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Summary: Plants naturally harbor diverse microbiomes that can dramatically impact their health and productivity. However, it remains unclear how fungal microbiome diversity, especially in the phyllosphere, impacts intermicrobial interactions and consequent nonadditive effects on plant productivity.Combining manipulative experiments, field collections, culturing, microbiome sequencing, and synthetic consortia, we experimentally tested for the first time how foliar fungal community diversity impacts plant productivity. We inoculated morning glories (Ipomoea hederifolia L.) with 32 phyllosphere consortia of either low or high diversity or with single fungal taxa, and measured effects on plant productivity and allocation.We found the following: (1) nonadditive effects were pervasive with 56% of fungal consortia interacting synergistically or antagonistically to impact plant productivity, including some consortia capable of generating acute synergism (e.g. > 1000% increase in productivity above the additive expectation), (2) interactions among 'commensal' fungi were responsible for this nonadditivity in diverse consortia, (3) synergistic interactions were approximately four times stronger than antagonistic effects, (4) fungal diversity affected the magnitude but not frequency or direction of nonadditivity, and (5) diversity affected plant performance nonlinearly with the highest performance in low‐diversity treatments.These findings highlight the importance of interpreting plant–microbiome interactions under a framework that incorporates intermicrobial interactions and nonadditive outcomes to understand natural complexity. See also the Commentary on this article by Whitaker, 243: 2050–2051. [ABSTRACT FROM AUTHOR]

Summary: The phytohormone abscisic acid (ABA) functions in the control of plant stress responses, particularly in drought stress. A significant mechanism in attenuating and terminating ABA signals involves regulated protein turnover, with certain ABA receptors, despite their main presence in the cytosol and nucleus, subjected to vacuolar degradation via the Endosomal Sorting Complex Required for Transport (ESCRT) machinery.Collectively our findings show that discrete TOM1‐LIKE (TOL) proteins, which are functional ESCRT‐0 complex substitutes in plants, affect the trafficking for degradation of core components of the ABA signaling and transport machinery.TOL2,3,5 and 6 modulate ABA signaling where they function additively in degradation of ubiquitinated ABA receptors and transporters.TOLs colocalize with their cargo in different endocytic compartments in the root epidermis and in guard cells of stomata, where they potentially function in ABA‐controlled stomatal aperture.Although the tol2/3/5/6 quadruple mutant plant line is significantly more drought‐tolerant and has a higher ABA sensitivity than control plant lines, it has no obvious growth or development phenotype under standard conditions, making the TOL genes ideal candidates for engineering to improved plant performance. [ABSTRACT FROM AUTHOR]

Summary: Understanding how widespread species adapt to variation in abiotic conditions across their ranges is fundamental to ecology. Insight may come from studying how among‐population variation (APV) in the common garden corresponds with the environmental conditions of source populations. However, there are no such studies comparing native vs non‐native populations across multiple life stages.We examined APV in the performance and functional traits of 59 Conyza canadensis populations, in response to drought, across large aridity gradients in the native (North America) and non‐native (Eurasia) ranges in three experiments. Our treatment (dry vs wet) was applied at the recruitment, juvenile, and adult life stages.We found contrasting patterns of APV in drought responses between the two ranges. In the native range, plant performance was less reduced by drought in populations from xeric than mesic habitats, but such relationship was not apparent for non‐native populations. These range‐specific patterns were consistent across the life stages.The weak adaptive responses of non‐native populations indicate that they can become highly abundant even without complete local adaptation to abiotic environments and suggest that long‐established invaders may still be evolving to the abiotic environment. These findings may explain lag times in invasions and raise concern about future expansions. [ABSTRACT FROM AUTHOR]

Summary: Climate change is simultaneously increasing carbon dioxide concentrations ([CO2]) and temperature. These factors could interact to influence plant physiology and performance. Alternatively, increased [CO2] may offset costs associated with elevated temperatures. Furthermore, the interaction between elevated temperature and [CO2] may differentially affect populations from along an elevational gradient and disrupt local adaptation.We conducted a multifactorial growth chamber experiment to examine the interactive effects of temperature and [CO2] on fitness and ecophysiology of diverse accessions of Boechera stricta (Brassicaceae) sourced from a broad elevational gradient in Colorado. We tested whether increased [CO2] would enhance photosynthesis across accessions, and whether warmer conditions would depress the fitness of high‐elevation accessions owing to steep reductions in temperature with increasing elevation in this system. Elevational clines in [CO2] are not as evident, making it challenging to predict how locally adapted ecotypes will respond to elevated [CO2].This experiment revealed that elevated [CO2] increased photosynthesis and intrinsic water use efficiency across all accessions. However, these instantaneous responses to treatments did not translate to changes in fitness. Instead, increased temperatures reduced the probability of reproduction for all accessions. Elevated [CO2] and increased temperatures interacted to shift the adaptive landscape, favoring lower elevation accessions for the probability of survival and fecundity.Our results suggest that elevated temperatures and [CO2] associated with climate change could have severe negative consequences, especially for high‐elevation populations. [ABSTRACT FROM AUTHOR]

Summary: Plants can suppress the growth of other plants by modifying soil properties. These negative plant–soil feedbacks are often species‐specific, suggesting that some plants possess resistance strategies. However, the underlying mechanisms remain largely unknown.Here, we investigated whether benzoxazinoids, a class of dominant secondary metabolites that are exuded into the soil by maize and other cereals, allow maize plants to cope with plant–soil feedbacks.We find that three out of five tested crop species reduce maize (Zea mays L.) performance via negative plant–soil feedbacks relative to the mean across species. This effect is partially alleviated by the capacity of maize plants to produce benzoxazinoids. Soil complementation with purified benzoxazinoids restores the protective effect for benzoxazinoid‐deficient mutants. Sterilization and reinoculation experiments suggest that benzoxazinoid‐mediated protection acts via changes in soil biota. Substantial variation of the protective effect between experiments and soil types illustrates context dependency.In conclusion, exuded plant secondary metabolites allow plants to cope with plant–soil feedbacks. These findings expand the functional repertoire of plant secondary metabolites and reveal a mechanism by which plants can resist negative effects of soil feedbacks. The uncovered phenomenon may represent a promising avenue to stabilize plant performance in crop rotations. See also the Commentary on this article by Bass, 241: 2316–2319. [ABSTRACT FROM AUTHOR]

Summary: Controlled experiments at the level of individual plants show that legume species use different strategies for the regulation of symbiotic dinitrogen fixation in response to nitrogen availability. These strategies were suggested to improve legume fitness in the context of the plant community, although rarely studied at this level. We evaluated how nitrogen availability and conspecific vs heterospecific interactions influenced the strategy of regulation of nitrogen fixation.We grew two species of herbaceous legumes representing two different strategies of regulation without interaction, under treatments of deficient and sufficient nitrogen availability, with conspecific or heterospecific interaction.We found that Hymenocarpus circinnatus maintained a facultative strategy of downregulating nitrogen fixation when nitrogen was available under both con‐ and heterospecific interactions, as was also found for this species when grown alone. Vicia palaestina also downregulated nitrogen fixation under both con‐ and heterospecific interactions but did not regulate fixation when grown alone. Our results showed that under nitrogen limitation, interaction with a neighboring plant reduced fitness, reflecting a competitive effect.Our findings suggest that when interacting with other plants, downregulation of nitrogen fixation is more likely, therefore reducing the energetic cost of fixation, and improving plant performance in competitive ecological communities, especially when nitrogen is available. [ABSTRACT FROM AUTHOR]

Summary: Allelopathy is a common and important stressor that shapes plant communities and can alter soil microbiomes, yet little is known about the direct effects of allelochemical addition on bacterial and fungal communities or the potential for allelochemical‐selected microbiomes to mediate plant performance responses, especially in habitats naturally structured by allelopathy.Here, we present the first community‐wide investigation of microbial mediation of allelochemical effects on plant performance by testing how allelopathy affects soil microbiome structure and how these microbial changes impact germination and productivity across 13 plant species.The soil microbiome exhibited significant changes to 'core' bacterial and fungal taxa, bacterial composition, abundance of functionally important bacterial and fungal taxa, and predicted bacterial functional genes after the addition of the dominant allelochemical native to this habitat. Furthermore, plant performance was mediated by the allelochemical‐selected microbiome, with allelopathic inhibition of plant productivity moderately mitigated by the microbiome.Through our findings, we present a potential framework to understand the strength of plant–microbial interactions in the presence of environmental stressors, in which frequency of the ecological stress may be a key predictor of microbiome‐mediation strength. [ABSTRACT FROM AUTHOR]

Summary: Functional traits offer a promising avenue to improve predictions of species range shifts under climate change, which will entail warmer and often drier conditions. Although the conceptual foundation linking traits with plant performance and range shifts appears solid, the predictive ability of individual traits remains generally low. In this review, we address this apparent paradox, emphasizing examples of woody plants and traits associated with drought responses at the species' rear edge. Low predictive ability reflects the fact not only that range dynamics tend to be complex and multifactorial, as well as uncertainty in the identification of relevant traits and limited data availability, but also that trait effects are scale‐ and context‐dependent. The latter results from the complex interactions among traits (e.g. compensatory effects) and between them and the environment (e.g. exposure), which ultimately determine persistence and colonization capacity. To confront this complexity, a more balanced coverage of the main functional dimensions involved (stress tolerance, resource use, regeneration and dispersal) is needed, and modelling approaches must be developed that explicitly account for: trait coordination in a hierarchical context; trait variability in space and time and its relationship with exposure; and the effect of biotic interactions in an ecological community context. [ABSTRACT FROM AUTHOR]

Summary: Plant–nematode interactions are mainly considered from the negative aspect with a focus on plant‐parasitic nematodes (PPNs), which is justified considering the agronomic losses caused by PPNs. Despite the fact that PPNs are outnumbered by nonparasitic free‐living nematodes (FLNs), the functional importance of FLNs, especially with regard to plant performance, remains largely unknown. Here, we provide a comprehensive overview and most recent insights into soil nematodes by showing direct and indirect links of both PPNs and FLNs with plant performance. We especially emphasize the knowledge gaps and potential of FLNs as important indirect players in driving plant performance such as stimulating the resistance to pests via improving the disease suppressive activity of the rhizobiome. Together, we present a holistic view of soil nematodes as positive and negative contributors to plant performance, accentuating the positive but underexplored role of FLNs. [ABSTRACT FROM AUTHOR]

Summary: Plant growth is greatly influenced by the rhizosphere microbiome, which has been traditionally investigated from a bottom‐up perspective assessing how resources such as root exudates stimulate microbial growth and drive microbiome assembly. However, the importance of predation as top‐down force on the soil microbiome remains largely underestimated.Here, we planted wheat both in natural and in sterilized soils inoculated with the key microbiome predators – bacterivorous nematodes – to assess how plant performance responds to top‐down predation of the soil microbiome and specific plant growth‐promoting bacteria, namely phosphate‐solubilizing bacteria.We found that nematodes enriched certain groups (e.g. Actinobacteria, Chloroflexi, and Firmicutes) and strengthened microbial connectance (e.g. Actinobacteria and Proteobacteria). These changes in microbiome structure were associated with phosphate‐solubilizing bacteria that facilitated phosphorus (P) cycling, leading to greater P uptake and biomass of wheat in both soils. However, the enhancement varied between nematode species, which may be attributed to the divergence of feeding behavior, as nematodes with weaker grazing intensity supported greater abundance of phosphate‐solubilizing bacteria and better plant performance compared with nematodes with greater grazing intensity.These results confirmed the ecological importance of soil nematodes for ecosystem functions via microbial co‐occurrence networks and suggested that the predation strength of nematodes determines the soil bacteria contribution to P biogeochemical cycling and plant growth. [ABSTRACT FROM AUTHOR]

Summary: Drought causes soil feedback effects on plant performance. However, how the linkages between conditioned soil biota and root traits contribute to explain plant–soil feedback (PSF) as a function of drought is unknown.We utilized soil inoculum from a conditioning experiment where grassland species grew under well‐watered and drought conditions, and their soil fungi were analyzed. Under well‐watered conditions, we grew 21 grassland species with those inocula from either conspecific or heterospecific soils. At harvest, plant biomass and root traits were measured.Negative PSF (higher biomass in heterospecific than in conspecific soils) was predominant, and favored in drought‐conditioned soils. Previous drought affected the relationship between root traits and fungal groups. Specific root surface area (SRSA) was higher in heterospecific than in conspecific droughted soils and was linked to an increase in saprotroph richness. Overall, root diameter was higher in conspecific soils and was linked to mutualist and pathogen composition, whereas the decrease of root : shoot in heterospecific soils was linked to pathogenic fungi.Drought legacy affects biomass and root morphological traits via conditioned soil biota, even after the drought conditions have disappeared. This provides new insights into the role that soil biota have modulating PSF responses to drought. [ABSTRACT FROM AUTHOR]

Summary: Plant growth‐promoting rhizobacteria are involved in altering secondary root (SR) formation, but hitherto there has been no distinction between the different types of SRs upon induction of soil biota, and the genetic pathways involved.By using plate and soil systems, we studied the effects of the Pseudomonas strains CM11 and WCS417 on plant performance with a focus on root development. Through a combination of cellular, molecular and genetic analyses, we investigated the type of SRs induced upon CM11 and WCS417 root inoculation using genetic pathways associated with specific SR types.CM11 was shown to affect the root architecture differently from WCS417. CM11 inoculation leads to primary root arrest, whereas WCS417 reveals a longer primary root. Both CM11 and WCS417 activate the PLETHORA 3,5,7‐controlled lateral root pathway, rather than the WUSCHEL‐RELATED HOMEOBOX 11,12‐controlled adventitious (lateral) root pathway. In addition, CM11 promotes plant growth in model and various crop species. It improves plant fitness traits, such as bigger shoots, faster bolting and higher yield in terms of seeds.Our results indicate that the root system architecture can be promoted by activation of PLETHORA 3,5,7 dependent primed lateral pre‐branch sites upon inoculation with CM11, which creates great potential to gain a better understanding of root plasticity. [ABSTRACT FROM AUTHOR]

This supports not only the existence of a trade-off between growth/reproduction and defence to herbivory without the participation of the plant endophytes, but also that the trade-off persists, at least in this species, in symbiotic (E+) plants (Fig. From these studies, we assume that the experimental design (E+ and E- plants) effectively disrupts any potential positive effect of the plant-microbe symbiosis in E- plants. Keywords: biological interactions; extreme environments; fungal endophytes; symbiosis; trade-off EN biological interactions extreme environments fungal endophytes symbiosis trade-off 384 387 4 06/20/22 20220715 NES 220715 Acknowledgements Our thanks to Marc-André Selosse for his constructive comments that allowed us to focus and highlight the fundamental aspects of our I Letter i . Fungal endophytes improve the performance of host plants but do not eliminate the growth/defence trade-off. [Extracted from the article]

Summary: The great majority of plants gain access to soil nutrients and enhance their performance under stressful conditions through symbiosis with arbuscular mycorrhizal fungi (AMF). The benefits that AMF confer vary among species and taxonomic groups. However, a comparative analysis of the different benefits among AMF has not yet been performed.We conducted a global meta‐analysis of recent studies testing the benefits of individual AMF species and main taxonomic groups in terms of plant performance (growth and nutrition). Separately, we examined AMF benefits to plants facing biotic (pathogens, parasites, and herbivores) and abiotic (drought, salinity, and heavy metals) stress.AMF had stronger positive effects on phosphorus nutrition than on plant growth and nitrogen nutrition and the effects on the growth of plants facing biotic and abiotic stresses were similarly positive. While the AMF taxonomic groups showed positive effects on plant performance either with or without stress, Diversisporales were the most beneficial to plants without stress and Gigasporales to plants facing biotic stress.Our results provide a comprehensive analysis of the benefits of different AMF species and taxonomic groups on plant performance and useful insights for their management and use as bio‐inoculants for agriculture and restoration. [ABSTRACT FROM AUTHOR]

Summary: Indole‐3‐acetic acid (IAA) controls a plethora of developmental processes. Thus, regulation of its concentration is of great relevance for plant performance. Cellular IAA concentration depends on its transport, biosynthesis and the various pathways for IAA inactivation, including oxidation and conjugation.Group II members of the GRETCHEN HAGEN 3 (GH3) gene family code for acyl acid amido synthetases catalysing the conjugation of IAA to amino acids. However, the high degree of functional redundancy among them has hampered thorough analysis of their roles in plant development.In this work, we generated an Arabidopsis gh3.1,2,3,4,5,6,9,17 (gh3oct) mutant to knock out the group II GH3 pathway. The gh3oct plants had an elaborated root architecture, showed an increased tolerance to different osmotic stresses, including an IAA‐dependent tolerance to salinity, and were more tolerant to water deficit. Indole‐3‐acetic acid metabolite quantification in gh3oct plants suggested the existence of additional GH3‐like enzymes in IAA metabolism. Moreover, our data suggested that 2‐oxindole‐3‐acetic acid production depends, at least in part, on the GH3 pathway. Targeted stress‐hormone analysis further suggested involvement of abscisic acid in the differential response to salinity of gh3oct plants.Taken together, our data provide new insights into the roles of group II GH3s in IAA metabolism and hormone‐regulated plant development. [ABSTRACT FROM AUTHOR]

Summary: Feedback between plants and soil microbial communities can be a powerful driver of vegetation dynamics. Plants elicit changes in the soil microbiome that either promote or suppress conspecifics at the same location, thereby regulating population density‐dependence and species co‐existence. Such effects are often attributed to the accumulation of host‐specific antagonistic or beneficial microbiota in the rhizosphere. However, the identity and host‐specificity of the microbial taxa involved are rarely empirically assessed. Here we review the evidence for host‐specificity in plant‐associated microbes and propose that specific plant–soil feedbacks can also be driven by generalists. We outline the potential mechanisms by which generalist microbial pathogens, mutualists and decomposers can generate differential effects on plant hosts and synthesize existing evidence to predict these effects as a function of plant investments into defence, microbial mutualists and dispersal. Importantly, the capacity of generalist microbiota to drive plant–soil feedbacks depends not only on the traits of individual plants but also on the phylogenetic and functional diversity of plant communities. Identifying factors that promote specialization or generalism in plant–microbial interactions and thereby modulate the impact of microbiota on plant performance will advance our understanding of the mechanisms underlying plant–soil feedback and the ways it contributes to plant co‐existence. [ABSTRACT FROM AUTHOR]

Summary: Plants form complex interaction networks with diverse microbiomes in the environment, and the intricate interplay between plants and their associated microbiomes can greatly influence ecosystem processes and functions. The phyllosphere, the aerial part of the plant, provides a unique habitat for diverse microbes, and in return the phyllosphere microbiome greatly affects plant performance. As an open system, the phyllosphere is subjected to environmental perturbations, including global change, which will impact the crosstalk between plants and their microbiomes. In this review, we aim to provide a synthesis of current knowledge of the complex interactions between plants and the phyllosphere microbiome under global changes and to identify future priority areas of research on this topic. [ABSTRACT FROM AUTHOR]

Summary: Climate change is increasing global temperatures and the frequency and severity of droughts in many regions. These anthropogenic stresses pose a significant threat to plant performance and crop production. The plant‐associated microbiome modulates the impacts of biotic and abiotic stresses on plant fitness. However, climate change‐induced alteration in composition and activities of plant microbiomes can affect host functions. Here, we highlight recent advancements in our understanding of the impact of climate change (warming and drought) on plant–microbiome interactions and on their ecological functions from genome to ecosystem scales. We identify knowledge gaps, propose new concepts and make recommendations for future research directions. It is proposed that in the short term (years to decades), the adaptation of plants to climate change is mainly driven by the plant microbiome, whereas in the long term (century to millennia), the adaptation of plants will be driven equally by eco‐evolutionary interactions between the plant microbiome and its host. A better understanding of the response of the plant and its microbiome interactions to climate change and the ways in which microbiomes can mitigate the negative impacts will better inform predictions of climate change impacts on primary productivity and aid in developing management and policy tools to improve the resilience of plant systems. [ABSTRACT FROM AUTHOR]

Summary: Climate change‐related soil salinization increases plant stress and decreases productivity. Soil microorganisms are thought to reduce salt stress through multiple mechanisms, so diverse assemblages could improve plant growth under such conditions. Previous studies have shown that microbiome selection can promote desired plant phenotypes, but with high variability. We hypothesized that microbiome selection would be more consistent in saline soils by increasing potential benefits to the plants.In both salt‐amended and untreated soils, we transferred forward Brassica rapa root microbiomes (from high‐biomass or randomly selected pots) across six planting generations while assessing bacterial (16S rRNA) and fungal (ITS) composition in detail. Uniquely, we included an add‐back control (re‐adding initial frozen soil microbiome) as a within‐generation reference for microbiome and plant phenotype selection.We observed inconsistent effects of microbiome selection on plant biomass across generations, but microbial composition consistently diverged from the add‐back control. Although salt amendment strongly impacted microbial composition, it did not increase the predictability of microbiome effects on plant phenotype, but it did increase the rate at which microbiome selection plateaued.These data highlight a disconnect in the trajectories of microbiomes and plant phenotypes during microbiome selection, emphasizing the role of standard controls to explain microbiome selection outcomes. [ABSTRACT FROM AUTHOR]

Summary: Fire plays a major role in structuring plant communities across the globe. Interactions with soil microbes impact plant fitness, scaling up to influence plant populations and distributions. Here we present the first factorial manipulation of both fire and soil microbiome presence to investigate their interactive effects on plant performance across a suite of plant species with varying life history traits.We conducted fully factorial experiments on 11 species from the Florida scrub ecosystem to test plant performance responses to soils with varying fire histories (36 soil sources), the presence/absence of a microbiome, and exposure to an experimental burn.Results revealed interactive 'pulse' effects between fire and the soil microbiome on plant performance. On average, post‐fire soil microbiomes strongly reduced plant productivity compared to unburned or sterilized soils. Interestingly, longer‐term fire 'legacy' effects had minor impacts on plant performance and were unrelated to soil microbiomes.While pulse fire effects on plant–microbiome interactions are short‐term, they could have long‐term consequences for plant communities by establishing differential microbiome‐mediated priority effects during post‐disturbance succession. The prominence of pulse fire effects on plant–microbe interactions has even greater import due to expected increases in fire disturbances resulting from anthropogenic climate change. [ABSTRACT FROM AUTHOR]

Summary: Plants allocate resources to processes related to growth and enemy defence. Simultaneously, they interact with complex soil microbiomes that also affect plant performance. While the influence of individual microbial groups on single plants is increasingly studied, effects of microbial interactions on growth, defence and growth–defence relationships remain unknown, especially at the plant community level.We investigated how three microbial groups (bacteria, fungi, protists), alone and in full‐factorial combinations, affect plant performance and potential growth–defence relationships by measuring phenolics composition in early‐ and mid‐successional grass and forb communities in a glasshouse experiment.Microbial groups did not affect plant growth and only fungi increased defence compounds in early‐ and mid‐successional forbs, while grasses were not affected. Shoot biomass–defence relationships were negatively correlated in most microbial treatments in early‐successional forbs, but positively in several microbial treatments in mid‐successional forbs. The growth–defence relationship was generally negative in early‐successional but not in mid‐successional grasses. The presence of different microbiomes commonly removed the observed growth–defence relationships.We conclude that soil microorganisms and their interactions can shift growth–defence relationships differentially for plant functional groups and the relationships vary between successional stages. Microbial interaction‐induced growth–defence shifts might therefore underlie distinct plant strategies and fitness. See also the Commentary on this article by Bender, 233: 1015–1017. [ABSTRACT FROM AUTHOR]

Summary: Habitat fragmentation is a leading cause of biodiversity and ecosystem function loss in the Anthropocene. Despite the importance of plant–microbiome interactions to ecosystem productivity, we have limited knowledge of how fragmentation affects microbiomes and even less knowledge of its consequences for microbial interactions with plants.Combining field surveys, microbiome sequencing, manipulative experiments, and random forest models, we investigated fragmentation legacy effects on soil microbiomes in imperiled pine rocklands, tested how compositional shifts across 14 fragmentation‐altered soil microbiomes affected performance and resource allocation of three native plant species, and identified fragmentation‐responding microbial families underpinning plant performance.Legacies of habitat fragmentation were associated with significant changes in microbial diversity and composition (across three of four community axes). Experiments showed plants often strongly benefited from the microbiome's presence, but fragmentation‐associated changes in microbiome composition also significantly affected plant performance and resource allocation across all seven metrics examined. Finally, random forest models identified ten fungal and six bacterial families important for plant performance that changed significantly with fragmentation.Our findings not only support the existence of significant fragmentation effects on natural microbiomes, but also demonstrate for the first time that fragmentation‐associated changes in microbiomes can have meaningful consequences for native plant performance and investment. [ABSTRACT FROM AUTHOR]

Summary: Recent studies show that the variation in root functional traits can be explained by a two‐dimensional trait framework, containing a 'collaboration' axis in addition to the classical fast–slow 'conservation' axis. This collaboration axis spans from thin and highly branched roots that employ a 'do‐it‐yourself' strategy to thick and sparsely branched roots that 'outsource' nutrient uptake to symbiotic arbuscular mycorrhizal fungi (AMF).Here, we explore the functionality of this collaboration axis by quantifying how interactions with AMF change the impact of root traits on plant performance. To this end, we developed a novel functional–structural plant (FSP) modelling approach that simulates plants competing for light and nutrients in the presence or absence of AMF.Our simulation results support the notion that in the absence of AMF, plants rely on thin, highly branched roots for their nutrient uptake. The presence of AMF, however, promotes thick, unbranched roots as an alternative strategy for uptake of immobile phosphorus, but not for mobile nitrogen.This provides further support for a root trait framework that accommodates for the interactive effect of roots and AMF. Our modelling study offers unique opportunities to incorporate soil microbial interactions into root functionality as it integrates consequences of belowground trait expression. [ABSTRACT FROM AUTHOR]

Summary: A host‐plant and its associated microbiota depend on one another. However, the assembly process and the functioning of host‐associated microbiota are poorly understood.Herein, rice was used as model plant to investigate the assemblage of bacterial microbiota, including those in the seed, root endosphere and rhizosphere. We also assessed the degree to which endosphere and rhizosphere communities were influenced by vertical transmission through seed and identified the core microbes that potentially associated with plant phenotypic properties.Plant microhabitat, rather than subspecies type, was the major driver shaping plant‐associated bacterial microbiota. Deterministic processes were primarily responsible for community assembly in all microhabitats. The influence of vertical transmission from seed to root‐associated bacterial communities appeared to be quite weak (endosphere) or even absent (rhizosphere). A core microbial community composed of 15 generalist species persisted across different microhabitats and represented key connectors in networks. Host‐plant functional traits were linked to the relative abundance of these generalist core microbes and could be predicted from them using machine learning algorithms.Overall, bacterial microbiota is assembled by host‐plant interactions in a deterministic‐based manner. This study enhances our understanding of the driving mechanisms and associations of microbiota in various plant microhabitats and provides new perspectives to improve plant performance. [ABSTRACT FROM AUTHOR]

Summary: Elevated atmospheric CO2 (eCa) may benefit plants during drought by reducing stomatal conductance (gs) but any 'water savings effect' could be neutralized by concurrent stimulation of leaf area. We investigated whether eCa enhanced water savings, thereby ameliorating the impact of drought on carbon and water relations in trees.We report leaf‐level gas exchange and whole‐plant and soil water relations during a short‐term dry‐down in two Eucalyptus species with contrasting drought tolerance. Plants had previously been established for 9 to 11 months in steady‐state conditions of ambient atmospheric CO2 (aCa) and eCa, with half of each treatment group exposed to sustained drought for 5 to 7 months.The lower stomatal conductance under eCa did not lead to soil moisture savings during the dry‐down due to the counteractive effect of increased whole‐plant leaf area. Nonetheless, eCa‐grown plants maintained higher photosynthetic rates and leaf water potentials, making them less stressed during the dry‐down, despite being larger. These effects were more pronounced in the xeric species than the mesic species, and in previously water‐stressed plants.Our findings indicate that eCa may enhance plant performance during drought despite a lack of soil water savings, especially in species with more conservative growth and water‐use strategies. [ABSTRACT FROM AUTHOR]

Summary: Different phosphorus (P)‐acquisition strategies may be relevant for species coexistence and plant performance in terrestrial communities on P‐deficient soils. However, how interspecific P facilitation functions in natural systems is largely unknown.We investigated the root physiological activities for P mobilization across 19 coexisting plant species in steppe vegetation, and then grew plants with various abilities to mobilize sorbed P in a microcosm in a glasshouse.We show that P facilitation mediated by rhizosphere processes of P‐mobilizing species promoted growth and increased P content of neighbors in a species‐specific manner. When roots interacted with a facilitating neighbor, Cleistogenes squarrosa and Bromus inermis tended to show greater plasticity of root proliferation or rhizosheath acid phosphatase activity compared with other non‐P‐mobilizing species. Greater variation in these root traits was strongly correlated with increased performance in the presence of a facilitator. The results also show, for the first time, that P facilitation was an important mechanism underlying a positive complementarity effect.Our study highlights that interspecific P‐acquisition facilitation requires that facilitated neighbors exhibit a better match of root traits with a facilitating species. It provides a better understanding of species coexistence in P‐limited communities. [ABSTRACT FROM AUTHOR]

Summary: Plant–soil feedbacks (PSFs) and plant–plant competition influence performance and abundance of plants. To what extent the two biotic interactions are interrelated and thus affect plant performance in combination rather than in isolation remains poorly explored. It is also unclear how the abiotic context, such as resource availability, modifies individual and joint effects of PSFs and of plant–plant competition.Using a garden experiment, we assessed the strengths of PSFs, competition, and their combined effects explored under low and high nutrient levels, and related them to abundance of 46 plant species and their ecological optima with respect to soil nutrients.We found that PSFs reduced but did not eliminate differences in competitive ability of plant species. Isolated and combined effects of the biotic interactions poorly predicted local or regional abundance of species. They were rather related to species' ecological optima, as nutrient‐demanding plants experienced less negative biotic effects but only in a nutrient‐rich environment.Our study demonstrates that soil biota can mitigate differences in competitive ability among species. It remains to be tested whether such an equalizing effect can maintain coexistence under high nutrient availability, in which nutrient‐demanding species may disproportionately benefit from less negative competition and PSF effects. [ABSTRACT FROM AUTHOR]

Summary: Endogenous (˜24 circadian) rhythms control an enormously diverse range of processes in plants and are, increasingly, the target of studies aimed at understanding plant performance. Although in the previous few decades most plant circadian research has focused on Arabidopsis, there is a pressing need for low‐cost, high‐throughput tools for analyzing rhythms in a wider variety of species. The present contribution investigates using circadian temperature oscillations as a novel marker for assaying plant circadian rhythms.A thermal imaging platform was set up to measure diel and circadian rhythms in different plant species, in wild‐type and circadian mutant plants, and in leaves and flowers. Results from the thermal imaging technique were compared with those from other established circadian assay techniques.All of the dicot and monocot species examined showed robust circadian rhythms of leaf surface temperature; the effects of circadian mutations on thermocycles were similar to those reported using other techniques. In Petunia × atkinsiana plants circadian oscillations were observed in both leaves and flowers.Thermal imaging is an extremely useful technique for analyzing circadian rhythms in plants. It is predicted that the ability to make very high temporal resolution measurements may facilitate the discovery of novel aspects of circadian control. [ABSTRACT FROM AUTHOR]

Summary: Ecological interaction and adaptation both depend on phenotypic characteristics. In contrast with the common conception of the 'adult' phenotype, plant bodies develop continuously during their lives. Furthermore, the different units (metamers) that comprise plant bodies are not identical copies, but vary extensively within individuals. These characteristics foster recognition of plant phenotypes as dynamic mosaics. We elaborate this conception based largely on a wide‐ranging review of developmental, ecological and evolutionary studies of plant reproduction, and identify its utility in the analysis of plant form, function and diversification. An expanded phenotypic conception is warranted because dynamic mosaic features affect plant performance and evolve. Evidence demonstrates that dynamic mosaic phenotypes enable functional ontogeny, division of labour, resource and mating efficiency. In addition, dynamic mosaic features differ between individuals and experience phenotypic selection. Investigation of the characteristics and roles of dynamic and mosaic features of plant phenotypes benefits from considering within‐individual variation as a function‐valued trait that can be analysed with functional data methods. Phenotypic dynamics and within‐individual variation arise despite an individual's genetic uniformity, and develop largely by heterogeneous gene expression and associated hormonal control. These characteristics can be heritable, so that dynamic mosaic phenotypes can evolve and diversify by natural selection. [ABSTRACT FROM AUTHOR]

Summary: Given the rising risk of extreme weather caused by climate change, enhancement of abiotic stress resistance in crops is increasingly urgent. But will the development of stress‐resistant cultivars come at the cost of yield under ideal conditions? We hypothesize that this need not be inevitable, because resistance alleles with minimal pleiotropic costs may evade artificial selection and be retained in crop germplasm.Genome‐wide association (GWA) analyses for variation in plant performance and flooding response were conducted in cultivated sunflower, a globally important oilseed.We observed broad variation in flooding responses among genotypes. Flooding resistance was not strongly correlated with performance in control conditions, suggesting no inherent trade‐offs. Consistent with this finding, we identified a subset of loci conferring flooding resistance, but lacking antagonistic effects on growth. Genetic diversity loss at candidate genes underlying these loci was significantly less than for other resistance genes during cultivated sunflower evolution.Despite bottlenecks associated with domestication and improvement, low‐cost resistance alleles remain within the cultivated sunflower gene pool. Thus, development of cultivars that are both flooding‐tolerant and highly productive should be straightforward. Results further indicate that estimates of pleiotropic costs from GWA analyses explain, in part, patterns of diversity loss in crop genomes. [ABSTRACT FROM AUTHOR]

Summary: In his foundational list of 'ideal weed' characteristics, Baker (1965) proposed that weedy plants maximize reproductive output under high resource availability. Since then, the idea that invasive plant species are more responsive to fluctuating resources compared with native or noninvasive species has gained considerable traction, although few studies extend this hypothesis to include reproductive output. We revisit Baker's hypothesis in the context of invasion and drought in California grasslands, exploring whether invasives show greater growth and reproductive responses to water availability compared with the native wildflowers they displace.In an outdoor potted study, we grew eight native and eight invasive species of annuals commonly found in southern California grasslands to reproductive maturity under both well‐watered and drought conditions.While drought negatively impacted plant performance overall, invasives showed more negative responses for growth and reproductive traits. Invasives also grew larger than native species, especially under well‐watered conditions, and produced seed with higher rates of germination.Invasives may be more negatively impacted by drought compared with natives, but they are also able to capitalize on high resource conditions and greatly increase reproductive output. Such opportunistic responses exhibited by invasives might explain previously observed fluctuations in their abundance under variable precipitation. [ABSTRACT FROM AUTHOR]

Summary: Microplastic effects in terrestrial ecosystems have recently moved into focus, after about a decade of research being limited to aquatic systems. While effects on soil physical properties and soil biota are starting to become apparent, there is not much information on the consequences for plant performance. We here propose and discuss mechanistic pathways through which microplastics could impact plant growth, either positively or negatively. These effects will vary as a function of plant species, and plastic type, and thus are likely to translate to changes in plant community composition and perhaps primary production. Our mechanistic framework serves to guide ongoing and future research on this important topic. [ABSTRACT FROM AUTHOR]

Summary: By means of meta‐analyses we determined how 70 traits related to plant anatomy, morphology, chemistry, physiology, growth and reproduction are affected by daily light integral (DLI; mol photons m−2 d−1). A large database including 500 experiments with 760 plant species enabled us to determine generalized dose–response curves. Many traits increase with DLI in a saturating fashion. Some showed a more than 10‐fold increase over the DLI range of 1–50 mol m−2 d−1, such as the number of seeds produced per plant and the actual rate of photosynthesis. Strong decreases with DLI (up to three‐fold) were observed for leaf area ratio and leaf payback time. Plasticity differences among species groups were generally small compared with the overall responses to DLI. However, for a number of traits, including photosynthetic capacity and realized growth, we found woody and shade‐tolerant species to have lower plasticity. We further conclude that the direction and degree of trait changes adheres with responses to plant density and to vertical light gradients within plant canopies. This synthesis provides a strong quantitative basis for understanding plant acclimation to light, from molecular to whole plant responses, but also identifies the variables that currently form weak spots in our knowledge, such as respiration and reproductive characteristics. [ABSTRACT FROM AUTHOR]

Summary: Vascular plants are wired with a remarkable long‐distance communication system. This network can span from as little as a few centimeters (or less) in species like Arabidopsis, up to 100 m in the tallest giant sequoia, linking distant organ systems into a unified, multicellular organism. Grafting is a fundamental technique that allows researchers to physically break apart and reassemble the long‐distance transport system, enabling the discovery of molecular signals that underlie intraorganismal communication. In this review, we highlight how plant grafting has facilitated the discovery of new long‐distance signaling molecules that function in coordinating developmental transitions, abiotic and biotic responses, and cross‐species interactions. This rapidly expanding area of research offers sustainable approaches for improving plant performance in the laboratory, the field, the orchard, and beyond. [ABSTRACT FROM AUTHOR]

This article is an Editorial on: Cho et al.,229: 57–63;Hartmanet al.,229: 64–70; Labandera et al., 229: 126–139; Lee Bailey‐Serres, 229: 71–78; Lee et al., 229: 156–172; Licausi & Giuntoli, 229: 50–56;Müller et al., 229: 140–155; Nghi et al., 229: 85–93; Pedersen et al., (a) 229: 42–49; Pedersen et al., (b) 229: 94–105; Tang et al., 229: 106–125; Valeri et al., 229: 173–185; van Veen & Sasidharan, 229: 79–84;Weits et al., 229: 24–35; Yu et al., 229: 36–41. [ABSTRACT FROM AUTHOR]

Summary: The search for a root economics spectrum (RES) has been sparked by recent interest in trait‐based plant ecology. By analogy with the one‐dimensional leaf economics spectrum (LES), fine‐root traits are hypothesised to match leaf traits which are coordinated along one axis from resource acquisitive to conservative traits. However, our literature review and meta‐level analysis reveal no consistent evidence of an RES mirroring an LES. Instead the RES appears to be multidimensional. We discuss three fundamental differences contributing to the discrepancy between these spectra. First, root traits are simultaneously constrained by various environmental drivers not necessarily related to resource uptake. Second, above‐ and belowground traits cannot be considered analogues, because they function differently and might not be related to resource uptake in a similar manner. Third, mycorrhizal interactions may offset selection for an RES. Understanding and explaining the belowground mechanisms and trade‐offs that drive variation in root traits, resource acquisition and plant performance across species, thus requires a fundamentally different approach than applied aboveground. We therefore call for studies that can functionally incorporate the root traits involved in resource uptake, the complex soil environment and the various soil resource uptake mechanisms – particularly the mycorrhizal pathway – in a multidimensional root trait framework. ContentsSummary1159I.Introduction1159II.The root economics spectrum1161III.Why the one‐dimensional resource economics spectrum does not work for tree roots1164IV.Outlook1166Acknowledgements1167References1167 [ABSTRACT FROM AUTHOR]

Summary: Climate warming may affect biological invasions by altering competition between native and non‐native species, but these effects may depend on biotic interactions.In field surveys at 33 sites in China along a latitudinal and temperature gradient from 21°N to 30.5°N and a 2‐yr field experiment at 30.5°N, we tested the role of the biocontrol beetle Agasicles hygrophila in mediating warming effects on competition between the invasive plant Alternanthera philoxeroides and the native plant Alternanthera sessilis.In surveys, native populations were perennial below 25.8°N but only annual populations were found above 26.5°N where the invader dominated the community. Beetles were present throughout the gradient. Experimental warming (+ 1.8°C) increased native plant performance directly by shifting its lifecycle from annual to perennial, and indirectly by releasing the native from competition via disproportionate increases in herbivory on the invader. Consequently, warming shifted the plant community from invader‐dominated to native‐dominated but only in the presence of the beetle.Our results show that herbivores can play a critical role in determining warming effects on plant communities and species invasions. Understanding how biotic interactions shape responses of communities to climate change is crucial for predicting the risk of plant invasions. [ABSTRACT FROM AUTHOR]

The article offers information on a meeting to discuss the shifts in ecosystems and its impacts on environment at the American Geophysical Union Fall Meeting in New Orleans, Louisiana on December, 11 2017. Topics discussed include interaction of biotic and abiotic drivers to regulate ecosystem responses; approaches for detecting ecosystem thresholds in space and time; and the impacts of aridity on plant performance.

Leaf venation networks provide an integrative linkage between plant form, function and climate niche, because leaf water transport underlies variation in plant performance., Here, we develop theory based on leaf physiology that uses community-mean vein density to predict growing season temperature and atmospheric CO2 concentration. The key assumption is that leaf water supply is matched to water demand in the local environment. We test model predictions using leaves from 17 temperate and tropical sites that span broad climatic gradients., We find quantitative agreement between predicted and observed climate values. We also highlight additional leaf traits that may improve predictions., Our study provides a novel approach for understanding the functional linkages between functional traits and climate that may improve the reconstruction of paleoclimate from fossil assemblages. [ABSTRACT FROM AUTHOR]

Manganese (Mn) is an essential nutrient required for plant growth, in particular in the process of photosynthesis. Plant performance is influenced by various environmental stresses including contrasting temperatures, light or nutrient deficiencies. The molecular responses of plants exposed to such stress factors in combination are largely unknown., Screening of 108 Arabidopsis thaliana (Arabidopsis) accessions for reduced photosynthetic performance at chilling temperatures was performed and one accession (Hog) was isolated. Using genetic and molecular approaches, the molecular basis of this particular response to temperature (G × E interaction) was identified., Hog showed an induction of a severe leaf chlorosis and impaired growth after transfer to lower temperatures. We demonstrated that this response was dependent on the nutrient content of the soil. Genetic mapping and complementation identified NRAMP1 as the causal gene. Chlorotic phenotype was associated with a histidine to tyrosine (H239Y) substitution in the allele of Hog NRAMP1. This led to lethality when Hog seedlings were directly grown at 4°C., Chemical complementation and hydroponic culture experiments showed that Mn deficiency was the major cause of this G × E interaction. For the first time, the NRAMP-specific highly conserved histidine was shown to be crucial for plant performance. [ABSTRACT FROM AUTHOR]

983I.983II.983III.984IV.990V.992VI.992VII.993VIII.995IX.996996References996 Summary: The design and function of leaf venation are important to plant performance, with key implications for the distribution and productivity of ecosystems, and applications in paleobiology, agriculture and technology. We synthesize classical concepts and the recent literature on a wide range of aspects of leaf venation. We describe 10 major structural features that contribute to multiple key functions, and scale up to leaf and plant performance. We describe the development and plasticity of leaf venation and its adaptation across environments globally, and a new global data compilation indicating trends relating vein length per unit area to climate, growth form and habitat worldwide. We synthesize the evolution of vein traits in the major plant lineages throughout paleohistory, highlighting the multiple origins of individual traits. We summarize the strikingly diverse current applications of leaf vein research in multiple fields of science and industry. A unified core understanding will enable an increasing range of plant biologists to incorporate leaf venation into their research. [ABSTRACT FROM AUTHOR]

In this article the author reflects on the relationship among stem anatomy, plant performance, and life history in studying functional traits of plants. The author focuses on a certain trait: wood density, which is related to a plant's growth rate, water storage, mechanical strength, efficiency and safety of hydraulic transport. The author discusses the factors that affect the variations in wood density in different species of plants.

The article offers the authors' views on the study conducted by E. T. Kiers and colleagues regarding the potential problems of single-strain inoculation. They argue on the findings of the study that fitness alignment can be considered as consequence of the methods used in the analysis. They state that the study revealed that the differences in nodulation speed could be associated to the positive correlations of nodulation competitiveness and plant performance in the study by Maren L. Friesen .