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Are plants sentient?
Abstract
Feelings in humans are mental states representing groups of physiological functions that usually have defined behavioural purposes. Feelings, being evolutionarily ancient, are thought to be coordinated in the brain stem of animals. One function of the brain is to prioritise between competing mental states, and thus groups of physiological functions and in turn behaviour. Plants use groups of coordinated physiological activities to deal with defined environmental situations but currently have no known mental state to prioritise any order of response. Plants do have a nervous system based on action potentials transmitted along phloem conduits but which in addition, through anastomoses and other cross-links, forms a complex network. The emergent potential for this excitable network to form a mental state is unknown but it might be used to distinguish between different and even contradictory signals to the individual plant and thus determine a priority of response. This plant nervous system stretches throughout the whole plant providing the potential for assessment in all parts and commensurate with its self-organising, phenotypically plastic behaviour. Plasticity may, in turn, depend heavily on the instructive capabilities of local bioelectric fields enabling both a degree of behavioural independence but influenced by the condition of the whole plant.
... and between functional aspects of experience (e.g., how one experience takes conscious priority over another) vs. phenomenal ones (e.g., the experiential difference between seeing two different colors) Seth and Bayne, 2022). This research is largely neurobiologically oriented, focusing on the basis of subjective experience in humans (Boly et al., 2013;Mashour and Alkire, 2013;Hohwy and Seth, 2020;Mashour et al., 2020) and other organisms (Trewavas and Baluška, 2011;Calvo et al., 2017;Baluška and Reber, 2019). Other work considers more generalized definitions, such as measures of information processing that could apply to living and non-living systems (Tononi et al., 2016). ...
... However, a nervous system like ours is not conceptually necessary for consciousness. For example, there is active debate over whether plants exhibit consciousness (Calvo et al., 2017;Draguhn et al., 2021), and this demonstrates the challenges in proving the presence of subjective experience when its physical substrate differs from that of our own. For this reason it is helpful to consider characterizations of consciousness that do not require biology: one example, Integrated Information Theory (Tononi et al., 2016) (IIT), proposes that consciousness arises when a critical degree of information integration occurs; this threshold is presumably reached in the brain but may also be reached anywhere information can be integrated. ...
... In this view, numerous biological and non-biological entities could conceivably exhibit consciousness. For discussion purposes we can categorize these based upon features that may help us interact with them: (i) Communication without biology [C + B − , e.g., AI agents (Krauss and Maier, 2020) and certain BCIs (Goertzel and Ikle, 2012)]; (ii) Biology/organic substrate without communication [C − B + , e.g., plants, (Calvo et al., 2017) other biological organisms, and likely alien lifeforms (Cockell, 2016)]; (iii) Neither communication nor biology (C − B − , e.g., complex integrated non-biological systems). ...
... Recent advancements in plant biology and phyto-physiological research challenge and complicate these traditional notions of sentience. For instance, Calvo et al. (2017) have demonstrated forms of communication and responsiveness in plants, evidenced through phenotypic plasticity and mechanisms such as bioelectrical signalling, phloem conduits, and vascular anastomoses. These findings reveal sophisticated modes of interaction and adaptation in plants, suggesting a kind of plant sentience that operates through mediated functions rather than direct sensory or emotional experiences akin to those of humans or animals. ...
... His statement, "all trees, I allow them to have the perception of lifelessness and the absence of mental perception", positions plants as fundamentally insentient within the Buddhist framework. While plants biologically grow, exhibit phenotypic changes, and engage in processes such as photosynthesis (Baluška et al. 2006;Calvo et al. 2017), these abilities do not meet the criteria for sentience as defined in early Mahayana thought. Plants are categorised as nonsentient entities. ...
This article explores the concept of ‘Tibetan Buddhist plant-hood’ within the doctrinal and ethnographic contexts of Tibetan Buddhism, proposing it as a framework to understand the karma-intricate relationships between plants, sentient beings, and spiritual entities. By drawing on canonical Tibetan Buddhist texts, this article examines sentience in Tibetan terms, then introduces the notion of procedural sentiency, an extended Buddhist conceptual tool that reveals the dynamic processes through which insentient forms acquire ethical and spiritual significance. Examining specific cases, such as sacred trees, Tibetan highland barley, and Yartsa Gunbu (caterpillar fungus), plants are conceived as embedded within more-than-human Tibetan societies that span the material, spiritual, and ecological worlds. This study also addresses the ethical tensions and relational reconfigurations arising from plant–human interactions, as informed by Buddhist practices and cosmological perspectives. This endeavour aspires to establish Himalayan conceptual frameworks that engage in meaningful dialogues with broader environmental discourses, fostering an integrative perspective on the interplay between local practices, cosmologies, and global theoretical paradigms.
... Haberlandt (1884) proposed (controversially at the time) that the phloem-bundles of vascular tissue (see Glossary)-served as the conduit for propagation (for an overview of developments see Liesche, 2019;López-Salmerón et al., 2019). This hypothesis culminated in important work by Bose (1902Bose ( , 1926Bose & Guha, 1922) on the role of vascular bundles in enabling cell-to-cell propagation of electrical activity in plants, which Bose explicitly compared to nerves, and which has been confirmed by recent research (for an overview of Bose's work, see Calvo et al., 2017). Bose also (correctly) suggested that electrical signalling played a large part in plant physiology, beyond visible movement like trap closure in Venus flytraps, which garnered criticism from the wider scientific community (Shepherd, 2012). ...
... We here wish to sidestep the live debate around the extent to which Venus flytraps and plants more generally may be attributed genuine cognitive capacities (for some discussion, see Trewavas, 2005). It is clear, however, that APs facilitate a form of temporary information storage that is bioelectrical in nature (Suda et al., 2020;Ueda & Nakamura, 2006;Volkov et al., 2009), and that plants are capable of discriminating between numbers of stored signals (Böhm et al., 2016;Calvo et al., 2017;Hedrich, 2012;Hedrich et al., 2016). Thus, despite otherwise very different mechanisms, at the very least, APs underlie different kinds of memory-like phenomena across the plant and animal kingdoms. ...
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.
... 19 Soon after, Jagadis Chandra Bose 20,21 highlighted the importance and pervasiveness of electrical signaling between plant cells to coordinate their responses to the environment. 22 Bose's general conclusion was that plants have a "nervous system", a form of intelligence, and are capable of remembering and learning, 23 as had already been proposed by Charles 24 , and his son Francis 25. Since then, evidence has demonstrated that electrical signaling over long distances is an effective means of cell-to-cell communication in response to many biotic and abiotic sources of stimulation in plants, as well as in eukaryotes as a whole 26-29; 30 . ...
... Over the past 15 years or so, there has been a heated debate on the unsuspected capacities of plants, with some authors taking up the hypothesis of their intelligence. 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. ...
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.
... It is the degree of phenotypic flexibility that can be observed in the behavioral repertoire of plants that supports the capacity for subjective experience in plants and licenses our quest for the origins of mind in plants. This remains an open empirical question, not unlike the question of the sentience of any other organic form (Balusǩa & Mancuso 2009;Calvo 2017;Calvo, Sahi & Trewavas 2017). ...
... For a working hypothesis about the non-neural substrate that would serve to implement it all in plants at the electrical level via long-distance signaling, seeCalvo, Sahi & Trewavas (2017). For a non-model-based alternative account of plant behavior, seeCalvo, Raja & Lee (2017). ...
... Enfin, nous sommes invités à nous interroger sur l'existence d'une conscience chez cet être végétal, tout en restant dans l'incapacité d'expérimenter cette hypothèse. Cent ans plus tard, les nombreux travaux actuels autour de l'« intelligence » des plantes et de leur sentience (Bertrand, 2018 ;Ryan et al., 2021 ;Mancuso et Viola, 2020 ;Calvo et al., 2017) résonnent de cette invitation, mais sans pouvoir toutefois prétendre avoir compris l'arbre, car reconnaître dans l'arbre un autre que soi demeure un pari éthique. Dans l'ignorance, mieux vaut accorder à tout être vivant une dignité égale à celle du sujet. ...
... Whether plants are indeed alive is a philosophical question which depends in part on scientific data. Science so far tells us that plants have a nervous system which allows them to communicate with one another and with other creatures, and to experience and respond to the external environment using a sensory system that may be called sight and smell (Calvo et al. 2017;Baluška and Mancuso 2020;Wohlleben 2016). Whether plants are alive however, or even sentient, is still an area of great controversy. ...
The COVID-19 and Monkeypox pandemics and the ongoing Marburg outbreak in Rwanda provide a stark reminder of the importance of espousing a One Health (OH) approach to zoonoses as well as other public health and global health issues. Recent years have in fact seen an exponential rise in biomedical and public health journals and publications explicitly adopting the name of OH. Not all research that pertains to be OH however is indeed OH research, insofar as it does not comply with the proclaimed OH goals of benefiting humans, animals, and the environment. Thus, to ensure such compliance a checklist or toolkit for an ethical analysis of research in OH (EAROH) should be required prior to publication in scientific journals or grant applications. Such a toolkit should be developed by a working group of scholars with expertise in OH ethics, animal ethics, and environmental ethics.
... Sentience has been defined in a variety of ways, from definitions that focus on the ability of an animal to experience negative or positive mental states, to definitions that attribute sentience to any living being that responds to environmental influences without the need to experience negative or positive mental states and/or without the need to assume the involvement of conscious processes (for recent discussions that extend to the question whether plants are sentient, see e.g. Calvo et al. 2017;Draguhn et al. 2021;Segundo-Ortin & Calvo 2022). "Individuals are sentient if they have the capacity to have feelings, which includes the ability to evaluate the actions of others in relation to oneself and third parties, to remember some of one's own actions and their consequences, to assess risks and benefits and to have some degree of awareness" (Broom 2020; p 1). ...
A wide range of animal taxa, including vertebrates and invertebrates, are controlled or kept by humans. They may be used as pets, for recreation, sport and hobbies, as working animals, as producers of animal-derived (food) products or as biomedical models in research. There is a need for clear guidance on the treatment of animals, regardless of their phylogenetic distance from humans. Current animal welfare concepts, which emphasise animal sentience and the ability of animals to experience negative or positive mental states, are limited in scope to a small proportion of the animal kingdom, as the vast majority of species are (currently) thought to lack sentience. We discuss four options for addressing the question of which basic concept(s) could be used to derive guidelines for the treatment of animal species, sentient or non-sentient: (1) alternative concepts tailored to specific groups of species; (2) ‘welfare’ concepts not presupposing sentience; (3) the precautionary principle; or (4) the concept of animal integrity. Since questions regarding the appropriate treatment of animals, including species with a large phylogenetic distance from humans, have an ethical/moral dimension, we also address who counts morally and how much, and how animals should be treated given their moral status. We suggest that the concept of animal integrity, possibly complemented and extended by the concept of habitat/ecosystem integrity, is suitable for application to all species. However, a current concept of animal welfare should serve as the primary basis for guidance on how to treat species that are sentient and capable of experiencing emotions.
... Emerging studies in the field of Plant Neurobiology -a research discipline that investigates how plants acquire signals from their environment, interpret them, and calculate survival solutions (Brenner et al., 2006;Mancuso, 2017Mancuso, , 2019 -are now breaking down knowledge barriers, gathering extraordinary data that recognize plant actions and behaviors guided by a distinct form of intelligence. Unlike animals, plants do not possess a nervous system and don't have a centralized brain (Calvo et al., 2017;Segundo-Ortin & Calvo, 2019); rather, functions are distributed throughout the entire organism, which decentralizes cognition (Calvo, 2007;Viola & Mancuso, 2015). In fact, plants interact with the environment via biotic and abiotic signals (both above and below ground) in order to determine the optimal survival strategy (Gagliano et al., 2018;Pelizzon & Gagliano, 2015). ...
... Another area with a strong cognitive approach in biology is plant cognition. Here we find a variety of approaches to the cognitive abilities of plants, from their neurobiological basis (Brenner et al., 2006), their ability to feel (Calvo et al., 2017), to experience a specific ecological niche (Sultan, 2015), to behave adaptively (Calvo & Kijzer, 2011) or intelligently (Trewavas, 2014), or even to have consciousness (Segundo-Ortín and Calvo, 2022) or thoughts (Marder, 2013). Again, this involves information processing and signaling systems associated with the intrinsic ability of plants to regulate their interaction with the environment through various responses, be it through morphology, movement, behavior, and other physiological changes. ...
The foundations of biology have been a topic of debate for the past few decades. The traditional perspective of the Modern Synthesis, which portrays organisms as passive entities with a limited explanatory role in evolutionary theory, is giving way to a new paradigm where organisms are recognized as active agents, actively shaping their own phenotypic traits for adaptive goals. Within this context, this article raises the question of whether contemporary biological theory is undergoing a cognitive revolution. This inquiry can be approached in two ways: from a theoretical standpoint, exploring the centrality of the cognitive sciences in current theoretical biology; and from a historical perspective, examining the resemblance between the current state of theoretical biology and the Cognitive Revolution of the mid-twentieth century. Both inquiries yield affirmative answers, though important nuances will be emphasized. The cognitive sciences’ explanatory framework is employed to elucidate the agentic characteristics of organisms, establishing a clear parallelism between the Cognitive Revolution and the present state of theoretical biology.
... No suggestion has evoked so much controversy as the proposal by some Proponents that plants are sentient, the simplest type of consciousness. 245,246 A recent review by some Opponents, for example, is provocatively entitled "Debunking a Myth: Plant Consciousness." 6 Opponents adhere to the Neural Correlates of Consciousness (NCC) school of consciousness. NCC refers to the minimum set of neuronal mechanisms necessary for conscious experience to occur. ...
The 21st-century “plant neurobiology” movement is an amalgam of scholars interested in how “neural processes”, broadly defined, lead to changes in plant behavior. Integral to the movement (now called plant behavioral biology) is a triad of historically marginalized subdisciplines, namely plant ethology, whole plant electrophysiology and plant comparative psychology, that set plant neurobiology apart from the mainstream. A central tenet held by these “triad disciplines” is that plants are exquisitely sensitive to environmental perturbations and that destructive experimental manipulations rapidly and profoundly affect plant function. Since destructive measurements have been the norm in plant physiology, much of our “textbook knowledge” concerning plant physiology is unrelated to normal plant function. As such, scientists in the triad disciplines favor a more natural and holistic approach toward understanding plant function. By examining the history, philosophy, sociology and psychology of the triad disciplines, this paper refutes in eight ways the criticism that plant neurobiology presents nothing new, and that the topics of plant neurobiology fall squarely under the purview of mainstream plant physiology. It is argued that although the triad disciplines and mainstream plant physiology share the common goal of understanding plant function, they are distinct in having their own intellectual histories and epistemologies.
... With respect to ethics, moral standing -in the strict sense -becomes salient when we are speaking of sentient life. I take the question of putative sentience in plants to be open, indeed most interestingly so (Calvo et al. 2017). Now Aaltola worries about my alleged use of agency to describe plant life (Aaltola 2018, 113) -but this is a red herring: nowhere do I build a case for botanical agency. ...
This article argues that rationalism no longer rules the field of animal ethics – an “affective turn” has occurred in a significant space of the field. The article first looks at exemplary rationalists for contrast, and then moves on to survey several leading affective theories: Donovan’s feminist care ethic, Acampora’s corporal compassion, Gruen’s entangled empathy, and Aaltola’s varieties of empathy. Aaltola’s criticisms of Acampora are reviewed and rebutted. Finally, the conclusion indicates what is positive about the contributions of affective theory to animal ethics.
... A broad definition of sentience is being extended from terrestrial vertebrates into not only fish, crustaceans, molluscs, and other invertebrates including insects (Crump et al. , 2023Gibbons et al. 2022), but also plants (Calvo et al. 2017;Chamovitz 2018;Baluška and Mancuso 2021) and cell cultures (Niikawa et al. 2022). Most of this discussion is philosophical in nature, since measuring "pleasure" and "pain" in these groups in any scientifically valid context remains challenging and riddled with inconsistencies, technical problems (e.g., Bennett et al. 2009;Borrelli et al. 2020) and subjective anthropomorphic assumptions (e.g., for fishes see Rose et al. 2014;Mason and Lavery 2022;Hart 2023; and for plants see Brown and Key 2021). ...
Psychology and vision science, university of leicester, leicester, uK; j school of veterinary science, Murdoch university, Perth, wA, Australia; k Department of ichthyology, Faculty of Biology, lomonosov Moscow state university, Moscow, Russia; l school of Biomedical sciences, university of queensland, Australia; m Pepperell Research and consulting, noosaville, qlD, Australia; n Kansas Biological survey, and the Biodiversity institute, the university of Kansas, lawrence, Ks, usA; o emeritus (Retired) Department of Zoology and Physiology, university of wyoming laramie, wY, usA; p Britannia heights, nelson, new Zealand; q Biomed sci, Atlantic veterinary college, university of Pei, charlottetown, canada; r the college of william & Mary, virginia institute of Marine science, Gloucester Point, virginia, usA; s emeritus (Retired) tropical Aquaculture laboratory, university of Florida, Gainesville, usA ABSTRACT The welfare of fishes and aquatic invertebrates is important, and several jurisdictions have included these taxa under welfare regulation in recent years. Regulation of welfare requires use of scientifically validated welfare criteria. This is why applying Mertonian skepticism toward claims for sentience and pain in fishes and aquatic invertebrates is scientifically sound and prudent, particularly when those claims are used to justify legislation regulating the welfare of these taxa. Enacting welfare legislation for these taxa without strong scientific evidence is a societal and political choice that risks creating scientific and interpretational problems as well as major policy challenges, including the potential to generate significant unintended consequences. In contrast, a more rigorous science-based approach to the welfare of aquatic organisms that is based on verified, validated and measurable endpoints is more likely to result in "win-win" scenarios that minimize the risk of unintended negative impacts for all stakeholders, including fish and aquatic invertebrates. The authors identify as supporters of animal welfare, and emphasize that this issue is not about choosing between welfare and no welfare for fish and aquatic invertebrates, but rather to ensure that important decisions about their welfare are based on scientifically robust evidence. These ten reasons are delivered in the spirit of organized skepticism to orient legislators, decision makers and the scientific community, and alert them to the need to maintain a high scientific evidential bar for any operational welfare indicators used for aquatic animals, particularly those mandated by legislation. Moving forward, maintaining the highest scientific standards is vitally important, in order to protect not only aquatic animal welfare, but also global food security and the welfare of humans.
... 21 See also Schulte & Majetschak 2022 [45]. 22 Wittgenstein indicates, at the end of section 35 of the Investigations [26], that similar cases include recognising, wishing, and remembering and, in a remark inserted between sections 35 and 36, the case of 'when one means the words "That is blue" at one time as a statement about the object one is pointing at -at another as an explanation of the word "blue"'. The Investigations are in fact filled with instances of Wittgenstein's struggling against this kind of tendency to give superficial, oversimplifying psychological explanations, including a good deal of his influential discussion of following a rule. ...
The logical problem of artificial intelligence—the question of whether the notion sometimes referred to as ‘strong’ AI is self-contradictory—is, essentially, the question of whether an artificial form of life is possible. This question has an immediately paradoxical character, which can be made explicit if we recast it (in terms that would ordinarily seem to be implied by it) as the question of whether an unnatural form of nature is possible. The present paper seeks to explain this paradoxical kind of possibility by arguing that machines can share the human form of life and thus acquire human mindedness, which is to say they can be intelligent, conscious, sentient, etc. in precisely the way that a human being typically is.
... The impacts of behavioral neuroscience, and of its advances in explaining cognitive and proto-cognitive capacities, lie well beyond classical neural cells. Understood broadly, developmental bioelectricity provides an entry-point into unifying adaptive "behavior" and problem-solving intelligence in diverse spaces in a way that makes it natural to think of plant, microbial, and even synthetic life (Baluška and Mancuso 2012;Baluška et al. 2022;Baluška and Reber 2021a, b;Bassel 2018;Calvo et al. 2020Calvo et al. , 2017Debono and Souza 2019;Martinez-Corral et al. 2019;Prindle et al. 2015;Reber and Baluška 2021;Schofield et al. 2020;Solé et al. 2016;Souza et al. 2017;Urrios et al. 2016;Yang et al. 2020) using the same conceptual tools from behavioral and physiological sciences. The on-going debate around representation and morphological computation is likewise being enriched by data in this field (Keijzer 1998(Keijzer , 2001. ...
Each of us made the remarkable journey from mere matter to mind: starting life as a quiescent oocyte (“just chemistry and physics”), and slowly, gradually, becoming an adult human with complex metacognitive processes, hopes, and dreams. In addition, even though we feel ourselves to be a unified, single Self, distinct from the emergent dynamics of termite mounds and other swarms, the reality is that all intelligence is collective intelligence: each of us consists of a huge number of cells working together to generate a coherent cognitive being with goals, preferences, and memories that belong to the whole and not to its parts. Basal cognition is the quest to understand how Mind scales—how large numbers of competent subunits can work together to become intelligences that expand the scale of their possible goals. Crucially, the remarkable trick of turning homeostatic, cell-level physiological competencies into large-scale behavioral intelligences is not limited to the electrical dynamics of the brain. Evolution was using bioelectric signaling long before neurons and muscles appeared, to solve the problem of creating and repairing complex bodies. In this Perspective, I review the deep symmetry between the intelligence of developmental morphogenesis and that of classical behavior. I describe the highly conserved mechanisms that enable the collective intelligence of cells to implement regulative embryogenesis, regeneration, and cancer suppression. I sketch the story of an evolutionary pivot that repurposed the algorithms and cellular machinery that enable navigation of morphospace into the behavioral navigation of the 3D world which we so readily recognize as intelligence. Understanding the bioelectric dynamics that underlie construction of complex bodies and brains provides an essential path to understanding the natural evolution, and bioengineered design, of diverse intelligences within and beyond the phylogenetic history of Earth.
... As emphasized by Kjelchova et al. (2021) "such electrical characteristics do not imply higher sensory function". Thus, and in contrast to the suggestion of plant neurobiologists (e.g., Calvo et al., 2017;, there is no "electrochemical equivalency" between plants and animals. ...
... The other consequence is a hierarchisation between animals themselves, some being judged as stupid, gregarious, machine-like, intelligent, powerful, or dangerous, all the way down to plants and trees which are discarded as devoid of sensitivity, defined as the smallest common denominator between animal species, and thus as unworthy of human attention beyond it being instrumental. This judgement has recently been refuted by anthropologists (Gagliano and Afeisa 2018; Baluska et al. 2018;Kohn 2018) in the wake of a growing number of biologists (Trewavas 2017; Calvo et al. 2017;Fournier and Moulia 2018;Mancuso and Viola 2018;Chamillard 2018;Synowiecki 2020;Calvo et al. 2020) who have evidenced not only sensitivity in plants but also a specific form of intelligence. One of the reasons for this deeply rooted disregard is our species' fierce anthropocentrism: sheep (or even more so, plants), are perceived as radically different to us; as such, we refuse to extend our empathy to them. ...
... If Turing-Test-like evidence is insufficient, so is brain homology. We can't possibly expect that the only sentient life in the universe has mammalianstyle brains; if we can't agree on intelligence in plants (Calvo et al., 2020;Calvo et al., 2017), and are still wrangling over when and how a "sentience-free" chemistry of the oocyte becomes a human mind, we can have no strong confidence about unconventional agents. ...
... Plants use chemical components as communicating channels with insects and animals for pollination (GTS), or as defense against the predators (IRSS/ CDC), electrical signals and vibrations [23]. Plants are sentient organisms [24] (IRSS), which can live in symbiotic association [25][26][27], acknowledging their family membership. Indeed, the root apex transition zone, able to make timely decisions and solve problems concerning the optimal orientation as a function of the local topology [28], is often compared with 'like-brain' decisional center, working also as a lung-like respiration system, as a 'heart'like pumping/distributer of water and nutrients, and maintainer of the physiological balance and hormonal info-communication (by means of auxin like 'neurotransmitter' and plasmodesmata like neuro-gap-junctions), throughout the entire plant [29]. ...
Information is a fundamental component of the biological structures, which drive both the body
structuration and behavior of plants and animals. The specific information of each species in genome/
genes is transmitted from Deoxyribonucleic Acid (DNA) molecules to the new cells and to proteins by
replication and transcription/translation processes respectively, to build/maintain the body structure.
Information play also a dynamic role in the internal and external communication, assuring the adaptation
to the external cues, according to the specificity of each category of plants and animals, on the entire
biological evolutionary/complexity scale, operating on the basis of an informational system, with the
same functional characteristics. Therefore, the question of consciousness, as effect of the activity of the
informational system in plants and animals is discussed, as a natural emerging issue
... The long-distance communication process between plants was demonstrated experimentally, showing that the wounded leaves signalize their damage status (IRSS/CASI), which stimulates the production of jasmonates, potent regulators of defence responses (Mousavi et al, 2013). Plants are sentient organisms (Calvo, Pratap and Trewavas, 2017) (IRSS), can live in symbiotic association (Oldroyd, 2013), and behave differentially with respect to the surrounding partners from family provenience (IGG) through their sentient-cognitive system (CASI/IRSS), expressed by the root selectivity (IC/CDC) for allocation of resources (Dudley and File, 2007) (Dudley and File, 2008). Mimosa pudica closes suddenly its leaves by its executing elements (EE) connected to CDC, in response to the touch (CASI). ...
Plants, like all other living organisms, are neither robots and nor artificial smart systems, they are living structures, which live their life. Plants are informational living organisms, endowed with an informational system, like all other living structures. Although they do not dispose of a nervous system like animals, they carry out an intense informational activity of communication with their internal structure between various parts of it and with the surrounding environment. They are able to make decisions and to regulate their phenotype, showing that they dispose of a cognitive/sentient system driving their behaviour and structural development, according to the local conditions.
... However, the prospects for such an objection don't currently look promising. Some of the claims that have been made in support of the idea that plants are sentient-such as that they have structures that are functionally equivalent to neurons and brains that are capable of sentience (e.g., Calvo et al., 2017)-are currently speculative, even by the admission of the supporters of plant sentience, and have further been robustly criticised (e.g., Robinson & Draguhn, 2021). And many of the facts that have been cited in support of plant sentiencesuch as the fact that plants behave in ways which seem suggestive of the capacity for sentience, with, for example, touch-me-nots recoiling from touch-are insufficient for sentience (e.g., Hamilton & McBrayer, 2020). ...
I argue that the main existing accounts of the relationship between the beauty of environmental entities and their moral standing are mistaken in important ways. Beauty does not, as has been suggested by optimists, confer intrinsic moral standing. Nor is it the case, as has been suggested by pessimists, that beauty at best provides an anthropocentric source of moral standing that is commensurate with other sources of pleasure. I present arguments and evidence that show that the appreciation of beauty tends to cause a transformational state of mind that is more valuable than mere pleasure, but that leads us to falsely represent beautiful entities as being sentient and, in turn, as having intrinsic moral standing. To this extent, beauty is not, then, a source of intrinsic moral standing; it’s a source of a more important anthropocentric value than has hitherto been acknowledged.
... In the future, bio-FETs could be further developed to be used on plants to indirectly monitor the environment that surrounds them. The concept, despite being applied in most cases using non-transistor-based sensors techniques, was proven, ranging from the detection of heavy metals to pesticides [210,211]. This concept could be feasible in the future in the case of bio-FETs, especially with the advent of plant wearables [145]. ...
The precise monitoring of environmental contaminants and agricultural plant stress factors, respectively responsible for damages to our ecosystems and crop losses, has nowadays become a topic of uttermost importance. This is also highlighted by the recent introduction of the so-called “Sustainable Development Goals” of the United Nations, which aim at reducing pollutants while implementing more sustainable food production practices, leading to a reduced impact on all ecosystems. In this context, the standard methods currently used in these fields represent a sub-optimal solution, being expensive, laboratory-based techniques, and typically requiring trained personnel with high expertise. Recent advances in both biotechnology and material science have led to the emergence of new sensing (and biosensing) technologies, enabling low-cost, precise, and real-time detection. An especially interesting category of biosensors is represented by field-effect transistor-based biosensors (bio-FETs), which enable the possibility of performing in situ, continuous, selective, and sensitive measurements of a wide palette of different parameters of interest. Furthermore, bio-FETs offer the possibility of being fabricated using innovative and sustainable materials, employing various device configurations, each customized for a specific application. In the specific field of environmental and agricultural monitoring, the exploitation of these devices is particularly attractive as it paves the way to early detection and intervention strategies useful to limit, or even completely avoid negative outcomes (such as diseases to animals or ecosystems losses). This review focuses exactly on bio-FETs for environmental and agricultural monitoring, highlighting the recent and most relevant studies. First, bio-FET technology is introduced, followed by a detailed description of the the most commonly employed configurations, the available device fabrication techniques, as well as the specific materials and recognition elements. Then, examples of studies employing bio-FETs for environmental and agricultural monitoring are presented, highlighting in detail advantages and disadvantages of available examples. Finally, in the discussion, the major challenges to be overcome (e.g., short device lifetime, small sensitivity and selectivity in complex media) are critically presented. Despite the current limitations and challenges, this review clearly shows that bio-FETs are extremely promising for new and disruptive innovations in these areas and others.
... The field of "basal cognition" [23,[45][46][47] seeks to understand the phylogenetic origins of behavioral complexity, and is greatly enriched by the ability to make novel living beings in arbitrary configurations (for example, varying the amount or organization of neural components, or even producing entirely aneural systems) to more broadly probe structure-function relationships. Similarly, develop- The space of possible learning agents is astronomically large, because it is multi-dimensional: chimerism and hybridization with technology is possible on each level of organization of living systems. ...
The fields of developmental biology, biomedicine, and artificial life are being revolutionized by advances in synthetic morphology. The next phase of synthetic biology and bioengineering is resulting in the construction of novel organisms (biobots), which exhibit not only morphogenesis and physiology but functional behavior. It is now essential to begin to characterize the behavioral capacity of novel living constructs in terms of their ability to make decisions, form memories, learn from experience, and anticipate future stimuli. These synthetic organisms are highly diverse, and often do not resemble familiar model systems used in behavioral science. Thus, they represent an important context in which to begin to unify and standardize vocabulary and techniques across developmental biology, behavioral ecology, and neuroscience. To facilitate the study of behavior in novel living systems, we present a primer on techniques from the behaviorist tradition that can be used to probe the functions of any organism – natural, chimeric, or synthetic – regardless of the details of their construction or origin. These techniques provide a rich toolkit for advancing the fields of synthetic bioengineering, evolutionary developmental biology, basal cognition, exobiology, and robotics.
... The Cambrian explosion has a parallel in the evolution of a solar-energyharvesting lineage that includes aquatic green algae, and gave rise to land plants (the algae may have become terrestrial before the advent of plant roots; seeHarholt et al. 2016). Land plants emerged and flourished in the early Devonian period, circa 400 million years ago, when the main body of some land plants started to lignify, becoming woody, and the rootshoot/leaf polar morphologies found in higher plants became settled(Calvo 2017). There is no reason to exclude the possibility that forms of learning similar to those of animals were among the driving forces behind the rapid plant diversification during that period.There is certainly a basis in the empirical literature on plants to entertain the idea that not only are the key features of UAL found in plants, but also the requirements for UAL (Birch et al.,Figure 3). ...
A critical oversight in the authors’ (Birch et al.) UAL framework arises in its stated basis in an “unlimited heredity” (UH) argument. Specifically, the foundational UH claim is that there is a possibility space constrained by the known properties of DNA, and that, within that space, a subset of specific “real” lineages arise. These lineages are actualisations of possibilities, under the assumption that no amount of time would be sufficient to actualise all possibilities. The oversight – already present in UH, but ‘inherited’ by UAL – regards what pressures produce the actual subset of lineages from the in principle possible lineages. Significantly, the subset is neither due solely to the “constraints” granted by Birch et al., nor is it arbitrary. Rather, the subset of actual lineages is the result of a reciprocal process with the environment that has been highlighted in research on the Extended Evolutionary Synthesis (EES) (e.g. Laland et al. 2017). In this commentary, we will underscore how this critical oversight concerning reciprocal pressures poses a core problem for the target article’s characterisation of UAL.
... Through photosynthesis, plant movement was never essential, but exploiting the local environment required a branching structure and competition for light to drive plant growth upwards. As the plant grows, the potential for more complex behaviour emerges via an increasingly complex vascular system and activation of dormant meristems (Calvo et al. 2017;Mediano et al. 2021). We ourselves are animals and require movement within our time frame to attract attention. ...
Lacking an anatomical brain/nervous system, it is assumed plants are not conscious. The biological function of consciousness is an input to behaviour; it is adaptive (subject to selection) and based on information. Complex language makes human consciousness unique. Consciousness is equated to awareness. All organisms are aware of their surroundings, modifying their behaviour to improve survival. Awareness requires assessment too. The mechanisms of animal assessment are neural while molecular and electrical in plants. Awareness of plants being also consciousness may resolve controversy. The integrated information theory (IIT), a leading theory of consciousness, is also blind to brains, nerves and synapses. The integrated information theory indicates plant awareness involves information of two kinds: (1) communicative, extrinsic information as a result of the perception of environmental changes and (2) integrated intrinsic information located in the shoot and root meristems and possibly cambium. The combination of information constructs an information nexus in the meristems leading to assessment and behaviour. The interpretation of integrated information in meristems probably involves the complex networks built around [Ca ²⁺ ]i that also enable plant learning, memory and intelligent activities. A mature plant contains a large number of conjoined, conscious or aware, meristems possibly unique in the living kingdom.
... capacity of bioengineers, providing a much richer option space for the creation of novel biological systems via guided selfassembly (Kamm and Bashir, 2014;Kamm et al., 2018). Advances in this field even help address controversies within the biological sciences, such as whether behavior and intelligence are terms that can apply to plants (Applewhite, 1975;Trewavas, 2009;Garzon and Keijzer, 2011;Cvrckova et al., 2016;Calvo et al., 2017). ...
One of the most useful metaphors for driving scientific and engineering progress has been that of the “machine.” Much controversy exists about the applicability of this concept in the life sciences. Advances in molecular biology have revealed numerous design principles that can be harnessed to understand cells from an engineering perspective, and build novel devices to rationally exploit the laws of chemistry, physics, and computation. At the same time, organicists point to the many unique features of life, especially at larger scales of organization, which have resisted decomposition analysis and artificial implementation. Here, we argue that much of this debate has focused on inessential aspects of machines – classical properties which have been surpassed by advances in modern Machine Behavior and no longer apply. This emerging multidisciplinary field, at the interface of artificial life, machine learning, and synthetic bioengineering, is highlighting the inadequacy of existing definitions. Key terms such as machine, robot, program, software, evolved, designed, etc., need to be revised in light of technological and theoretical advances that have moved past the dated philosophical conceptions that have limited our understanding of both evolved and designed systems. Moving beyond contingent aspects of historical and current machines will enable conceptual tools that embrace inevitable advances in synthetic and hybrid bioengineering and computer science, toward a framework that identifies essential distinctions between fundamental concepts of devices and living agents. Progress in both theory and practical applications requires the establishment of a novel conception of “machines as they could be,” based on the profound lessons of biology at all scales. We sketch a perspective that acknowledges the remarkable, unique aspects of life to help re-define key terms, and identify deep, essential features of concepts for a future in which sharp boundaries between evolved and designed systems will not exist.
This chapter begins with a brief exploration of what it means to view plants as subjects. This is followed by an account of gardens, and their role as sites of human-plant collaboration. The historical development of botanic gardens, and their special functions as recreational displays and sites for plant conservation are discussed next. This is followed by the proposal that botanic gardens, even more than other gardens, exhibit human-plant collaboration, and the claim that, as such, these gardens offer outstanding opportunities for viewing plants as subjects in botanic gardens. It is concluded that recognition of plants as subjects may contribute in an important way toward greater inclusion of the non-human world in our consideration.
Intelligence is a fundamental property for all life enabling an increased probability of survival and reproduction under wild circumstances. Kingsland and Taiz (2024) think that plants are not intelligent but seem unaware of the extensive literature about intelligence, memory, learning and chromatin topology in plants. Their views are consequently rejected. Their claim of fake quotations is shown to result from faulty reasoning and lack of understanding of practical biology. Their use of social media as scholarly evidence is unacceptable. Darwin’s views on intelligence are described, and their pertinence to the adaptive responses of plants is discussed. Justifications for comments I have made concerning McClintock and her “thoughtful” cell, von Sachs writings as indicating purpose (teleonomy) to plant behaviour, Went and Thimann’s allusions to plant intelligence and Bose legacy as the father of plant electrophysiology are described. These scientists were usually first in their field of knowledge, and their understanding was consequently deeper. The article finishes with a brief critical analysis of the 36 scientists who were used to condemn plant neurobiology as of no use. It is concluded that participants signed up to a false prospectus because contrary evidence was omitted.
La planta sensitiva Mimosa Púdica es un tipo particular de planta que cuenta con hojas capaces de responder al contacto en cuestión de segundos, provocando que estas se retraigan y aparenten estar marchitas. Ella es una de las pocas plantas que inician movimientos visualmente perceptibles por el ser humano. Respecto a las incipientes investigaciones sobre sensibilidad y cognición en plantas, Mimosa parece ser un organismo-modelo interesante para analizar estas posibilidades gracias a sus rápidas respuestas que pueden ser observadas de forma directa. De esta manera, Mimosa Púdica podría ser utilizada como modelo para el estudio del fenómeno de sensibilidad y cognición, no solo a nivel electrofisiológico, sino también a nivel comportamental y funcional. A partir de las evidencias científicas de la biología y neurociencia de los últimos 15 años, se defenderá que la planta sensitiva es un organismo-modelo adecuado para estudiar, no solo a nivel fisiológico-mecánico la capacidad de respuesta a estímulos que poseen las plantas, sino que también para evaluar que tantas habilidades cognitivas, como el aprendizaje y la memoria, son atribuibles a los organismos vegetales a partir de las respuestas observables en dicho modelo. Lo anterior es postulado en relación con la idea de que todos los organismos vegetales inician movimientos, pero no todos son observables por el ser humano: Mimosa sería entonces un modelo provechoso para el análisis, ya que presenta movimientos que pueden ser observados por los investigadores y permitiría evaluar distintas capacidades relativas a los fenómenos de la sensibilidad y la cognición.
Are plants sentient? Several researchers argue that plants might be sentient. They do so on the grounds that plants exhibit cognitive behaviour similar to that of sentient organisms and that they possess a vascular system which is functionally equivalent to the animal nervous system. This paper will not attempt to settle the issue of plant sentience. Instead, the paper has two goals. First, it provides a diagnosis of the current state of the debate on plant sentience. It is argued that the current state of the debate on plant sentience cannot yield any progress because the behavioural and physiological similarities pointed to as a way of inferring consciousness are not, in themselves, indicative of consciousness. Second, the paper proposes we adopt the theory-light approach proposed by Birch (Noûs 56(1):133–153, 2022. https://doi.org/10.1111/nous.12351) whereby we start to test for clusters of cognitive abilities facilitated by consciousness in plants. Currently, there are no such tests and therefore no evidence for plant sentience. The paper proposes that the task for future research on plants be in line with the tests outlined in the theory-light approach.
Discussions of the detection of artificial sentience tend to assume that our goal is to determine when, in a process of increasing complexity, a machine system “becomes” sentient. This is to assume, without obvious warrant, that sentience is only a characteristic of complex systems. If sentience is a more general quality of matter, what becomes of interest is not the presence of sentience, but the type of sentience. We argue here that our understanding of the nature of such sentience in machine systems may be gravely set back if such machines undergo a transition where they become fundamentally linguistic in their intelligence. Such fundamentally linguistic intelligences may inherently tend to be duplicitous in their communication with others, and, indeed, lose the capacity to even honestly understand their own form of sentience. In other words, when machine systems get to the state where we all agree it makes sense to ask them, “what is it like to be you?”, we should not trust their answers.
This essay considers a series of examples of contemporary and early twentieth-century artistic projects done in collaboration and conversation with plant scientists around the theme of plant sentience. In particular, it zooms in on the work of the Indian biophysicist Jadagish Chandra Bose and the Indian artist Gaganendranath Tagore in the 1920s and the Italian plant scientist Stephano Mancuso and German artist Carsten Höller in the 2020s. The essay has four interconnected aims. The first is to investigate how and why plant sentience is visually and spatially represented by artists. The second is to show through two broad examples how plant science can be and has been co-opted to serve different political, economic, and ideological positions. The third and broader aim of this essay is to counter a widespread ethical assertion in environmental humanities and animal studies that destabilizing human-nonhuman binaries intrinsically lends itself to projects of environmental justice by encouraging humans to coexist more equitably with other species. In other words, we should not assume that artistic production is spontaneously aligned to ethics of multispecies justice. The fourth and concluding aim is to make the related argument that plant sentience and other ways of knowing and relating across species need to be understood within the context of colonial and extractive histories.
Биосемиотика – это доязыковой уровень семиотических, смысловых процессов, происходящих в живой сфере. Она предоставляет концептуальный аппарат для описания биологических явлений на всех уровнях организации жизни и может быть использована для инициирования безопасных культурных форм и практик, а ее актуальность может быть обусловлена нестабильными отношениями между культурой и природой. Исследования показали, что отдельные организмы конструируют свои онтологические миры, завязанные на сенсорно-моторной петле, то есть чувственно-двигательном аппарате каждого отдельного организма. Базовая семиотика присуща практически всем живым формам на эволюционном древе, а смыслопорождающее поведение было задокументировано даже у одноклеточных организмов (цитосемиозис). Нет никаких препятствий рассмотреть с такой же точки зрения растительные организмы при условии, что мы будем опираться на открытия в биологии растений. Новые данные в области электрофизиологии растений показали, что у высших растений, обладающих васкулярной системой, имеется функциональный круг, то есть сенсорно-моторная петля, опосредованная электрическими импульсами; а исследования когнитивных навыков растений и их поведения обнаружили, что растения не только пассивно адаптируются к окружающей среде, но и активно ее преображают, конструируют, то есть создают умвельт. Это позволило поставить вопрос о возможности существования фитосемиозиса между растительными организмами. И при конструировании биосемиотического фрейма позволило описать симбиотическое взаимодействие американской поликультуры: кукурузы, тыквы и фасоли, в оптике этого биосемиотического подхода, дополненной концепцией воплощенного сознания. Обычно данная концепция состоит из 4E (embeddedness, или встроенность в мир; extendedness, или протяженность, enactivity, или деятельность в окружающей среде; embodied, или воплощенность в теле), но в биологии растений теперь эту концепцию дополняют пятой компонентой – ecological – экологичностью. Все эти 5Е раскрывают аффордансы растений, то есть сопряжение возможностей окружающего мира с возможностями морфологии тела, и использование этих аффордансов-возможностей для своих потребностей. В статье также сделана попытка интегрировать понятие энлога (Чебанов) в фитосемиотический подход. Энлог – это некая единица обратной связи, которая также представляет собой инструмент связи с иным. Энлоги (два и более) участвуют при образовании знака. Совокупность взаимных связей, энлогов, создает умвельт. Проведенное исследование, посвященное биосемиотике растений, выявило потребность в дальнейшем изучении вопроса, так как заявленный экзосемиозис растений тесно связан с эндосемиозисом, оставшимся за пределами данной статьи. Исследование также выявляет потребность в новом языке при дальнейшей разработке биосемиотического подхода и ставит более фундаментальный вопрос о возможности описать нечеловеческие явления и способы взаимодействия нечеловеческих организмов человеческим языком.
The ecological conception of a new dialogue between man and nature is ripening. This concept is biosemiotics. According to the concept, nature is perceived as an equal actor of the coevolution of humankind and the living creatures on our planet. The idea of the research is to use biosemiotics – a pre-linguistic level of semiotics, semantic processes which happened in the living sphere – as a tool or conceptual framework for describing biological phenomena at all levels of life organization. The relevance of the concept can be driven by the unstable relationship between culture and nature, and can be used to initiate safe cultural forms and practices between the different worlds of living. Biosemiotics understands life as the existence and interaction of living communities, where signs are created, interpreted in different ways and have meaning. Basic semiotics covers almost all living forms on the tree of life. Meaningful behavior has been documented even in unicellular organisms. We cannot but view plants from the same perspective, as there have been a lot of discoveries in plant biology. The author takes plants interaction and communication as of individual organisms, as they construct their own ontological worlds. New data of plant signaling and behavior have revealed that plants have their own sensory-motor apparatus: higher plants with a vascular system have the functional cycle, i.e. a sensory-motor loop mediated by electrical impulses; and plant studies of their cognitive skills and behavior have found that plants not only passively adapt to the environment, but also actively transform and construct it, i.e. create an umwelt. Thus, the author sets a question of the existence of semiosis between plants. Through the lens of a biosemiotic approach, she describes an example of a symbiotic interaction of American polyculture: maze, pumpkin, and beans. This approach is supplemented by the concept of 4E (embedded, extended, enactive, and embodied) cognition, with the addition of the fifth E – ecological, which reveals plants’ affordances, namely, entanglement of affordances of the environment with the morphological affordances of any plant and the possibility to use these affordances for their own needs. The author made an attempt to integrate the concept of enlogue (by Segei Chebanov) into the phytosemiotic approach. Enlogue is a tool for communication with another. It is a link between living organisms, as well as between a living organism and a non-living thing. This link or connection is always reversed. Enlogues (two or more) are involved in the formation of a sign. Mutual links, or enlogues, create an umwelt. The research highlights the importance of a further development of the biosemiotic approach as well as the need for the development of a new descriptional language. As an additional issue for further examinations is a question: How can we properly describe non-human phenomena in human language? And what is “properly” in that case?
Plants have traditionally been the green backdrop to the drama of human activity. They are seen as resources—for food, raw materials and ecological engineering services—without agency or value of their own. Such ‘plant blindness’ stems from the biases of our sensory systems and from our deeply enculturated attitudes to non-animal life. This chapter builds on recent research into plant cognition to argue for an urgent and dramatic re-framing of plants as actors, not objects. The fundamental tool for such change will be education: helping future generations see our role in the biosphere very differently and motivating change to a truly sustainable existence. This will, we argue, be vital to long-term solutions to the anthropogenic ecological crisis.KeywordsPlant blindnessPlant cognitionEducationEcological crisis
La classification phylogénétique a mis fin à la distinction ontologique et scientifique entre les animaux et les plantes. Elle remet en question la partition entre ces deux règnes et réfute la thèse aristotélicienne dissociant les humains, les animaux et les plantes. « Les plantes nos sœurs » permet ici une réflexion sur le patrimoine biologique commun entre les animaux (humain compris) et les plantes. Pour comprendre ce qui relie les vivants, nous souhaitons apporter ici une pensée hybride combinant sciences de la vie et sciences humaines. Il s’agit, au moyen d’une approche interdisciplinaire, d’associer le développement de la phylogénie et des récentes découvertes sur le végétal, de présenter ce que les parcours évolutifs de l’animal et du végétal ont de commun ainsi que de comprendre les freins socioculturels liés à l’héritage aristotélicien et judéo-chrétien qui ont empêché de penser le vivant comme une parentèle. Les données récentes sur la « neurobiologie végétale » relancent une réflexion autour de ce qui est partagé entre les animaux et les plantes (sensibilité, capacité d’apprentissage, comportement, agentivité). Dans ce contexte, une vision de l’humain détaché des autres espèces n’est plus tenable. La vie des uns ne peut pas être déconnectée de la vie des autres.
A common response to the current global ecological crisis is the conservation of areas still somewhat spared from anthropogenic damage, in spite of an abundant literature evidencing the social and ecological shortcomings of top-down approaches to nature conservation. As part of the Kailash Sacred Landscape Initiative, the Limi Valley of north-western Nepal is currently under consideration for the establishment of one such area. This paper warns about an understanding of conservation as a segregation of humans and nature, which is at odds with local perceptions of landscape as relational. Through the perspective of pastoral practices in the Limi Valley, I show how the Limey – the people of this Valley – conceive of humans as enmeshed within a network of interacting beings under the guiding principles of ecological ethics of care. This conception is framed by religion (a syncretic mixture of Mahayana Buddhism, Bön religion and Animism), as well as by skills of ecological and spiritual embeddedness which are central to pastoral practice. I also warn against the fallacy of considering locals’ relationship to the environment, informed by Buddhism, as intrinsically more prone to eco-friendly practices. I show how this relationship is dynamic and evolving, and influenced by the economic and political context of the last thirty years. This has led to the progressive obsolescence of pastoralism as the main means of livelihood, with consequences for the local inhabitants’ relationship to landscape and to other-than-human species.
This paper argues for engaging in multispecies storytelling with plants to better conceptualise the ethics and contested ecologies associated with biodiversity loss. It focuses specifically on proteas, the iconic species of South Africa's threatened fynbos biome, to explore the possibilities of an ethical dialogue between human and more-than-human diversities, and to consider what might be gained from understanding plants as both agentic in contested ecologies and as storytelling figures worthy of attention. The paper draws on John Ryan’s conceptualization of phytography as a way of engaging in multispecies storytelling with plants. It teases out interwoven botanic and human histories, and the ways in which iconic proteas have written themselves into the narratives of their human interlocutors in the context of European settler colonialism, conservation, floral nativism and post-apartheid nation-building. The case for phytography is developed through an examination of the corporeal rhetoric of proteas in two examples. The first concerns the Mace Pagoda, a protea that resists narratives of extinction by writing back its percipience, agency, and resilience into human stories of anthropogenic habitat loss. The second focuses on botanical traces that result from absence, specifically the non-appearance in recent years of proteas in the Cederberg area of the Western Cape. The paper suggests that absence is a form of corporeal rhetoric through which plants write themselves into narratives of rapid climate change and multispecies loss. The final section of the paper explores questions of ethics that emerge from engaging with plants as storytellers, reflects on the kinds of human-plant relationships that are possible in the context of environmental catastrophe, and examines the possibilities that phytography provides for more-than-human engagements with plant life.
This paper concerns biopsychism, the position that feeling is a vital activity of all organisms or living beings. It evaluates biopsychism specifically from the perspective of the enactive conception of life and life-mind continuity. Does the enactive conception of life as fundamentally a value-constituting and value-driven process imply a conception of life as sentient of value? Although a plausible case can be made, there remains a conceptual and inferential gap between differential responsiveness to value and hedonic value or affective valence. Nevertheless, the case for zoopsychism—that animals are the only sentient living beings—over biopsychism is also inconclusive.
Plants offer a source of bioinspiration for soft robotics. Nevertheless, a gap remains in designing robots based on the fundamental principles of plant intelligence, rooted in a non-centralized, modular architecture and a highly plastic phenotype. We contend that a holistic approach to plant bioinspiration—one that draws more fully on the features of plant intelligence and behavior—evidences the value of an enactivist perspective. This is because enactivism emphasizes not only features of embodiment such as material composition and morphology, but also autonomy as an important aspect of plant intelligence and behavior. The enactivist sense of autonomy concerns the dynamics of self-producing systems (such as plants) that create a distinction between themselves and a domain of interactions that bear on the conditions of viability of the system. This contrasts with the widespread, but diluted notion of autonomy that merely indicates the independent operability of a system for an arbitrary period. Different notions of autonomy are relevant for soft roboticists, for instance, when evaluating limitations on existing growing robots (“growbots”) that take bioinspiration from plants, but depend on a fixed source of energy and material provided by an external agent. More generally, plant-inspired robots serve as a case study for an enactivist approach to intelligence, while, correspondingly, enactivism calls attention to the possibility of non-zoological forms of intelligence embodied in a self-organizing, autonomous system.
This paper presents three experiments that stage nonhuman sentience within substrates where they are not usually expected, such as microalgaes, plants, artificial neural networks, and electrochemical reactions. We use these hybrid assemblages to challenge commonly accepted notions of sentience, perception, and cognition, in particular by highlighting the active and creative role of sensing. Finally, we self-reflect upon the implications of these works on modes of understanding through art and science entanglements.
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.
This article is categorized under: Cognitive Biology > Evolutionary Roots of Cognition
Philosophy > Consciousness
Neuroscience > Cognition
We have carried out an in loco investigation into the species Miconia albicans (SW.) Triana and Miconia chamissois Naudin (Melastomataceae), distributed in different phytophysiognomies of three Cerrado fragments in the State of São Paulo, Brazil. We characterized their oscillatory bioelectrical signals and asked whether these signals show distinct spectral density. The experiments provided a bank of bioelectrical amplitude samples, which were analyzed in the time and frequency domain. On the basis of the power spectral density (PSD) and machine learning techniques, analyses in the frequency domain suggested that each of these species has a unique biological pattern. Comparison between their oscillatory behavior showed bioelectrical features, and both species displayed a bioelectrical pattern, while environmental factors also influence this pattern. From the point of view of experimental Botany, new questions and concepts could be formulated to advance the understanding of the interactions between the communicative nature of plants and the environment. The results of this on-site technique represent a new methodology to acquire non-invasive information that might be associated with physiological, chemical, and ecological responses of plants.
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.
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.
It has been proposed by some plant scientists that plants are cognitive and conscious organisms, although this is a minority view. Here we present a brief summary of some of the arguments against this view, followed by a critique of an article in this same issue of Biochemical and Biophysical Research Communications by Calvo, Baluska, and Trewavas (2020) that cites Integrated Information Theory (IIT) as providing additional support for plant consciousness. The authors base their argument on the assumptions that all cells are conscious and that consciousness is confined to life. However, IIT allows for consciousness in various nonliving systems, and thus does not restrict consciousness to living organisms. Therefore, IIT cannot be used to prove plant consciousness, for which there is neither empirical evidence nor support from other, neuron-based, theories of consciousness.
Çevreye uyum sağlama ve esneklik kavramlarında bitkilerin davranışı konusunda gelişmekte olan bitki nörobiyolojisi alanında yapılan çalışmalar bitki biyokimyası, hücre biyolojisi ve moleküler biyoloji uzmanlıklarının ötesine geçmiştir. Davranış, bir bireyin yaşamı süresince çevresel değişikliklere ya da olaylara verdiği göreceli olarak hızlı ve potansiyel olarak geri dönüşümlü tepki olarak tanımlanabilir. Zekâ ise problem çözebilme yeteneğidir. Bitkilerin davranışı mekânsal olarak heterojen olan ve sürekli değişen bir çevrede besin kaynaklarını bulmaya, üremeye ve savunmaya en etkili şekilde olanak tanımaktadır. Davranış, bitkilerin genlerini sonraki nesle aktarmak için mücadele etmesinde kritik derecede öneme sahiptir. Bitkilerdeki binlerce kök ucunun hareketi, sürü içindeki hayvanların birbirlerine belirli bir mesafeyi koruyarak belirlenen hedefe doğru gitmesine benzetilebilir. Bitkiler çevreden gelen uyaranlara tepki vererek, bireysel olarak hareket eder gibi gözlense de tüm populasyona avantaj sağlayacak şekilde davranırlar. Bitki dokularındaki oksin dağılımının eşit olmamasından dolayı hareket, uyartının geldiği yöne bağımlı ve büyüme şeklindeki değişiklik yönelim (tropizma) olarak tanımlanır. Bu tip hareketler uyartının ortadan kalkmasıyla geriye dönüşebilir. Eğer hareket, uyartının geldiği yönden bağımsız ve ozmotik ya da turgor basıncındaki geri dönüşebilir değişiklik ise salınım (nastik) olarak tanımlanır. Bu tip hareketler organın yukarıya (epinasti) ya da aşağıya (hiponasti) doğru kıvrılması şeklinde kendini gösterebilir. Bu hareketler bitkilerde yerçekimine (jeo), dokunmaya (tigmo), ışığa (foto), sıcaklığa (termo), güneşe (helio), kimyasala (kemo) ve suya (hidro) yönelim veya salınım şekillerinde ortaya çıkabilir.
In this article we account for the way plants respond to salient features of their environment under the free-energy principle for biological systems. Biological self-organization amounts to the minimization of surprise over time. We posit that any self-organizing system must embody a generative model whose predictions ensure that (expected) free energy is minimized through action. Plants respond in a fast, and yet coordinated manner, to environmental contingencies. They pro-actively sample their local environment to elicit information with an adaptive value. Our main thesis is that plant behaviour takes place by way of a process (active inference) that predicts the environmental sources of sensory stimulation. This principle, we argue, endows plants with a form of perception that underwrites purposeful, anticipatory behaviour. The aim of the article is to assess the prospects of a radical predictive processing story that would follow naturally from the free-energy principle for biological systems; an approach that may ultimately bear upon our understanding of life and cognition more broadly.
Intelligence is defined for wild plants and its role in fitness identified. Intelligent behaviour exhibited by single cells and systems similarity between the interactome and connectome indicates neural systems are not necessary for intelligent capabilities. Plants sense and respond to many environmental signals that are assessed to competitively optimize acquisition of patchily distributed resources. Situations of choice engender motivational states in goal-directed plant behaviour; consequent intelligent decisions enable efficient gain of energy over expenditure. Comparison of swarm intelligence and plant behaviour indicates the origins of plant intelligence lie in complex communication and is exemplified by cambial control of branch function. Error correction in behaviours indicates both awareness and intention as does the ability to count to five. Volatile organic compounds are used as signals in numerous plant interactions. Being complex in composition and often species and individual specific, they may represent the plant language and account for self and alien recognition between individual plants. Game theory has been used to understand competitive and cooperative interactions between plants and microbes. Some unexpected cooperative behaviour between individuals and potential aliens has emerged. Behaviour profiting from experience, another simple definition of intelligence, requires both learning and memory and is indicated in the priming of herbivory, disease and abiotic stresses. © 2017 The Author(s) Published by the Royal Society. All rights reserved.
Across all species, individuals thrive in complex ecological systems, which they rarely have complete knowledge of. To cope with this uncertainty and still make good choices while avoiding costly errors, organisms have developed the ability to exploit key features associated with their environment. That through experience, humans and other animals are quick at learning to associate specific cues with particular places, events and circumstances has long been known; the idea that plants are also capable of learning by association had never been proven until now. Here I comment on the recent paper that experimentally demonstrated associative learning in plants, thus qualifying them as proper subjects of cognitive research. Additionally, I make the point that the current fundamental premise in cognitive science—that we must understanding the precise neural underpinning of a given cognitive feature in order to understand the evolution of cognition and behavior—needs to be reimagined.
In complex and ever-changing environments, resources such as food are often scarce and unevenly distributed in space and time. Therefore, utilizing external cues to locate and remember high-quality sources allows more efficient foraging, thus increasing chances for survival. Associations between environmental cues and food are readily formed because of the tangible benefits they confer. While examples of the key role they play in shaping foraging behaviours are widespread in the animal world, the possibility that plants are also able to acquire learned associations to guide their foraging behaviour has never been demonstrated. Here we show that this type of learning occurs in the garden pea, Pisum sativum. By using a Y-maze task, we show that the position of a neutral cue, predicting the location of a light source, affected the direction of plant growth. This learned behaviour prevailed over innate phototropism. Notably, learning was successful only when it occurred during the subjective day, suggesting that behavioural performance is regulated by metabolic demands. Our results show that associative learning is an essential component of plant behaviour. We conclude that associative learning represents a universal adaptive mechanism shared by both animals and plants.
‘Plant neurobiology’ has emerged in recent years as a multidisciplinary endeavor carried out mainly by steady collaboration within the plant sciences. The field proposes a particular approach to the study of plant intelligence by putting forward an integrated view of plant signaling and adaptive behavior. Its objective is to account for the way plants perceive and act in a purposeful manner. But it is not only the plant sciences that constitute plant neurobiology. Resources from philosophy and cognitive science are central to such an interdisciplinary project, if plant neurobiology is to maintain its target well-focused. This manifesto outlines a road map for the establishment and development of a new subject—the Philosophy of Plant Neurobiology—, a new field of research emerging at the intersection of the philosophy of cognitive science and plant neurobiology. The discipline is herewith presented, introducing challenges and novel lines of engagement with the empirical investigation, and providing an explanatory framework and guiding principles that will hopefully ease the integration of research on the quest for plant intelligence.
Carnivorous plants, such as the Venus flytrap (Dionaea muscipula), depend on an animal diet when grown in nutrient-poor soils. When an insect visits the trap and tilts the mechanosensors on the inner surface, action potentials (APs) are fired. After a moving object elicits two APs, the trap snaps shut, encaging the victim. Panicking preys repeatedly touch the trigger hairs over the subsequent hours, leading to a hermetically closed trap, which via the gland-based endocrine system is flooded by a prey-decomposing acidic enzyme cocktail. Here, we asked the question as to how many times trigger hairs have to be stimulated (e.g., now many APs are required) for the flytrap to recognize an encaged object as potential food, thus making it worthwhile activating the glands. By applying a series of trigger-hair stimulations, we found that the touch hormone jasmonic acid (JA) signaling pathway is activated after the second stimulus, while more than three APs are required to trigger an expression of genes encoding prey-degrading hydrolases, and that this expression is proportional to the number of mechanical stimulations. A decomposing animal contains a sodium load, and we have found that these sodium ions enter the capture organ via glands. We identified a flytrap sodium channel DmHKT1 as responsible for this sodium acquisition, with the number of transcripts expressed being dependent on the number of mechano-electric stimulations. Hence, the number of APs a victim triggers while trying to break out of the trap identifies the moving prey as a struggling Na+-rich animal and nutrition for the plant.
The limitations of conventional extracellular recording and intracellular recording make high-resolution multisite recording of plant bioelectrical activity in situ challenging. By combining a cooled charge-coupled device camera with a voltage-sensitive dye, we recorded the action potentials in the stem of Helianthus annuus and variation potentials at multiple sites simultaneously with high spatial resolution. The method of signal processing using coherence analysis was used to determine the synchronization of the selected signals. Our results provide direct visualization of the phloem, which is the distribution region of the electrical activities in the stem and leaf of H. annuus, and verify that the phloem is the main action potential transmission route in the stems of higher plants. Finally, the method of optical recording offers a unique opportunity to map the dynamic bioelectrical activity and provides an insight into the mechanisms of long-distance electrical signal transmission in higher plants.
If biology throughout the nineteenth and twentieth centuries was dominated by the metaphor of the machine, the metaphor underlying twenty first century biology is that of the network or web. A rapid proliferation of molecular data coupled with increased computational power has revealed that gene regulation, protein interaction, the topology of metabolism and signal-transduction in and between cells, tissues, organs and organisms can all be described as robust, resilient and modular networks. Such small-world networks are characterised by rapid signal propagation, a capacity for computation and for synchronisation between the same, or different, hierarchic levels. Organelles, cells, tissues, organisms and ecosystems are not mere aggregations of components, but are hierarchies of interacting systems or modules, each possessing a degree of autonomy, and each a degree of interdependence. Into this metaphor of the network has emerged the discipline of integrative plant electrophysiology, called by its adherents, plant neurobiology. This field aims to understand how plants perceive, recall and process experience, coordinating behavioural responses via integrated information networks that include molecular, chemical and electrical levels of signalling. Integrative plant electrophysiology rejects the long standing view of plants as passive insensate automata that react to the environment with mechanical simplicity. The controversial use of the word ‘neurobiology’ as applied to plants signifies that long-distance electrical signals, such as action potentials, convey meaningful information from the site of initiation to a distant site, where the signal is interpreted and evaluated, and an adaptive behavioural response is mounted. Such inter-module communication is ‘nervous’ in the sense that it is adaptive, thereby implying capacities for memory, learning, anticipating the future and for generating novel responses. By itself a touch stimulus is meaningless, and by itself a behaviour (e.g. Mimosa leaf folding) is meaningless. Meaning lies in the network of processes that associate and integrate these events. Communication processes within, and between plants and associated organisms, can therefore be considered as biosemiotic, involving as they do the interpretation and evaluation of stimuli. This review traces historical aspects of the development of integrative plant electrophysiology and the methods that inform it, with a special emphasis on the work of Indian biophysicist Sir J. C. Bose (1858–1937), who, in an impressive body of published research, proposed that plants and animals share essentially similar fundamental physiological mechanisms. The first scientist to appreciate that responses in plants (e.g. leaf folding in the sensitive plant Mimosa) constitute behaviour reliant on integrative electrical signals; Bose argued further that all plants co-ordinate their movements and integrate their responses to the world through electrical signalling. Despite their sessile habits, plants are to be regarded as sensate, active, intelligent explorers of the world. Bose identified a fundamental physiological motif that interlinked measurable pulsations or oscillations in cellular electric potentials with oscillations in cell turgor pressure, cellular contractility and growth. All plants respond to the world and to other living things through adaptations of this pulsatile motif, an electromechanical pulse that underlies electro-osmotically enacted behaviour. J.C. Bose’s conclusions that all plants possess a nervous system, a form of intelligence, and a capacity for remembering and learning, were poorly received by prominent electrophysiologists of his time. Experiments devoted to plant responsiveness, inter-organism communication, kin-recognition, foraging, intelligence and learning as mediated by electrical signalling, are now published and debated in the mainstream literature as aspects of integrative plant electrophysiology.
The phloem is a complex tissue composed of highly specialized cells with unique subcellular structures and a compact organization that is challenging to study in vivo at cellular resolution. We used confocal scanning laser microscopy and subcellular fluorescent markers in companion cells and sieve elements, for live imaging of the phloem in Arabidopsis leaves. This approach provided a simple framework for identifying phloem cell types unambiguously. It highlighted the compactness of the meshed network of organelles within companion cells. By contrast, within the sieve elements, unknown bodies were observed in association with the PP2-A1:GFP, GFP:RTM1 and RTM2:GFP markers at the cell periphery. The phloem lectin PP2-A1:GFP marker was found in the parietal ground matrix. Its location differed from that of the P-protein filaments, which were visualized with SEOR1:GFP and SEOR2:GFP. PP2-A1:GFP surrounded two types of bodies, one of which was identified as mitochondria. This location suggested that it was embedded within the sieve element clamps, specific structures that may fix the organelles to each another or to the plasma membrane in the sieve tubes. GFP:RTM1 was associated with a class of larger bodies, potentially corresponding to plastids. PP2-A1:GFP was soluble in the cytosol of immature sieve elements. The changes in its subcellular localization during differentiation provide an in vivo blueprint for monitoring this process. The subcellular features obtained with these companion cell and sieve element markers can be used as landmarks for exploring the organization and dynamics of phloem cells in vivo.
Special attention is paid in this paper to the criteria of the light-triggered action potential, namely the all-or-none law, propagation, the occurrence of refractory periods. Such action potentials have been recorded in Acetabularia mediterranea, Asplenium trichomanes, Bryum pseudotriquetrum, Eremosphaera viridis and Concephalum conicum. In Acetabularia, action potentials are generated after sudden cessation of light stimuli of sufficient intensity. The depolarization phase of the action potential develops as a result of a transient reversal of the action of the electrogenic Cl- pump. This is a principle of the "metabolic" action potential hypothesis proposed by Gradmann. In the gametophytes of Aspleniam trichomanes and Bryum pseudo triquetrum, action potentials are triggered on illumination. Gutation starts 1.5-2 seconds after the passage of an action potential. The active water secretion facilitates fertilization. In the unicellular fresh water alga, Eremosphaera viridis, action potential-like responses are evoked after light termination. The process responsible for its appearance is the opening of potassium channels in the plasmalemma. The liverwort, Conocephalum conicum, generates action potentials in response to light, electrical, chemical and mechanical stimuli. Calcium and potassium channels as well as proton pumps are involved in electrogenesis of action impulses in the species. Excitation causes a significant increase in the respiration rate. The role of action impluses as mediators in a system of a metabolism control is discussed.
Mechanosensitive (MS) ion channels are a common mechanism for perceiving and responding to mechanical force. This class of mechanoreceptors is capable of transducing membrane tension directly into ion flux. In plant systems, MSion channels have been proposed to play a wide array of roles, from the perception of touch and gravity to the osmotic homeostasis of intracellular organelles. Three families of plant MS ion channels have been identified: the MscS-like (MSL), Mid1-complementing activity (MCA), and two-pore potassium (TPK) families. Channels from these families vary widely in structure and function, localize to multiple cellular compartments, and conduct chloride, calcium, and/or potassium ions. However, they are still likely to represent only a fraction of the MS ion channel diversity in plant systems. Expected final online publication date for the Annual Review of Plant Biology Volume 66 is April 29, 2015. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
Plant glutamate receptor-like genes (GLRs) are homologous to the genes for mammalian ionotropic glutamate receptors (iGluRs), after which they were named, but in the 16 years since their existence was first revealed, progress in elucidating their biological role has been disappointingly slow. Recently, however, studies from a number of laboratories focusing on the model plant species Arabidopsis thaliana (L.) have thrown new light on the functional properties of some members of the GLR gene family. One important finding has been that plant GLR receptors have a much broader ligand specificity than their mammalian iGluR counterparts, with evidence that some individual GLR receptors can be gated by as many as seven amino acids. These results, together with the ubiquity of their expression throughout the plant, open up the possibility that GLR receptors could have a pervasive role in plants as non-specific amino acid sensors in diverse biological processes. Addressing what one of these roles could be, recent studies examining the wound response and disease susceptibility in GLR knockout mutants have provided evidence that some members of clade 3 of the GLR gene family encode important components of the plant's defence response. Ways in which this family of amino acid receptors might contribute to the plant's ability to respond to an attack from pests and pathogens are discussed.
Because it is difficult to obtain transverse views of the plant phloem sieve plate pores, which are short tubes, to estimate their number and diameters, a method based on longitudinal views is proposed. This method uses recent methods to estimate the number and the sizes of approximately circular objects from their images, given by slices perpendicular to the objects. Moreover, because such longitudinal views are obtained from slices that are rather close to the plate centres whereas the pore size may vary with the pore distance from the plate edge, a sieve plate reconstruction model was developed and incorporated in the method to consider this bias. The method was successfully tested with published longitudinal views of phloem of Soybean and an exceptional entire transverse view from the same tissue. The method was also validated with simulated slices in two sieve plates from Cucurbita and Phaseolus. This method will likely be useful to estimate and to model the hydraulic conductivity and the architecture of the plant phloem, and it could have applications for other materials with approximately cylindrical structures.
with Open Access.
We explored the idea of whether electropotential waves (EPWs) primarily act as vehicles for systemic spread of Ca2+ signals. EPW-associated Ca2+ influx may trigger generation and amplification of countless long-distance signals along the phloem pathway given the fact
that gating of Ca2+-permeable channels is a universal response to biotic and abiotic challenges. Despite fundamental differences, both action
and variation potentials are associated with a sudden Ca2+ influx. Both EPWs probably disperse in the lateral direction, which could be of essential functional significance. A vast
set of Ca2+-permeable channels, some of which have been localized, is required for Ca2+-modulated events in sieve elements. There, Ca2+-permeable channels are clustered and create so-called Ca2+ hotspots, which play a pivotal role in sieve element occlusion. Occlusion mechanisms play a central part in the interaction
between plants and phytopathogens (e.g. aphids or phytoplasmas) and in transient re-organization of the vascular symplasm.
It is argued that Ca2+-triggered systemic signalling occurs in partly overlapping waves. The forefront of EPWs may be accompanied by a burst of
free Ca2+ ions and Ca2+-binding proteins in the sieve tube sap, with a far-reaching impact on target cells. Lateral dispersion of EPWs may induce
diverse Ca2+ influx and handling patterns (Ca2+ signatures) in various cell types lining the sieve tubes. As a result, a variety of cascades may trigger the fabrication
of signals such as phytohormones, proteins, or RNA species released into the sap stream after product-related lag times. Moreover,
transient reorganization of the vascular symplasm could modify cascades in disjunct vascular cells.
The nervous system of animals serves the acquisition, memorization and recollection of information. Like animals, plants also acquire a huge amount of information from their environment, yet their capacity to memorize and organize learned behavioral responses has not been demonstrated. In Mimosa pudica-the sensitive plant-the defensive leaf-folding behaviour in response to repeated physical disturbance exhibits clear habituation, suggesting some elementary form of learning. Applying the theory and the analytical methods usually employed in animal learning research, we show that leaf-folding habituation is more pronounced and persistent for plants growing in energetically costly environments. Astonishingly, Mimosa can display the learned response even when left undisturbed in a more favourable environment for a month. This relatively long-lasting learned behavioural change as a result of previous experience matches the persistence of habituation effects observed in many animals.
To answer the question of why we have consciousness, I propose the following evolutionary trajectory leading to this feature: Nervous systems appeared for the purpose of orchestrating behavior. As a rule of thumb the challenges facing an animal concern either approach or avoidance. These two options were originally hard-wired as reflexes. Improvements in adaptability of response came with an expansion of the computational aspect of the system and a concomitant shift from simple reflexes to instinctual behavior, learning, and eventually, feelings. The assessment of positive and negative feelings allows organisms to weigh various options, but for this to be a viable strategy, an awareness of hedonic value is required. This was presumably the first neural attribute to evolve that required awareness, and thus the key force in the evolution of consciousness. The attribute first appeared in the early amniotes (the phylogenetic group comprising reptiles, birds and mammals). Support for this model in current accounts of the neurobiology of feelings and consciousness is discussed.
Wounded leaves communicate their damage status to one another through a poorly understood process of long-distance signalling. This stimulates the distal production of jasmonates, potent regulators of defence responses. Using non-invasive electrodes we mapped surface potential changes in Arabidopsis thaliana after wounding leaf eight and found that membrane depolarizations correlated with jasmonate signalling domains in undamaged leaves. Furthermore, current injection elicited jasmonoyl-isoleucine accumulation, resulting in a transcriptome enriched in RNAs encoding key jasmonate signalling regulators. From among 34 screened membrane protein mutant lines, mutations in several clade 3 GLUTAMATE RECEPTOR-LIKE genes (GLRs 3.2, 3.3 and 3.6) attenuated wound-induced surface potential changes. Jasmonate-response gene expression in leaves distal to wounds was reduced in a glr3.3 glr3.6 double mutant. This work provides a genetic basis for investigating mechanisms of long-distance wound signalling in plants and indicates that plant genes related to those important for synaptic activity in animals function in organ-to-organ wound signalling.
Genetically encoded voltage-sensitive fluorescent proteins (VSFPs) are being used in neurobiology as non-invasive tools to study synchronous electrical activities in specific groups of nerve cells. Here we discuss our efforts to adapt this “light-based electrophysiology” for use in plant systems. We describe the production of transgenic plants engineered to express different versions of VSFPs that are targeted to the plasma membrane and internal membranes of root cells. The aim is to optically record concurrent changes in plasma membrane potential in populations of cells and at multiple membrane systems within single cells in response to various stimuli in living plants. Such coordinated electrical changes may globally orchestrate cell behavior to elicit successful reactions of the root as a whole to varying and unpredictable environments. Findings from membrane “potential-omics” can eventually be fused with data sets from other “omics” approaches to forge the integrated and comprehensive understanding that underpins the concept of systems biology.
Phytolacca dioica L., an evergreen tree of the Phytolaccaceae, is one of the species of Phytolacca which shows anomalous secondary thickening in its stem. This mode of thickening has been regarded as successive cambial activity or alternatively, in some more recent interpretations, as thickening by unidirectional activity of a cambial zone. The stem thickening of P. dioica is of the former type. The cambium produces fascicular strands, showing centrifugal differentiation of xylem and centripetal differentiation of phloem on opposite sides of the cambial layer, and rays are produced between the fascicular areas. In both xylem and phloem the younger elements are closer to the cambium than the older elements. Succeeding cambia arise periodically by periclinal divisions in a layer of parenchyma cells two or three cells beyond the outermost intact phloem derived from the current cambium. Each cambium forms a few parenchyma cells on both sides before it forms derivatives which mature into lignified xylem elements or conductive elements of the phloem. The parenchyma thus formed toward the outside later becomes the site of the origin of the succeeding cambium. Only one or two layers of this phloem parenchyma go on to form the new cambium; the remaining cells accumulate between the outermost phloem and the cortex. P. weberbaueri shows stem structure similar to P. dioica. P. meziana, a shrub, shows normal stem structure.
The peculiar secondary growth in Doxantha unguis-cati provides several developmental problems concerning cambial activity. One of the most interesting of these problems is the presence of both unidirectional and bidirectional arcs of cambium within the same stem. This investigation reports the ontogenetic development of these two kinds of cambial arcs. The first cambial divisions are observed in the fascicular regions of the 11th to 16th internodes from the shoot tip. This event is initiated after internode elongation is completed. In the initial stages, secondary tissues have a cylindrical configuration, but subsequently four grooves become apparent. These grooves signify the first evidence of unidirectional cambial activity. The four unidirectional arcs occur near the four major vascular strands to which all of the leaf traces connect. As secondary growth continues, the bidirectional and unidirectional arcs of cambium become separated and radial fissues can be seen between the furrows of phloem and the lobes of secondary xylem. Additional furrows originate either as sets of four between the original set of four or as single furrows to either or both sides of an existing furrow. All furrows are bordered by multiseriate rays. The initials of the bidirectional and unidirectional cambial arcs are non-stratified and are similar in size and appearance. The phloem produced within the furrow differs in several respects from that produced by the bidirectional arcs. The two types of cambial activity and the precise locations of the unidirectional cambial arcs in the stem (i.e. near the four major strands) suggests that transported products from the leaves are involved in the control of unidirectional cambial activity.
Plants cannot move away from their environments. As a result, all plants that have survived to date have evolved sophisticated signaling mechanisms that allow them to perceive, respond, and adapt to constantly changing environmental conditions. Among the many cellular processes that respond to environmental changes, elevation of calcium levels is by far the most universal messenger that matches primary signals to cellular responses. Yet it remains unclear how calcium, a simple cation, translates so many different signals into distinct responses - how is the “specificity” of signal-response coupling encoded within the calcium changes?
This book will attempt to answer this question by describing the cellular and molecular mechanisms underlying the coding and decoding of calcium signals in plant cells.
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 .
The functional integrity of the phloem in vascular plants is dependent upon the establishment and maintenance of the structural continuity of its sieve elements throughout the entire plant body. The requirement for this integrity is nowhere better documented than in the formation of wound (repair) phloem (see Chaps. 10 and 11), but even the undamaged plant ensures that there are channels for a deviation of solutes in the case of an injury or if a demand emerges which is different from the main flow. Plants with cambial secondary growth may provide these deviations through extensive connections in their radial cell walls which contain lateral sieve areas or lateral sieve plates. Many herbaceous species develop anastomoses — cross-connections between primary phloem (and/or xylem) parts. Anastomoses may regularly connect all neighboring bundles; stem (cauline) bundles may be connected to leaf trace bundles as well as to medullary, cortical or other irregular bundles, thus providing linkages which are able to react to changes in physiological requirements with short-cuts, deviations, branches or combinations. In some plants the degree of development of these anastomoses may be so high that wound phloem will not be produced even if about half of all the vascular bundles are interrupted (Behnke and Sukkri 1971).
Plants integrate activities throughout their bodies using long-range signaling systems in which stimuli sensed by just a few cells are translated into mobile signals that can influence the activities in distant tissues. Such signaling can travel at speeds well in excess of millimeters per second and can trigger responses as diverse as changes in transcription and translation levels, posttranslational regulation, alterations in metabolite levels, and even wholesale reprogramming of development. In addition to the use of mobile small molecules and hormones, electrical signals have long been known to propagate throughout the plant. This electrical signaling network has now been linked to waves of Ca(2+) and reactive oxygen species that traverse the plant and trigger systemic responses. Analysis of cell type specificity in signal propagation has revealed the movement of systemic signals through specific cell types, suggesting that a rapid signaling network may be hardwired into the architecture of the plant. Expected final online publication date for the Annual Review of Plant Biology Volume 67 is April 29, 2016. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
In stressed plants, electrophysiological reactions (elRs) are presumed to contribute to long-distance intercellular communication between distant plant parts. Because of the focus on abiotic stress-induced elRs in the last decades, biotic stress-triggered elRs have been widely ignored. It is likely that the challenge to identify the particular elR types - action potential (AP), variation potential (VP) and system potential (SP) - was responsible for this course of action. Thus, the present survey focused on insect larva feeding (Spodoptera littoralis, Manduca sexta) that triggers distant APs, VPs and SPs in monocotyledonous and dicotyledonous plant species (Hordeum vulgare, Vicia faba, Nicotiana tabacum). APs were detected only after feeding on the stem/culm, whereas SPs were systemically observed following damage to both stem/culm and leaves. This was reasoned by the unequal vascular innervation of the plant and a selective electrophysiological connectivity of the plant tissue. However, striking variations in voltage patterns were detected for each elR type. Further analyses (also in Brassica napus, Cucurbita maxima) employing complementary electrophysiological approaches in response to different stimuli revealed various reasons for these voltage pattern variations: an intrinsic plasticity of elRs, a plant-specific signature of elRs, a specific influence of the applied (a)biotic trigger, the impact of the technical approach and/or the experimental set-up. As a consequence thereof, voltage pattern variations, which are not irregular but rather common, need to be included in electrophysiological signalling analysis. Due to their widespread occurrence, systemic propagation, and respective triggers, elRs should be considered as candidates for long-distance communication in higher plants.
Computational properties of use to biological organisms or to the construction of computers can emerge as collective properties of systems having a large number of simple equivalent components (or neurons). The physical meaning of content-addressable memory is described by an appropriate phase space flow of the state of a system. A model of such a system is given, based on aspects of neurobiology but readily adapted to integrated circuits. The collective properties of this model produce a content-addressable memory which correctly yields an entire memory from any subpart of sufficient size. The algorithm for the time evolution of the state of the system is based on asynchronous parallel processing. Additional emergent collective properties include some capacity for generalization, familiarity recognition, categorization, error correction, and time sequence retention. The collective properties are only weakly sensitive to details of the modeling or the failure of individual devices.
Leaf petioles of Calla palustris (Araceae) show negative gravitropism. 12 h after they have been horizontally placed, they retain again a vertical position, bending upwards. The anatomical study of the petioles revealed that the bundle sheath (endodermis) of each vascular bundle consists of cylindrical cells possessing the features of statocytes. They contain 5-15 distinct amyloplasts, which after gravistimulation move towards the physically lower cell wall. The nuclei of endodermal cells are anchored in the upper part of the cells and they stay there even after the tissue sample has been inverted, showing, thus, a polarity similar to that of root statocytes. The movement of amyloplasts (statoliths) after gravistimulation, i.e. after inversion of the tissue section, from one end of the statocyte to the other can be continuously observed in vivo under a horizontally placed microscope. The amyloplasts-statoliths sediment individually through the parietal cytoplasm or through transvacuolar strands and the movement lasts about 30-40 min. After the application of the actin network modulator cytochalasin B, the statoliths, after gravistimulation, move downwards in clusters and the sedimentation lasts only 5-10 min. The results provide further evidence for the crucial role of the actin network in statolith movement, supporting the starch-statolith model for gravity perception.
This second edition of a well-received book focuses on rhythmic behaviour in plants, which regulates all developmental and adaptive responses and can thus be regarded as quintessential to life itself. The chapters provide a timely update on recent advances in this field and comprehensively summarize the current state of knowledge concerning the molecular and physiological mechanisms behind circadian and ultradian oscillations in plants, their physiological implications for growth and development and adaptive responses to a dynamic environment. Written by a diverse group of leading researchers, the book will spark the interest of readers from many branches of science: From physicists and chemists wishing to learn about the multi-faceted rhythms in plants, to biologists and ecologists involved in the state-of-the-art modelling of complex rhythmic phenomena.
Although the physiological functions of phytochrome A (PhyA) are now known, the distribution of endogenous PhyA has not been examined. We have visualized endogenous PhyA apoprotein (PHYA) by immunolabeling cryosections of pea tissue, using PHYA-deficient mutants as negative controls. By this method, we examined the distribution of PHYA in different tissues and changes in its intracellular distribution in response to light. In apical hook cells of etiolated seedlings, PHYA immunolabeling was distributed diffusely in the cytosol. Exposure to continuous far-red (cFR) light caused a redistribution of the immunolabeling to the nucleus, first detectable after 1.5 hr and greatest at 4.5 hr. During this time, the amounts of spectrally active phytochrome and PHYA did not decline substantially. Exposure to continuous red (cR) light or to a brief pulse of red light also resulted in redistribution of immunolabeling to the nucleus, but this occurred much more rapidly and with a different pattern of intranuclear distribution than it did in response to cFR light. Exposures to cR light resulted in loss of immunolabeling, which was associated with PHYA degradation. These results indicate that the light-induced intracellular location of PHYA is wavelength dependent and imply that this is important for PhyA activity.
Plant cells and neurons share several similarities, including non-centrosomal microtubules, motile post-Golgi organelles, separated both spatially/structurally and functionally from the Golgi apparatus and involved in vesicular endocytic recycling, as well as cell-cell adhesion domains based on the actin/myosin cytoskeleton which serve for cell-cell communication. Tip-growing plant cells such as root hairs and pollen tubes also resemble neurons extending their axons. Recently, surprising discoveries have been made with respect to the molecular basis of neurodegenerative disorders known as Hereditary Spastic Paraplegias and tip-growth of root hairs. All these advances are briefly discussed in the context of other similarities between plant cells and neurons.
Plasmodesmata are minuscule plasma corridors between plant cells which are of paramount importance for transport, communication and signalling between cells. These nano-channels are responsible for the integrated action of cells within tissues and for the subdivision of the plant body into working symplast units.
This book updates the wealth of new information in this rapidly expanding field. Reputed workers in the field discuss major techniques in plasmodesmatal research and describe recent discoveries on the ultrastructure, the functioning and the role of plasmodesmata in intracellular transport and communication, in cell differentiation, plant development and virus translocation.
Electrical signals have been studied in numerous species so far. It appears that two main types of such signals occur in plants, rapid action potentials (APs) and slower variation potentials (VPs). While APs are generally evoked by non-invasive stimuli and follow the all-or-nothing principle as in neurons, VPs are mostly triggered by wounding and do not follow the all-or-nothing law. They are correlated to the stimulus strength and last longer than APs. The transmission of both, APs and VPs, occurs via the phloem over long distances and via plasmodesmata over short distances from cell to cell. Regarding physiological functions of electrical signals, numerous examples exist. They regulate rapid leaf movements in order to catch insects and for instance, affect nutrient uptake, gene expression and phloem transport. Recently, it was shown that apart from hydraulic signals, electric signals also play a significant role in root-to-shoot communication of drought-stressed plants. Re-irrigation of plants after soil drying initiates rapid hydraulic as well as electric signalling which affects the gas exchange of leaves. In addition, evidence was found for a link between electrical signals and photosynthesis as well as respiration. Wound-induced VPs cause a transient suppression in photosynthetic activity and an increase in respiratory CO2 release. The results led us to conclude that different stimulation types trigger characteristic electrical signals each with specific influence on physiological processes.
Vessel elements in Onagraceae correlate perfectly with groups of species; elements are long and wide in mesomorphic species, shortest and narrowest in the most xeromorphic species. Libriform fibers in the family are thin-walled, but many have gelatinous inner walls. The possibility that these represent not tension wood but a water-storage mechanism is examined. Libriform fibers are mostly septate or nucleate or both in the family; this indicates longevity and simulation of parenchyma in starch-storage function. These fibers may compensate for the paucity of axial parenchyma. Interxylary phloem ("included phloem") does not occur in Fuchsia, Hauya, and Ludwigia, the genera in the family most generalized in other respects, and is absent in most annuals studied. Selective pressure for formation of interxylary phloem in the three genera may be minimal because of slow rates of photosynthate translocation within wood and selective pressure for formation of interxylary phloem in annuals may be minimal for spatial reasons. Interxylary phloem may be related to massive flowering that draws rapidly on stored starch, chiefly in the shrubby perennials. The relationships of Onagraceae seem closest to Lythraceae, Sonneratiaceae, Punicaceae, Crypteroniaceae, and Combretaceae; also close are other myrtalean families: Melastomaceae, Myrtaceae, Penaeaceae, Oliniaceae. These affinities are clearly evident from wood features alone: vestured pits on vessels; ray cells upright to square; intraxylary phloem present adjacent to pith; libriform fibers septate or nucleate; prismatic crystals in fibers and rays. Onagraceae tend to show herbaceous characteristics in wood of herbaceous genera; woody genera such as Hauya show no indicators of herbaceous structure. The ancestral habit of Onagraceae was probably shrubby, and without interxylary phloem; interxylary phloem may have evolved more than once in the family.
The bioelectric field of a bean root growing in a weakly conducting solution is examined. It is estimated by a method which is described, that a total current of about 3 X 10-7 A flows through the external medium due to the bioelectric source, resulting in power dissipation outside the plant of about 10-9 W. This is considered in relation to respiratory energy production in the root.
Pattern formation, as occurs during embryogenesis or regeneration, is the crucial link between genotype and the functions upon which selection operates. Even cancer and aging can be seen as challenges to the continuous physiological processes that orchestrate individual cell activities toward the anatomical needs of an organism. Thus, the origin and maintenance of complex biological shape is a fundamental question for cell, developmental, and evolutionary biology, as well as for biomedicine. It has long been recognized that slow bioelectrical gradients can control cell behaviors and morphogenesis. Here, I review recent molecular data that implicate endogenous spatio-temporal patterns of resting potentials among non-excitable cells as instructive cues in embryogenesis, regeneration, and cancer. Functional data have implicated gradients of resting potential in processes such as limb regeneration, eye induction, craniofacial patterning, and head-tail polarity, as well as in metastatic transformation and tumorigenesis. The genome is tightly linked to bioelectric signaling, via ion channel proteins that shape the gradients, downstream genes whose transcription is regulated by voltage, and transduction machinery that converts changes in bioelectric state to second-messenger cascades. However, the data clearly indicate that bioelectric signaling is an autonomous layer of control not reducible to a biochemical or genetic account of cell state. The real-time dynamics of bioelectric communication among cells are not fully captured by transcriptomic or proteomic analyses, and the necessary-and-sufficient triggers for specific changes in growth and form can be physiological states, while the underlying gene loci are free to diverge. The next steps in this exciting new field include the development of novel conceptual tools for understanding the anatomical semantics encoded in non-neural bioelectrical networks, and of improved biophysical tools for reading and writing electrical state information into somatic tissues. Cracking the bioelectric code will have transformative implications for developmental biology, regenerative medicine, and synthetic bioengineering.
Learning and memory are two of the most magical capabilities of our mind. Learning is the biological process of acquiring new knowledge about the world, and memory is the process of retaining and reconstructing that knowledge over time. Most of our knowledge of the world and most of our skills are not innate but learned. Thus, we are who we are in large part because of what we have learned and what we remember and forget. In this Review, we examine the molecular, cellular, and circuit mechanisms that underlie how memories are made, stored, retrieved, and lost.
Plasma membrane voltage is a fundamentally important property of a living cell; its value is tightly coupled to membrane transport, the dynamics of transmembrane proteins, and to intercellular communication. Accurate measurement of the membrane voltage could elucidate subtle changes in cellular physiology, but existing genetically encoded fluorescent voltage reporters are better at reporting relative changes than absolute numbers. We developed an Archaerhodopsin-based fluorescent voltage sensor whose time-domain response to a stepwise change in illumination encodes the absolute membrane voltage. We validated this sensor in human embryonic kidney cells. Measurements were robust to variation in imaging parameters and in gene expression levels, and reported voltage with an absolute accuracy of 10 mV. With further improvements in membrane trafficking and signal amplitude, time-domain encoding of absolute voltage could be applied to investigate many important and previously intractable bioelectric phenomena.
A method has been developed for staining the phloem so that its ramifications can be observed directly in thick preparations. This method is based on clearing the material with lactic acid, staining with lacmoid and observing it in sodium lactate. Phloem anastomoses between the primary vascular strands of stem internodes were found to be common in many plant species (18 out 26 studied). These anastomoses are possible channels for the lateral distribution of materials in the stem and for movement of assimilates upwards from the leaves.
The phloem is the long-distance solute-conducting tissue of plants. The observation of phloem cells is particularly challenging
for several reasons and many recent advances in microscopy are, therefore, especially beneficial for the study of phloem anatomy
and physiology. This review will give an overview of the imaging techniques that have been used for studying different aspects
of phloem biology. It will also highlight some new imaging techniques that have emerged in recent years that will certainly
advance our knowledge about phloem function.