answering yes or no: broadening the definition of a nervous system to include plants. We claim that a definition broader than the current one, which is based only on a phylogenetic viewpoint, would be helpful in obtaining a deeper understanding of how evolution has driven the features of signal generation, transmission and processing in multicellular beings. Also, we propose two possible definitions and exemplify how broader a definition allows for new viewpoints on the evolution of plants, animals and the nervous system.
... Despite these repeated demonstrations, the concept of the "plant nervous system" was neglected by most of the scientific community until the beginning of our century. [31][32][33][34][35] ...
... 22,26,[73][74][75][76][77] In 2005, Stefano Mancuso and František Baluška, building on the work of intellectual forebears such as Wilhelm Pfeffer, Charles Darwin, Jagadis Chandra Bose or Julius von Sachs, 78,79 and following the discovery in plants of a large number of characteristics found in the neuronal system of animals, proposed the concept of 'plant neurobiology'. 34 This initiative very quickly led to a strong controversy. Scientists from no less than thirty-three institutions working in plant research claimed that plant neurobiology was based only on superficial analogies and dubious extrapolations that added nothing to the understanding of plant biology. ...
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Before the upheaval brought about by phylogenetic classification, classical taxonomy separated living beings into two distinct kingdoms, animals and plants. Rooted in ‘naturalist’ cosmology, Western science has built its theoretical apparatus on this dichotomy mostly based on ancient Aristotelian ideas. Nowadays, despite the adoption of the Darwinian paradigm that unifies living organisms as a kinship, the concept of the “scale of beings” continues to structure our analysis and understanding of living species. Our aim is to combine developments in phylogeny, recent advances in biology, and renewed interest in plant agency to craft an interdisciplinary stance on the living realm. The lines at the origin of plant or animal have a common evolutionary history dating back to about 3.9 Ga, separating only 1.6 Ga ago. From a phylogenetic perspective of living species history, plants and animals belong to sister groups. With recent data related to the field of Plant Neurobiology, our aim is to discuss some socio-cultural obstacles, mainly in Western naturalist epistemology, that have prevented the integration of living organisms as relatives, while suggesting a few avenues inspired by practices principally from other ontologies that could help overcome these obstacles and build bridges between different ways of connecting to life.
... Ultimately, the creationist idea of "intelligent design" uses intelligence as a name-giving feature of the creator. On the other side, current debates tend to extend the attribute of intelligence to non-humans, including animals, computers, robots and, most recently, even plants (Brenner et al., 2006;Trewavas, 2016). All these discourses make use of ideas or facts about the material basis for intelligence. ...
... Publications from this recently developing branch of science range from articles in established scientific journals to popular books attributing human-like behaviors and experience to plants (e.g. Brenner et al., 2006;Trewavas, 2016;Wohlleben, 2015Wohlleben, , 2016. "Plant Neurobiology" has become a small discipline in its own right. ...
... This terminology refers to the analogies the authors observe between neurology and some aspects of the plant. This relatively new science advocates the concepts of "plant consciousness" and "plant intelligence" (Brenner et al., 2006). The latter paper could be considered to be the manifesto for the PNB. ...
... The authors also propose a plant-specific synaptic cell-cell adhesion domain similar to a model found in relation to animals, proposed by Yamada and Nelson (2007). Plants synthesize neurotransmitters as animals do, such as glutamate, including their receptor homolog (Brenner et al., 2006). These features, including the Darwinian brain-like zone at the root apex that acts as a decision-making centre (Baluška et al., 2004(Baluška et al., , 2009, help plants integrate into coherent units (Baluška and Mancoso, 2021), and adapt to their environment. ...
Article
The paper aims at proposing a representation of plants as individuals. The first section selects the population of plants to which this study is addressed. The second section describes the effective architecture of plants as modular systems with fixed and mobile elements, in other words, plants and their extensions. The third section presents how plants integrate the fixed and mobile modules into functional units through three areas of particular relevance to plant growth and development: nutrition, defence and pollination. Based on the tangible elements introduced in the previous sections, the fourth section presents the main issue of the proposal which is not apparent at first glance, namely, the local-global relationship in plants’ architecture that determines their individuality as organisms. Finally, in the conclusion, we issue the challenge of developing a collective presentation of plants which satisfies their complementary dimension.
... External factors, such as temperature, and water status, have been evaluated also in Picea abies individuals [9]. Trees are renowned for their salient intelligence, capabilities to implement distributed information processing, showing indicators of advanced perception, cognition and adaptive behaviour, anticipatory responses and swarm intelligence [10,11,12,13,14]. Trees employ impulses of electrical activity to coordinate actions of their bodies and longdistance communication [11,15,16]. ...
... In the dissipative dynamics, mathematical consistency requires [32,33,34,37] that the state of the system of NG dwq at temperature T is given by the two modes SU(1,1) generalized coherent state [38] , (10) k with β = 1/kBT, whose time dependence, β = β(t), is not explicitly shown for notational simplicity. |0(θ(β))i is normalized to 1, h0(θ(β))|0(θ(β))i = 1, ∀θ(β), ∀β, ∀t. ...
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Electrical activity is used by plants in long term signalling and information transfer between the distant parts of the plant. Biopotential recordings from trees in a natural environment have been so far less discussed in scientific literature. Here we present our data about the open science experiment TRee-hUMAn iNterface (TRUMAN) located in Paneveggio forest (Valle di Fiemme, Trento, Italy), cultivated since one thousand years for the production of harmonic wood from Picea abies (red fir). We show that: i) biopotential features based on xylem can be correlated with the solar (and lunar) cycle ii) dead tree logs show an electrical activity that is correlated with that of neighbouring trees iii) statistical features of the spike-like peaks are evidenced, including amplitude, frequency, propagation speed, entropy iv) a quantum field theory is presented to highlight the collective behaviour of the forest, supported by preliminar correlation analyses between electrical signal Kolmogorov entropy and thermographies Shannon entropy.
... External factors, such as temperature, and water status, have been evaluated also in Picea abies individuals [9]. Trees are renowned for their salient intelligence, capabilities to implement distributed information processing, showing indicators of advanced perception, cognition and adaptive behaviour, anticipatory responses and swarm intelligence [10,11,12,13,14]. Trees employ impulses of electrical activity to coordinate actions of their bodies and longdistance communication [11,15,16]. ...
... In the dissipative dynamics, mathematical consistency requires [32,33,34,37] that the state of the system of NG dwq at temperature T is given by the two modes SU(1,1) generalized coherent state [38] , (10) k with β = 1/kBT, whose time dependence, β = β(t), is not explicitly shown for notational simplicity. |0(θ(β))i is normalized to 1, h0(θ(β))|0(θ(β))i = 1, ∀θ(β), ∀β, ∀t. ...
Preprint
Electrical activity is used by plants in long term signalling and information transfer between the distant parts of the plant. Biopotential recordings from trees in a natural environment have been so far less discussed in scientific literature. Here we present our data about the open science experiment TRee-hUMAn iNterface (TRUMAN) located in Paneveggio forest (Valle di Fiemme, Trento, Italy), cultivated since one thousand years for the production of harmonic wood from Picea abies (red fir). We show that: i) biopotential features based on xylem can be correlated with the solar (and lunar) cycle ii) dead tree logs show an electrical activity that is correlated with that of neighbouring trees iii) statistical features of the spike-like peaks are evidenced, including amplitude, frequency, propagation speed, entropy iv) a quantum field theory is presented to highlight the collective behaviour of the forest, supported by preliminar correlation analyses between electrical signal Kolmogorov entropy and thermographies Shannon entropy.
... This means that all organisms are, in essence, cognitive (Gagliano 2015;Baluška and Levin 2016;Varela et al., 2016;Cazalis et al., 2017;Lyon et al., 2021;Reber and Baluška 2021;Shapiro 2021). Indeed, amazing cognitive capabilities have been recognised even in non-neural organisms such as bacteria (Shapiro 2007(Shapiro , 2021, slime moulds (Latty and Beekman 2011;Boussard et al., 2021), amoebae (Schaap 2021), fungi (Aleklett and Boddy 2021), and plants (Brenner et al., 2006;Trewavas 2003;Marder 2012;Calvo et al., 2020;Castiello 2021). ...
... We propose that this claim can be supported by studies on plant electrophysiology, at least at the level of plant organs. Electrophysiology is particularly important in this process because electrical signalling is one of the main routes for rapid information integration in the plant body when plants face environmental changes (Brenner et al., 2006;Fromm and Lautner 2007;Baluška and Mancuso 2009a, b;Choi et al., 2016b;Huber and Bauerle 2016;de Toledo et al., 2019;Miguel-Tomé and Llinás 2021). Attention here is intended as a cognitive process that allows organisms to handle a selected piece of all the relevant information in the environment at the time (Grondin 2016). ...
Article
Attention is the important ability of flexibly controlling limited cognitive resources. It ensures that organisms engage with the activities and stimuli that are relevant to their survival. Despite the cognitive capabilities of plants and their complex behavioural repertoire, the study of attention in plants has been largely neglected. In this article, we advance the hypothesis that plants are endowed with the ability of attaining attentive states. We depart from a transdisciplinary basis of philosophy, psychology, physics and plant ecophysiology to propose a framework that seeks to explain how plant attention might operate and how it could be studied empirically. In particular, the phenomenological approach seems particularly important to explain plant attention theoretically, and plant electrophysiology seems particularly suited to study it empirically. We propose the use of electrophysiological techniques as a viable way for studying it, and we revisit previous work to support our hypothesis. We conclude this essay with some remarks on future directions for the study of plant attention and its implications to botany.
... External factors, such as temperature and water status, have also been evaluated in Picea abies individuals [9]. Trees are renowned for their salient intelligence, capability to implement distributed information processing, showing indicators of advanced perception, cognition and adaptive behavior, anticipatory responses, and swarm intelligence [10][11][12][13][14]. Trees employ impulses of electrical activity to coordinate actions of their bodies and long-distance communication [11,15,16]. ...
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Trees employ impulses of electrical activity to coordinate actions of their bodies and long-distance communication. There are indications that the vascular system might act as a network of pathways for traveling electrical impulses. A question arises about the correlation and interplay between the molecular (microscopic) level and the macroscopic observable behavior of the system (the electrical impulses), for individual trees and as a component of the larger living ecosystem, the forest. Results from the “Cyberforest Experiment” in the Paneveggio forest (Valle di Fiemme, Trento, Italy) are presented. It is shown that: (i) biopotential features of xylem biomolecular activity can be correlated with the solar (and lunar) cycle, (ii) tree stubs show an electrical molecular activity that is correlated with that of neighboring trees, (iii) statistical features of spike-like peaks and entropy can be correlated with corresponding thermal entropy, and (iv) basic symmetries of the quantum field theory dynamics are responsible for the entanglement phenomenon in the molecular interactions resulting in the molecular collective behavior of the forest. Findings suggest implementing technology that goes in the direction of understanding the language of trees, eventually of fungi, which have created a universal living network perhaps using a common language.
... In this regard, it might be worth noting how there is evidence that nonneuronal multicellular organisms also show forms of intelligence. At the turn of the millennium, terms like 'plant neurobiology' j emerged, drawing parallels between the complex information processing and signaling system in plants and the animal's neuronal activity [67,68]. ...
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According to the current scientific paradigm, what we call ‘life’, ‘mind’, and ‘consciousness’ are considered epiphenomenal occurrences, or emergent properties or functions of matter and energy. Science does not associate these with an inherent and distinct existence beyond a materialistic/energetic conception. ‘Life’ is a word pointing at cellular and multicellular processes forming organisms capable of specific functions and skills. ‘Mind’ is a cognitive ability emerging from a matrix of complex interactions of neuronal processes, while ‘consciousness’ is an even more elusive concept, deemed a subjective epiphenomenon of brain activity. Historically, however, this has not always been the case, even in the scientific and academic context. Several prominent figures took vitalism seriously, while some schools of Western philosophical idealism and Eastern traditions promoted conceptions in which reality is reducible to mind or consciousness rather than matter. We will argue that current biological sciences did not falsify these alternative paradigms and that some forms of vitalism could be linked to some forms of idealism if we posit life and cognition as two distinct aspects of consciousness preeminent over matter. However, we will not argue in favor of vitalistic and idealistic conceptions. Rather, contrary to a physicalist doctrine, these were and remain coherent worldviews and cannot be ruled out by modern science.
... In fact, blood is toxic to neurons, and the blood-brain-barrier (BBB) effectively prevents direct contact of brain neurons with blood (Hagan and Ben-Zvi 2015;Righy et al. 2016;Abdullahi et al. 2018;Madangarli et al. 2019;Nian et al. 2020;Segara et al. 2021). Intriguingly, the etymological origin of the term neuron comes from the ancient Greek, meaning 'vegetal fibre' (Brenner et al. 2006;Mehta et al. 2020). More importantly, the allegedly unique features of neurons, formulated and popularized as the 'Neuron Doctrine' by Wilhelm Waldeyer in 1891 (Shepherd 1991;Jones 1994), are no longer considered to be so unique (Gold and Stoljar 1999;Guillery 2007). ...
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Plant roots are generally hidden from our sight, growing and living underground in alliances with symbiotic fungi. In order to find enough water and critical mineral nutrients, they explore large areas of soil with their root apices acting as plant cognition-based brain-like organs allowing them to use kin recognition, self/non-self recognition as well as swarm intelligence. Importantly, fungal hyphae integrate root systems into huge root-wide webs which allow not only the sharing of water and mineral nutrients, but also support long-distance chemical and electric signals. Roots use neuronal molecules such as glutamate and GABA supported by their specific receptors, as well as actin-based synapses and the plant-specific action potentials, to perform all their social activities and cognitive navigation for soil exploration.
... La thèse d'une intelligence des plantes propose une synthèse inédite de la vie végétale, en lien étroit avec l'émergence d'une nouvelle discipline, la neurobiologie des plantes (Brenner et al., 2006) 2 . Elle s'affirme comme un nouveau front de science et revendique la coopération de disciplines différentes allant de la biologie à la philosophie (Calvo, 2011). ...
Article
L’intelligence des plantes met l’intelligence artificielle au défi de répondre de façon adaptée aux enjeux de la transition écologique et du changement climatique. L’approche éthico-biologique adoptée ici considère la portée d’une redéfinition de la vie végétale entre « dignification » subjective et conditionnement numérique. L’intelligence des plantes suppose qu’on leur reconnaisse une capacité à poursuivre leurs propres fins, et donc une entéléchie. Elle en appelle à notre propre intelligence pour interpréter avec précision la cohérence organisée et orientée des mouvements morphiques de métamorphose. Ce qui ne peut être calculé exige notre participation dans de nouvelles pratiques éthico-esthétiques où la relation avec les plantes représente une forme d’écosophie indispensable au déploiement de l’agro-écologie.
... Whilst antecedents of the field can be traced from the early 2000s (e.g. Pollan, 2001;Miller, 2002), the term 'critical plant studies' emerged in the early 2010s, alongside a flourishing of interest in the metaphysical lives of plants and the diverse methodologies required to approach them (Ryan, 2011(Ryan, , 2012. 1 Importantly, advances in a newly developed field of plant sciences termed 'plant neurobiology' had recently recast the plant as an intelligent organism capable of coordinated response and signalling behaviours (Brenner et al., 2006); capacities brought to public attention by Michael Pollan in his 2013 New Yorker article The Intelligent Plant. This growing scientific appreciation of plant 'liveliness' forms a significant body of literature within CPS and has precipitated renewed interest in the ethical and philosophical position of plants (see Chamovitz, 2017;Gagliano, 2018;Simard, 2021;Trewavas, 2014;Viola and Mancuso, 2015). ...
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Attention to plant life is currently flourishing across the social sciences and humanities. This paper introduces recent work in the informal sub-discipline of ‘vegetal geography’, placing it into conversation with the transdisciplinary field of ‘critical plant studies’ [CPS], a broad framework for re-evaluating plants and human-plant interactions informed by principles of agency, ethics, cognition and language. I explore three key themes of interest to multispecies scholars looking to attend more closely to vegetal life, namely: (1) plant otherness; (2) plant ethics; (3) plant-human attunements, in the hope of encouraging greater cross-pollination between more-than-human geography and critical plant studies.
... Most higher plants rely on plant electrophysiological signals to regulate their physiological functions [31]. Studies in recent years have shown that plant electrophysiological signal transducers are ubiquitous in higher plants and are the first response of plants to various stimuli in the external environment, which is reflected in plant growth, material metabolism and other aspects [32]. However, plant drought resistance can be analyzed by the initial response of photosynthesis, and electrophysiology has a strong correlation with this, so it can quickly reflect the photosynthetic characteristics of plants. ...
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Drought is a key factor restricting plant survival, growth and development. The physiological parameters of plants are commonly used to determine the water status, in order to irrigate appropriately and save water. In this study, mulberry (Morus alba L.) and paper mulberry (Brous-sonetia papyrifera (L.) Vent.) seedlings were used as experimental materials, and four soil moisture treatments were set up for both plant species: 70-75% (CK: the control group, referred to as T0), 55-60% (T1: mild drought), 40-45% (T2: moderate drought), and 25-30% (T3: severe drought). The growth parameter of the plants was measured every two days from the onset of the treatment, the photosynthetic and electrophysiological parameters of the plants were measured every other week for a total of five times. The physiological responses and electrophysiological traits of leaves under different treatment levels were analyzed. The results showed that the photosynthetic and electro-physiological parameters could characterize the response of mulberry growth and development to soil water, and the growth and electrophysiological parameters could characterize the response of paper mulberry growth and development to soil water. Mild drought had no significant effects on the growth and development of mulberry and paper mulberry.
... It is also found that weak electrical signals of the chrysanthemum plant were tested by a touching test system of self-made double shields with platinum sensors [14]. Several studies have reported the effect of different stimuli that induce action potential gradients in plants, mainly light/dark [15,16] temperature variations [17,18], intense cold [19,20], water availability [21,22], mechanical wounding [23], and insects [22]. Also, it has been suggested that electrical signals could induce genetic programming [24,25]. ...
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In the area of biorobotics, intense research work is being done based on plant intelligence. Any living cell continuously receives information from the environment. In this paper, research is conducted on the plant named descoingsii x haworthioides (Pepe) obtaining the action potential signals and its responses to stimulations of different light modes. The plant electrical signal is the reaction of plant’s stimulation owing to various environmental conditions. Action potentials are responsible for signaling between plant cells and communication from the plants can be achieved through modulation of various parameters of the electrical signal in the plant tissue. The modulated signals are used for providing information to the microcontroller’s algorithm for working of the bio-machine. The changes of frequency of action potentials in plant are studied. Electromyography (EMG) electrodes and needle-type conductive electrodes along with electronic modules are used to collect and transform the information from the plant. Inverse fast Fourier transform (IFFT) is used to convert signal in frequency domain into voltage signal for real-time analysis. The changes in frequency of the plant action potentials to different light modes are used for the control of the bio-machine. This work has paved the way for an extensive research towards plant intelligence.
... Generalising the mechanisms for APs, and using plants as model organisms, may also affect our conception of how fields interrelate. For instance, there is ongoing controversy over the nascent field of 'plant neurobiology' (Brenner et al., 2006). Some have argued that as plants lack neurons and synapses, studying the so-called 'neurobiology' of plants speaks to conceptual confusion or will result in an empirical dead-end (Alpi et al., 2007). ...
Article
The mechanism underlying action potentials is routinely used to explicate the mechanistic model of explanation in the philosophy of science. However, characterisations of action potentials often fixate on neurons, mentioning plant cells in passing or ignoring them entirely. The plant sciences are also prone to neglecting non-neuronal action potentials and their role in plant biology. This oversight is significant because plant action potentials bear instructive similarities to those generated by neurons. This paper helps correct the imbalance in representations of action potentials by offering an overview of the mechanism for plant action potentials and highlighting their similarity to those in neurons. Furthermore, it affirms the role of plant action potentials in discovering the evolution and function of mechanisms of action potentials more broadly. We stress the potential of plants for producing generalisations about action potentials and the possible role of plants as model organisms.
... Several studies have been conducted that considers temperature, humidity, light, and other factors. Special attention has been paid to the studies of Mimosa pudica (sensitive plant), Drosera (sundew), Dionaea muscipula (flytrap) the significant action potential that generates when stimulated [94,95,4,66]. ...
Article
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Plants have mechanisms to perceive and transmit information between their organs and tissues to respond quickly to abiotic and biotic external stimuli from the environment, producing different electrical potential types. It is reported on the generation and conduction of electrochemical impulses within different tissues and organs of the plant, which have been acquired using different methods to use them in various applications in the improvement of the agro-industrial sector and the development of different types of phytosensors. In this review paper, the various studies that have been carried out since Pfeffer, Burdon-Sanderson, Darwin, Haberlandt, and Bose discovered electrical activity in plants until today are reported. Plants provide mechanisms to perform biosensors based on responding to environmental changes, opening a great path for the design of low-cost and highly sensitive sensors and sensor networks, the current trend is towards experimental analysis using various stimuli.
... The communication mechanisms within the system are still poorly understood, but the possibility of having electrical currents as a means of fast information transfer would provide a system akin to a central neuronal system that could result in a coordinated behaviour required in such a complex system as a soil. Electrical currents have been shown not only to be important for the coordination of cell behaviour at all biological levels, i.e. from bacteria to humans (Piccolino 1997;Brenner et al. 2006;Prindle et al. 2015;Canales, Henriquez-Valencia and Brauchi 2018), but also for intracolony or interspecies communication (Clarke et al. 2013;Beagle and Lockless 2015;Prindle et al. 2015). The cell morphology and growth mode of filamentous fungi provides, in theory, an ideal system for electrical signalling, but the use of traditional electrophysiological methods for measuring these signals is extremely challenging (Adamatzky 2022). ...
Article
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Fungi, with their enormous diversity, bear essential roles both in nature and our everyday lives. They inhabit a range of ecosystems, such as soil, where they are involved in organic matter degradation and bioremediation processes. More recently, fungi have been recognised as key components of the microbiome in other eukaryotes, such as humans, where they play a fundamental role not only in human pathogenesis, but also likely as commensals. In the food sector, fungi are used either directly or as fermenting agents and are often key players in the biotechnological industry, where they are responsible for the production of both bulk chemicals and antibiotics. Although the macroscopic fruiting bodies are immediately recognisable by most observers, the structure, function and interactions of fungi with other microbes at the microscopic scale still remain largely hidden. Herein, we shed light on new advances in the emerging field of Fungi-on-a-Chip microfluidic technologies for single-cell studies on fungi. We discuss the development and application of microfluidic tools in the fields of medicine and biotechnology, as well as in-depth biological studies having significance for ecology and general natural processes. Finally, a future perspective is provided, highlighting new frontiers in which microfluidic technology can benefit this field.
... Several recent advances in cell and molecular biology support the hypothesis that the root apex may act as the "brain" of the plant, being the centre of control for interaction coordination [7]. This concept was first proposed by Charles and Francis Darwin in 1880 in the Power of Movement in Plants, but later other authors [8][9][10] proposed that the transition zone (TZ) of the root plays the role of control for interaction coordination in plants. Support for their hypothesis comes from physiological and cytological properties 2 of 14 of the TZ including: (a) ion flux oscillation and other specific transport processes related with oxygen and auxin; (b) oscillating electric spike activities [10,11]; (c) endocytosis-driven vescicle recycling [12][13][14]; (d) high oxygen demands [15]. ...
Article
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Mechanical stress in tree roots induces the production of reaction wood (RW) and the formation of new branch roots, both functioning to avoid anchorage failure and limb damage. The vascular cambium (VC) is the factor responsible for the onset of these responses as shown by their occurrence when all primary tissues and the root tips are removed. The data presented confirm that the VC is able to evaluate both the direction and magnitude of the mechanical forces experienced before coordinating the most fitting responses along the root axis whenever and wherever these are necessary. The coordination of these responses requires intense crosstalk between meristematic cells of the VC which may be very distant from the place where the mechanical stress is first detected. Signaling could be facilitated through plasmodesmata between meristematic cells. The mechanism of RW production also seems to be well conserved in the stem and this fact suggests that the VC could behave as a single structure spread along the plant body axis as a means to control the relationship between the plant and its environment. The observation that there are numerous morphological and functional similarities between different meristems and that some important regulatory mechanisms of meristem activity, such as homeostasis, are common to several meristems, supports the hypothesis that not only the VC but all apical, primary and secondary meristems present in the plant body behave as a single interconnected structure. We propose to name this structure “meristematic connectome” given the possibility that the sequence of meristems from root apex to shoot apex could represent a pluricellular network that facilitates long-distance signaling in the plant body. The possibility that the “meristematic connectome” could act as a single structure active in adjusting the plant body to its surrounding environment throughout the life of a plant is now proposed.
... Researchers have found that the electrical signals produced by plants may be related to the plant response to adversity stress. For example, plants produce significant action potentials after mechanical damage or insect attack [17]. Studies by Schroeder and Hedrich [18] showed that plant osmosis affects electrical signal production from the perspective of ion. ...
Article
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Drought area expansion has a great impact on the growth and development of plants. To contribute to the water management of strawberry, this work aims to study the chronological relationship between the electrical signals and representative physiological parameters of strawberry seedlings under drought stress. This study analyzed the characteristic variables of the electrical signals; physiological parameters under drought; and control treatments. Moreover, we compared the chronological sequence of the appearance of significant differences between drought and control treatment in terms of their physiological parameters and electrical signals. The results showed that with the increase of drought treatment, the time domain parameters (peak-to-peak value, standard deviation) and frequency domain parameters (spectral of central gravity, power spectrum entropy) of the drought-treated electrical signals showed significant differences from the control on Day 2 and Day 6, respectively (p < 0.05). The root vitality of the drought treatment was significantly different from the control on Day 4 (p < 0.05); the Fv/Fm and the SPAD were significantly different (p < 0.05) on Day 7. Electrical signals first start to show a significant difference between drought and control treatment, followed by physiological parameters. Therefore, the electrical signal can be used as an early indicator of drought stress conditions. This will provide a scientific basis for the actual water management of strawberry seedlings. It also provides a methodological and theoretical basis for other studies analyzing the relationship between plant physiological parameters and electrical signals under other stress conditions.
... Основной электрической характеристикой клетки служит мембранный потенциал, возникающей в первую очередь в результате диффузии и активного процесса переноса ионов между внеклеточной средой и внутриклеточными компартментами (2). Активному транспорту наиболее подвержены ионы K + , Na + , Ca 2+ , Mg 2+ , NO3  , C1  , H2PO4  , SO4  . ...
... The effect of BMAA has been studied mainly on various animal models and human cell cultures due to its harmful consequences for health [78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96][97]. There are several studies on the effects of BMAA on plant cells [98][99][100][101][102], diatoms [103], and cyanobacteria [27,37,[104][105][106][107][108][109][110][111]. The biological actions of BMAA on eukaryotic and prokaryotic cells can be explained by various mechanisms [13,78] (Figure 3). ...
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Research interest in a non-protein amino acid β-N-methylamino-L-alanine (BMAA) arose due to the discovery of a connection between exposure to BMAA and the occurrence of neurodegenerative diseases. Previous reviews on this topic either considered BMAA as a risk factor for neurodegenerative diseases or focused on the problems of detecting BMAA in various environmental samples. Our review is devoted to a wide range of fundamental biological problems related to BMAA, including the molecular mechanisms of biological activity of BMAA and the complex relationships between producers of BMAA and the environment in various natural ecosystems. At the beginning, we briefly recall the most important facts about the producers of BMAA (cyanobacteria, microalgae, and bacteria), the pathways of BMAA biosynthesis, and reliable methods of identification of BMAA. The main distinctive feature of our review is a detailed examination of the molecular mechanisms underlying the toxicity of BMAA to living cells. A brand new aspect, not previously discussed in any reviews, is the effect of BMAA on cyanobacterial cells. These recent studies, conducted using transcriptomics and proteomics, revealed potent regulatory effects of BMAA on the basic metabolism and cell development of these ancient photoautotrophic prokaryotes. Exogenous BMAA strongly influences cell differentiation and primary metabolic processes in cyanobacteria, such as nitrogen fixation, photosynthesis, carbon fixation, and various biosynthetic processes involving 2-oxoglutarate and glutamate. Cyanobacteria were found to be more sensitive to exogenous BMAA under nitrogen-limited growth conditions. We suggest a hypothesis that this toxic diaminoacid can be used by phytoplankton organisms as a possible allelopathic tool for controlling the population of cyanobacterial cells during a period of intense competition for nitrogen and other resources in various ecosystems.
... We report acetylcholine, glycine, gamma-aminobutyric acid, taurine, L-aspartic acid, Lglutamic acid, adenosine, histamine, and L-glutamate to significantly change in expression levels in eviscerated individuals, and individuals subjected to heat stress, and for all to be involved in the "neuroactive ligand-receptor interaction" pathway. Neurotransmitters such as acetylcholine, histamine, taurine, and L-glutamate are important in information processing, locomotion, sensing, and development (Brenner et al., 2006;Talman et al., 1980). Acetylcholine causes strong contractions in the body wall musculature of the sea cucumber Thyone briareus (Smith and Greenberg, 1973). ...
Article
When encountering adverse environmental conditions, some holothurians can eject their internal organs in a process called evisceration. As global warming intensified, eviscerated and intact sea cucumbers both experience heat stress, but how they performed was uncertain. We constructed 24 metabolomics profiles to reveal the metabolite changes of eviscerated and intact sea cucumbers under normal and high temperature conditions, respectively. Carboxylic acids and fatty acyls were the most abundant metabolic categories in evisceration and heat stress treatments, respectively. Neural transduction was involved in sea cucumber evisceration and stress response, and the commonly enriched pathway was “neuroactive ligand-receptor interaction”. Lipid metabolism in eviscerated sea cucumbers differed from those of intact individuals and was more seriously affected by heat stress. Choline is a key metabolite for revealing the evisceration mechanism. Our results contribute to understanding the mechanisms of evisceration in sea cucumbers, and how sea cucumbers might respond to increasingly warming ocean conditions.
... This work met with great reluctance and criticism, but eventually gained global acceptance. Most of his observations have been accepted and in the last two decades, interest in 'plant neurobiology' has been rekindled [8,31,34] and plant memory has emerged as an interesting area among the plant biologists. ...
Article
Memory is an essential feature of all living organisms. However, memory in plants though recognised, has been largely unexplored by the scientific community. This field has gained interest only recently and emerging pieces of evidence indicate memory and perception in plants is consolidated yet very different from the established animal systems. Through this commentary we attempt herein to gain an understanding of the recent developments in area of plant memory and the molecular mechanisms involved in propagation of memory in plants.
... then, plant scientists have studied the mechanisms that underwrite plant signaling and their similarities to those thought to underwrite cognition. Based on the fruits of these findings, several researchers have adopted the controversial title of "plant neurobiology" for their nascent subdiscipline (Brenner et al., 2006;Calvo Garzón, 2007). ...
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Philosophers and scientists propose the idea that plants are cognitive, which has been met with criticisms. These criticisms focus on the fact that plants do not possess the properties traditionally associated with cognition. By contrast, several proponents introduce novel ways to conceptualize cognition. How should we make sense of this debate? In this paper, I argue that the plant cognition debate is not about whether plants meet a set of well-delineated and agreed-upon criteria according to which they count as cognitive. Rather, many proponents are hypothesizing about cognition. They construe COGNITION not as an expression of what cognition is, but rather as a conjecture about what cognition might be. These conjectures orient research that can uncover novel similarities amongst the phenomena to which these concepts extend. In defending this view, I argue that investigating plant cognition is valuable, even if the results of these investigations lead us to reject the claim that plants are cognitive.
... Here we propose a model where the maximal root growth rate and position can be adjusted and thus analyzed on different developmental zones of the apex, regulated by a signaling network that transmits excitation and inhibition signals akin to an artificial neuronal network. The comparison between neural networks and plants has created a great debate in the scientific community [42][43][44][45], opening new frontiers in the understanding of plants [46]. Despite this, it is not our intention to assert a close analogy between plants and neural networks as in animals, foraging the debate, but rather to analyze some of the plant's behaviors through their description with artificial networks that can well describe plant's behavior functions. ...
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The plant root system shows remarkably complex behaviors driven by environmental cues and internal dynamics, whose interplay remains largely unknown. A notable example is circumnutation growth movements, which are growth oscillations from side to side of the root apex. Here we describe a model capable of replicating root growth behaviors, which we used to analyze the role of circumnuntations, revealing their emergence I) under gravitropic stress, as a combination of signal propagation and sensitivity to the signal carriers; II) as a result of the interplay between gravitropic and thigmotropic responses; and III) as a behavioral strategy to detect and react to resource gradients. The latter function requires the presence of a hypothetical internal oscillator whose parameters are regulated by the perception of environmental resources.
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The alleged existence of so-called synapses or equivalent structures in plants provided the basis for the concept of Plant Neurobiology (Baluska et al., 2005; Brenner et al., 2006). More recently, supporters of this controversial theory have even speculated that the phloem acts as a kind of nerve system serving long distance electrical signaling (Mediano et al., 2021; Baluska and Mancuso, 2021). In this review we have critically examined the literature cited by these authors and arrive at a completely different conclusion. Plants do not have any structures resembling animal synapses (neither chemical nor electrical). While they certainly do have complex cell contacts and signaling mechanisms, none of these structures provides a basis for neuronal-like synaptic transmission. Likewise, the phloem is undoubtedly a conduit for the propagation of electrical signaling, but the characteristics of this process are in no way comparable to the events underlying information processing in neuronal networks. This has obvious implications in regard to far-going speculations into the realms of cognition, sentience and consciousness.
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Despite the fact that plants make up 80% of biomass on Earth, sociology rarely examines human–plant relationships. Human societies are inherently dependent on plants, most obviously as the basis of food supply, ecosystems, atmospheric and climate regulation, and water cycles, as well as for sources of oxygen, medicine, fuel, and fibre. Society, or terrestrial animal life for that matter, could not exist without plants. Based on this recognition, here we lay the foundations for sociological plant studies, a field that studies the dialectical relationship between human societies and plants. We ground this foundation in a realist-materialist perspective that recognises the ontological independence of plants and does not reduce them to human social constructions. We show how considering plants can help us to understand the emergence of civilisations, state formation, and mechanisation of production at the macro-level, and how human–plant interactions shape everyday life at a more micro-level. We present our formulation of sociological plant studies as a starting point for future research.
Chapter
Der ad hoc auffallendste Unterschied zwischen pflanzlichen und tierischen Zellen sind die grünen Chloroplasten, die Zellwand und die große Vakuole. Es gibt vielfältige Regulationsmechanismen, die ein unbeweglicher Organismus braucht, um bei wechselnden Umweltbedingungen zu überleben. Indes brachten Genomanalysen eine ähnliche Zahl an Genen zutage wie bei tierischen Zellen, darunter solche, die uns von tierischen Zellen vertraut sind, und andere, die es ausschließlich in Pflanzen gibt. Ähnliche Funktionsbedürfnisse können von der Pflanzenzelle auf unterschiedlicher molekularer und ultrastruktureller Basis bewältigt werden.
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The myths take many forms depending on the cultures in which we find them; however, their function is always to explain natural phenomena that occur in their surroundings. As observed throughout human history, it is an inherent condition for the human species to believe in the metaphysical and to use their individual and introspective thinking as a way to achieve their dreams and goals, something that works as a responsible 'driving force' in many cases, for governing and inspiring the human individual. Additionally, populations or part of communities that obtain their livelihood and/or subsistence directly from agricultural activity spontaneously express a greater willingness to believe in the 'infallible' agroforestry myths, which explain the possible botanical phenomena. In light of this, our present study lists the main physiological bases refuting different botanical myths based on evidence proven in original articles. Furthermore, our phenomenological approach was carried out in an eclectic way in the field of botany and is not linked to any specific authority or philosophical school. Finally, we explore and integrate different, mutually compatible approaches to provide the reader with a global understanding of the 'infallibility' of botanical myths.
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Communication occurs when a sender emits a cue perceived by a receiver that changes the receiver's behavior. Plants perceive information regarding light, water, other nutrients, touch, herbivores, pathogens, mycorrhizae, and nitrogen-fixing bacteria. Plants also emit cues perceived by other plants, beneficial microbes, herbivores, enemies of herbivores, pollinators, and seed dispersers. Individuals responding to light cues experienced increased fitness. Evidence for benefits of responding to cues involving herbivores and pathogens is more limited. The benefits of emitting cues are also less clear, particularly for plant–plant communication. Reliance on multiple or dosage-dependent cues can reduce inappropriate responses, and plants often remember past cues. Plants have multiple needs and prioritize conflicting cues such that the risk of abiotic stress is treated as greater than that of shading, which is in turn treated as greater than that of consumption. Plants can distinguish self from nonself and kin from strangers. They can identify the species of competitor or consumer and respond appropriately. Cues involving mutualists often contain highly specific information. Expected final online publication date for the Annual Review of Ecology, Evolution, and Systematics, Volume 52 is November 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Salt stress causes several damaging effects in plant cells. These commonly observed effects are the results of oxidative, osmotic, and toxic stresses. To ensure normal growth and development of tissues, the cellular compartments of multicellular plants have a unique system that provides the specified parameters of growth and differentiation. The cell shape and the direction of division support the steady development of the organism, the habit, and the typical shape of the organs and the whole plant. When dividing, daughter cells evenly or unevenly distribute the components of cytoplasm. Factors such as impaired osmotic regulation, exposure to toxic compounds, and imbalance in the antioxidant system cause disorders associated with the moving of organelles, distribution transformations of the endoplasmic reticulum, and the vacuolar compartment. In some cases, one can observe a different degree of plasmolysis manifestation, local changes in the density of cytoplasm. Together, these processes can cause disturbances in the direction of cell division, the formation of a phragmoplast, the formation of nuclei of daughter cells, and a violation of their fine structural organization. These processes are often accompanied by significant damage to the cytoskeleton, the formation of nonspecific structures formed by proteins of the cytoskeleton. The consequences of these processes can lead to the death of some cells or to a significant change in their morphology and properties, deformation of newly formed tissues and organs, and changes in the plant phenotype. Thus, as a result of significant violations of the cytoskeleton, causing critical destabilization of the symmetric distribution of the cell content, disturbances in the distribution of chromosomes, especially in polyploid cells, may occur, resulting in the appearance of micronuclei. Hence, the asymmetry of a certain component of the plant cell is a marker of susceptibility to abiotic damage.
Conference Paper
The work is devoted to the study of the bioelectric potential gradient in the root zone using a non-invasive method. It is shown that the dynamics of biocurrents generated in the rhizosphere is associated with the development of the root system. The potential difference at the level of 250 mV is also present in the soil without a plant, it decreases with time and the depth of the soil layer. The increase of the bioelectropotential by 150 mV and more is observed in the presence of the root system, apparently, when it grows to the electrode.
Chapter
In this work, on the basis of the categorical theory of systems, using the apparatus of categorical splices, the construction of a mathematical model of a plant as a categorical functional system has begun, at the present level of development of the system approach. The categorical theory of systems formalizes the intuitive constructions of functional systems and, for the case of plants, makes it possible, on a strictly mathematical basis, to implement the remaining undeveloped approach to plants as functional systems, analogous to a large extent to the construction for humans and animals performed by P.K. Anokhin and his school. A general framework of a categorical model of a plant as a system is given and further steps for its development are outlined.
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Классическая концепция происхождения психики, предложенная А.Н.Леонтьевым, сопоставляется с современными данными из области биологии об особенностях жизнедеятельности живых организмов, не относящихся к царству животных. На основе этого сопоставления делается вывод, что критерий чувствительности, в его традиционном понимании, является недостаточным для четкого отделения живых систем, обладающих психикой, от систем, ею не наделенных. С привлечением современных психологических и биологических концепций конкретизируется и уточняется специфика того процесса жизнедеятельности, для регуляции которого возникает чувствительность. Специфичность психического отражения определяется как ориентация поведения субъекта во внешней предметной среде гетерогенных объектов в отличие от ориентации и регуляции жизнедеятельности субъекта внутри его собственного организма, осуществляемой на физиологическом уровне.
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If non-human animals have high moral status, then we commit a grave moral error by eating them. Eating animals is thus morally risky, while many agree that it is morally permissible to not eat animals. According to some philosophers, then, non-animal ethicists should err on the side of caution and refrain from eating animals. I argue that this precautionary argument assumes a false dichotomy of dietary options: a diet that includes farm-raised animals or a diet that does not include animals of any kind. There is a third dietary option, namely, a diet of plants and non-traditional animal protein, and there is evidence that such a diet results in the least amount of harm to animals. It follows therefore that moral uncertainty does not support the adoption of a vegetarian diet.
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In the face of rising sustainability issues, increasing numbers of organisations are trying to build compromises between their economic purpose and ecological objectives. Organisational studies focus on the analysis of such compromise processes but most studies do not seek to grasp the substantial changes advocated by ecological critiques. Our research is aimed at addressing that gap by clarifying the radical view sustained by ecological imaginary beyond conventional compromise processes. We engage in a qualitative study of biodynamics – an agricultural method based on a radical ecological imaginary – to evaluate its moral underpinnings through Boltanski and Thévenot’s Economies of Worth framework. Our findings help us to grasp the radical moral substance of ecological critique and to extend that framework beyond its dualist assumption. By highlighting antagonisms between meta-conceptions of justice rather than analysing compromises, our research provides insights into the radical organisational changes advocated by ecological critiques.
Chapter
Intelligence, defined as the capacity to solve problems through cognition, is strongly related to the brain and its functions. Neuroscience can therefore help to elucidate its natural history, biological constraints, and the causal mechanisms leading to the emergence of intelligence. Indeed, comparative approaches between species have identified brain regions and network properties of particular importance. Within the human species, several structural and functional determinants of intelligence have been identified. This pertains also to the “nature–nurture” problem, i.e., how far intelligence can be influenced by external factors. Our understanding of biological mechanisms and constraints is far from complete, but clearly indicates that favorable conditions are necessary and efficient to help people develop their full potential. Converging with other sciences and social practices neurobiological results indicate that intellectual development should be supported as early as possible, including a rich environment, variable cues and challenges, and reliable, close human relationships.
Chapter
The plasticity of living systems acts at several levels of evolutionary biology including self-organization, phenotypic, phylo-, onto-, and epigenetic processes, while mesology is an approach situated in between ecology and phenomenology. After a description of the specific objects of plasticity and mesology as non-dualist studies of the dynamical coupling between beings and their singular milieu, we will develop some arguments regarding the perception–action loop and the sensory flux of informations crossing the evolution of the living, before focusing on recent discoveries about plant electrome. Using for the first time mesological plasticity as a frame to reanalyze the Uexcküll’s assertions about Umwelt and meaning-making theories of plants, this chapter shows the leading rule of electromic interfaces in the generation of spontaneous low-voltage variations continuously emitted by plants via electrophytographic or EPG recordings. Used as early markers, EPGs are considered in this framework as natural systems of monitoring and discrimination of environmental stimuli that allow the identification of the electromic signature of a plant–stimulus pair in a given milieu. More generally, we will develop the trajections associated with complex behaviors of plants: a bottom-up transdisciplinary view of co-evolutionary or ecosemiotic processes highlighting their specific sensitive fields and cognitive accesses to experience (their otherness) as well as new phenomenologies about interactive ecosystems and phytosemiotics.KeywordsPlant electromeElectrophytographyPlasticity conceptInteractive ecosystemMesological plasticityCognitionPhytosemioticsTransdisciplinarity
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This paper argues for reorienting our investigation of the psychedelic zeitgeist towards the longitudinal history of psychedelia with a committed attention to its relationship to colonialism. It demonstrates that clinical psychedelic medicine appears to sustain the reproduction of modern colonial whiteness in line with Elizabeth Povinelli’s theorization of late liberalism. It also challenges the notion of a restricted or segregated academic area for psychedelic studies. Instead, it is imperative to place discussions of contemporary plant medicine in line with broader contemporary discussions in cultural anthropology around political ontology and decoloniality. This paper attempts to demonstrate that doing so may challenge our understanding of whiteness—reinterpreting it—by recourse to the history of the psychedelic counterculture, as a form of complex trauma, and thus potentially demonstrating new implications for decoloniality and its praxis.
Chapter
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Although plants are generally immobile and lack the most obvious brain activities of animals and humans, they are not only able to show all the attributes of intelligent behaviour but they are also equipped with neuronal molecules, especially synaptotaginins and glutamate/glycine-gated glutamate receptors. Recent advances in plant cell biology allowed identification of plant synapses transporting the plant-specific neurotransmitter-like molecule, auxin. This suggests that synaptic communication is not limited to animals and humans but seems to be widespread throughout plant tissues. Root apices seated at the anterior pole of the plant body show many features which allow us to propose that they, especially their transition zones, act in some way as "brain-like" command centres. The opposite posterior pole harbours sexual organs and is specialized for plant reproduction. Last but not least, we propose that vascular tissues represent highways for plant nervous activity allowing rapid exchange of information between the growing points of above-ground organs and the "brain-like" zones in the root apices.
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Action potentials (APs) belong to long-distance signals in plants. They fulfill the all-or-none law, propagate without decrement and their generation is limited by refractory periods. The ion mechanism of APs was elaborated in giant Characean algae and extended by another model plant - the liverwort Conocephalum conicum. It consists of an increase in cytoplasmic Ca2+ concentration ([Ca2+]cyt) which activates anion channels responsible for Cl- efflux and for membrane depolarization. Repolarization occurs after the opening of potassium channels and K+ efflux. The resting potential is restored by the electrogenic proton pump. A number of ion channels which may play a role in AP were identified by the patch-clamp technique. APs propagate on the principle of local electrical circuits. They cover whole plants, plant organs or definite tissues, mainly phloem, phloem parenchyma and protoxylem. APs mediate between local stimulation and movements in carnivorous Dionaea muscipula, Aldrovanda vesiculosa, and tigmonastic Mimosa pudica. The role of APs in regulation of respiration, photosynthesis, growth, pollination, fertilization and gene expression is well documented. An AP-coupled increase in [Ca2+]cyt seems to play a central role in signal transduction.
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J.C. Bose (1858-1937) was one of the world's first biophysicists. He was the first person to use a semi conducting crystal to detect radio waves, and the ingenious inventor of a portable apparatus for generating and detecting microwaves (~1 cm to 5 mm radio waves, frequency 12-60 GHz), as well as inventing many instruments now routinely used in microwave technology. Bose extended his specialist knowledge of the physics of electromagnetic radiation into insightful experiments on the life-processes of plants. He became a controversial figure in the west. He invented unique, delicate instruments for simultaneously measuring bioelectric potentials and for quantifying very small movements in plants. He worked with touch-sensitive plants, including Mimosa pudica, with plants that perform spontaneous movements, including the Indian telegraph plant Desmodium, and with plants and trees that did not make obvious rapid movements. Bose concluded that plants and animals have essentially the same fundamental physiological mechanisms. All plants co-ordinate their movements and responses to the environment through electrical signalling. All plants are sensitive explorers of their world, responding to it through a fundamental, pulsatile, motif involving coupled oscillations in electric potential, turgor pressure, contractility, and growth. His overall conclusion that plants have an electromechanical pulse, a nervous system, a form of intelligence, and are capable of remembering and learning, was not well received in its time. A hundred years later, concepts of plant intelligence, learning, and long-distance electrical signalling in plants have entered the mainstream literature.
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Localized heat wounding of tomato plants triggered rapid changes in growth and in electrical activity. The growth alterations were manifested as a transient increase in growth (petiole elongation), followed by a massive, long-lasting growth reduction. The electrical potential changes consisted of a wave of depolarization and re-polarization, i.e., a variation potential (VP). The tissue deformation apparently resulted from a pressure surge rapidly transmitted through the xylem, and preceded the changes in electrical potential. Externally-applied pressure mimicked flame wounding by triggering an electrical response resembling a VP. Our findings suggest that the VP results from a pressure surge in the xylem causing change in activity of mechanosensitive ion channels or pumps in adjacent living cells. The ensuing ion fluxes evoke plasma membrane depolarization, monitored extracellularly as a VP. Wounding also evoked a systemic decrease in polysomes, as well as a decrease in their protein synthesizing capacity in vitro. Very little of the newly-synthesized proteinase inhibitor (pin) and calmodulin (cal) mRNA was recruited into polysomes during the first hour following wounding. Since the VP appearance in distant tissue preceded the systemic molecular responses, the VP might be the long-distance signal up-regulating transcription of proteinase inhibitors and calmodulin, and down-regulating translation.
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The movement of systemin, the 18-amino-acid polypeptide inducer of proteinase inhibitors in tomato (Lycopersicon esculentum L.) plants, was investigated in young tomato plants following the application of [14C]systemin to wounds on the surface of leaves. Wholeleaf autoradiographic analyses revealed that [14C]systemin was distributed throughout the wounded leaf within 30 min, and then during the next several hours was transported to the petiole, to the main stem, and to the upper leaves. The movement of [14C]systemin was similar to the movement of [14C]sucrose when applied to leaf wounds, except that sucrose was slightly more mobile than systemin. Analyses of the radioactivity in the petiole phloem exudates at intervals over a 5-h period following the application of [14C]systemin to a wound demonstrated that intact [14C]systemin was present in the phloem over the entire time, indicating that the polypeptide was either stable for long periods in the phloem or was being continually loaded into the phloem from the source leaf. The translocation pathway of systemin was also investigated at the cellular level, using light microscopy and autoradiography. Within 15 min after application of [3H]systemin to a wound on a terminal leaflet, it was found distributed throughout the wounded leaf and was primarily concentrated in the xylem and phloem tissues within the leaf veins. After 30 min, the radioactivity was found mainly associated with vascular strands of phloem tissue in the petiole and, at 90 min, label was found in the phloem of the main stem. Altogether, these and previous results support a role for systemin as a systemic wound signal in tomato plants.
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The relationship between nitrate influx, BnNrt2 nitrate transporter gene expression and amino acid composition of phloem exudate was investigated during N-deprivation (short-term experiment) and over a growth cycle (long-term experiment) in Brassica napus L. The data showed a positive correlation between γ-aminobutyric acid (GABA) in phloem exudate and nitrate uptake in the short- and the long-term experiments. The hypothesis that this non-protein amino acid could up-regulate nitrate uptake via a long-distance signalling pathway was tested by providing an exogenous GABA supply to the roots. The effect of GABA was compared with the effects of Gln, Glu and Asn, each known to be inhibitors of nitrate uptake. The results showed that GABA treatment induced a significant increase of BnNrt2 mRNA expression, but had less effect on nitrate influx. By contrast, Gln, Glu and Asn significantly reduced nitrate influx and BnNrt2 mRNA expression compared with the control plants. This study provides the first evidence that GABA may act as a putative long-distance inter-organ signal molecule in plants in conjunction with negative control exerted by Gln. The up-regulation effect of GABA on nitrate uptake is discussed in the context of its role in N metabolism, nutritional stress and the recent discovery of a putative role of GABA as a signal molecule in plant development.
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Immunolocalization of auxin using a new specific antibody revealed, besides the expected diffuse cytoplasmic signal, enrichments of auxin at end-poles (cross-walls), within endosomes and within nuclei of those root apex cells which accumulate abundant F-actin at their end-poles. In Brefeldin A (BFA) treated roots, a strong auxin signal was scored within BFA-induced compartments of cells having abundant actin and auxin at their end-poles, as well as within adjacent endosomes, but not in other root cells. Importantly, several types of polar auxin transport (PAT) inhibitors exert similar inhibitory effects on endocytosis, vesicle recycling, and on the enrichments of F-actin at the end-poles. These findings indicate that auxin is transported across F-actin-enriched end-poles (synapses) via neurotransmitter-like secretion. This new concept finds genetic support from the semaphore1, rum1 and rum1/lrt1 mutants of maize which are impaired in PAT, endocytosis and vesicle recycling, as well as in recruitment of F-actin and auxin to the auxin transporting end-poles. Although PIN1 localizes abundantly to the end-poles, and they also fail to support the formation of in these mutants affected in PAT, auxin and F-actin are depleted from their end-poles which also fail to support formation of the large BFA-induced compartments.
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Melatonin (N-acetyl-5-methoxytryptamine), a well-known animal hormone, was discovered in plants in 1995 but very little research into it has been carried out since. It is present in different parts of all the plant species studied, including leaves, stems, roots, fruits and seeds. This brief review will attempt to provide an overview of melatonin (its discovery, presence and functions in different organisms, biosynthetic route, etc.) and to compile a practically complete bibliography on this compound in plants. The common biosynthetic pathways shared by the auxin, indole-3-acetic, and melatonin suggest a possible coordinated regulation in plants. More specifically, our knowledge to date of the role of melatonin in the vegetative and reproductive physiology of plants is presented in detail. The most interesting aspects for future physiological studies are presented.
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Repeated observations that shading (a drastic reduction in illumination rate) increased the generation of spikes (rapidly reversed depolarizations) in leaves and stems of many cucumber and sunflower plants suggests a phenomenon widespread among plant organs and species. Although shaded leaves occasionally generate spikes and have been suggested to trigger systemic action potentials (APs) in sunflower stems, we never found leaf-generated spikes to propagate out of the leaf and into the stem. On the contrary, our data consistently implicate the epicotyl as the location where most spikes and APs (propagating spikes) originate. Microelectrode studies of light and shading responses in mesophyll cells of leaf strips and in epidermis/cortex cells of epicotyl segments confirm this conclusion and show that spike induction is not confined to intact plants. 90% of the epicotyl-generated APs undergo basipetal propagation to the lower epicotyl, hypocotyl and root. They propagate with an average rate of 2 +/- 0.3 mm s(-1) and always undergo a large decrement from the hypocotyl to the root. The few epicotyl-derived APs that can be tracked to leaf blades (< 10%) undergo either a large decrement or fail to be transmitted at all. Occasionally (5% of the observations) spikes were be generated in hypocotyl and lower epicotyl that moved towards the upper epicotyl unaltered, decremented, or amplified. This study confirms that plant APs arise to natural, nontraumatic changes. In simultaneous recordings with epicotyl growth, AP generation was found to parallel the acceleration of stem growth under shade. The possible relatedness of both processes must be further investigated.
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The review tracks the history of electrical long-distance signals from the first recordings of action potentials (APs) in sensitive Dionea and Mimosa plants at the end of the 19(th) century to their re-discovery in common plants in the 1950's, from the first intracellular recordings of APs in giant algal cells to the identification of the ionic mechanisms by voltage-clamp experiments. An important aspect is the comparison of plant and animal signals and the resulting theoretical implications that accompany the field from the first assignment of the term "action potential" to plants to recent discussions of terms like plant neurobiology.
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1. When the opposite ends of a living leaf of Dionæa are placed on non-polarizable electrodes in metallic connexion with each other, and a Thomson’s reflecting galvanometer of high resistance is introduced into the circuit thus formed, a deflection is observed which indicates the existence of a current from the proximal to the distal end of the leaf. This current I call the normal leaf-current . If, instead of the leaf, the leaf-stalk is placed on the electrodes (the leaf remaining united to it) in such a way that the extreme end of the stalk rests on one electrode and a part of the stalk at a certain distance from the leaf on the other, a current is indicated which is opposed to that in the leaf. This I call the stalk-current .
Article
Plants have at least three kinds of propagating electrical signals. In addition to a sustained wound potential (WP) that stops a few millimeters from dying cells, these signals are action potentials (APs) and slow wave potentials (SWPs). All three signals consist of a transient change in the membrane potential of plant cells (depolarization and subsequent repolarization), but only SWPs and APs make use of the vascular bundles to achieve a potentially systemic spread through the entire plant. The principal difference used to differentiate SWPs from APs is that SWPs show longer, delayed repolarizations. Unfortunately, SWP repolarizations also show a large range of variation that makes a distinction difficult. SWPs and APs do differ more clearly, however, in the causal factors stimulating their appearance, the ionic mechanisms of their depolarization and repolarization phases as well as the mechanisms and pathways of propagation. The depolarizations of a SWP arise with an increase in turgor pressure cells experience in the wake of a hydraulic pressure wave that spreads through the xylem conduits after rain, embolism, bending, local wounds, organ excision and local burning. The generation of APs occurs under different environmental and internal influences (e.g. touch, light changes, cold treatment, cell expansion) that - mediated through varying generator potentials - trigger a voltage-dependent depolarization spike in an all-or-nothing manner. While APs and WPs can be triggered in excised organs, SWPs depend on the pressure difference between the atmosphere and an intact plant interior. High humidity and prolonged darkness will also suppress SWP signaling. The ionic mechanism of the SWP is thought to involve a transient shutdown of a P-type H+-ATPase in the plasma membrane and differs from the mechanism underlying APs. Another defining characteristic of SWPs is the hydraulic mode of propagation that enables them - but not APs - to pass through killed or poisoned areas. Unlike APs they can easily communicate between leaf and stem. SWPs can move in both directions of the plant axis, while their amplitudes show a decrement of about 2.5% cm-1 and move with speeds that can be slower than APs in darkness and faster in bright light. The SWPs move with a rapid pressure increase that establishes an axial pressure gradient in the xylem. This gradient translates distance (perhaps via changing kinetics in the rise of turgor pressure) into increasing lag phases for the pressure-induced depolarizations in the epidermis cells. Haberlandt (1890), after studying propagating responses in Mimosa pudica, suggested the existence of hydraulically propagated electric potentials at a time when only APs were conceivable. It took a century to realize that such signals do exist and that they coincide with the characteristics of SWPs rather than those of APs. Moreover, we begin to understand that SWPs are not only ubiquitous among higher plants but represent a unique, defining characteristic without parallels in lower plants or animals.
Book
Neurotransmitters acetylcholine and biogenic amines dopamine, noradrenaline, serotonin and histamine are present not only in animals, but also in plants and microorganisms. This book is a first attempt to consider the role of the substances in plant life and how to use their characteristics for medicine and agriculture. Neurotransmitters may play universal role as elementary molecular agents of irritation in any living cell -animal, plant and microbial. The other functions of the substances are also known. Neurotransmitters participate in the information processes in plant cells and many functions in plant organisms as a whole - from changes in ion permeability of membranes, energetic and metabolism to complex processeses such as a fertilization, motility and lastly germination, growth and morphogenesis. Content: Preface, Introduction, 4 Chapters, Conclusion Appendix 1, Appendix 2. References. Latin Index, Subject Index. 283 pp. First variant of the book has been published in Pushchino USSR Biological Center in 1991 year with title:
Article
The integration of activity of Chenopodium plants on a hydraulic-electrochemical level is expressed by a diurnal rhythm in the resting membrane potential measured with contact electrodes. The membrane state could be gated by the energy state of cells. From earlier studies we compiled evidence in favour of a circadian rhythm in overall energy transduction producing a circadian rhythm in energy charge and redox state (NADPH2/NADP). The ratio of metabolic coupling nucleotides would be relatively temperature independent and thus could fulfil the requirements for precise temperature-compensated time-keeping. The phytochrome photoreceptors, involved in photoperiodic control of development, could via changes in pyridine nucleotide pool sizes and changes in nucleotide ratios regulate transcription-translational loops by redox and phosphorylation controlled transcription factors. Spontaneous action potentials (APs) have been shown to correlate with turgor-controlled growth movements. The accumulation of spontaneous APs at specific times during daily light-dark spans were recorded, giving specific electrophysiograms, representative for flower-inducing and vegetative conditions. It is anticipated that hydraulic changes at the apex leading to flower initiation are mediated by a specific hydro-electrochemical communication between leaves, the shoot apex and the root system. These results have been used to substitute a flower-inducing photoperiod by specific timing of electric stimulation via surface electrodes.
Article
Adenosine diphosphate (ADP), adenosine triphosphate (ATP) and orthophosphate were determined in non-stimulated, stimulated and relaxed pulvini of mature Mimosa pudica L. leaves. Additional determinations were made with leaflets, rhachillae, petiole and the stem in the stimulated condition. Results show that the content of adenine nucleotides is approximately twice as high in the pulvini as in the tissues between the pulvini. Orthophosphate, in contrast, occurs at higher concentrations in the connecting tissues than in the pulvini. ATP content is highest in the primary pulvini (0.8 μmol/mg dry wt.) and lowest in the tertiary pulvini. Stimulation causes consumption of ATP with a simultaneous increase in ADP content; however, the response is different in each type of pulvinus. This difference is best expressed in the ATP:ADP ratio. Stimulation causes the most marked reduction of the ratio (9.5-1.4) in the secondary pulvini which react nyctinastically. Orthophosphate content is reduced by stimulation in all types of pulvini, and is increased during the recovery phase. By using a stylet bundle severed from a feeding aphid by a laser shot as tip for the microelectrode, changes of sieve tube membrane potentials were recorded. The changes of the electropotentials following stimulation show that the sieve tube is the pathway for the transmission of the excitation signal in the form of an action potential.
Article
Plants continually gather information about their environment. The conduction of bioelectrochemical excitation is a fundamental property of living organisms. Cells, tissues, and organs transmit electrochemical signals over short and long distances. The sensitive membranes in phloem cells facilitate the passage of electrical excitations in the form of action potentials. We have created a unique electrophysiological workstation that can effectively register this electrical activity in real time. It allows basic properties of electrical communication in green plants to be established. Our workstation has very high input impedance and a resolution of 0.01 ms. Excitation waves in higher plants are possible mechanisms for intercellular and intracellular communication in the presence of environmental changes. Ionic channels, as natural nanodevices, control the plasma membrane potential and the movement of ions across membranes regulating various biological functions. Some voltage-gated ion channels work as plasma membrane nanopotentiostats. Blockers of ionic channels, such as tetraethylammonium chloride and ZnCl2, stop the propagation of action potentials in soybean induced by blue light and inhibit phototropism in soybean plants. Voltage-gated ionic channels control the plasma membrane potential and the movement of ions across membranes regulating various biological functions. These biological nanodevices play vital roles in signal transduction in higher plants. Tetraethylammonium chloride and ZnCl2 block K+ and Ca2+ ionic channels. These blockers inhibit the propagation of action potentials induced by blue light, and inhibit phototropism in soybean plants. The irradiation of soybean plants at 450 ± 50 nm induces action potentials with duration times of about 1 ms and amplitudes around 60 mV. The role of the electrified interface of the plasma membrane in signal transduction is discussed.
Article
Auxin is transported across the plasma membrane of plant cells by diffusion and by two carriers operating in opposite directions, the influx and efflux carriers. Both carriers most likely play an important role in controlling auxin concentration and distribution in plants but little is known regarding their regulation. We describe the influence of modifications of the transmembrane pH gradient and the effect of agents interfering with protein synthesis, protein traffic, and protein phosphorylation on the activity of the auxin carriers in suspension-cultured tobacco (Nicotiana tabacum L.) cells. Carrier-mediated influx and efflux were monitored independently by measuring the accumulation of [¹⁴C]2,4-dichlorophenoxyacetic acid and [³H]naphthylacetic acid, respectively. The activity of the influx carrier decreased on increasing external pH and on decreasing internal pH, whereas that of the efflux carrier was only impaired on internal acidification. The efflux carrier activity was inhibited by cycloheximide, brefeldin A, and the protein kinase inhibitors staurosporine and K252a, as shown by the increased capability of treated cells to accumulate [³H]naphthylacetic acid. Kinetics and reversibility of the effect of brefeldin A were consistent with one or several components of the efflux system being turned over at the plasma membrane with a half-time of less than 10 min. Inhibition of efflux by protein kinase inhibitors suggested that protein phosphorylation was essential to sustain the activity of the efflux carrier. On the contrary, the pharmacological agents used in this study failed to inhibit [¹⁴C]2,4-dichlorophenoxyacetic acid accumulation, suggesting that rapidly turned-over proteins or proteins activated by phosphorylation are not essential to carrier-mediated auxin influx. Our data support the idea that the efflux carrier in plants constitutes a complex system regulated at multiple levels, in marked contrast with the influx carrier. Physiological implications of the kinetic features of this regulation are discussed.
Article
To explore the role of auxin-binding protein (ABP1) in planta, a number of transgenic tobacco (Nicotiana tabacum) lines were generated. The wild-type KDEL endoplasmic reticulum targeting signal was mutated to HDEL, another common retention sequence in plants, and to KEQL or KDELGL to compromise its activity. The auxin-binding kinetics of these forms of ABP1 were found to be similar to those of ABP1 purified from maize (Zea mays). To test for a physiological response mediated by auxin, intact guard cells of the transgenic plants were impaled with double-barreled microelectrodes, and auxin-dependent changes in K⁺ currents were recorded under voltage clamp. Exogenous auxin affected inwardly and outwardly rectifying K⁺ currents in a dose-dependent manner. Auxin sensitivity was markedly enhanced in all plants overexpressing ABP1, irrespective of the form present. Immunogold electron microscopy was used to investigate the localization of ABP1 in the transgenic plants. All forms were detected in the endoplasmic reticulum and the KEQL and KDELGL forms passed further across the Golgi stacks than KDEL and HDEL forms. However, neither electron microscopy nor silver-enhanced immunogold epipolarization microscopy revealed differences in cell surface ABP1 abundance for any of the plants, including control plants, which indicated that overexpression of ABP1 alone was sufficient to confer increased sensitivity to added auxin. Jones et al. ([1998] Science 282: 1114–1117) found increased cell expansion in transgenic plants overexpressing wild-type ABP1. Single cell recordings extend this observation, with the demonstration that the auxin sensitivity of guard cell K⁺ currents is mediated, at least in part, by ABP1.
Article
Ionotropic glutamate receptors (iGluRs) are ligand-gated ion channels that are the predominant neuroreceptors in the mammalian brain. Genes with high sequence similarity to animal iGluRs have been identified in Arabidopsis. To understand the role of Arabidopsis glutamate receptor-like (AtGLR) genes in plants, we have taken a pharmacological approach by examining the effects of BMAA [S(+)-β-methyl-α, β-diaminopropionic acid], a cycad-derived iGluR agonist, on Arabidopsis morphogenesis. When applied to Arabidopsis seedlings, BMAA caused a 2- to 3-fold increase in hypocotyl elongation and inhibited cotyledon opening during early seedling development. The effect of BMAA on hypocotyl elongation is light specific. Furthermore, BMAA effects on early morphogenesis of Arabidopsis can be reversed by the simultaneous application of glutamate, the native iGluR agonist in animals. To determine the targets of BMAA action in Arabidopsis, a genetic screen was devised to isolate Arabidopsis mutants with a BMAA insensitive morphology (bim). When grown in the light on BMAA,bim mutants exhibited short hypocotyls compared with wild type. bim mutants were grouped into three classes based on their morphology when grown in the dark in the absence of BMAA. Class-I bim mutants have a normal, etiolated morphology, similar to wild-type plants. Class-II bimmutants have shorter hypocotyls and closed cotyledons when grown in the dark. Class-III bim mutants have short hypocotyls and open cotyledons when grown in the dark, resembling the previously characterized constitutively photomorphogenic mutants (cop, det, fus, and shy). Further analysis of thebim mutants should help define whether plant-derived iGluR agonists target glutamate receptor signaling pathways in plants.
Article
Mechanical damage and heat stimulation were used to activate proteinase inhibitor II (Pin2) gene expression in tomato plants in both treated (local induction) and non-treated tissues (systemic induction). Both stimuli have been shown to generate electrical signals, leading to a systemic activation of gene expression. Treatment of tomato leaves with electrical current resulted in the accumulation of Pin2 mRNA in the local and systemic leaves. Additionally, all treatments inducing Pin2 gene activity gave rise to a significant alteration of stomatal aperture. However, heat stimulation provoked a different response in the stomatal parameters than mechanical wounding or electric treatment. Both mechanical damage and electrical stimulation activated two characteristic time constants in the gas exchange relaxation kinetics. Conversely, heat stimulation resulted in only one major time constant. The results clearly show that direct current application to tomato leaves initiates Pin2 mRNA accumulation locally and systemically. In addition, they suggest the participation of a second slow electrical/hydraulic component in the wound response mechanism of tomato plants and a possible alternative pathway regulating heat-induced Pin2 gene expression.
Article
Electrical coupling between adjacent cells of Elodea canadensis has been demonstrated using a microelectrode technique in which the membrane potentials were recorded during the passage of a current pulse from the vacuole of one cell to the external solution. The changes in membrane potential resulting from the passage of the current may be simulated by an equivalent circuit in which the tonoplast:plasmalemma:plasmodesmata resistances are in the ratio 1.0:5.6:2.2. On this basis, the specific resistances are 3.1 kΩ cm(2) for the plasmalemma, 1.0 kΩ cm(2) for the tonoplast and 0.051 kΩ cm(2) for the junction between the cells. Although the plasmodesmata permit the passage of current, it is estimated that they have a resistance about 60 times higher than would be the case if they were completely open channels. Electrical coupling has also been demonstrated between parenchymal cells in oat coleoptiles and between cortical cells in maize roots. The significance of these findings is discussed in relation to the symplastic transport of ions and other small molecules and in relation to the quantitative measurement of membrane resistance in multicellular tissue.
Article
Two different types of bioelectric potential changes have been registered in the style of Lilium longiflorum cv. Arai 5 after different treatments of the stigma. Self-pollination induces a bioelectric potential change different from the potential change induced by cross-pollination. Removal of the stigma or apllication of killed compatible pollen induced a bioelectrical response similar to the potential change recorded after cross-pollination. No bioelectric potential change was recorded after application of pollen of Petunia hybrida, pollen of Haemanthus katherinae, killed self-pollen, or no treatment at all.The mean generation time of the bioelectric potential change was 338 min after the treatment. The translocation velocity varied between 1.2 and 5.4 cm h(-1). Both responses are similar to the potential changes registered in Mimosa pudica after different types of stimulation and to the potential changes generated by the phytochrome in Avena coleoptiles. The translocation of the signals is discussed in relation to the models on the translocation in Mimosa. The relation between the bioelectric potential changes and the incompatibility reaction in Lilium longiflorum is discussed.
Article
The electrical response to auxin perfusion by cortex tissue of peeledAvena saliva L. coleoptiles was examined using microelectrode measurements of the membrane potential. Applied at 10 µM, the known auxins indole-3-acetic acid (IAA), a-naphthalene acetic acid (aNAA), 2,4-dichlorophenoxyacetic acid, and indole-3-butyric acid, the two analogues ß-naphthalene acetic acid and 2,3-dichlorophenoxyacetic acid, and acetic acid transiently (1–30 min) depolarized the membrane potential; but a subsequent hyperpolarization, possibly resulting from activation of the plasma-membrane H+-ATPase, occurred only with active auxins. The magnitude and duration of the depolarizations induced by the different compounds varied. The aNAA-induced depolarization consisted of two depolarization events. The first reached a maximum within 2–3 min and the second between 6 and 10 min. The magnitude of the first aNAA-induced depolarization varied with external concentration of Cl- suggesting that it represents an efflux of Cl-. A known anion-channel blocker, anthracene-9-carboxylic acid, at 1 µM prevented the Cl--sensitive depolarization induced by aNAA. The same concentration failed to block aNAA-induced elongation of peeled coleoptile segments, though higher concentrations (20 µM and 100 µM) increasingly inhibited growth. Applied at 10 µM, the naturally occurring auxin, IAA, induced a single depolarization (maximal between 6 and 8 min) which was insensitive to external Cl- concentration. The depolarization induced by 10 µM IAA, as well as that induced by acetic acid and the second depolarization induced by 10 µM aNAA, increased in magnitude when the pH of the perfusate was lowered from 6.0 to 4.5. When IAA was applied at a higher concentration (100 µM) the magnitude of the depolarization increased, lengthened, and also contained an early, Cl--sensitive, depolarization (maximal between 2 and 4 min). The Cl--sensitive depolarization induced by aNAA also increased when aNAA was increased from 10 to 100 µM, but, while 10 and 100 µM IAA and 10 µM aNAA induced elongation of peeledAvena coleoptile segments, 100 µM aNAA did not. Our results suggest that: (i) the putative Cl- currents induced by 10 µM aNAA and 100 µM IAA are the result of the opening of a population of Cl--permeable anion channels, (ii) activation of these channels is not required for the auxin-induced growth ofAvena coleoptiles, (iii) the pH-sensitive depolarization induced by aNAA and IAA is not an auxin-specific response and might result from a weak acid protonophore effect, and (iv) the delayed hyperpolarization is a specific response to auxins inAvena coleoptiles.
Article
The inhibition of phloem translocation caused by electric- and cold-shock was studied by macro- and microautoradiography in mature leaves of maize (Zea mays L.). In addition, both types of stimulation triggered action potentials with amplitudes of more than 50 mV which were transmitted without diminution in sieve tubes with velocities of 3-5 cm s-1. By utilizing X-ray microanalysis ion concentrations of sieve tubes were measured in non-stimulated and stimulated leaves. It was shown that potassium and chloride diminished about 3-fold after stimulation while the amount of cytoplasmic calcium may have increased. These displacements lead to the conclusion that calcium influx as well as potassium and chloride efflux are involved in the propagation of action potentials. A possible relationship between electric signalling and the reduction of phloem translocation is discussed.
Article
Localized wounding is known to induce systemic proteinase inhibitors (PI) in seedlings of tomato (Lycopersicon esculentum L.). Inhibitors of elastase (EC 3.4.21.36) were shown here to be among those systemically induced by wounding, and a simple rapid assay for PI based on elastase was developed. Using this assay, the nature of the systemic signalling system (‘PIIF’) was investigated. Hydraulic signals were shown to be induced in tomato by localized wounds. These signals travelled throughout the plant well within the lag time before appearance of systemic wound-induced PI. A number of correlations were drawn between the occurrence of the hydraulic signals and induction of systemic PI, suggesting that hydraulic signals might be the PIIF, or a component of it. It was shown that systemic hydraulic signals could be triggered, without significant wounding, by excision of a single leaflet through the submerged petiole. These hydraulic signals were similar in both kinetics and magnitude to those induced by localized wounding. However, they did not induce systemic PI. In addition, it was shown that systemic events almost as rapid as wound-induced hydraulic signals could be induced without wounding, under certain environmental conditions. This indicates that rapid hydraulic signals do not provide a specific signal of wounding. These findings demonstrate that hydraulic signals per se are not the PIIF.
Article
The plant polypeptide signal systemin induces proteinase inhibitor synthesis in tomato leaves. We show here that systemin elicits a transient depolarization of the tomato mesophyll cell membrane. Furthermore it triggers a transient decrease in the external pH of the mesophyll tissue which is followed by a sustained pH increase. In the presence of fusicoccin (which has been shown to antagonize the synthesis of proteinase inhibitors) the depolarization and transient H+ efflux are attenuated whereas the slower phase of the sustained electroneutral H+ influx persists. These results suggest that systemin-induced changes in ion transport play a role in the early phases of systemin signal transduction.
Article
Summary • In the sensitive species Mimosa pudica electric signals arise when the leaves are stimulated by touching or wounding. Experiments reported here provide informa- tion about a photosynthetic response that results from heat-induced electrical sig- nalling in leaves. • Electric potential measurements, combined with chlorophyll fluorescence, as well as gas exchange measurements showed that wounding evokes an electrical signal that travels rapidly into the neighbouring leaf pinna to eliminate the net-CO 2 uptake rate. At the same time the PSII quantum yield of electron transport is reduced from c . 0.6 to 0.2. Two-dimensional imaging analysis of the chlorophyll fluorescence signal revealed that the yield reduction spreads acropetally through the pinna and via the veins through the leaflets. •T o determine the speed of a chemical signal, a part of a pinna was exposed to 14 CO 2 . The remaining parts of the leaf were provided with label only when the translocation was extended to 12 h, indicating that a chemical signal is much too slow to account for the photosynthetic response after heat stimulation. • The results provide evidence for a role of the electrical signal in the regulation of photosynthesis because the high speed of the signal transduction rules out the involvement of a chemical signal, and the photosynthetic response occurs after the arrival of the electrical signal in the leaf pinna.
Article
Protoplasts of corn coleoptiles and Arabidopsis hypocotyls respond to the plant hormone auxin with a rapid change in volume. We checked the effect of antibodies directed against epitopes of auxin-binding protein 1 from Arabidopsis thaliana (AtERabp1) and Zea mays (ZmERabp1), respectively. Antibodies raised against the C-terminus of AtERabp1 inhibited the response to auxin, while antibodies raised against a part of box a, the putative auxin-binding domain, induced a swelling response similar to that caused by auxin treatment. Synthetic C-terminal oligopeptides of ZmERabp1 also caused a swelling response. These effects occurred regardless of whether the experiments were carried out with homologous (anti-AtERabp1 antibodies on Arabidopsis protoplasts or anti-ZmERabp1 antibodies in maize protoplasts) or heterologous immunological tools. The results indicate that the auxin signal for protoplast swelling is perceived by extracellular ABP1.
Article
Mature leaves of Mimosa pudica L. or parts of them were exposed to 14CO2, and translocation was recorded by macroautoradiography. It was observed that considerable amounts of labelled photoassimilates were accumulated in pulvini when the leaf was stimulated. In non-stimulated leaves, no such accumulation of label was observed. Microautoradiographs of pulvinar regions of the non-stimulated leaf showed 14C- label restricted to the phloem. When stimulated, the 14C- label was unloaded from the phloem of the pulvini. Labelled photoassimilates appeared most concentrated in the walls of the collenchymatous cells and beyond in the extensor region of the motor cortex. There, label was accumulated in the apoplastic compartments. Stimulation causes a sudden phloem unloading of sucrose, and its accumulation in the apoplast lowers the water potential which eventually exceeds the osmotic potential of the extensor cells of the motor cortex. By removal of cytoplasmic water the motor cells lose turgidity which results in the closing movement of the leaflets, and — some seconds later — in the bending down of the petiole. In late afternoon night-stimulation triggers sucrose unloading in secondary pulvini. During phases of relaxation, labelled material is taken up by motor cells of the extensor, which concomitantly gain turgor.
Article
Mature leaves ofMimosa pudica L. or parts of them were exposed to14CO2, and translocation was recorded by macroautoradiography. It was observed that considerable amounts of labelled photoassimilates were accumulated in pulvini when the leaf was stimulated. In non-stimulated leaves, no such accumulation of label was observed. Microautoradiographs of pulvinar regions of the non-stimulated leaf showed14C- label restricted to the phloem. When stimulated, the14C- label was unloaded from the phloem of the pulvini. Labelled photoassimilates appeared most concentrated in the walls of the collenchymatous cells and beyond in the extensor region of the motor cortex. There, label was accumulated in the apoplastic compartments. Stimulation causes a sudden phloem unloading of sucrose, and its accumulation in the apoplast lowers the water potential which eventually exceeds the osmotic potential of the extensor cells of the motor cortex. By removal of cytoplasmic water the motor cells lose turgidity which results in the closing movement of the leaflets, and — some seconds later — in the bending down of the petiole. In late afternoon night-stimulation triggers sucrose unloading in secondary pulvini. During phases of relaxation, labelled material is taken up by motor cells of the extensor, which concomitantly gain turgor.
Article
Plant peroxidases (EC 1.11.1.7) including horseradish peroxidase (HRP-C), but not the nonplant peroxidases, are known to be highly specific indole-3-acetic acid (IAA) oxygenases which oxidize IAA in the absence of H2O2, and superoxide anion radicals (02·-) are produced as by-products. Hypaphorine, a putative auxin antagonist isolated from ectomycorrhizal fungi, inhibited the IAA-dependent generation of 02·- by HRP-C, which occurs in the absence of H2O2. Hypaphorine has no effect on the nonspecific heme-catalyzed O2·- generation induced by high concentration of ethanol. It is probable that the inhibitory effect of hypaphorine on O2·- generation is highly specific to the IAA-dependent reaction. The mode of inhibition of the IAA-dependent O2·--generating reaction by hypaphorine was analyzed with a double-reciprocal plot and determined to be competitive inhibition, indicating that hypaphorine competes with IAA by binding to the putative IAA binding site on HRP-C. This implies the importance of structural similarity between hypaphorine and IAA. This work presented the first evidence for antagonism between IAA and a structurally related fungal alkaloid on binding to a purified protein which shares some structural similarity with auxin-binding proteins.
Article
THE wound response of several plant species involves the activation of proteinase inhibitor (pin) genes and the accumulation of pin proteins at the local site of injury and systemically throughout the unwounded aerial regions of the plant1,2. It has been suggested that a mobile chemical signal is the causal agent linking the local wound stimulus to the distant systemic response, and candidates such as oligosaccharides3, abscisic acid4 and a polypeptide5,6 have been put forward. But the speed of transmission is high for the transport of a chemical signal in the phloem. The wound response of tomato plants can be inhibited by salicylic acid7 and agents like fusicoccin that affect ion transport8, and wounding by heat9 or physical injury produces electrical activity that has similarities to the epithelial conduction system10 used to transmit a stimulus in the defence responses of some lower animals11. Here we design experiments to distinguish between a phloem-transmissible chemical signal and a physically propagated signal based on electrical activity. We show that translocation in the phloem of tomato seedlings can be completely inhibited without effect on the systemic accumulation of pin transcripts and pin activity, and without hindrance to propagated electrical signals.
Article
The electrical response of Zea mays coleoptiles and suspension cultured cells to several growth-promoting auxins (IAA, IBA, 2,4-D, 2,4,5-T, 1-NAA) and some of their structural analogues (2,3-D, 2-NAA) has been tested. In coleoptile two typical electrical responses to IAA are observed: an immediated rapid depolarization, and a hyperpolarization following 7-10 minutes after the first external addition of IAA. Of the other tested compounds only 1-NAA significantly depolarized the cells, whereas all auxins as well as the analogues evoked delayed hyperpolarizations. In contrast, the suspension cells were not hyperpolarized by any of the tested compounds, but were strongly depolarized by IAA, 1-NAA, and to a lesser extent by 2-NAA. In these cells IAA and 1-NAA induced inwardly directed currents of positive charge which both saturated around 12 mA/m2. The strong pH-dependence together with the half-maximal currents 0.49 microM IAA and 0.76 microM 1-NAA point to a symport of the anions with at least 2H+. The delayed plasma membrane hyperpolarization is a different response, and seems to be initiated by the protonated auxin species. In accordance with the current literature, it is interpreted as consequence of a stimulated proton extrusion. The finding that all tested compounds evoked a hyperpolarization, makes this response unspecific. It is concluded that a stimulation of proton extrusion is a necessary, but not sufficient step to induce elongation growth.