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Mycorrhizal Networks Facilitate Tree Communication, Learning, and Memory
Abstract
Mycorrhizal fungal networks linking the roots of trees in forests are increasingly recognized to facilitate inter-tree communication via resource, defense, and kin recognition signaling and thereby influence the sophisticated behavior of neighbors. These tree behaviors have cognitive qualities, including capabilities in perception, learning, and memory, and they influence plant traits indicative of fitness. Here, I present evidence that the topology of mycorrhizal networks is similar to neural networks, with scale-free patterns and small-world properties that are correlated with local and global efficiencies important in intelligence. Moreover, the multiple exploration strategies of interconnecting fungal species have parallels with crystallized and fluid intelligence that are important in memory-based learning. The biochemical signals that transmit between trees through the fungal linkages are thought to provide resource subsidies to receivers, particularly among regenerating seedlings, and some of these signals appear to have similarities with neurotransmitters. I provide examples of neighboring tree behavioral, learning, and memory responses facilitated by communication through mycorrhizal networks, including, respectively, (1) enhanced understory seedling survival, growth, nutrition, and mycorrhization, (2) increased defense chemistry and kin selection, and (3) collective memory-based interactions among trees, fungi, salmon, bears, and people that enhance the health of the whole forest ecosystem. Viewing this evidence through the lens of tree cognition, microbiome collaborations, and forest intelligence may contribute to a more holistic approach to studying ecosystems and a greater human empathy and caring for the health of our forests.
... Therefore, early terrestrial plants with fungi relationships had a selective advantage over those that did not. Survival and reproduction are assisted by the presence of mycorrhizae networks (Malloch et al. 1980;Simard 2018). Strong molecular evidence supports early plant and fungi relationships in fungal species from the Ascomycota, Basidiomycota, and Glomeromycota phyla (Bonfante and Anca 2009). ...
... ENF, characterized by the formation of arbuscules within cortical root cells, are generally associated with angiosperms (Marx 1980). ENF and EMF are not restricted to specific plant species (Simard 2018). Fungus and plant root interactions, therefore, are not entirely species specific. ...
... Plant interactions with fungi and bacteria drive biogeochemical cycles within an ecosystem. An example is that disruptions to ecosystem stability due to losing keystone species can be stabilized through networks with fungi or bacteria or both (Simard 2018). The symbiotic relationship between plants and fungi used to be considered a parasitic relationship due to the lack of strong evidence of plant derived benefits (Frank 1885;Masui 1926;Curtis 1939). ...
... Scholars, however, are turning attention to previously ignored possibilities in spaces of sentience, intelligence, and communication that species from non-animal queendoms 7 possess. In this realm, plants and fungi are frequently studied together due to the symbiotic nature of many of their relationships (see Simard 2018Simard , 2021Sheldrake 2020;Trewavas 2014;Wohlleben 2016) and it's useful to consider them simultaneously as they often work in unison to make communication possible among species. ...
... The question emerging from such interspecies eavesdropping that scientists have difficulty tackling is whether such communication is automated, intentional, altruistic, or pro-socialsubjective and telos-based terms Western science historically avoids in relation to the more-than -human world. Simard's (2018Simard's ( , 2021 work with tree communication via underground networks of roots and mycorrhizae, which she describes as the Wood Wide Web, shows how trees share nutrientsfor instance, salmon DNA has appeared in trees too far from riverbanks to have gathered nutrients themselves. Simard's work also illustrates kinship and communication between mother trees and their offspring, as some trees send nutrients specifically to their young, using fungi allies. ...
Environmental communication researchers have been listening to voices from the more-than-human for some time. Yet, despite intellectual and public acknowledgment that “nature” is always communicating, anthropocentric Western/ized and industrial/ized cultures continue to struggle to listen to, attune with, and ethically amplify these voices. Through contrasting examples of environmental communication practices of internatural listening within these same cultures, this chapter argues that active relating can help incite shifts from anthropocentric to ecocentric ecocultural identities. We illustrate how: (1) relational knowledge and protections of endangered marine mammals stemmed from the public understanding them as speaking for themselves; (2) practitioners in the sciences and arts hear and amplify plants, fungi, and lichen as agentic; (3) scientists searching for extraterrestrial intelligence investigate humpback whale communication to translate life in the universe; (4) researchers monitoring wildfires/bushfires’ recovery listen to forests; and (5) “citizen story-telling” and podcasting conveys and strengthens more-than-human attunement through the power of story and ecosonics. These examples illuminate efforts to understand interspecies and ecocentric identification and open space for discussions on attunement that can bring restorative change and catalyze ecocentric transformation in both environmental communication research and practice.
... In different ways, Indigenous peoples have long attributed agency and knowledge to plants (Viveiros de Castro 2012; Roncancio 2017). Even western scientists who have been held back (for better or worse) by conventional definitions and modernist preconceptions are now recognising that plants can learn, remember, communicate, and act (Gagliano 2018) and that their networks of mycorrhizal fungi function as neural processors enabling them to engage communally (Simard 2018). As Monica Gagliano explains, plants may not have neurons or brains, but they are nonetheless able to 'evaluate their world subjectively and use their own experiences and feelings as functional states that motivate their choices ' (2018, p. 218). ...
... As Monica Gagliano explains, plants may not have neurons or brains, but they are nonetheless able to 'evaluate their world subjectively and use their own experiences and feelings as functional states that motivate their choices ' (2018, p. 218). Like humans, plants constantly make choices to enhance their lives and survival, and even act communally to improve their ecosystems: 'Through sophisticated cognition that is facilitated by their microbiomes, trees and plants are more perceptive, intelligent, and in control of their destiny than humans have ever given them credit for' (Simard 2018;p. 207). ...
Even in its limited state-based form, human law owes its existence to the natural physical world with its self-created value systems. What is understood as human law is grounded in human-nonhuman entanglements, themselves a subset of a multi-dimensional natural nomos consisting of the intricately connected normative worlds of animals, plants, earth, and cosmos. Complex and intersecting plural normative fields include those associated with the nonliving world, the multiple ontological worlds produced by life forms, and the many strata of human becoming – cultural, cognitive, social, and representational. As plural the nomos contains many irreducible dimensions. Normative fields intersect, hybridise, and clash; they can mutually strengthen and also negate other normativities. In this article, I set out and explore some dimensions of the plural nomos with a focus on living beings, notably the connectedness of being, knowing and normativity. The living nomos co-emerges with being and with the embodied knowledge of even the simplest forms of life. Life is both cognitive and normative; living beings inherit ancestral norms but, in living and adapting, life creates new norms, biological, cultural, and behavioural. The living-knowing being is always normative – produced by the norming processes and constraints of life and matter at large. Normative elements are a critical part of the ontological and epistemological embeddedness of human beings in more than human worlds. Before law (or knowledge) can be about life, it is also of or from life. Expanding the analytical frame of law in this way is one method by which we might reshape western narratives of law, with the aims of promoting better openness to First Nations laws, discouraging western cultural superiority and human exceptionalism, and moving toward a more eco-sensitive view of the continuity between human law-culture-society and the natural world.
... In this sense, there are no studies that investigate how fungi aid in moving nutrients from one plant to another plant in its vicinity. Dr. Simard performed a study where she observed the effect that mycorrhizal fungi had on nutrient transfer between trees (1). Yet, like the other pre-existing studies, Dr. Simard's study did not investigate smaller plants such as the annual and perennial plants that we chose to explore, and the effect of the fungi on nutrient transfer. ...
... While there are several studies involving small plants, such as annuals and perennials, there is no research on the interaction between these species and their relationship with mycorrhizal fungi. Thus, this study set out to determine if smaller plants, such as annuals and perennials, had the same interaction with mycorrhizal fungi that the trees did in Dr. Simard's study (1). ...
The goal of our experiment was to determine if phosphate transfer occurred between plants, using mycorrhizal fungi. We hypothesized that a “communication” network existed between plants when the mycorrhizal fungi were present and that there would be no transfer of nutrients if the mycorrhizal fungi were not present. This study extended the analysis of Suzanne Simard who studied Paper Birch, Douglas Fir, and Western Red Cedar in Canada. She was able to confirm that there is a massive underground communication where different plants cooperate with resources using mycorrhizal fungi. The purpose of our experiment was to see if plants with nutrients would transfer their excess levels of phosphate to the plant that had a limited amount of nutrients. Overall, no definitive conclusion could be drawn from the treatments conducted. The measurements greatly deviated from the hypothesized results and demonstrated a more complicated relationship than originally thought. Further study will need to be conducted to determine if there are further conditions that must be met, such as a minimum amount of phosphate concentration or a minimum differential between the resources (in terms of this study, phosphate concentration) of the two plants, for this transfer to occur. The results of this study, if replicated and shown to be conclusive at long distances, could be used to aid forest management.
... In contrast to human, plants are devoid of a central nervous system and hence rely on alternative means to interact with the external environment (Van Loon 2016). In this context, mycorrhizal networks aid in plant communication and intelligence (learning and memory), particularly in forest ecosystems (Simard 2018). ...
... Eventually nutrients derived from salmon carcasses, are metabolized and stored in the tree rings for hundreds of years, thus facilitating massive forest growth. The storage in tree rings with the help of mycorrhizal fungi, and the corresponding promotion of tree growth was considered a potential 'salmon nutrient memory' present in the forest ecosystem (Simard 2018). ...
Mycorrhization has been an integral part of plants since colonization by the early land plants. Over decades, substantial research has highlighted its potential role in improving nutritional efficiency and growth, development and survival of crop plants. However, the focus of this review is trees. Evidence have been provided to explain ecological and physiological significance of mycorrhization in trees. Advances in recent technologies ( e.g. , metagenomics, artificial intelligence, machine learning, agricultural drones) may open new windows to apply this knowledge in promoting tree growth in forest ecosystems. Dual mycorrhization relationships in trees and even triple relationships among trees, mycorrhizal fungi and bacteria offer an interesting physiological system to understand how plants interact with other organisms for better survival. Besides, studies indicate additional roles of mycorrhization in learning, memorizing and communication between host trees through a common mycorrhizal network (CMN). Recent observations in trees suggest that mycorrhization may even promote tolerance to multiple abiotic ( e.g. , drought, salt, heavy metal stress) and biotic ( e.g. fungi) stresses. Due to the extent of physiological reliance, local adaptation of trees is heavily impacted by the mycorrhizal community. This knowledge opens the possibility of a non‐GMO avenue to promote tree growth and development. Indeed, mycorrhization could impact growth of trees in nurserys and subsequent survival of the inoculated trees in field conditions. Future studies might integrate hyperspectral imaging and drone technologies to identify tree communities that are deficient in nitrogen and spray mycorrhizal spore formulations on them.
... Furthermore, the association of AM fungi with these plant species helps to maintain the edaphic network of connections and interactions between them even after disturbance (van Der Heijden et al. 2015). Therefore, the persistence of mycorrhizal networks in the soil is essential for the ecological resilience of temperate forests (Simard 2018;Toju et al. 2018). ...
Arbuscular mycorrhizal (AM) fungi enhance plant flowering and fruiting by improving nutrient and water uptake. The aim of this study was to evaluate how AM fungal colonization percentage and edaphic factors, modulate flowering and fruiting in secondary vegetation (SV) species with different biological traits, in a temperate forest. We conducted the research in four sites at two elevation intervals in a temperate forest in Mexico, focusing on three SV species. We recorded flower, fruit and AM fungal colonization percentages during the rainy and the dry season. Soil was collected from the rhizosphere of each SV species to determine organic matter (OM), pH, relative soil moisture (RSM), available phosphorus (Ava-P) and nitrogen (Ava-N). The AM fungal colonization, flower and fruit percentages showed interspecific and temporal variations. Structural equation models showed that flowering was positively influenced by RSM in Acaena elongata and negatively influenced by AN in Solanum pubigerum . Fruiting was positively influenced by AM fungal colonization and negatively by AP in A. elongata , with a relevant indirect effect of OM. In S. pubigerum , the effect of AM fungal colonization was slightly positive, while AN and pH had a greater effect on fruiting. While in Ageratina glabrata the effect of AM fungal colonization on fructification was not evident. The study highlights the critical role of AM fungal colonization and soil properties such as OM, pH and N in flower and fruit production, which depend on the biological traits of the host plant species.
... In Treeam, players create tannins by collecting atoms Signaling: mycorrhizal network. Douglas-fir trees are able to emit signals back-and-forth through mycorrihizal networks 2 , including defense molecules [16]. In Treeam, the players have to reconnect roots of the tree to the mycorrhizal network in order to broadcast the fact their tree is attacked by a herbivore. ...
The interactions between trees in the forest have raised questions about their potential collaborations and environmental adaptation. Addressing these themes, we introduce Treeam, an immersive serious game that simulates the internal functioning of trees through collaborative gameplay. This paper presents the game’s mechanics, emphasizing its role in raising environmental awareness. We conclude with a critical analysis of the game’s limitations and propose directions for future development and research questions.
... For instance, introducing elements of permaculture(Holmgren, 2020) can teach students to design systems that mimic natural plant ecosystems, focusing on diversity, interdependence, and sustainability. In this regard, systems thinking, strategic thinking, and integrated problem-solving are valuable for successfully incorporating these ideas into the classroom.Discussions and debates that encourage students to question assumptions about plant memory and communication(Simard, 2018) are not only well-positioned within Marder's framework but can also be facilitated by normative, critical thinking, systems thinking, and selfawareness competencies. Encouraging slow observation and adopting nonhuman timeframes(Bang & Marin, 2015) can be another valuable plant thinking educational direction. ...
Societal Impact Statement
Lack of plant awareness represents a significant phenomenon characterized by the underestimation of plants, with clear implications for sustainability. This study explores the potential of key competencies in education for sustainable development as an effective framework for mitigating this phenomenon. Through conceptual analysis, these competencies emerge as a valuable tool for enhancing plant awareness. This has significant implications for both the educational community and the general public, as it offers an additional pathway for fostering plant awareness, which can ultimately lead to increased public pressure and stronger mobilization by policymakers on critical issues such as biodiversity conservation and climate change.
Summary
The phenomenon of “plant blindness” or “lack of plant awareness” has received much attention from researchers over the last years. Recognizing education as both a contributing factor to and a potential solution for this issue, this study explores key competencies in education for sustainable development as a framework to enhance plant awareness.
A conceptual analysis was conducted to identify thematic relationships between this framework and plant awareness.
The analysis suggests that enhancing systems thinking and integrated problem‐solving competencies can help learners better recognize and understand the importance of plants for both human welfare and planet Earth. Through the development of critical thinking, normative, and self‐awareness competencies, learners are encouraged to question existing personal and societal perspectives on plants, thereby reshaping their perception of flora. Moreover, the application of anticipatory, strategic, and collaboration competencies allows learners to explore the intrinsic values of the plant world more deeply, fostering respect and empathy, which can lead to a broader shift in attitudes toward flora.
Through the integration of these elements into plant education, botany classes can become more engaging and relevant to real‐world issues. This approach can help bridge the gap between traditional science education and the development of pro‐conservation behaviors, while also enriching the evaluation methods used to assess plant awareness. Additionally, key competencies in education for sustainable development within plant education can promote not only a less utilitarian perspective of plants as organisms but also a more holistic approach to science education, reducing its emphasis on instrumentalization.
... Hoy en día, existen evidencias de procesos de comunicación inter-específicos en el suelo y sus consecuencias para la vida vegetal. Estas muestran como las plantas son capaces, mediante señales bioquímicas y la activación de rutas metabólicas, de memorizar y aprender de estímulos ambientales promovidos por microorganismos [41], [42]. ...
Los hongos son organismos presentes en todos los ecosistemas terrestres y cumplen diversos papeles ecológicos en los nichos que habitan. El suelo es una matriz de intenso intercambio de señales, que los hongos ha aprovechado para establecer todo tipo de interacciones. Sus relaciones particulares con las raíces de las plantas están determinadas por procesos de comunicación que se establecen entre ambos organismos a nivel celular y tisular. Si bien el concepto de inteligencia en organismos que no sean animales es todavía un tema controversial, existen evidencias científicas que apuntan al menos a un nivel basal de inteligencia para guiar estos procesos de comunicación y respuesta. En este contexto se describen los conocimientos más recientes sobre los hongos rizosféricos, micorrícicos y endófitos; donde se destacan sus efectos en la regulación del crecimiento de las plantas, la nutrición y el intercambio de carbono y agua, la inducción o la supresión de la resistencia sistémica, la colonización celular y la producción de metabolitos secundarios, ya sea en relaciones simbióticas o patogénicas. Pese a los nuevos avances, existen grandes oportunidades de investigación básica y aplicada para el aprovechamiento de este diálogo molecular. El objetivo de esta revisión fue presentar algunos de los fenómenos descritos en la interacción hongo-planta en el suelo y mostrar su relevancia desde la perspectiva de una “comunicación inteligente”.
... Cutting-edge biological research has unveiled the root zone as a well-connected underground network of mycorrhizal fungi, akin to a nervous system, through which resources and information are exchanged among plants (Simard, 2018). This underscores that plants and their roots are integral components of a cohesive ecosystem rather than isolated entities. ...
The root zone is a vital part of the Earth system and a key element in hydrology, ecology, agronomy, and land surface processes. However, its definition varies across disciplines, creating barriers to interdisciplinary understanding. Moreover, characterizing the root zone is challenging due to a lack of consensus on definitions, estimation methods, and their merits and limitations. This opinion paper provides a holistic definition of the root zone from a hydrology perspective, including its moisture storage, deficit, and storage capacity. We demonstrate that the root zone plays a critical role in the biosphere, pedosphere, rhizosphere, lithosphere, atmosphere, and cryosphere of the Earth system. We underscore the limitations of the traditional reductionist approach in modelling this complex and dynamic zone and advocate for a shift towards a holistic, ecosystem-centred approach. We argue that a holistic approach offers a more systematic, simple, dynamic, scalable, and observable way to describe and predict the role of the root zone in Earth system science.
... A stream of popular books supported this enterprise and broadened its audience (Mancuso and Viola 2015;Wohlleben 2016;Mancuso 2018;Gagliano 2018;Ryan et al. 2021;Calvo and Lawrence 2023). Suzanne Simard, a forest scientist and ecologist, extended these ideas to include mycorrhizae, positing that the networks created through these symbiotic relationships were similar to the neural networks of animals, and therefore could give rise to a form of intelligence (Simard 2018;. In 2024 journalist Zoë Schlanger published a sympathetic profile of the plant intelligence community, as well as of other scientists investigating plant adaptations (Schlanger 2024). ...
In their recent paper, Kingsland and Taiz argue that proponents of plant intelligence and plant neurobiology misuse historical sources to support their claims, suggesting a pattern of bias. They critique the reliance on subjective judgments and the systematic misuse of past literature by notable scientists. This response addresses their criticisms while adhering to Rapoport’s rules to foster constructive academic dialogue. We emphasize the importance of evidence-based research and highlight areas of agreement, including the fallacy of appealing to authority and the necessity for more robust empirical evidence. However, we also challenge their selective citation practices and argue that their narrative itself is subject to the same criticisms they levy. By examining recent works and pointing out overlooked rebuttals, we aim to clarify misconceptions and advocate for a more nuanced understanding of plant intelligence research. This dialogue underscores the need for rigorous, respectful scientific discourse to advance the field.
... The vegetal world is populated with a multitude of other organisms that coexist forming such complex ecological communions (Karban, 2015) like the lichens, corals or mycorrhizal nodules of plants (Simard, 2018). These communities lead to constructive symbiotic but also parasitic and mutualistic relations. ...
This paper explores the potential for extending relational ontologies to include a specific focus on human-plant relations. We theorise the emergence of a vegetal ontology, as a novel way of working and remaking theories around human-plant relations that can be applied to the field of environmental education. A vegetal ontological approach, as applied in the environmental education research project that informs this article, abandons hierarchical comparisons of plants, which are often historically positioned as “lesser species,” mere “objects” and “resources” even. We start our paper with a modest review of key theoretical approaches informing past and recent environmental education studies on child-plant relations. We then return to the discussion started within the introduction to the paper on how we have theorised a vegetal ontology as a mode of a relational ontology focussing particularly on human-plant relations and drawing on posthumanist, new materialist and Indigenous approaches. To conclude the paper, we then put this newly named vegetal ontology to work. We apply it to a recent study on childhood-plant encounters where researchers engaged with young children and their families in a botanical garden setting and a group of environmental education elders reflected on the significance of plant relations in their childhoods.
... A stream of popular books supported this enterprise and broadened its audience (Mancuso and Viola 2015;Wohlleben 2016;Mancuso 2018;Gagliano 2018;Ryan et al. 2021;Calvo and Lawrence 2022). Suzanne Simard, a forest scientist and ecologist, extended these ideas to include mycorrhizae, positing that the networks created through these symbiotic relationships were similar to the neural networks of animals, and therefore could give rise to a form of intelligence (Simard 2018(Simard , 2022. In 2024, journalist Zoë Schlanger published a sympathetic profile of the plant intelligence community, as well as of other scientists investigating plant adaptations (Schlanger 2024). ...
Proponents of the concepts of plant intelligence and plant neurobiology often use historical sources as “evidence” and argue that eminent past scientists have supported ideas of plant intelligence, memory, learning, decision-making, agency, and consciousness. Historical sources include writings by Charles Darwin, Julius von Sachs, F. W. Went, K. V. Thimann, Barbara McClintock, and J. B. Lamarck. Advocates of plant neurobiology also argue that the ideas of J. C. Bose, an Indian scientist who is considered an important forerunner of plant neurobiology, were suppressed chiefly because of racism. Plant neurobiology has been criticized on scientific grounds, but there has not been close scrutiny of the use of historical sources as a form of evidence. We provide the first in-depth analysis of how historical sources have been used and misused, and conclude that there is a consistent pattern of distortion of these sources. Distortions include the use of erroneous quotations, alteration of quotations, selective quotations without context, and misinterpretation and exaggeration of historical statements. In the case of Bose, we show that there were legitimate scientific reasons for questioning his interpretations of botanical experiments and argue that this context cannot be ignored in evaluating contemporary responses to Bose. Overall, the common practice by proponents of plant intelligence and plant consciousness of uncritically citing the words of eminent scientists of the past, taken out of their historical context to bolster their arguments, should not be confused with scientific evidence supporting these concepts, even when the quotations, themselves, are accurate.
... The mycorrhizal fungal networks [120] enable advanced communication between trees in a forest. These networks allows resource sharing, defensive signaling, and kin recognition. ...
This research explores the transformative potential of advanced technologies like IoE, 6G, Internet of Fungus and IoNT in addressing critical agricultural challenges, thereby enhancing food security, efficiency, and sustainability in precision agriculture.
... A cambio de este beneficio, los hongos se comportan como verdaderos protectores y extensiones de las raíces, que exploran e interactúan con el suelo, facilitando su absorción. Además, el micelio explorador de los hongos puede asociarse con varios otros árboles simultáneamente, lo que permite que los árboles del bosque se unan físicamente y establezcan complejas redes de comunicación subterráneas (Molina & Horton 2015;Simard, 2018). Algunos estudios han demostrado un alto grado de colonización de hongos micorrícicos en las raíces de los árboles de pewen (Diehl & Fontenla, 2010;Godoy & Marín, 2019). ...
Las relaciones entre la gente y los árboles se construyen y reconstruyen continuamente en sistemas socioecológicos situados. En los estudios sobre sistemas socioecológicos vinculados con árboles, comúnmente encontramos dos enfoques: el primero se centra en ‘entidades biológicas’, examinando la dinámica ecológica de las especies de árboles y la biodiversidad asociada. El segundo enfoque se centra en las personas, analizando la ‘agencia humana’ junto con las fuerzas políticas, históricas y contemporáneas que dan forma, estimulan o dañan a las relaciones humano-árbol. En este trabajo, exploramos críticamente los sistemas socioecológicos asociados al pewen (Araucaria araucana), uno de los árboles más icónicos y sagrados del sur de los Andes. Primero describimos algunos de nuestros hallazgos de investigación sobre el pewen para los dos primeros enfoquesdescritos anteriormente. Luego, desarrollamos una tercera perspectiva, que llamamos ‘relacional’, la cual destaca las relaciones bioculturales, superando las dicotomías ‘ecológica/social’ y ‘entidad biológica/agencia humana’. Nuestro enfoque relacional permite indagar en cómo los actores (árboles y semillas, fauna silvestre y gente, entre otros) interactúan en redes bioculturales complejas y simpoiéticas, identificando a la memoria biocultural del sistema como un conjunto de relaciones dinámicas y cotidianas que se construyen y reconstruyen continuamente en sistemas abiertos y sujetos a impulsores de cambio históricos y contemporáneos.
... In forest ecosystems, MX plants occur in the understory, and their associated fungi are shared with neighbouring plants, forming common mycorrhizal networks (CMNs) (Selosse et al. 2006;Beiler et al. 2010;Simard et al. 2012;Simard 2018). CMNs have been suggested to transport carbon, nutrients, and water (Simard et al. 1997(Simard et al. , 2003(Simard et al. , 2012Selosse et al. 2006), and despite recent claims that CMNs are overstated (Karst et al. 2023), mycoheterotrophic and MX plants are likely the strongest evidence that CMNs can be functional. ...
Pyrola japonica, a member of the family Ericaceae, is a mixotroph that grows on forest floors and obtains carbon (C) from both its photosynthesis and its mycorrhizal fungi. Its mycorrhizal community is dominated by Russulaceae. However, the mechanism of its C acquisition and its flexibility are not well understood. Our aim was to assess the impact of disturbance of the mycorrhizal fungal communities on C acquisition by P. japonica. We repeatedly applied a fungicide (Benomyl) to soils around P. japonica plants in a broad-leaved forest of central Japan, in order to disturb fungal associates near roots. After fungicide treatment, P. japonica roots were collected and subjected to barcoding by next-generation sequencing, focusing on the ITS2 region. The rate of mycorrhizal formation and α-diversity did not significantly change upon fungicide treatments. Irrespective of the treatments, Russulaceae represented more than 80% of the taxa. Leaves and seeds of the plants were analysed for ¹³C stable isotope ratios that reflect fungal C gain. Leaf and seed δ¹³C values with the fungicide treatment were significantly lower than those with the other treatments. Thus the fungicide did not affect mycorrhizal communities in the roots, but disturbed mycorrhizal fungal pathways via extraradical hyphae, and resulted in a more photosynthetic behaviour of P. japonica for leaves and seeds.
... Trees and plants are seen to have a deliberate purpose and aim to control their own existence [26,27]. They communicate and are socially connected, taking care of their fellow community members, and keeping them alive [28] using "a vast network of roots and fungi working together", in a 'wood-wide web' [29,30]. So, trees and plants do have a language and they communicate and talk, at least with each other [31], but their intelligence is often not included in any (human) deliberation or decision-making. ...
Current decision-making regarding urban design, architecture, and spatial planning often emphasizes existing power balances, which historically have excluded other humans, such as indigenous people, and nature from conversations and decision-making. The purpose of this study is to explore if and how an empathic experience could give insights into how nature can be given a voice, and, more concretely, how a group of trees on the TEC campus in Monterrey would feel about a sudden change in their direct environment. The methodology is divided into three parts. The first is the explanation of the case study and immersion of the (human) participants in the site. The second stage consists of deep listening and reproducing the imagined expressions of the trees. In the third stage, the participants return from the site, evaluate, and formulate a manifesto. The experience suggests that it is possible to inspire human beings to imagine what trees would have to say if we only imagined their language. It also shows that it is possible to gain access to a formerly hidden environment. The conclusion is that the empathic access to these formerly muted worlds, such as those of nature or socially marginalized peoples, can strengthen our understanding of, and our ability to resolve, the current environmental crisis.
... Cross-kingdom stress signaling has also been documented extensively in forests where trees and mycelium establish subterranean communication networks (Simard 2018;Liang et al. 2020;Fortey 2021;Thomas and Cooper 2022). A possible reason NTE were dismissed for so long as having any relevance in environmental radiobiology may be because the focus was on cell death as an endpoint to demonstrate bystander effects and chromosome damage or lethal mutations to reveal genomic instability (Hei et al. 2011;Schofield and Kondratowicz 2018), none of which would appear to be important to conserve in evolution. ...
It is now well accepted that the mechanisms induced by low-dose exposures to ionizing radiation (LDR) are different from those occurring after high-dose exposures. However, the downstream effects of these mechanisms are unclear as are the quantitative relationships between exposure, effect, harm, and risk. In this paper, we will discuss the mechanisms known to be important with an overall emphasis on how so-called "non-targeted effects" (NTE) communicate and coordinate responses to LDR. Targeted deposition of ionizing radiation energy in cells causing DNA damage is still regarded as the dominant trigger leading to all downstream events whether targeted or non-targeted. We regard this as an over-simplification dating back to formal target theory. It ignores that last 100 y of biological research into stress responses and signaling mechanisms in organisms exposed to toxic substances, including ionizing radiation. We will provide evidence for situations where energy deposition in cellular targets alone cannot be plausible as a mechanism for LDR effects. An example is where the energy deposition takes place in an organism not receiving the radiation dose. We will also discuss how effects after LDR depend more on dose rate and radiation quality rather than actual dose, which appears rather irrelevant. Finally, we will use recent evidence from studies of cataract and melanoma induction to suggest that after LDR, post-translational effects, such as protein misfolding or defects in energy metabolism or mitochondrial function, may dominate the etiology and progression of the disease. A focus on such novel pathways may open the way to successful prophylaxis and development of new biomarkers for better risk assessment after low dose exposures.
... AMF improve plant nutrition by accessing nutrient sources that are otherwise inaccessible to roots Andrino et al., 2021). The great majority of AM fungi build extensive colonization networks with numerous neighboring plants for their carbon or nutritional supplies through CMNs, which are not host-specific (Rhodes, 2017;Simard, 2018;He et al., 2019;. CMNs play a crucial role in plant-plant interactions by generating warning signals and activating defense information (Song et al., 2015;Gilbert and Johnson, 2017;Oelmüller, 2019). ...
Plants engage in a variety of interactions, including sharing nutrients through common mycorrhizal networks (CMNs), which are facilitated by arbuscular mycorrhizal fungi (AMF). These networks can promote the establishment, growth, and distribution of limited nutrients that are important for plant growth, which in turn benefits the entire network of plants. Interactions between plants and microbes in the rhizosphere are complex and can either be socialist or capitalist in nature, and the knowledge of these interactions is equally important for the progress of sustainable agricultural practice. In the socialist network, resources are distributed more evenly, providing benefits for all connected plants, such as symbiosis. For example, direct or indirect transfer of nutrients to plants, direct stimulation of growth through phytohormones, antagonism toward pathogenic microorganisms, and mitigation of stresses. For the capitalist network, AMF would be privately controlled for the profit of certain groups of plants, hence increasing competition between connected plants. Such plant interactions invading by microbes act as saprophytic and cause necrotrophy in the colonizing plants. In the first case, an excess of the nutritional resources may be donated to the receiver plants by direct transfer. In the second case, an unequal distribution of resources occurs, which certainly favor individual groups and increases competition between interactions. This largely depends on which of these responses is predominant (“socialist” or “capitalist”) at the moment plants are connected. Therefore, some plant species might benefit from CMNs more than others, depending on the fungal species and plant species involved in the association. Nevertheless, benefits and disadvantages from the interactions between the connected plants are hard to distinguish in nature once most of the plants are colonized simultaneously by multiple fungal species, each with its own cost-benefits. Classifying plant–microbe interactions based on their habitat specificity, such as their presence on leaf surfaces (phyllospheric), within plant tissues (endophytic), on root surfaces (rhizospheric), or as surface-dwelling organisms (epiphytic), helps to highlight the dense and intricate connections between plants and microbes that occur both above and below ground. In these complex relationships, microbes often engage in mutualistic interactions where both parties derive mutual benefits, exemplifying the socialistic or capitalistic nature of these interactions. This review discusses the ubiquity, functioning, and management interventions of different types of plant–plant and plant–microbe interactions in CMNs, and how they promote plant growth and address environmental challenges for sustainable agriculture.
... Similarly, we can expect evolution of defence induction in response to neighbourhood composition. Such a plastic response in defence strategies to neighbourhood composition requires interaction among plants, which can be mediated by ambient VOCs or through underground connections (Brosset and Blande 2021;Karban 2021;Simard 2018). Most studies on such interactions focus on within-species interactions where plants without herbivores are exposed to volatiles from plants with herbivores, and then often show priming to respond to herbivory or induction of defences (e.g. ...
To what extent particular plant defences against herbivorous insects are constitutive or inducible will depend on the costs and benefits in their neighbourhood. Some defensive chemicals in leaves are thought to be costly and hard to produce rapidly, while others, including volatile organic compounds that attract natural enemies, might be cheaper and can be released rapidly. When surrounding tree species are more closely related, trees can face an increased abundance of both specialist herbivores and their parasitoids, potentially increasing the benefits of constitutive and inducible defences. To test if oaks (Quercus robur) respond more to herbivore attacks with volatile emission than with changes in leaf phenolic chemistry and carbon to nitrogen ratio (C: N), and whether oaks respond to the neighbouring tree species, we performed an experiment in a forest in Poland. Oak saplings were placed in neighbourhoods dominated by oak, beech, or pine trees, and half of them were treated with the phytohormone methyl jasmonate (elicitor of anti-herbivore responses). Oaks responded to the treatment by emitting a different volatile blend within 24 h, while leaf phenolic chemistry and C: N remained largely unaffected after 16 days and multiple treatments. Leaf phenolics were subtly affected by the neighbouring trees with elevated flavan-3-ols concentrations in pine-dominated plots. Our results suggest that these oaks rely on phenols as a constitutive defence and when attacked emit volatiles to attract natural enemies. Further studies might determine if the small effect of the neighbourhood on leaf phenolics is a response to different levels of shading, or if oaks use volatile cues to assess the composition of their neighbourhood.
... Self-regulating systems exist from cells to ecosystems, where innumerable species and individuals form a web of interconnections to ensure the system's survival in the face of disturbance. For instance, roots in a forest form networks with fungi to facilitate information sharing between trees, so the forest may respond pre-emptively to an external threat such as an insect outbreak [9]. Just as self-regulating ecosystems exist via the free (i.e., unregulated) interactions between consumers, producers, and decomposers, self-regulating economies exist via the unregulated interactions between businesses and consumers across all levels of production and consumption. ...
The current global economic system undermines sustainability efforts such as green infrastructure and circularity, while jeopardizing social and environmental values in rich and poor countries alike. These chronic failures stem in part from a poor understanding of an economy’s structure. While many scientists view economic and ecological systems as homologous to one another (i.e., similar structures and processes), an understanding of the foundational components of these systems is lacking. A primary objective of this paper is to refine the understanding of those foundational components, and their interactions. Dozens of ecological processes have functional equivalents in economies, such as succession, evolution, symbiosis, and competition. The central hypothesis here is that three components—diversity, energy, and trade (i.e., resource transfers)—constitute the foundational components of self-regulating economies and ecosystems. A secondary hypothesis is that the interaction of these components regionally, rather than at a global scale, is a limiting factor to the long-term success of sustainability elements such as circularity, green infrastructure, and others. This article evaluates diversity, energy, and trade relative to measures such as net productivity, stability, resource-use efficiency, and biomass (i.e., capital) accumulation. In closing, the concept of economic restoration is summarized, as informed by principles of ecological restoration.
... The following research proves the unique ability of the mycelium network. Suzanne explained in her studies that trees using mycelium networks are motivated by the need to secure their sources of carbon and to ensure the distribution and conveyance of information, which provides multiple opportunities for trees to take action to interact with their neighbors and adapt to the rapidly changing environment [3]. In another study in which Douglas fir trees were injured, the Douglas fir dumped its carbon into the network, and the ponderosa pine took it up; then, the defense enzymes of the Douglas fir and the ponderosa pine were 'upregulated' in response to this injury [4]. ...
In today’s world, merging sensor-based security systems with contemporary principles has become crucial. As we witness the ever-growing number of interconnected devices in the Internet of Things (IoT), it is imperative to have robust and trustworthy security measures in place. In this paper, we examine the idea of virtualizing the communication infrastructure for smart farming in the context of IoT. Our approach utilizes a metaverse-based framework that mimics natural processes such as mycelium network growth communication with a security-concept-based srtificial immune system (AIS) and transaction models of a multi-agent system (MAS). The mycelium, a bridge that transfers nutrients from one plant to another, is an underground network (IoT below ground) that can interconnect multiple plants. Our objective is to study and simulate the mycelium’s behavior, which serves as an underground IoT, and we anticipate that the simulation results, supported by diverse aspects, can be a reference for future IoT network development. A proof of concept is presented, demonstrating the capabilities of such a virtualized network for dedicated sensor communication and easy reconfiguration for various needs.
... This was followed by information about the internet and subsequent online social networks. Oddly, there was nothing about ecological systems thinking until the exhibition mentioned Suzanne Simard's research that revealed how mycorrhizal fungi create communicative 'underground networks' among trees that, she claims, facilitate their sharing of resources (Simard 2021(Simard , 2018. ...
Paganism is a construction that religionists and scholars alike define according to their understandings and purposes. Herein I seek to explode common understandings of Paganism, which assume it always involves beliefs and practices about putatively divine natural entities, beings, or forces, and to consider such phenomena more broadly, as a sensory and affective sensibility – and a perception that is often entirely naturalistic (e.g., scientific and agnostic if not avowedly atheistic) – about the proper place of humans in, and obligations to, nature. When understood in this way one can discern that a host of cultural creatives, including those orchestrating pageants and ritual-resembling ceremonies, artists of all sorts, curators of science museums, and even some developers of theme parks, have affinity with Pagan worldviews and values. By expanding the boundary of what many confine as Paganism it becomes possible to consider whether Paganism is more widespread, and growing more rapidly, than many perceive.
This article explores affinities between New Materialisms, anarchism, and varieties of Indigenous thought. It is suggested that all three share an animist ontology, a certain pragmatist and “meta-fetishistic" stance, a distrust of vertical thinking, a preference for horizontal arrangements, and even a kind of comedic “theory of life”. Taken together, these set New Materialisms on a firmly antifascist basis, helping to answer the frequent charge that they lack clear political commitments. Having made that argument, I then want to open up for consideration some ethical questions about life so theorised and explore some possible ways forward.
Mycoforestry, the synthesis of mycology and forestry, offers a uniquely viable solution for improving both environmental health and industrial outcomes in forestry. Over the past few decades, the concept of sustainability in forestry has evolved significantly. Despite advancements, significant challenges persist in reforestation, particularly regarding tree regrowth rates and the quality of regenerating forests; and I would argue that the bottom line remains profit. Recent breakthroughs by researchers such as (but not limited to), Suzanne Simard and Paul Stamets, however, have shed light on the critical role fungi play in forest ecosystems. Their work demonstrates that trees and fungi are intricately interconnected. Forest regeneration efforts that overlook these relationships risk not only failure, but also further harm. Research highlights the profound ecological benefits provided by fungi and catering to its needs. This paper seeks to explore the critical role of fungi in forest sustainability and advocate for integrating mycoforestry principles into modern forestry practices. Forests managed under mycoforestry principles benefit from higher tree success rates, greater biodiversity, and healthier soils compared to conventional forestry methods. Practices such as clearcutting have devastating, long-term effects on fungal networks, contributing to unsustainable forest ecosystems and overall harmful ideas of how forests work. The integration of mycology into forestry has profound implications for biodiversity conservation, climate crisis mitigation, and sustainable timber production.
Experiments have shown that when one plant is attacked by a pathogen or herbivore, this can lead to other plants connected to the same mycorrhizal network up-regulating their defense mechanisms. It has been hypothesized that this represents signaling, with attacked plants producing a signal to warn other plants of impending harm. We examined the evolutionary plausibility of this and other hypotheses theoretically. We found that the evolution of plant signaling about an attack requires restrictive conditions, and so will rarely be evolutionarily stable. The problem is that signaling about an attack provides a benefit to competing neighbors, even if they are kin, and so reduces the relative fitness of signaling plants. Indeed, selection is often more likely to push plant behavior in the opposite direction—with plants signaling dishonestly about an attack that has not occurred, or suppressing a cue that they have been attacked. Instead, we show that there are two viable alternatives that could explain the empirical data: 1) the process of being attacked leads to a cue (information about the attack) which is too costly for the attacked plant to fully suppress; 2) mycorrhizal fungi monitor their host plants, detect when they are attacked, and then the fungi signal this information to warn other plants in their network. Our results suggest the empirical work that would be required to distinguish between these possibilities.
This paper aims to propose a relational approach to the study of cognition that can offer a perspective on the cognitive behaviours of plants – sessile organisms without a nervous system – when considered in the reciprocal interrogation of philosophy and the cognitive and ecological sciences. When leveraging the inspiring, clarifying, and occasionally heuristic potential of different epistemic tools, plant cognition can be understood as the result of processes constantly shaped by multiple co-constructive
relationships between organisms and their ecological niches. Organisms and niches are conceivable as dense multi-functional systems of resources and information interchange. The concepts of network and ramification are fruitful keys to frame forms of dynamic relationships between elements. In their alternatively iconical, metaphorical, and conceptual-modelling potentialities, networks and ramifications have been used to identify different types of relationships and transmitted information. The explanatory and heuristic scope of these two concepts needs to be further investigated when linked to cognitive aspects, especially with regard the concept of ramification. Looking at the plant world, whilst much has been written about networks, relatively little has been said explicitly about ramifications (branching capacity, branching characteristics and habits) and their relationship with aspects related to plant behaviour and cognition.
In questo articolo ci si domanda se ricorrere a una qualche concezione di rappresentazione per spiegare la cognizione delle piante sia utile o meno. Dopo aver richiamato una pluralità di visioni sul concetto di rappresentazione in vari approcci alle scienze cognitive, ci si soffermerà sull’eventuale presenza di una particolare concezione di rappresentazione – un tipo di rappresentazione molecolare –pertinente il caso vegetale. all’insegna di un approccio processuale e relazionale alla cognizione, ci si interrogherà sulla possibile relazione di aspetti rappresentazionali 1) con il ruolo svolto dalle reti biologiche di segnalazione chimico-elettrica interne ai corpi vegetali, e, in particolare, 2) con le capacità di rilevamento, memorizzazione e apprendimento dell’informazione ambientale da parte delle piante. Nello specifico, ci si chiederà se e che tipo di ruolo abbia la memoria vegetale, ai suoi vari livelli di operatività, con la capacità sia di strutturare un insieme di elementi e di dinamiche processuali, sia con la capacità di richiamare tali elementi e dinamiche al ripresentarsi di situazioni simili. Ci si domanderà se e che rapporto abbia la memoria delle piante con una possibile concezione molecolare di rappresentazione. La questione è aperta.
Going beyond translation studies’ foundational anthropocentrism, this article proposes a new conceptualization of translation as negotiating the needs of different interdependent species—animal, plant and human—in a shared environment. It proposes a dynamic encounter between three conversation partners: recent scientific discoveries on plant communication (reading a source text that is not composed of human words); the work of the French philosopher Baptiste Morizot; and the U.S. novelist Richard Powers. The task at hand is to interpret the filaments that connect humans and a more-than-human world and to help humans find cultural understanding and meaning beyond ontological isolation.
This article brings the emerging ecohumanistic idea of ‘phytopoetics’ into dialogue with the established scientific concept of the ‘phytosphere’ to understand poetry concerning human-flora interdependencies. Developing a phytospheric framework, I analyse poetry of the root-soil interface (rhizosphere), leaves (phyllosphere) and plants’ interior domain (endosphere). Countering a view of flora as passive, phytospherically contoured poetry foregrounds the agencies of plants within their multifaceted spheres of relation. I ground the article’s theoretical assertions in an examination of the rhizospheric poetics of Louise Glück and Brenda Hillman; phyllosperic poetics of Ted Hughes and Kathy Jetn̄il-Kijiner; and endospheric poetics of Michael McClure and the Microcosms project. In addition to its ecological function, the phytosphere is a nexus of language propagation and catalyst of identification with vegetal life. Shaped by phytospheric delineations, contemporary phytopoems particularise plants, liberating vegetal life from the backdrop of consciousness and enabling the human to be called by plants in their own voices.
In this paper, we explore Bahnar perspectives on the agency of plants and forest, and human–forest relations in Vietnam. The Bahnar are among Vietnam's 54 recognized ethnic minority peoples ¹ , many of whom live in proximity to the forest, gather its resources, and regard it as a spiritual abode in their cosmology. The Bahnar (Ba Na) people who inhabit the Central Highlands and are the main focus of this article have traditionally relied on the forest for subsistence, practising swidden cultivation, hunting birds and mammals, and gathering plants. Their forest knowledge is transmitted primarily orally; through the lexicon, everyday discourses, stories, and songs. It is acquired through participation in forest-related activities and informal learning of arts such as vernacular architecture, basketry, canoe-building, and textiles. The Bahnar see spirits in things in nature with which they have a connection or routine interactions (stones, streams, and trees) but not in everything. The Bahnar spiritual connection with the forest also guides their husbandry of increasingly scarce forest resources, such as rattan used in basketry, and large trees needed to make canoes. Certain plants and trees are protected by taboos, and certain parts of the forest are considered sacred, inhabited by gods and spirits, and not to be touched. Forests possess animacy for the Bahnar in that they are sensitive and responsive to a wide range of human behaviours, and must be treated with respect and care. This human–forest–spirit relationship is the primary lens through which the Bahnar perceive nature, and guides their daily interactions with it.
The term “fungal internet,” coined by Dr. Suzanne Simard and popularized by Dr. Paul Stamets, describes the intricate networks of mycorrhizal fungi connecting trees and facilitating communication and resource exchange in forest ecosystems. These “wood wide web” networks enable nutrient transfer, chemical signaling, and disease resistance among trees, illustrating the profound interconnectedness and complexity of forest ecosystems. Highlighting the sophisticated interactions between fungi and plants, this concept underscores the vital role of fungal networks in maintaining ecosystem health and resilience. Furthermore, in this chapter, the comprehension has been made more pragmatic through case studies on fungal internet. Thus, exploration and research on the functions of fungal internet is crucial for ecological management, conservation strategies, and enhancing pollution remediation efforts by leveraging fungi’s ability to improve soil health and plant resilience.
This study surveys the area of East Brook Farm, Walton, NY, for its macrofungi biodiversity in seven site locations
over a five week period from July – August 2021. Macrofungi specimens were collected, photographed, described, and dehydrated
for preservation in herbarium archives stored at Binghamton University. A total of 41 species were collected and described. Species
descriptions, location details, and phylogenetic information are provided in this survey. The importance of citizen science and
collaborative surveying is also discussed
Indian tribes in the United States manage more land than the National Park Service and have a strong record of effective conservation and wildlife stewardship. Several studies have shown that Indigenous-managed lands have a higher biodiversity than other areas, including conservation lands managed by other entities. Despite these successes, tribes have had to fight hard to maintain the recognition of their inherent sovereignty—a status enshrined in the US Constitution and upheld by numerous Supreme Court cases. In this chapter, we will briefly review the history of tribes’ fight for the recognition of sovereignty over land, water, and wildlife; discuss the ramifications of tribal sovereignty and the trust responsibility of the United States as it relates to tribal land and wildlife management; offer suggestions for the proactive coproduction of biodiversity research; and describe how innovative tribal wildlife management projects are reshaping the dialog over land stewardship in North America.
Holobiomes are functional ecological units composed of various species of microbes that are associated with plants. The relationship between plants and microbes ranges from the existence of microbes on rhizoplane/rhizosphere to endophytes (microbes live between plant cells) to endosymbiosis of microbes in plants. In short, some microbes are associated with plant roots, while others are free living, and they directly or indirectly support plant development. Root exudates act as chemical signals that help the microbes to colonize and grow in the rhizosphere. Plant roots release various organic compounds (carbohydrates, fatty acids, amino acids, sterols, amides, etc.) that act as a source of energy for microbes, and in turn, they convert the nutrient into readily available forms for plants. They fix the atmospheric nitrogen and improve soil fertility. They synthesize phytohormones that act as growth promoters and proliferate plants above and below ground parts. They also modulate the synthesis of phytohormones in plants as they have an impact on a wide array of signaling and metabolic network in plants. So, they not only control the growth but also activate stress-related mechanisms. They perform the function of biocontrol by restricting the energy source for pathogens or by secreting antibiotics in the soil.
It is crucial to achieve economic and ecological sustainability in the production of plantation crops in view of their importance to support the livelihood of millions of farmers and agro-industrial entrepreneurs by supplying food, fiber, and industrial raw materials. Plantations are developed by clearing forests, and these perennial crops are confined to the same piece of land for decades. Due to the practice of unsustainable agronomic practices and enhanced influence of climate change on crops in recent years, the production system of plantation crops is confronted with several serious challenges. As soils influence agroecosystem productivity, new directions in soil health management based on ecological principles are required to attain sustainable intensification in plantations. The new paradigms in soil health management and crop nutrition in plantation crops need to be based on remediation, maintenance, and enhancement of soil health. Recent research efforts did result in the development of several low cost, simple, and viable technologies to enhance soil health and plantation ecosystem properties capable of achieving sustainability in the plantations. Management strategies for soil carbon sequestration by enhancing above-ground diversity and proper recycling of lignin-rich biomass have been shown to enhance below-ground biodiversity and together, these practices will contribute to achieve resilience in plantation farming systems. A holistic approach in soil health management in an agroecosystem mode, using integrated nutrient sources, harnessing the potential of biodiversity and carbon sequestration by recycling lignocellulosic plantation biomass will not only help to restore the degraded soils but also will enable to achieve sustainability in plantation crops by enhancing resilience of farming systems to extreme climatic events.
Elif Shafak's 2021 novel The Island of Missing Trees describes fictional events that occur on the real island of Cyprus during the war between the Greek and the Turkish inhabitants of the island. This story is told from multiple points of view at various points in time in both Cyprus and London, where the characters move to and live following the events of the war and their families’ disagreements with their relationship. What is unique about Shafak's storytelling is her use of a fig tree as a primary narrator of events. While the use of non-human narrators is not a new strategy, most of these occurrences involve animal speakers rather than plants or objects. In delivering a fiction narrative from the point of view of a fig tree, Elif Shafak's The Island of Missing Trees introduces readers to multispecies encounters by providing an example of how arboreal figures communicate and experience history alongside humans in an anthropocentric world, and further encourages prosocial behavior between human and non-human species. Based on Shafak's novel, theories of attentiveness and slow-violence, and studies on the effect of non-human narrators on readers, including these "non-living" narrators in widely accessible pieces of fiction not only informs audiences of the multispecies encounters that occur in everyday life, but also opens more avenues of multispecies conservation.
Biofertilizers, such as arbuscular mycorrhiza fungi and phosphate-solubilizing bacteria (PSB), have been reported to enhance plant growth under water stress conditions. This study aimed to investigate the effect of different biofertilizers on potato photosynthesis and growth under water deficit stress. The experiment was conducted over two crop years (2019 and 2020) using a randomized complete block design with three replications. Four irrigation intervals (70, 90, 110 and 130 mm of cumulative evaporation) and six biofertilizer treatments (PSB, Funneliformis mosseae [FM], Rhizoglomus fasciculatum [RF], PSB + FM, PSB + RF and no use) were applied. Severe moisture stress (130 mm evaporation) compared to no stress (70 mm evaporation) increased substomatal carbon dioxide concentration. The application of biofertilizers improved tuber yield under severe moisture stress, with FM showing the highest increase (62.9%), followed by RF (59.8%) and PSB (48.4%). The use of PSB along with mycorrhizae led to a significant decrease in mycorrhizal colonization percentage at all irrigation levels. The highest percentage of colonization and net photosynthesis was obtained from the application of both mycorrhizal species under irrigation conditions after 70 mm of evaporation. The application of PSB alone resulted in a 14.6% increase in the transpiration rate, additionally, the use of mycorrhiza led to an 18.7% increase in stomatal conductivity compared to no-biofertilizer. The results suggest that the simultaneous use of PSB and mycorrhizae can be effective in mild moisture stress, but in severe moisture stress, the use of mycorrhizal species alone is more effective.
Concepts like flourishing, well-being, health, and happiness are of increasing interest across many fields, from psychology and medicine to politics and economics. However, these terms are used in diverse and contested ways, which makes it hard to find common ground and understanding. To attempt to help remedy the confusion, this paper offers an overarching conceptual "map" within which these concepts can be situated, thereby providing a common language and framework for their consideration. Moreover, while the overall configuration of this map is conceptually and logically stable, its specific elements are more flexible, particularly in terms of scalable granularity (allowing fine-grained differentiation of internal regions) and epistemological openness (allowing revisions in light of gains in knowledge). As such, the map can be adapted to suit different fields, and updated to accommodate advances in understanding. To that end, we clarify topics of investigation that are still in need of development, providing a roadmap for future research.
Pyrola japonica , an Ericaceae, is a mixotroph growing on forest floors, obtaining carbon (C) from both photosynthetic and root-associated mycorrhizal fungal pathways. The mycorrhizal community structures of the plant are well characterised and are dominated by Russulaceae fungi. However, the mechanism of its C acquisition is not well understood. The aim of this study was to identify mycorrhizal fungal communities that are directly involved in C acquisition. We repeatedly applied a fungicide (Benomyl) solution to soils around P. japonica plants in a broad-leaved forest in central Japan to disturb fungal associations near their roots. After fungicide treatment, P. japonica roots were collected and subjected to next-generation sequencing, focusing on the ITS2 region, to infer taxonomic identities. The leaves and seeds of the plants were analysed for C stable isotope ratios. The rate of mycorrhizal formations and α-diversity did not significantly change by the fungicide treatments. Irrespective of the treatments, more than 80% of the detected mycorrhizal taxa were assigned to Russulaceae. For δ ¹³ C values, leaves and seeds in the fungicide were significantly lower than those of the other treatments. Our results suggest that the fungicide did not affect mycorrhizal communities, but likely disturbed mycorrhizal fungal pathways via extraradical hyphae, which may result in a relative increase in its own photosynthetic pathways.
This white paper lays out a vision of research and development in the field of artificial intelligence for the next decade (and beyond). Its denouement is a cyber-physical ecosystem of natural and synthetic sense-making, in which humans are integral participants—what we call “shared intelligence.” This vision is premised on active inference, a formulation of adaptive behavior that can be read as a physics of intelligence, and which inherits from the physics of self-organization. In this context, we understand intelligence as the capacity to accumulate evidence for a generative model of one’s sensed world—also known as self-evidencing. Formally, this corresponds to maximizing (Bayesian) model evidence, via belief updating over several scales, that is, inference, learning, and model selection. Operationally, this self-evidencing can be realized via (variational) message passing or belief propagation on a factor graph. Crucially, active inference foregrounds an existential imperative of intelligent systems; namely, curiosity or the resolution of uncertainty. This same imperative underwrites belief sharing in ensembles of agents, in which certain aspects (i.e., factors) of each agent’s generative world model provide a common ground or frame of reference. Active inference plays a foundational role in this ecology of belief sharing—leading to a formal account of collective intelligence that rests on shared narratives and goals. We also consider the kinds of communication protocols that must be developed to enable such an ecosystem of intelligences and motivate the development of a shared hyper-spatial modeling language and transaction protocol, as a first—and key—step towards such an ecology.
The word “optimization” describes the process of selecting one of multiple viable options while according to a finite set of constraints. The optimization theory, which teaches how to define and achieve an optimal, is an example of how the human yearning for perfection finds expression. Through optimization, system performance is sought to be improved in the direction of the optimal point or points (El-Ela et al. in Modern optimization techniques for smart grids, Department of Electromechanics Engineering, Springer International Publishing, Cham, 2023 [1]). According to one stress theoretical aspect or one stress practical aspect, optimization can be defined as a component of applied or numerical mathematics or a method for system design by computer (Tyagi M et al. in Optimization methods in engineering. Lecture notes on multidisciplinary industrial engineering. Springer Singapore, Singapore, 2021 [2]). An optimization problem’s analytical solution (Yakimov in Analytical solution methods for boundary value problems, 1st edn. Nikki Levy, London, UK, 2016 [3]) depends on the shape of the criterion and constraint functions. The unconstrained optimization issue is the easiest scenario to take into account, since there are no restrictions placed on the decision variable in such a situation, different calculus can be utilized to analyze it. Another relatively simple form of the general optimization problem is the case in which all the constraints of the problem can be expressed as equality relationships.
An enduring aim of research in the psychological and brain sciences is to understand the nature of individual differences in human intelligence, examining the stunning breadth and diversity of intellectual abilities and the remarkable neurobiological mechanisms from which they arise. In this Opinion article, we survey recent neuroscience evidence to elucidate how general intelligence (g) emerges from individual differences in the network architecture of the human brain. The reviewed findings motivate new insights about how network topology and dynamics account for individual differences in g, represented by the Network Neuroscience Theory. According to this framework, g emerges from the small-world topology of brain networks and the dynamic reorganization of its community structure in the service of system-wide flexibility and adaptation.
Sound and its use in communication have significantly contributed to shaping the ecology, evolution, behavior, and ultimately
the success of many animal species. Yet, the ability to use sound is not a prerogative of animals. Plants may also use sound,
but we have been unable to effectively research what the ecological and evolutionary implications might be in a plant’s life.
Why should plants emit and receive sound and is there information contained in those sounds? I hypothesize that it would be
particularly advantageous for plants to learn about the surrounding environment using sound, as acoustic signals propagate
rapidly and with minimal energetic or fitness costs. In fact, both emission and detection of sound may have adaptive value
in plants by affecting responses in other organisms, plants, and animals alike. The systematic exploration of the functional,
ecological, and evolutionary significance of sound in the life of plants is expected to prompt a reinterpretation of our understanding
of these organisms and galvanize the emergence of novel concepts and perspectives on their communicative complexity.
Processes governing the fixation, partitioning, and mineralization of carbon in soils are under increasing scrutiny as we develop a more comprehensive understanding of global carbon cycling. Here we examined fixation by Douglas‐fir seedlings and transfer to associated ectomycorrhizal fungi, soil microbes, and full‐sibling or nonsibling neighbouring seedlings.
Stable isotope probing with 99% ¹³ C‐ CO 2 was applied to trace ¹³ C‐labelled photosynthate throughout plants, fungi, and soil microbes in an experiment designed to assess the effect of relatedness on ¹³ C transfer between plant pairs. The fixation and transfer of the ¹³ C label to plant, fungal, and soil microbial tissue was examined in biomass and phospholipid fatty acids.
After a 6 d chase period, c . 26.8% of the ¹³ C remaining in the system was translocated below ground. Enrichment was proportionally greatest in ectomycorrhizal biomass. The presence of mesh barriers (0.5 or 35 μm) between seedlings did not restrict ¹³ C transfer.
Fungi were the primary recipients of ¹³ C‐labelled photosynthate throughout the system, representing 60–70% of total ¹³ C‐enriched phospholipids. Full‐sibling pairs exhibited significantly greater ¹³ C transfer to recipient roots in two of four Douglas‐fir families, representing three‐ and fourfold increases (+ c . 4 μg excess ¹³ C) compared with nonsibling pairs. The existence of a root/mycorrhizal exudation–hyphal uptake pathway was supported.
The establishment of common mycelial networks by mycorrhizal fungi shared between host plants depends on the ability of neighboring plants to enter into mycorrhizal associations with compatible fungal species. Such compatibility is governed by the potential mycorrhiza specificities of the symbionts. Mycorrhiza specificities exist along a continuum from low specificity (association with multiple partners) to high specificity (association with one or few partners). Although the ability of symbionts to form mycorrhizas may be largely governed by host-fungus gene interactions as influenced by co-evolutionary events, mycorrhizal associations in natural ecosystems can also be influenced by environmental factors (e.g. soil) and biological factors (e.g. different neighboring host species), phenomena referred to as “ecological specificity.” For example, in natural settings, mycorrhizal fungi often express “host preference” wherein fungi may be more common on a particular host in mixed-host settings than would be expected by random species assemblage within the fungal and plant communities. Mycorrhiza specificity phenomena significantly influence plant community dynamics, particularly plant succession. Early seral plants can positively affect the establishment of later-seral plants by maintaining commonly shared mycorrhizal fungi, and thus affecting the function of common mycelial networks over time. Such knowledge provides guidance for ecosystem managers to maintain “legacy” early -seral plants that benefit later-seral plants via shared mycorrhizal fungus species. Understanding specificity phenomena is also crucial for predicting the successful migration of plants and compatible mycorrhizal fungi during climate change. We review mycorrhiza specificity terminology and types of specificity phenomena, and suggest use of common terms to provide consistency in addressing this research topic. We also provide extensive examples from diverse ecosystems on the ability (or inability) of neighboring plants to develop common mycelial networks.
Almost all higher organisms, including plants, insects, and mammals, are colonized by complex microbial communities and harbor a microbiome. Emerging studies with plants reveal that these microbiomes are structured and form complex, interconnected microbial networks. Within these networks, different taxa have different roles, and keystone species have been identified that could be crucial for plant health and ecosystem functioning. A new paper in this issue of PLOS Biology by Agler et al. highlights the presence of microbial hubs in these networks that may act as mediators between the plant and its microbiome. A next major frontier is now to link microbiome composition to function. In order to do this, we present a number of hypothetical examples of how microbiome diversity and function potentially influence host performance.
Language is often considered a key feature of being human, and human linguistic behavior has been adopted as the universal template for studying the nature of language and its evolution. Yet it is not always clear what ''language'' actually is, and the lack of definition calls into question the notion that human language is unique because it has no equivalent in any nonhuman species. We ask whether the use of language is truly an activity, a form of behavior, which makes us so unique and unlike other species. We tackle this question by examining language from an ecological perspective and then considering language from a wider biological viewpoint, one that enables us to explore language as a meaning-making activity at the core of every form of life, including plants. We examine how innovative philosophical thinking and scientific research similarly call into question the current limits of language in describing the botanical world and human-plant dynamics. By providing an overview of the most recent empirically grounded advances in our understanding of the ''language'' of others, and particularly plants, we propose that the nonhuman world is not lacking in language the way we think it is. Ultimately, the overall aim is to invite the emergence of a new truly interdisciplinary dialogue to inspire novel approaches in further philosophical and scientific investigations, where language and its power are re-focused toward conceptualizing a more integrated perception of the world.
Adaptive behavior of plants, including rapid changes in physiology, gene regulation and defense response can be altered when linked to neighbouring plants by a mycorrhizal network. Mechanisms underlying the behavioral changes include mycorrhizal fungal colonization by the mycorrhizal network or interplant communication via transfer of nutrients, defense signals or allelochemicals. We focus this review on our new findings in ectomycorrhizal ecosystems, but also review recent advances in arbuscular mycorrhizal systems. We have found that the behavioral changes in ectomycorrhizal plants can depend on environmental cues, the identity of the plant neighbor and the characteristics of the mycorrhizal network. The hierarchical integration of this phenomenon with other biological networks at broader scales in forest ecosystems, and the consequences we have observed when it is interrupted, indicates that underground 'tree talk' is a foundational process in the complex adaptive nature of forest ecosystems.
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Arbuscular mycorrhizal (AM) fungi are mutualistic symbionts living in the roots of 80% of land plant species, and developing extensive, belowground extraradical hyphae fundamental for the uptake of soil nutrients and their transfer to host plants. Since AM fungi have a wide host range, they are able to colonize and interconnect contiguous plants by means of hyphae extending from one root system to another. Such hyphae may fuse due to the widespread occurrence of anastomoses, whose formation depends on a highly regulated mechanism of self recognition. Here, we examine evidences of self recognition and nonself incompatibility in hyphal networks formed by AM fungi and discuss recent results showing that the root systems of plants belonging to different species, genera and families may be connected by means of anastomosis formation between extraradical mycorrhizal networks, which can create indefinitely large numbers of belowground fungal linkages within plant communities.
Extensive regions of interior Douglas-fir (Pseudotsuga menziesii var. glauca, IDF) forests in North America are being damaged by drought and western spruce budworm (Choristoneura occidentalis). This damage is resulting from warmer and drier summers associated with climate change. To test whether defoliated IDF can directly transfer resources to ponderosa pine (Pinus ponderosae) regenerating nearby, thus aiding in forest recovery, we examined photosynthetic carbon transfer and defense enzyme response. We grew pairs of ectomycorrhizal IDF 'donor' and ponderosa pine 'receiver' seedlings in pots and isolated transfer pathways by comparing 35 μm, 0.5 μm and no mesh treatments; we then stressed IDF donors either through manual defoliation or infestation by the budworm. We found that manual defoliation of IDF donors led to transfer of photosynthetic carbon to neighboring receivers through mycorrhizal networks, but not through soil or root pathways. Both manual and insect defoliation of donors led to increased activity of peroxidase, polyphenol oxidase and superoxide dismutase in the ponderosa pine receivers, via a mechanism primarily dependent on the mycorrhizal network. These findings indicate that IDF can transfer resources and stress signals to interspecific neighbors, suggesting ectomycorrhizal networks can serve as agents of interspecific communication facilitating recovery and succession of forests after disturbance.
From the phytocentric perspective, a mycorrhizal network ( MN ) is formed when the roots of two or more plants are colonized by the same fungal genet. MN s can be modelled as interaction networks with plants as nodes and fungal genets as links. The potential effects of MN s on facilitation or competition between plants are increasingly recognized, but their network topologies remain largely unknown. This information is needed to understand the ecological significance of MN functional traits.
The objectives of this study were to describe the interaction network topologies of MN s formed between two ectomycorrhizal fungal species, Rhizopogon vesiculosus and R. vinicolor , and interior Douglas‐fir trees at the forest stand scale, identify factors leading to this structure and to contrast MN structures between forest plots with xeric versus mesic soil moisture regimes.
Tuberculate mycorrhizas were sampled in six 10 × 10 m plots with either xeric or mesic soil moisture regimes. Microsatellite DNA markers were used to identify tree and fungal genotypes isolated from mycorrhizas and for comparison with reference tree boles above‐ground.
In all six plots, trees and fungal genets were highly interconnected. Size asymmetries between different tree cohorts led to non‐random MN topologies, while differences in size and connectivity between Rhizopogon species‐specific subnetwork components contributed towards MN nestedness. Large mature trees acted as network hubs with a significantly higher node degree compared to smaller trees. MN s representing trees linked by R. vinicolor genets were mostly nested within larger, more highly connected R. vesiculosus ‐linked MN s.
Attributes of network nodes showed that hub trees were more important to MN topology on xeric than mesic sites, but the emergent structures of MN s were similar in the two soil moisture regimes.
Synthesis . This study suggests MN s formed between interior Douglas‐fir trees and R. vesiculosus and R. vinicolor genets are resilient to the random loss of participants, and to soil water stress, but may be susceptible to the loss of large trees or fungal genets. Our results regarding the topology of MN s contribute to the understanding of forest stand dynamics and the resilience of forests to stress or disturbance.
The most common system responses attributed to microfloral grazers (protozoa, nematodes, microarthropods) in the literature are increased plant growth, increased N uptake by plants, decreased or increased bacterial populations, increased CO"2 evolution, increased N and P mineralization, and increased substrate utilization. Based on this evidence in the literature, a conceptual model was proposed in which microfloral grazers were considered as separate state variables. To help evaluate the model, the effects of microbivorous nematodes on microbial growth, nutrient cycling, plant growth, and nutrient uptake were examined with reference to activities within and outside of the rhizosphere. Blue grama grass (Bouteloua gracilis) was grown in gnotobiotic microcosms containing sandy loam soil low in inorganic N, with or without chitin amendments as a source of organic N. The soil was inoculated with bacteria (Pseudomonas paucimobilis or P. stutzeri) or fungus (Fusarium oxysporum), with half the bacterial microcosms inoculated with bacterial-feeding nematodes (Pelodera sp. or Acrobeloides sp.) and half the fungal microcosms inoculated with fungal-feeding nematodes (Aphelenchus avenae). Similar results were obtained from both the unamended and the chitin-amended experiments. Bacteria, fungi, and both trophic groups of nematodes were more abundant in the rhizosphere than in nonrhizosphere soil. All treatments containing nematodes and bacteria had higher bacterial densities than similar treatments without nematodes. Plants growing in soil with bacteria and bacterial-feeding nematodes grew faster and initially took up more N than plants in soil with only bacteria, because of increased N mineralization by bacteria, NH"4^+-N excretion by nematodes, and greater initial exploitation of soil by plant roots. Addition of fungal-feeding nematodes did not increase plant growth or N uptake because these nematodes excreted less NH"4^+-N than did bacterial-feeding nematode populations and because the N mineralized by the fungus alone was sufficient for plant growth. Total shoot P was significantly greater in treatments with fungus or Pelodera sp. than in the sterile plant control or treatments with plants plus Pseudomonas stutzeri until the end of the experiment. The additional mineralization that occurs due to the activities of microbial grazers may be significant for increasing plant growth only when mineralization by microflora alone is insufficient to meet the plants' requirements. However, while the advantage of increased N mineralization by microbial grazers may be short-term, it may occur in many ecosystems in those short periods of ideal conditions when plant growth can occur. Thus, these results support other claims in the literature that microbial grazers may perform important regulatory functions at critical times in the growth of plants.
I. II. III. IV. V. VI. References SUMMARY: For survival, plants have to efficiently adjust their phenotype to environmental challenges, finely coordinating their responses to balance growth and defence. Such phenotypic plasticity can be modulated by their associated microbiota. The widespread mycorrhizal symbioses modify plant responses to external stimuli, generally improving the resilience of the symbiotic system to environmental stresses. Phytohormones, central regulators of plant development and immunity, are instrumental in orchestrating plant responses to the fluctuating environment, but also in the regulation of mycorrhizal symbioses. Exciting advances in the molecular regulation of phytohormone signalling are providing mechanistic insights into how plants coordinate their responses to environmental cues and mycorrhizal functioning. Here, we summarize how these mechanisms permit the fine-tuning of the symbiosis according to the ever-changing environment.
© 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.
It is increasingly recognised that plants are highly sensitive organisms that perceive, assess, learn, remember, resolve problems, make decisions and communicate with each other by actively acquiring information from their environment. However, the fact that many of the sophisticated behaviours plants exhibit reveal cognitive competences, which are generally attributed to humans and some non-human animals has remained unappreciated. Here, I will outline the theoretical barriers that have precluded the opportunity to experimentally test such behavioural/cognitive phenomena in plants. I will then suggest concrete alternative approaches to cognition by highlighting how (1) the environment offers a multitude of opportunities for decision-making and action and makes behaviours possible, rather than causing them; (2) perception in itself is action in the form of a continuous flow of information; (3) all living organisms viewed within this context become agents endowed with autonomy rather than objects in a mechanistically conceived world. These viewpoints, combined with recent evidence, may contribute to move the entire field towards an integrated study of cognitive biology.
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Plant-mycorrhizal fungal interactions are ubiquitous in forest ecosystems. While ectomycorrhizal plants and their fungi generally dominate temperate forests, arbuscular mycorrhizal symbiosis is common in the tropics. In subtropical regions, however, ectomycorrhizal and arbuscular mycorrhizal plants co-occur at comparable abundances in single forests, presumably generating complex community structures of root-associated fungi. To reveal root-associated fungal community structure in a mixed forest of ectomycorrhizal and arbuscular mycorrhizal plants, we conducted a massively-parallel pyrosequencing analysis, targeting fungi in the roots of 36 plant species that co-occur in a subtropical forest. In total, 580 fungal operational taxonomic units were detected, of which 132 and 58 were probably ectomycorrhizal and arbuscular mycorrhizal, respectively. As expected, the composition of fungal symbionts differed between fagaceous (ectomycorrhizal) and non-fagaceous (possibly arbuscular mycorrhizal) plants. However, non-fagaceous plants were associated with not only arbuscular mycorrhizal fungi but also several clades of ectomycorrhizal (e.g., Russula) and root-endophytic ascomycete fungi. Many of the ectomycorrhizal and root-endophytic fungi were detected from both fagaceous and non-fagaceous plants in the community. Interestingly, ectomycorrhizal and arbuscular mycorrhizal fungi were concurrently detected from tiny root fragments of non-fagaceous plants. The plant-fungal associations in the forest were spatially structured, and non-fagaceous plant roots hosted ectomycorrhizal fungi more often in the proximity of ectomycorrhizal plant roots. Overall, this study suggests that belowground plant-fungal symbiosis in subtropical forests is complex in that it includes "non-typical" plant-fungal combinations (e.g., ectomycorrhizal fungi on possibly arbuscular mycorrhizal plants) that do not fall within the conventional classification of mycorrhizal symbioses, and in that associations with multiple functional (or phylogenetic) groups of fungi are ubiquitous among plants. Moreover, ectomycorrhizal fungal symbionts of fagaceous plants may "invade" the roots of neighboring non-fagaceous plants, potentially influencing the interactions between non-fagaceous plants and their arbuscular-mycorrhizal fungal symbionts at a fine spatial scale.
Volatile communication between plants causing enhanced defence has been controversial. Early studies were not replicated, and influential reviews questioned the validity of the phenomenon. We collected 48 well-replicated studies and found overall support for the hypothesis that resistance increased for individuals with damaged neighbours. Laboratory or greenhouse studies and those conducted on agricultural crops showed stronger induced resistance than field studies on undomesticated species, presumably because other variation had been reduced. A cumulative analysis revealed that early, non-replicated studies were more variable and showed less evidence for communication. Effects of habitat and plant growth form were undetectable. In most cases, the mechanisms of resistance and alternative hypotheses were not considered. There was no indication that some response variables were more likely to produce large effects. These results indicate that plants of diverse taxonomic affinities and ecological conditions become more resistant to herbivores when exposed to volatiles from damaged neighbours.
Mycelial fungi grow as indeterminate adaptive networks that have to forage for scarce resources in a patchy and unpredictable environment under constant onslaught from mycophagous animals. Development of contrast-independent network extraction algorithms has dramatically improved our ability to characterise these dynamic macroscopic networks and promises to bridge the gap between experiments in realistic experimental microcosms and graph-theoretic network analysis, greatly facilitating quantitative description of their complex behaviour. Furthermore, using digitised networks as inputs, empirically-based minimal biophysical mass-flow models already provide a high degree of explanation for patterns of long-distance radiolabel movement, and hint at global control mechanisms emerging naturally as a consequence of the intrinsic hydraulic connectivity. Network resilience is also critical to survival and can be explored both in silico by removing links in the digitised networks according to particular rules, or in vivo by allowing different mycophagous invertebrates to graze on the networks. Survival depends on both the intrinsic architecture adopted by each species and the ability to reconnect following damage. It is hoped that a comparative approach may yield useful insights into not just fungal ecology, but also biologically inspired rules governing the combinatorial trade-off between cost, transport efficiency, resilience and control complexity for self-organised adaptive networks in other domains.
Ectomycorrhizal (EM) networks are hypothesized to facilitate regeneration under abiotic stress. We tested the role of networks in interactions between P. menziesii var. glauca trees and conspecific seedlings along a climatic moisture gradient to: (1) determine the effects of climatic factors on network facilitation of Pseudotsuga menziesii (Mirb.) Franco var. glauca (Mayr) seedling establishment, (2) infer the changing importance of P. menziesii var. glauca parent trees in conspecific regeneration with climate, and (3) parse the competitive from facilitative effects of P. menziesii var. glauca trees on seedlings. When drought conditions were greatest, seedling growth increased when seedlings could form a network with trees in the absence of root competition, but was reduced when unable to form a network. Survival was maximized when seedlings were able to form a network in the absence of root competition. Seedling stem natural abundance δ13C increased with drought due to increasing water use efficiency, but was unaffected by distance from tree or network potential. We conclude that P. menziesii seedlings may benefit from the presence of established P. menziesii trees when growing under climatic drought, but that this benefit is contingent upon the establishment of an EM network prior to the onset of summer drought. These results suggest that networks are an important mechanism for EM plants establishing in a pattern consistent with the stress-gradient hypothesis, and therefore the importance of EM networks to facilitation in regeneration of EM trees is expected to increase with drought.
In the course of plant evolution, there is an obvious trend toward an increased complexity of plant bodies, as well as an increased sophistication of plant behavior and communication. Phenotypic plasticity of plants is based on the polar auxin transport machinery that is directly linked with plant sensory systems impinging on plant behavior and adaptive responses. Similar to the emergence and evolution of eukaryotic cells, evolution of land plants was also shaped and driven by infective and symbiotic microorganisms. These microorganisms are the driving force behind the evolution of plant synapses and other neuronal aspects of higher plants; this is especially pronounced in the root apices. Plant synapses allow synaptic cell–cell communication and coordination in plants, as well as sensory-motor integration in root apices searching for water and mineral nutrition. These neuronal aspects of higher plants are closely linked with their unique ability to adapt to environmental changes.
Mycorrhizal networks, defined as a common mycorrhizal mycelium linking the roots of at least two plants, occur in all major terrestrial ecosystems. This review discusses the recent progress and challenges in our understanding of the characteristics, functions, ecology and models of mycorrhizal networks, with the goal of encouraging future research to improve our understanding of their ecology, adaptability and evolution. We focus on four themes in the recent literature: (1) the physical, physiological and molecular evidence for the existence of mycorrhizal networks, as well as the genetic characteristics and topology of networks in natural ecosystems; (2) the types, amounts and mechanisms of interplant material transfer (including carbon, nutrients, water, defence signals and allelochemicals) in autotrophic, mycoheterotrophic or partial mycoheterotrophic plants, with particular focus on carbon transfer; (3) the influence of mycorrhizal networks on plant establishment, survival and growth, and the implications for community diversity or stability in response to environmental stress; and (4) insights into emerging methods for modelling the spatial configuration and temporal dynamics of mycorrhizal networks, including the inclusion of mycorrhizal networks in conceptual models of complex adaptive systems. We suggest that mycorrhizal networks are fundamental agents of complex adaptive systems (ecosystems) because they provide avenues for feedbacks and cross-scale interactions that lead to self-organization and emergent properties in ecosystems. We have found that research in the genetics of mycorrhizal networks has accelerated rapidly in the past 5 y with increasing resolution and throughput of molecular tools, but there still remains a large gap between understanding genes and understanding the physiology, ecology and evolution of mycorrhizal networks in our changing environment. There is now enormous and exciting potential for mycorrhizal researchers to address these higher level questions and thus inform ecosystem and evolutionary research more broadly.
Extraradical mycelia of mycorrhizal fungi are normally the "hidden half" of the symbiosis, but they are powerful underground influences upon biogeochemical cycling, the composition of plant communities, and agroecosystem functioning. Mycorrhizal mycelial networks are the most dynamic and functionally diverse components of the symbiosis, and recent estimates suggest they are empowered by receiving as much as 10% or more of the net photosynthate of their host plants. They often constitute 20%-30% of total soil microbial biomass yet are undetected by standard measures of biomass used by soil scientists and agromomists. Mycorrhizal mycelia provide extensive path- ways for carbon and nutrient fluxes through soil, often exceeding tens of metres per gram of soil. We consider the amounts of photosynthate "power" allocated to these mycelial networks and how this is used in fungal respiration, bio- mass, and growth and in influencing soil, plant, and ecosystem processes. The costs and functional "benefits" to plants linking to these networks are fungal specific and, because of variations in physiology and host specificity, are not shared equally; some plants even depend exclusively on these networks for carbon. We briefly assess the potential con- tribution of extraradical mycorrhizal mycelium to sustainable agriculture and maintenance of biodiversity and highlight technologies that promise new vistas and improved fine-scale resolution of the dynamic spatial and temporal function- ing of these networks in soil.
Understanding ectomycorrhizal fungal (EMF) community structure is limited by a lack of taxonomic resolution and autecological information. Rhizopogon vesiculosus and Rhizopogon vinicolor (Basidiomycota) are morphologically and genetically related species. They are dominant members of interior Douglas-fir (Pseudotsuga menziesii var. glauca) EMF communities, but mechanisms leading to their coexistence are unknown. We investigated the microsite associations and foraging strategy of individual R. vesiculosus and R. vinicolor genets. Mycelia spatial patterns, pervasiveness and root colonization patterns of fungal genets were compared between Rhizopogon species and between xeric and mesic soil moisture regimes. Rhizopogon spp. mycelia were systematically excavated from the soil and identified using microsatellite DNA markers. Rhizopogon vesiculosus mycelia occurred at greater depth, were more spatially pervasive, and colonized more tree roots than R. vinicolor mycelia. Both species were frequently encountered in organic layers and between the interface of organic and mineral horizons. They were particularly abundant within microsites associated with soil moisture retention. The occurrence of R. vesiculosus shifted in the presence of R. vinicolor towards mineral soil horizons, where R. vinicolor was mostly absent. This suggests that competition and foraging strategy may contribute towards the vertical partitioning observed between these species. Rhizopogon vesiculosus and R. vinicolor mycelia systems occurred at greater mean depths and were more pervasive in mesic plots compared with xeric plots. The spatial continuity and number of trees colonized by genets of each species did not significantly differ between soil moisture regimes.
The arbuscular mycorrhizal (AM) symbiosis is responsible for huge fluxes of photosynthetically fixed carbon from plants to the soil. Carbon is transferred from the plant to the fungus as hexose, but the main form of carbon stored by the mycobiont at all stages of its life cycle is triacylglycerol. Previous isotopic labeling experiments showed that the fungus exports this storage lipid from the intraradical mycelium (IRM) to the extraradical mycelium (ERM). Here, in vivo multiphoton microscopy was used to observe the movement of lipid bodies through the fungal colony and to determine their sizes, distribution, and velocities. The distribution of lipid bodies along fungal hyphae suggests that they are progressively consumed as they move toward growing tips. We report the isolation and measurements of expression of an AM fungal expressed sequence tag that encodes a putative acyl-coenzyme A dehydrogenase; its deduced amino acid sequence suggests that it may function in the anabolic flux of carbon from lipid to carbohydrate. Time-lapse image sequences show lipid bodies moving in both directions along hyphae and nuclear magnetic resonance analysis of labeling patterns after supplying ¹³C-labeled glycerol to either extraradical hyphae or colonized roots shows that there is indeed significant bidirectional translocation between IRM and ERM. We conclude that large amounts of lipid are translocated within the AM fungal colony and that, whereas net movement is from the IRM to the ERM, there is also substantial recirculation throughout the fungus.
The roots of most plants are colonized by symbiotic fungi to form mycorrhiza, which play a critical role in the capture of nutrients from the soil and therefore in plant nutrition. Mycorrhizal Symbiosis is recognized as the definitive work in this area. Since the last edition was published there have been major advances in the field, particularly in the area of molecular biology, and the new edition has been fully revised and updated to incorporate these exciting new developments. . Over 50% new material . Includes expanded color plate section . Covers all aspects of mycorrhiza . Presents new taxonomy . Discusses the impact of proteomics and genomics on research in this area.
We are re-addressing species concepts in the Rhizopogon vinicolor species complex (Boletales, Basidiomycota) using sequence data from the internal-transcribed spacer (ITS) region of the nuclear ribosomal repeat, as well as genotypic data from five microsatellite loci. The R. vinicolor species complex by our definition includes, but is not limited to, collections referred to as R. vinicolor Smith, R. diabolicus Smith, R. ochraceisporus Smith, R. parvulus Smith or R. vesiculosus Smith. Holo- and/or paratype material for the named species is included. Analyses of both ITS sequences and microsatellite loci separate collections of the R. vinicolor species complex into two distinct clades or clusters, suggestive of two biological species that subsequently are referred to as R. vinicolor sensu Kretzer et al and R. vesiculosus sensu Kretzer et al. Choice of the latter names, as well as morphological characters, are discussed.
Terrestrial fungi are commonly studied in the laboratory, growing on artificial media in which nutrients are typically homogeneously distributed and supplied in superabundance, the environment is sterile and microclimate (temperature, moisture, gaseous regime) usually relatively constant. This contrasts with the natural environment, in which: nutrients are often patchily and sparsely distributed or not readily available, because they are locked in recalcitrant material (e.g. lignin); many other organisms are encountered, including other fungi, bacteria and invertebrates; and microclimate is constantly changing, both temporally and spatially. This chapter explores the ways in which fungi cope with environmental heterogeneity. Similar situations are faced by macroorganisms and analogies are drawn. Emphasis is placed on basidiomycetes, not only because they have been studied in most detail, but because of their dominant role as decomposers and mutualistic symbionts (Boddy & Watkinson, 1995; Smith & Read, 1997) and because they are better adapted to respond to environmental heterogeneity over scales ranging from micrometres to many metres than are other fungi. Both saprotrophic and ectomycorrhizal Basidiomycota form extensive mycelial systems in woodland soil and litter, but it is the former that are the focus of this review. Saprotrophic, cord-forming Basidiomycota that ramify at the soil–litter interface, interconnecting disparate litter components, provide most examples. The key feature of these fungi that fits them for growth in environments where resources are heterogeneously distributed is that they are non-resource-unit restricted, i.e. they can grow out of one resource in search of others. © Cambridge University Press 2007 and Cambridge University Press, 2009.
Systems as diverse as genetic networks or the World Wide Web are best described as networks with complex topology. A common property of many large networks is that the vertex connectivities follow a scale-free power-law distribution. This feature was found to be a consequence of two generic mech-anisms: (i) networks expand continuously by the addition of new vertices, and (ii) new vertices attach preferentially to sites that are already well connected. A model based on these two ingredients reproduces the observed stationary scale-free distributions, which indicates that the development of large networks is governed by robust self-organizing phenomena that go beyond the particulars of the individual systems.
Rhizopogon is the largest genus of hypogeous Basidiomycota, with worldwide distribution among Pinaceae. Several Rhizopogon species are important members of ectomycorrhizal (ECM) fungal communities, contributing significantly to sporocarp productivity and ECM dominance. They occur in young and old forest stands alike and in diverse habitats. This ecological amplitude was recognized early in the twentieth century when Rhizopogon species were observed as dominant ECM fungi on Pinus in exotic plantations. Consequently, Rhizopogon has been the focus of considerable application research in forestry. The ease of culturing from sporocarps, manipulation of pure cultures of Rhizopogon and practical use of spore inoculation has made Rhizopogon a model genus to explore morphological, physiological, ecological, and symbiotic mutualisms of ECM. Nearly 200 papers have been published on Rhizopogon taxonomy, host range and specificity, ECM morphology, distribution, ecology, physiology, and applications in forestry.
Dendroctonus ponderosae has killed millions of Pinus contorta in western North America with subsequent effects on stand conditions, including changes in light intensity, needle deposition, and the composition of fungal community mutualists, namely ectomycorrhizal fungi. It is unknown whether these changes in stand conditions will have cascading consequences for the next generation of pine seedlings. To test for transgenerational cascades on pine seedlings, we tested the effects of fungal inoculum origin (beetle-killed or undisturbed stands), light intensity and litter (origin and presence) on seedling secondary chemistry and growth in a glasshouse. We also tracked survival of seedlings over two growing seasons in the same stands from which fungi and litter were collected. Fungal communities differed by inoculum origin. Seedlings grown with fungi collected from beetle-killed stands had lower monoterpene concentrations and fewer monoterpene compounds present compared with seedlings grown with fungi collected from undisturbed stands. Litter affected neither monoterpenes nor seedling growth. Seedling survival in the field was lower in beetle-killed than in undisturbed stands. We demonstrate that stand mortality caused by prior beetle attacks of mature pines have cascading effects on seedling secondary chemistry, growth and survival, probably mediated through effects on below-ground mutualisms.
© 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.
Summary
1. Carbon (C), nutrients and water (H2O) have been known for five decades to flow between plants through ectomycorrhizal (EM) networks. This flux has the potential to affect plant and fungal performance and resource distribution within communities.
2. We asked two questions: 1) What are the pathways and mechanisms for C, nutrient and H2O fluxes between plants through EM networks? 2) What are the magnitude, fate and importance of C, nutrient and H2O transfer among EM plants?
3. Mycorrhizal networks provide a distinct pathway for resource fluxes among plants and mycorrhizal fungi, partitioning them away from other competing soil microbes and plant roots in the soil matrix, and potentially providing a competitive advantage (or disadvantage) for some individuals involved in the network. Carbon and nutrients flow symplastically and apoplastically through mycorrhizal symbionts, hyphae and rhizomorphs along source-sink gradients across the networking mycelia and plant community. Hydraulic redistribution from wetter to drier soil or plant pools can also be facilitated by mycorrhizal networks following water potential gradients.
4. Carbon fluxes through EM networks have been shown to supply 0-10% of autotrophic, up to 85% of partial myco-heterotrophic (MH), and 100% of fully MH plant C. This C supply has been loosely associated with increased survival and growth of autotrophic plants, but shown to be essential for survival of MH plants. Network-mediated nitrogen (N) fluxes between N2-fixing and non-N2-fixing plants have supplied up to 40% of receiver N, and this has been associated with increased plant productivity. Fluxes between non-N2-fixing plants have supplied <5% of receiver N. Hydraulic redistribution involving EM fungi has supplied up to 50% of plant water, and in some cases this has been shown as essential for plant survival, but how much of this water transfers through EM networks remains uncertain. Phosphorus transfer through EM networks has not been adequately demonstrated.
5. Overall, this review chapter shows that resource fluxes though EM networks are sufficiently large in some cases to facilitate plant establishment and growth. Resource fluxes through EM networks may thus serve as a method for interactions and cross-scale feedbacks for development of communities, consistent with complex adaptive system theory. How this may affect ecosystem stability depends on the environment.
Plants recognize their kin and respond to growing with relatives with changes in functional traits. Here, we integrate competition and evolutionary theory to evaluate these changes.
We draw parallels between the definitions and empirical measurement of competitive effect and competitive response from competition theory, and the costs and benefits of altruistic and selfish behaviours from kin selection theory.
Do plants compete less with relatives, as these parallels suggest? While functional traits respond to the presence of relatives or strangers, no study has directly demonstrated that plants are less competitive with siblings.
However, there are empirical challenges in identifying the competitive value of traits that are measured destructively, such as root allocation.
If these challenges can be addressed, kin recognition responses can offer new insights into plant competition.
Common mycorrhizal networks (CMNs) link multiple plants together. We hypothesized that CMNs can serve as an underground conduit for transferring herbivore-induced defence signals. We established CMN between two tomato plants in pots with mycorrhizal fungus Funneliformis mosseae, challenged a 'donor' plant with caterpillar Spodoptera litura, and investigated defence responses and insect resistance in neighbouring CMN-connected 'receiver' plants. After CMN establishment caterpillar infestation on 'donor' plant led to increased insect resistance and activities of putative defensive enzymes, induction of defence-related genes and activation of jasmonate (JA) pathway in the 'receiver' plant. However, use of a JA biosynthesis defective mutant spr2 as 'donor' plants resulted in no induction of defence responses and no change in insect resistance in 'receiver' plants, suggesting that JA signalling is required for CMN-mediated interplant communication. These results indicate that plants are able to hijack CMNs for herbivore-induced defence signal transfer and interplant defence communication.
Forest die-off caused by mountain pine beetle (MPB) is rapidly transforming western North American landscapes. The rapid and widespread death of lodgepole pine will likely have cascading effects on biodiversity. One group particularly prone to such declines associated with MPB are ectomycorrhizal fungi, symbiotic organisms that can depend on pine for their survival, and are critical for stand regeneration. We evaluated the indirect effects of MPB on above- (community composition of epigeous sporocarps) and belowground (hyphal abundance) occurrences of ectomycorrhizal fungi across 11 forest stands. Along a gradient of mortality (0-82% pine killed), macromycete community composition changed; this shift was driven by a decrease in the species richness of ectomycorrhizal fungi. Both the proportion of species that were ectomycorrhizal and hyphal length in the soil declined with increased MPB-caused pine mortality; less than 10% of sporocarp species were ectomycorrhizal in stands with high pine mortality compared with greater than 70% in stands without MPB attacks. The rapid range expansion of a native insect results not only in the widespread mortality of an ecologically and economically important pine species, but the effect of MPB may also be exacerbated by the concomitant decline of fungi crucial for recovery of these forests.
The year 1970 saw the publication of Origin of Eukaryotic Cells by Lynn Margulis. This influential book brought the exciting and weighty problems of cellular evolution to the scientific mainstream, simultaneously breaking new ground and ‘re-discovering’ the decades-old ideas of German and Russian biologists. In this commemorative review, I discuss the 40 years that have elapsed since this landmark publication, with a focus on the ‘molecular era’: how DNA sequencing and comparative genomics have proven beyond all doubt the central tenets of the endosymbiont hypothesis for the origin of mitochondria and plastids, and, at the same time, revealed a genetic and genomic complexity in modern-day eukaryotes that could not have been imagined in decades past.
Anthropogenic nitrogen (N) deposition alters ectomycorrhizal fungal communities, but the effect on functional diversity is not clear. In this review we explore whether fungi that respond differently to N deposition also differ in functional traits, including organic N use, hydrophobicity and exploration type (extent and pattern of extraradical hyphae). Cortinarius, Tricholoma, Piloderma, and Suillus had the strongest evidence of consistent negative effects of N deposition. Cortinarius, Tricholoma and Piloderma display consistent protein use and produce medium-distance fringe exploration types with hydrophobic mycorrhizas and rhizomorphs. Genera that produce long-distance exploration types (mostly Boletales) and contact short-distance exploration types (e.g., Russulaceae, Thelephoraceae, some athelioid genera) vary in sensitivity to N deposition. Members of Bankeraceae have declined in Europe but their enzymatic activity and belowground occurrence are largely unknown. Bankeraceae produce a distinct hydrophobic mat exploration type that may also be important in N acquisition under conditions of low N availability.
It is well known from laboratory studies that a single mycorrhizal fungal isolate can colonize different plant species, form interplant linkages, and provide a conduit for interplant transfer of isotopic carbon, nitrogen, phosphorus, or water. There is increasing laboratory and field evidence that the magnitude and direction of transfer is influenced by physiological source-sink gradients between plants. There is also evidence that mycorrhizal fungi play a role in regulating transfer through their own source-sink patterns, frequency of links, and mycorrhizal dependency. Although it is plausible that connections are extensive in nature, field studies have been hampered by our inability to observe them in situ and by belowground complexity. In future, isotopic tracers, morphological observations, microsatellite techniques, and fluorescent dyes will be useful in the study of networks in nature. Mycorrhizal networks have the potential to influence patterns of seedling establishment, interplant competition, plant diversity, and plant community dynamics, but studies in this area are just beginning. Future plant community studies would benefit from concurrent experimental use of fungal network controls, isotopic labeling, direct observation of interplant linkages, and long-term observation in the field. In this paper, we review recent literature on mycorrhizal networks and interplant carbon transfer, suggest future research directions, and highlight promising scientific approaches.
summaryPinus sylvestris L. and Larix eurolepis Henry seedlings were grown together in non–sterile laboratory microcosms containing functional mycelial networks of one of three different ectomyeorrhizal Fungi. The fungi used were Suillus bovinus (Fr.) O. Kuntze, and two Fungi which are commonly considered to be specific to Larix spp., Suillus grevillei (Klotzsch) Sing, and Boletirms cavipes (Opat.) Kalchbr. Patterns of mycorrhizal infection, transport of labelled assimilate and phosphorus uptake within the microcosms were studied in order to evaluate tine functional attributes of associations formed between P. sylvestris and the two‘larch specific’fungi. Fungal colonization of lateral roots and accumulation of labelled assimilate from adjacent plants fed with 14CO2 was significantly greater in the roots of Pinus plants when the ectomycorrhizal fungus was S. bovinu, and significantly greater in Larix roots when the fungus was V. grevillei or li. cavipes. Kctomycorrhizas formed between P. sylvestris and Ii, cavipes were fully functional in terms of transfer of labelled assimilate to the fungal mycelium. In mixed communities infected by B. caripes, myeclial uptake and translocation of 32P-labelled orthophosphate was significantly greater to Larix plants than to Pinus plants. Formation of sheathed lateral roots on the Pinus plants was low. There was some autoradiographic evidence of phosphorus translocation from mycorrhizal pine roots to stem and leaf tissue hut levels of activity in the shoots were low, indicating limited translocation across the host-fungus interface.
Using perspex observation chambers, the uptake, translocation and distribution of 32P-labelled phosphorus was studied in ectomycorrhizal mycelial networks of Suillus bovinus (Fr.) O. Kuntze interconnecting plants of Pinus contorta Dougl. ex Loud and Pinus sylvestris L. Label was fed either directly to the cut ends of individual mycelial strands, to plant roots, or to the unsterile peat in the vicinity of advancing mycelial fans. Where 32P was fed to individual strands or mycelial fans it was taken up and translocated through the mycelium, over distances exceeding 40 cm, to all host plants connected to the mycelial network. Ectomycorrhizal roots acted as major sinks for phosphate but the label did not move exclusively towards the plant and was distributed throughout the mycelial system. Calculated translocation rates and flux rates suggest that transport is primarily by symplastic flow rather than turgor driven bulk flow. The amount of label accumulated by each plant was significantly related both to the size of the plant shoot and to the number of mycorrhizal root tips but did not appear to be influenced by the transpiration rates of individual plants. Phosphorus supplied directly to plant roots did not move to other plants via the mycelial connections suggesting that movement of phosphorus between the fungus and host is unidirectional.
S ummary
Ammonia assimilation has been followed in ectomycorrhizal roots of Fagus sylvatica. The absorption of ammonium ions was associated with a rapid synthesis of free amino acids in mycorrhizal tissues, glutamine being the most prominent. In the presence of [ ¹⁵ N]ammonium, glutamate, glutamine and alanine became the most strongly labelled metabolites of ectomycor‐rhizas. Nitrogen‐15 nuclear magnetic resonance spectroscopy demonstrated that the glutamine amide‐N was the most highly enriched component of the extracts. Methionine sulphoximine and albizine, inhibitors of glutamine synthetase and glutamate synthase, almost completely blocked the incorporation of ¹⁵ N label into amino acids and induced an accumulation of NH 4 ⁺ . These observations suggest that in the ammonia‐fed beech ectomycorrhizas, ammonia assimilation occurs mainly via the glutamine synthetase/glutamate synthase pathway, and that glutamate dehydrogenase plays little, if any, part in this process. Alternative models for the nitrogen assimilation pathways in fungal and host tissues are presented.
Uptake and translocation of nitrogen was studied in laboratory microcosms consisting of Alnus glutinosa (L.) Gaertn., Frankia sp., Paxillus involutus (Fr.) Fr. and Pinus contorta Dougl. ex Loud. P. involutus was shown to form a fully functional ectomycorrhizal association with alder as well as pine, and the seedlings thus became interconnected by a common mycelium.
When microcosms were exposed to 15N2 gas, interplant translocation of 15N was observed in two out of three experiments. 15N2 was fixed by Frankia and translocated to all other parts of the system. In the two experiments in which interplant translocation occurred, between 5 and 15% of the 15N recovered was found in the pine seedlings.
Within seven days, fixed N2 was incorporated into amino acids in the Frankia nodules, translocated to both the A. glutinosa and P. contorta seedlings and incorporated into macromolecules. In alder seedlings, citrulline and ornithine were the free amino acids that had both the highest 15N enrichment levels and concentrations. In pine, glutamine and citrulline had the highest 15N concentrations, and glutamine had the highest level of 15N enrichment. 15N enrichment levels were greatest in the nodules, at between 5.5 and 29% in the different amino acids and 12% in the macromolecular fraction. Enrichment levels decreased with increasing distance from the nodules.
The uptake and translocation of 15N applied as 15NH4Cl to the mycelium was also studied. 15N was incorporated into amino acids in the mycelium and translocated further in this form. Generally, free amino acids had high 15N enrichment levels in the mycelium, decreasing along the translocation pathway. Citrulline and glutamine were the amino acids with highest 15N concentrations in all parts of the system. 15N was also found in the macromolecular fraction.
The mutually beneficial interactions between plants and their animal pollinators and seed dispersers form complex networks of species interdependence. Until very recently, the complexity of these networks precluded a community-wide approach to the investigation of mutualism. However, recent studies using tools and concepts from physics and sociology have allowed the exploration of this complexity within a rational framework. Regardless of differences across sites or species composition, networks of mutual benefit have a similar structure. Describing these network patterns is important for understanding both the generation of biodiversity and its responses to anthropogenic disturbances, such as habitat loss and species extinctions. This network approach is currently being applied to restoration ecology, biological invasions, and the conservation of endangered species.
summaryThe aims of this study were to evaluate the effect of macronutrients on nitrogen fixation in mycorrhizal and non-mycorrhizal grey alder (Alnus incana (L.) Moench), and to evaluate the effect of ectomycorrhizal mycelium on the transfer of symbolically fixed nitrogen from grey alder to Scots pine (Pinus sylvestris L). One alder and one pine were grown together in pots with root systems separated by a 20μm mesh nylon filter which allowed hyphae but not roots to penetrate. Half the plants of both species were inoculated with Paxillus involutus (Ft.) Ft. and all alders were inoculated with Frankia. Nutrient solutions were added with macronutrient (N, K, P, Ca, Mg and S) concentrations varied according to a two-level fractional factorial design. The plants were harvested after two growing periods in a growth chamber. Nitrogen fixation by alder and transfer of symbiotically fixed N from alder to pine was measured by 15N-dilution. Fixed N (mg) correlated with nodule biomass in both mycorrhizal and non-mycorrhizal alders. On average, specific nodule activity over the two periods was 510 mg N fixed R' nodule d. wt. This was not affected by mycorrhizal infection or by the different nutrient treatments. By contrast there was a strong nutrient effect on the proportion of N derived from fixation. These results indicate that the regulation of nitrogen fixation was via nodule growth rather than via nodule specific activity. Nitrogen had a strong negative effect and P a positive effect on the percentage of N derived from fixation (%Ndfa). However, the effect of N depended on the level of P. This N × P interaction resulted in a %Ndfa when N was high, of 5-10%, at low P and 45–48%, at high P. The highest value of 90% Ndfa was found at the combination of low N and high P. Potassium had a small but statistically significant effect on the %Ndfa but Ca, Mg and S had no significant effects. No mycorrhizal effect was found on the %Ndfa in alder. By contrast, the %Ndfa and biomass were lower in mycorrhizal than in non-mycorrhizal alders. The proportion of fixed N in pine, transferred from alder, was greatest (9%) when the pine was nitrogen starved and mycorrhizal and the alder was fixing maximally (low N and high P). However, the amount of fixed N transferred to pine was not statistically different from zero.
The roots of most land plants are colonised by mycorrhizal fungi that provide mineral nutrients in exchange for carbon. Here, we show that mycorrhizal mycelia can also act as a conduit for signalling between plants, acting as an early warning system for herbivore attack. Insect herbivory causes systemic changes in the production of plant volatiles, particularly methyl salicylate, making bean plants, Vicia faba, repellent to aphids but attractive to aphid enemies such as parasitoids. We demonstrate that these effects can also occur in aphid-free plants but only when they are connected to aphid-infested plants via a common mycorrhizal mycelial network. This underground messaging system allows neighbouring plants to invoke herbivore defences before attack. Our findings demonstrate that common mycorrhizal mycelial networks can determine the outcome of multitrophic interactions by communicating information on herbivore attack between plants, thereby influencing the behaviour of both herbivores and their natural enemies.
summaryTo test the effect of ectomycorrhizal fungi (EMF) on interactions between host plants, Pseudotsuga menziesii (Mirb.) Franco and Pinus ponderosa Dougl. ex. Laws., seedlings were grown in replacement series in pasteurized soil with (a) no EMF added, (A) two EMF species added - Rhizopogon vinicolor Smith (specific to Douglas-fir) and R. ochraceorubens Smith (specific to pine), and (c) tour EMF species added - the two Rhizopogon species plus two host generalists, Laccaria laccata (Scop, ex Fr.) Bk. & Br, and Hebeloma crustuliniforme (Bull.) Quel. A replacement series in unpasteurized forest soil also was included. Seedlings without added EMF were colonized by the greenhouse contaminant, Thelephora terrestris. Without added EMF (but with T. terrestris), the tree species mutually inhibited one another, producing Relative Yield Totals significantly < 1; with EMF added, mutual inhibition disappeared. With four EMF species added, Pseudotsuga menziesii seedlings were significantly larger in mixture than in monoculture, with no corresponding decrease in the size of Pinus ponderoso seedlings; this was due solely to seedlings with L. laccata, which apparently enhanced nitrogen (N) and phosphorus (P) uptake by Pseudotsuga menziesii at the expense of luxury consumption by Pinus ponderosa. Graphical analysis suggested that better growth of Pseudotosuga menziesii in mixture with EMF added was related to improved P nitrogen. Both N and P nutrition of Pinus ponderosa was better in mixture with two than no EMF species added; there was no clear nutrient effect with four EMF species added. Results indicate that EMF can reduce competition between plant species and perhaps increase overall community P uptake. However, patterns were specific to both EMF and tree species and were quite different in unpasteurized soils. Hence generalizations about the effects of EMF on plant-plant interactions must be made cautiously.
Background and aims We conducted a mesocosm study to investigate the extent to which the process of hydraulic redistribution of soil water by plant roots is affected by mycorrhizosphere disturbance. Methods We used deuterium-labeled water to track the transfer of hydraulically lifted water (HLW) from well-hydrated donor oaks (Quercus agrifolia Nee.) to drought-stressed receiver seedlings growing together in mycorrhizal or fungicide-treated mesocosms. We hypothesized that the transfer of HLW from donor to receiver plants would be enhanced in undisturbed (non-fungicide-treated) mesocosms where an intact mycorrhizal hyphal network was present.
Results Contrary to expectations, both upper soil and receiver seedlings contained significantly greater pro- portions of HLW in mesocosms where the abundance of mycorrhizal hyphal links between donor and receiver roots had been sharply reduced by fungicide application. Reduced soil hyphal density and viability likely ham- pered soil moisture retention properties in fungicide- treated mesocosms, thus leading to faster soil water depletion in upper compartments. The resulting steeper soil water potential gradient between taproot and upper compartments enhanced hydraulic redistribution in fungicide-treated mesocosms.
PLANTS and soils are a critically important element in the global carbon–energy equation. It is estimated that in forest ecosystems over two-thirds of the carbon is contained in soils and peat deposits1. Despite the importance of forest soils in the global car-bon cycle, fluxes of carbon associated with fundamental processes and soil functional groups are inadequately quantified, limiting our understanding of carbon movement and sequestration in soils. We report here the direct measurement of carbon in and through all major pools of a mycorrhizal (fungus-root) coniferous seedling (a complete carbon budget). The mycorrhizal symbiont reduces over-all retention of carbon in the plant–fungus symbiosis by increasing carbon in roots and below-ground respiration and reducing its retention and release above ground. Below ground, mycorrhizal plants shifted allocation of carbon to pools that are rapidly turned over, primarily to fine roots and fungal hyphae, and host root and fungal respiration. Mycorrhizae alter the size of below-ground carbon pools, the quality and, therefore, the retention time of carbon below ground. Our data indicate that if elevated atmos-pheric CO2 and altered climate stressors alter mycorrhizal colonization in forests, the role of forests in sequestering carbon could be altered.