Plant Biology

Published studies have reported species-variance between profiles of Calvin-Benson cycle (CBC) intermediates, not only between C4 species and C3 species, but also within C3 species (Arrivault et al., 2019, Borghi et al. 2019). It was proposed that this variance reflects lineage-dependent changes in the balance between different reactions, or poising, of the CBC. These earlier studies investigated phylogenetically-unrelated C3 species. In the current study, CBC intermediates were profiled in five closely-related species from Solanum sect. lycopersicon subsect. Lycopersicum. The levels of individual CBC intermediates showed many significant differences. In a principal component analysis, whilst three species (Solanum lycopersicum, Solanum cheesmaniae, Solanum neorickii) overlapped, Solanum pimpinellifolium and especially Solanum pennellii grouped separately, and were at opposing ends of the distribution. When combined with published data, whilst the separation between Solanum species was retained, they formed a group that was separated from five other C3 species, as well as two C4 species. It is discussed that the observed variation in CBC metabolites profiles within Solanum, together with their separation from other C3 species, supports the idea that CBC evolution is shaped both by phylogenetic relatedness and lineage-specific adaptation. HighlightVariance of intermediate levels points to poising of the Calvin-Benson cycle varying between closely-related species in the tomato clade Solanum sect. lycopersicon subsect. Lycopersicum

Little is known about environmental drivers of opportunities for hybridization, but its phylogenetic distribution across species and areas is heterogeneous, suggesting that ecological traits may play an important role in concert with postzygotic isolation. Because plant-pollinator interactions are responsible for gene flow in most plant species, differences in the mosaic landscape of plant-pollinator interactions could explain why some plants are particularly prone to hybridization. Prezygotic isolation is mediated by sometimes complex pollen presentation; conversely, conserved pollination strategies would lead to evolutionary constraints on pollinator assemblage divergence in the speciation process and therefore predict higher opportunities for gene flow, although this hypothesis has yet to be tested. The plant taxonomic tribe Heuchereae (Saxifragaceae) is a well-characterized system for pollinator interactions and particularly for floral scent, the primary pollinator attractant in the group. Floral volatile organic compounds (VOCs) in this clade are hypervariable at the population level and are thought to be responsible for pollination selectivity, leading to divergent pollinator assemblages. Observing a contrast of hybridizing and non-hybridizing species, the levels of attractant divergence may therefore predict levels of hybridization. We investigated pollination biology in the plant genus Heuchera, notable for frequent interspecific gene flow compared to tribal relatives, asking whether high rates of hybridization may be associated with low interspecific divergence of VOCs and the pollinator assemblages they shape, using as our system the hybrid zone between H. americana var. americana and H. richardsonii in the midwestern USA. We optimized a closed-space collection and GC-MS (gas chromatography-mass spectrometry) protocol to characterize VOCs in Heuchera flowers. To identify floral visitation and effective pollinators we conducted pollination observations at 40 Heuchera populations over the span of two field seasons. GC-MS data from 89 Heuchera specimens representing 69 populations suggests that classes of VOCs, and to a large extent individual compounds, are shared within the hybrid complex while other Heuchera that are not thought to hybridize with these species have distinct species-specific compounds. Pollination observations and metabarcoding of pollinator pollen loads confirm shared effective pollinators in the hybrid zone and between adjacent parental populations. Attractant and visitation data considered together suggest that conservatism of pollinator interactions may be a typical feature associated with frequent hybridizers, perhaps arising from developmental or biochemical constraints on prezygotic isolation, and more broadly that the macroevolution of isolation mechanisms may be predictive of natural hybridization rate.

CoverCress is a new winter annual oilseed crop developed from field pennycress within the past 20 years. Field pennycress is commonly considered to be self-pollinated but little basic research has been published and there is some misalignment of conclusions. Our experience working with pennycress plant growth in greenhouse and field conditions over the past 13 years suggests that outcrossing is uncommon. We conducted lab, greenhouse, and field experiments to strengthen the body of work. Pollen viability kinetics analysis showed that longevity of pollen viability is negatively impacted by increasing temperatures and by direct exposure to light. Samples treated at 4C declined to 50% viability in 12 hours while it took just 2.5 hrs at 37C, and 1.6 hrs in full sunlight on a cool early April day. Cross-pollination was absent among greenhouse-grown plants flowering inside an agitated plastic pollen-containment covering. Across greenhouse tests, high rates of cross-pollination occurred only in an emasculation treatment that rendered flowers male sterile and opened the pistil to cross-fertilization. Field trials designed to measure pollen flow distance using a trackable fae1 knockout reporter gene failed to show detectable movement of pollen under field conditions in two locations. This data strongly suggests that domesticated field pennycress may be considered a self-pollinated crop and managed as such.

The objective of this study is to determine the quality and define the different classes of honeys produced in the Ivorian forest region according to their pollen content. This involves the analysis of five honey samples from the sub-prefecture of Cechi. Four of the honey samples were wild-harvested, and one was from experimental beekeeping in the Cechi reserve. A total of 54 pollen taxa were identified. The most represented botanical families are: Fabaceae (9 species, or 16.67%), Apocynaceae, and Combretaceae, each with 5 species, or 9.27%. The pollen taxon richness of the honeys varies from 18 to 34 taxa. Most are polyfloral honeys, with the exception of the honey from the reserve, which contains 66.13% Bridelia micrantha pollen (Euphorbiaceae), a monofloral honey. These samples contain highly variable pollen content and fall into three categories of honey: honeys rich in pollen, honeys very rich in pollen, and honeys extremely rich in pollen, attesting to their high quality and natural origin.

O_LIQuantifying relationships between traits and climate using plants collected from diverse climatic origins, grown under common conditions, potentially provides valuable insights into climate adaptation. C_LIO_LIWe report on fifteen accessions of kangaroo grass (Themeda triandra), a C4 species distributed across Australia, Asia, the Middle East and Africa from the Andropogoneae clade of grasses that is vital to global agriculture. Plants were grown to maturity in glasshouses under two thermal regimes, with ample water supplied. Numerous physiological, "economic" and developmental traits were characterised. C_LIO_LIAs expected, plants grown at 20{degrees}C maxima had lower photosynthetic rates (Asat) and dark respiration rates, reduced leaf expansion, and delayed flowering compared with plants grown at 30{degrees}C. However, surprisingly few traits varied with climate-of-origin: accessions from colder climates had higher Asat alongside lower leaf mass per area, but only when grown at 20{degrees}C; flowering time showed the strongest correlation with site climate, with plants from wetter, warmer or less variable climates taking longer to flower. C_LIO_LIOur findings highlight remarkable phenotypic flexibility in key traits of T. triandra; this flexibility is likely key to its wide distribution. The strong relationship between flowering time and climate-of-origin underscores the importance of reproductive phenology as an adaptive trait. C_LI

1) Differences in specialized metabolites are common both within and between plant species and are often thought to have regulating functions in ecological interactions, including herbivores like aphids. Although ants commonly rely on chemical cues in their behaviour and resource finding, very little is known about whether specialized plant chemistry regulates ant behaviour to foster successful ant-aphid mutualisms on plants and in the surrounding vegetation. 2) Using a chemodiversity experiment containing 84 plots with 6 chemotypes of Tansy (Tanacetum vulgare L. Asteraceae) planted in different proportions, i.e., plot-level chemotype richness, we tested the effects of plot-level chemotype richness, plot-level chemodiversity metrics, and individual chemotype presence on black garden ant (Lasius niger Linnaeus) nesting, patrolling and recruitment behaviour to plants and plots. Furthermore, we assessed the influence of plant chemotype on the pink tansy aphid (Metopeurum fuscoviride H.L.G. Stroyan) presence and abundance, as well as ant occurrence on Tansy plants. 3) We found that Tansy plot-level chemodiversity only minimally affected most of the observed ant behaviour, except for nesting, which was marginally positively impacted by plot-level chemotype richness. Clear effects of individual terpenoid chemotypes were observed on ant visitation rates, as well as on aphid presence and abundance. Strongly significant relationships between the probability of ant occurrence and aphid abundance and occurrence observed in our study suggest that ants and aphids are most strongly guided by the presence and abundance of their mutualist partners, rather than by specialized chemistry alone in the Tansy system.

O_LIFrugivores vary in their selection of fruit traits and their fruit handling methods, leading to differences in the plant species they consume for fruits. While fruit consumption patterns of birds are relatively well understood, much less is known about those of mammals. C_LIO_LIGiven the wide morphological and physiological diversity of mammals, fruit consumption patterns and fruit traits selected by different mammal groups may vary substantially. C_LIO_LIWe investigated differences in fruit consumption among three mammal groups - primates, herbivores, and carnivores - in Asia based on peer-reviewed and secondary literature. We assessed both morphological traits and taxonomic composition and compared patterns across vegetation types and for figs and non-figs. We found that primates (29%) and carnivores (21%) consumed more unique fruit genera than herbivores (6%). Carnivores and primates shared more fruit genera with each other (17%) than with herbivores. These patterns were consistent across vegetation types and for figs and non-figs. C_LIO_LIMorphological traits such as fruit size, colour, type, habit, seed number, and seed arillation showed no major differences among mammal groups. C_LIO_LIThere was no significant relationship between mammal body size and the mean or maximum fruit diameter consumed. However, among mammals that handle fruits exclusively with their mouthparts, body size was positively related to the maximum fruit diameter consumed. In contrast, for mammals that handle fruits using opposable thumbs (primates), body size showed a negative relationship with the mean fruit size consumed. There was no significant relationship between mammal activity patterns and the colour of the fruits they consumed. C_LIO_LIOur results suggest that fruit consumption patterns among mammal groups are not strongly differentiated by the morphological traits investigated; however, carnivores and primates are more similar in their preferred fruit genera. Moreover, morphological trait selection may be influenced by fruit handling methods. C_LIO_LIHerbivores consumed larger fruits and, like primates, preferred dull-coloured fruits, whereas carnivores more often fed on liana and shrub fruits across a wider colour range C_LIO_LIFuture research should focus on chemical and quantitative visual traits, such as volatile profiles and nutritional composition, to better understand the drivers of mammal fruit consumption. C_LI

The objective of this study was to re-analyse the molecular phylogeny and/or the morphology of all species, which have been attributed to the so-far mono-generic fungal family Ambisporaceae. The genus Ambispora has been well-known for its spore bi-morphy described even from single spore clusters. Triple-walled spores are differentiated on sporiferous saccules, while mono-walled spores are formed on simple subtending hyphae. New phylogenetic analyses reveal dissimilarities of [≥]10% in partial nrDNA gene of three different stable phylogenetic clades and thus suggest the division of Ambispora into three genera, which simultaneously request for advanced morphological separations. These advances are primarily based on the more diverse spore wall composition of the ambisporoid-acaulosporoid morph rather than on the rather simple-glomoid morph. While all known species of the triple-walled morph have an evanescent to semi-permanent outer spore wall, i) Am. fennica, Am. brasiliensis, Am. gerdemannii and Am. nicolsonii have a smooth, permanent central spore wall (Am. fennica clade, A), ii) the central wall of Am. appendicula, Am. callosa, Am. leptoticha and Am. jimgerdemannii is alveolate (Am. appendicula clade, B), and iii) the central wall of Am. granatensis is smooth, but easily degraded, thus rather short-lived and not permanent but evanescent (Am. granatensis clade, C). In conclusion, species of the Am. fennica clade represent the genus Ambispora, while species of the Am. appendicula clade represent the new genus Appendiculaspora, and the mono-specific Am. granatensis clade represents the new genus Ephemerapareta. Species of an additional morph, with triple-walled spores, but apparently formed on subtending hyphae, and having a diagnostic reticulate, football-like middle wall, are here separated from the revised genus Ambispora based solely on morphological analyses, since molecular identification analyses so far failed and remained merely unknown. This later morph and genus is based on the type species Pelotaspora reticulata comb. nov, and on P. austrolatina sp. nov. Concomitant molecular phylogenetic and morphological analyses are needed to attribute not only Pelotaspora spp., but also those species, for which hitherto only the ambisporoid-glomoid morph has been observed correctly within the family Ambisporaceae. Without molecular analyses, such species with glomoid but unknown ambisporoid-acaulosporoid morph have to be retained within Ambispora.

Diversisporales comprises species with worldwide distribution that produce glomoid, otosporoid, or tricisporoid spores. The recent reorganization of the order by Oehl et al. (2016) recognizes two families, Diversisporaceae and Corymbiglomeraceae, comprising one and five genera, respectively. Several Glomeromycotan specimens collected in northern and southeastern Mexico and in French Polynesian atolls were characterized using both morphological and molecular analyses. Phylogenetic inference revealed that they represent new members in the Diversisporales, supporting the reorganization of the genus Redeckera into three independent lineages: Albocarpum gen. nov., with A. arenaceum sp. nov., A. leptohyphum sp. nov., and A. fulvum comb. nov., Pulvinocarpum pulvinatum gen. et comb. nov., and Redeckera, which retains five species, including R. varelae sp. nov. In addition, we described Melanocarpum mexicanum gen. et sp. nov. and Diversispora papillosa sp. nov. A broader phylogeny, based on eDNA sequences and representative of Diversisporales species, including the newly described taxa, further supported the split of Redeckera and suggested three additional clades likely corresponding to a new family and two new genera, awaiting the discovery of representative morphospecies to be formally described. Using eDNA sequences metadata, the occurrences of the newly described taxa were mapped, allowing to recognize distribution patterns, mostly in the pantropical zone, distinguish widespread and rare species, and suggest possible endemisms. Finally, the coexistence of species forming large sporocarps (A. fulvum and A. leptohyphum) alongside species forming spores in loose aggregates (A. arenaceum), prompted us to propose a possible sporulation dimorphism in Albocarpum, an argument previously raised to explain the nested placement of Corymbiglomus and Paracorymbiglomus within the Redeckera clade.

Climate change is increasing the frequency, duration and severity of extreme events such as heatwaves and droughts, pushing trees near or beyond their ecophysiological limits. Understanding what governs variability in how trees respond to drought - such as intrinsic factors related to their size, age, and species, or extrinsic factors shaped by their local competitive environment - is critical for predicting long-term forest resilience to climate change and developing climate-smart forest management strategies. Here, we use tree ring data from 2909 trees belonging to sixteen species distributed across Europes major forest types to comprehensively assess what factors contribute most to a trees ability to withstand and recover from extreme drought events. We found that trees with larger living crowns generally exhibited higher post-drought growth recovery and resilience, while trees exposed to lower drought intensities showed greater resistance. Conversely, neither the density nor the diversity of a trees local competitive neighbourhood had any clear influence on its response to drought. More generally, we found that our ability to predict whether a tree would exhibit resilience to drought was low (R2 = 13-21) and was largely driven by species-specific responses and topographic variation across forest types, rather than by tree- and stand-level attributes. These findings highlight that drought responses are inherently complex and strongly influenced by forest type and by heterogeneous responses among species. Integrating tree-ring, physiological, and remote-sensing data with mechanistic models represents a promising avenue for improving forecasts of future forest resilience to climate change.

BackgroundMelastomes are well known for their striking diversity in stamen morphologies mostly adapted to buzz pollination by bees. The variously modified connective appendages and heteranthery in the family have fascinated botanists for more than two centuries and a variety of functions associated with pollination have been discovered for these staminal traits over the years. The repeated evolutionary shifts in these traits have been linked to pollinator shifts, likely contributing to diversification in the family. The evolutionary lability of staminal traits, especially the connective morphology, led us to hypothesize that these traits might be controlled by relatively simple genetic mechanisms and we here take the first steps to test this hypothesis by using a comparative transcriptomics approach with Arthrostemma ciliatum as our model. We also tested the functional significance of heteranthery and whether the classical division of labour hypothesis holds true for this species by comparing the number, size and viability of pollen in the two stamen types. ResultsStaminal development of this species was studied and suitable stages for transcriptome comparisons were identified. Differential expression analyses between the morphologically distinct stamen whorls at four developmental stages showed the differential expression of several transcripts involved in stamen development/elongation. Pollen comparisons between the two whorls showed that the antepetalous/inner whorl stamens have a significantly higher number of pollen and higher germination rates while the antesepalous/outer whorl stamens have significantly larger pollen. ConclusionsWe identified Jasmonate and Gibberellin signalling pathway genes (JAZ, GID1, DELLA and ARF homologs), EPF/EPFL family genes, autophagy related genes (VPE homologs) and S Locus ELF homologs as putative candidates involved in causing staminal dimorphism in A. ciliatum. Our results indicate that, for the heterantherous morph of this species, the shorter stamens (antepetalous/inner whorl) have both pollinating and feeding functions contradicting the division of labour theory. We also report the possible existence of heterostyly in A. ciliatum as an outbreeding mechanism.

Belowground, plants are exposed to a wide range of biotic stresses that vary in severity and nature, including tissue damage, disruption of vascular connectivity, and depletion of assimilates. How plants adapt their root systems to cope with different types of belowground biotic stresses is not well known. In this paper we compare above- and belowground plant adaptations to three nematode species with distinct tissue migration and feeding behaviours to study mechanisms underlying tolerance to different types of biotic stresses. We monitored both green canopy growth and changes in root system architecture of Arabidopsis inoculated with Pratylenchus penetrans, Heterodera schachtii, and Meloidogyne incognita. This revealed three distinct phases in aboveground plant responses: (i) initial growth inhibition associated with host invasion and tissue damage, (ii) persistent growth reduction associated with nematode sedentarism, and (iii) late growth stimulus in more advanced stages of infection. Specific adaptations in the root systems further revealed fundamentally different stress coping strategies. Tissue damage and intermittent feeding by P. penetrans in the root cortex did not induce significant changes in root system architecture. Tissue damage to the root cortex and prolonged feeding on host vascular cells by H. schachtii induced secondary root formation compensating for primary root growth inhibition. Prolonged feeding on host vascular cell by M. incognita alone did not induce secondary root formation, but was accompanied by typical local tissue swelling instead. Our data suggest that local secondary root formation and tissue swelling are two distinct compensatory mechanisms underlying tolerance to sedentarism by root-feeding nematodes. HighlightHow plants utilize root system plasticity to cope with different types of biotic stresses by root feeding nematodes remains largely unknown. Here, we report on specific adaptive growth responses in Arabidopsis roots to three nematode species, Pratylenchus penetrans, Heterodera schachtii, and Meloidogyne incognita, with fundamentally different strategies for host invasion, subsequent migration through host tissue, and feeding on host cells.

PremiseHerbarium specimens are increasingly used to extract morphological traits for ecological and evolutionary studies, yet the effects of tissue desiccation on trait measurements remain poorly understood. Here, we tested whether higher tissue water content leads to greater measurement changes after herborization (H1) and whether fresh trait values can be reliably predicted from herbarium measurements (H2). MethodsWe evaluated the reliability of herbarium-based measurements by comparing fresh and dried traits of leaves, flowers, fleshy fruits, and seeds across 262 individuals representing 133 Neotropical Myrtaceae species. Phylogenetic least square models and machine-learning regressions were used to test H1 and H2. ResultsLeaves and flowers generally shrank after herborization, fruits size metrics tended to increase, and seeds were largely unaffected. Water content was significantly associated with the magnitude of herborization effects in flowers and some leaf and seed traits. Fresh trait values were accurately predicted from herbarium measurements. Prediction errors were lowest for leaf traits, followed by fruits, flowers, and seeds. DiscussionThese results partially support H1 and support H2, indicating that herbarium specimens can be reliably used for trait analyses when organ-specific responses are considered, providing a practical framework to account for potential desiccation bias in functional trait research.

BackgroundPlants are exposed to various environmental challenges. With ongoing climate change, droughts and insect outbreaks are expected to become more frequent. Thus, a better understanding is needed of how different plant species respond to such single and combined challenges. This study investigated common versus species-specific responses to environmental challenges in three perennial plant species of different growth forms and whether responses differ intraspecifically among accessions. Clones of different accessions of the herbaceous species Tanacetum vulgare, the woody vine Solanum dulcamara, and the tree Populus nigra were subjected to similar control, herbivory, drought, and combined (drought and herbivory) treatments for the same periods. After the exposure, concentrations of foliar phytohormones and various morphological traits were measured. ResultsAcross all species, several foliar phytohormones and one of ten morphological traits responded consistently to the environmental challenges. Jasmonoyl-isoleucine was induced by herbivory and the combined treatment, abscisic acid (ABA) by drought and the combined treatment, and indole acetic acid by the combined treatment in all species. Root mass remained unchanged in all species. However, structural equation models (SEMs) revealed a shared regulatory pathway across species in which ABA connected treatment and root mass, indicating a common hormonal response potentially linking challenges to growth responses. Despite these common patterns, species-specific responses were pronounced. In P. nigra, a unique induction of salicylic acid was found under the combined treatment, while aboveground mass and root-shoot ratio remained unaffected by any treatment, in contrast to the other two species. Species-specific SEMs further indicated distinct phytohormone-mediated pathways underlying morphological variation. Phenotypic plasticity reflected these species-specific patterns, with none of the phytohormones or morphological traits exhibiting uniform plasticity across species. Intraspecific variation further shaped responses, as phytohormone and morphological trait plasticity depended on accession, indicating substantial accession-specific plant responses. ConclusionsOur results indicate that some responses to comparable challenges may be conserved across species, while others are species-specific. The combined treatment elicited the most pronounced responses, and such complex responses may become more frequent under current global change. Our study highlights that comprehensive understanding of plant responses requires systematic comparisons at both interspecific and intraspecific scales.

Climate change is expected to alter forest community composition and functioning, with consequences for the ecosystem services forests provide. However, most macroecological projections focus on individual species distributions and offer limited insight into whether entire communities will remain functionally compatible with future climatic conditions. Here we quantify the risk that present-day forest communities will become functionally misaligned with projected climates using a trait-based approach. We analysed forest inventory data from more than 42,000 mature plots across the United States and Canada. For each plot we estimated community-weighted means for 24 functional traits describing leaf economics, hydraulic function, wood structure, abiotic tolerances and symbiotic strategies. We modelled relationships between community functional composition and environmental conditions, and used these relationships to estimate the trait profiles most compatible with projected late-century climates (2080-2100). Trait-environment misalignment (TEM) risk was quantified as the multivariate distance between current community trait composition and the trait profile associated with the projected future climate at each location, accounting for covariance among traits and intraspecific trait variation. Projected climatic conditions favour trait combinations associated with greater hydraulic capacity and reduced cold and shade tolerance. However, the magnitude of functional misalignment varies strongly across space. The highest TEM risk occurs in high-latitude and montane conifer forests across western and central North America, whereas many mid-latitude broadleaf and mixed forests show lower risk because projected climatic changes reinforce existing drought-adapted functional strategies. Critically, high species richness was the strongest predictor of reduced risk, reinforcing the importance of biodiversity in buffering against adverse outcomes. Our results suggest that many forests are projected to experience climatic conditions associated with functional strategies that differ from those characterising the current community. By identifying where the largest functional adjustments are implied, this trait-based framework provides a scalable way to pinpoint forests most likely to experience suboptimal climate conditions and to prioritise monitoring and climate-adapted management.

While most plant lineages are pigmented by anthocyanins, several families in the Caryophyllales represent a major exception by showing a replacement of anthocyanin pigmentation by betalain pigmentation. The mutual exclusion of anthocyanins and betalains at the family level has been well established for over 50 years and has been mechanistically explained. Chenopodiaceae are a betalain-pigmented lineage lacking a key anthocyanin biosynthesis gene and lacking the key activating transcription factor of the anthocyanin biosynthesis. A publication by Zhang et al., 2024 claims that anthocyanins would be responsible for the red pigmentation in leaves of Chenopodium quinoa. Here, we assessed this study and reanalyzed the RNA-seq datasets generated in this study to demonstrate that there is no evidence for anthocyanin biosynthesis, but activity of the betalain and carotenoid biosynthesis could explain the observed pigmentation of quinoa leaves.

Biomass and surface area allocation affect resource uptake and carbon (C) residence time in forests, but the influence of tree diversity on allocation remains poorly understood. Moreover, mycorrhizal associations can alter this relationship, which has been rarely tested in mature forests. We investigated the role of both the proportion of ectomycorrhizal (ECM) trees and tree diversity on tree biomass and surface area allocation across a dual gradient of tree diversity (0 - 1.68 Shannon diversity) and ECM dominance (0 - 100 %) in a mixed deciduous forest area in Central Germany. We found that the two gradients affected tree biomass and surface area differently and mostly independently. Tree diversity had no significant effect on biomass or surface area in the investigated forest area, but increased the spatial variability of the leaf area index (LAI) from 21 % to 40 %. In contrast, a higher proportion of ECM trees was associated with an increase in fruit biomass (from 10 to 141 g m-2) and LAI (from 4 to 7 m2 m-2). Although tree diversity and the portion of ECM produced similar parsimonious models for explaining belowground biomass and surface area, neither showed a significant direct effect. Notably, their interaction enhanced the spatial variability of fine root biomass and root surface area; that is, forests with high diversity and a greater proportion of ECM trees exhibited a more heterogeneous distribution of fine roots. Allocation to fine root biomass appeared independent of tree diversity and the proportion of ECM trees, being influenced primarily by stand structure, with higher allocations observed in stands with lower stem basal area. We conclude that biomass allocation in this Central European Forest, where resource availability is relatively uniform, is primarily productivity-driven. A comparison of the biotic influences shows that ECM trees have a stronger control on aboveground surface area and fruit biomass than tree diversity, which may contribute to the ability of dominant ECM trees, such as European beech, to outcompete light competitors, but also puts temperate ECM forests at risk of physiological failures in increasingly drier future conditions.

Breadfruit (Artocarpus altilis (Parkinson) Fosberg) is a culturally and nutritionally significant perennial crop of the Pacific Islands. National Tropical Botanical Gardens Kahanu Garden (Maui, Hawai i) maintains a breadfruit collection representing more than 150 traditional varieties, some unique or irreplaceable and requiring safety duplication to safeguard genetic diversity. However, aging trees exhibit variable vigor, potentially limiting clonal propagation outcomes. We assessed air layering as a strategy for conservation duplication, conducting 163 air-layer attempts across 26 priority accessions. We evaluated the influence of tree vigor, age, and branch characteristics on rooting success and survival to out-planting. Overall, 17% successfully rooted and 75% of those survived to out-planting, resulting in successful duplication of 16 of 26 at-risk accessions. Rooting success differed among vigor classes (33% for high-vigor trees; 11-16% for normal and feeble trees) and increased modestly with source tree age, while survival to out-planting declined with increasing age. Branch length and fruiting season were not associated with outcomes. These findings indicate that air layering can support conservation propagation in living collections, but success is strongly influenced by source tree age and condition. Initiating safety duplication while trees are physiologically robust is likely to improve long-term conservation outcomes.

Reduced competition or facilitation between kin relative to nonkin can improve plant performance, particularly under resource-limited conditions. Understanding whether kin interactions differ between invasive and native species may provide insights into the mechanisms underlying the persistence and spread of invasive species, particularly for species that spread clonally. To explore this, we conducted a greenhouse experiment using the invasive Alternanthera philoxeroides and its native congener A. sessilis in China. For both species, we grew central plants without or with neighbors, and for the latter we had three intraspecific neighbor kinship treatments (kin only, nonkin only, and both kin and nonkin [mixed] neighbors). To test whether kinship effects are affected by resource limitation, we grew the plants under two watering conditions (well-watered and drought-stressed). Our findings revealed that at both the group (i.e., pot-level) and individual levels, invasive plants had a higher biomass production and experienced a less negative relative neighbor effect in kin groups than in nonkin groups, while these patterns were reversed in the native species. Although aboveground architecture of central plants did not differ significantly between kin and nonkin neighbors in either species, neighbor plants of the invasive species produced fewer nodes in kin groups than in nonkin groups, while the reverse was true for the native species. These patterns were not affected by the watering treatment. Together, these results indicate that while the native plants has stronger kin competition, the invasive species has reduced kin competition. Such reduced competition among kin in the invasive Alternanthera philoxeroides may enhance its population dominance and facilitate its spread.

Virus induced gene silencing (VIGS) is a method that exploits plant antiviral defence mechanisms to downregulate endogenous genes. The technique is versatile, rapid, and widely used for functional genomics studies. Here we report a method for VIGS in the medicinal plant, Calendula officinalis (pot marigold). This species produces anti-inflammatory triterpenoids and has also been bred and cultivated as an ornamental plant. We describe a method for the injection of Agrobacterium tumefaciens cultures into leaf midribs and compare visual marker genes for tracking VIGS utilising constructs that simultaneously target visual marker and target genes. We use these tools to demonstrate that silencing a gene encoding cycloartenol synthase results in changes to leaf phytosterols. This method could be used to further investigate the genetic basis of specialised metabolism in this species and could be adapted to other members of the Asteraceae family, many of which are of economical and chemical value.