The vast majority of land plants transfer part of the organic carbon they produce by photosynthesis to arbuscular mycorrhizal (AM) fungi inside their root cells; the fungi in turn help plants to take up nutrients and water from the soil. This carbon can subsequently be acquired from mycorrhizal fungi by rare nonphotosynthetic 'mycoheterotrophic' plants that tap into the same fungal network. However, recent findings suggest that carbon uptake from AM fungi may exist among some green plants too. If so, this would qualify them as partial mycoheterotrophs (mixotrophs) rather than as pure autotrophs. Here, we discuss the evolutionary, ecophysiological, morphological, genetic, and environmental evidence for the existence and prevalence of this trait. We conclude that there is strong, albeit indirect, evidence for its existence, although its taxonomic distribution remains to be determined. This knowledge gap currently prevents us from inferring the magnitude of AM partial mycoheterotrophy in terrestrial ecosystems, which in turn severely limits our understanding of its role in plant establishment and survival and in ecosystem structure and function.

Fully mycoheterotrophic orchids rely entirely on fungal symbionts for carbon acquisition, are often highly specialized in their fungal associations, and exhibit stable isotope signatures distinct from autotrophic plants. Danxiaorchis yangii is a rare, leafless orchid endemic to subtropical China whose nutritional ecology has not been previously examined. We combined high-throughput fungal community profiling with multi-element stable isotope natural abundance analyses (δ¹³C, δ¹⁵N, δ²H, δ¹⁸O) to investigate fungal associations and nutrient acquisition in D. yangii. Mycorrhizal rhizomes were dominated by a single operational taxonomic unit affiliated with the wood-decaying saprotroph Candolleomyces candolleanus (Psathyrellaceae), with additional low-abundance taxa related to Ramariopsis (Clavariaceae). Stable isotope signatures showed strong enrichment in ¹³C, ¹⁵N, and ²H relative to co-occurring autotrophic plants, confirming a fully mycoheterotrophic nutritional mode. Notably, the magnitude of nitrogen isotope enrichment differed from that reported for other Psathyrellaceae-associated orchids, suggesting greater complexity in nitrogen acquisition within saprotroph-based mycoheterotrophic systems.

OBJECTIVE:This study aimed to compare 5-year overall survival between primary debulking surgery and neoadjuvant chemotherapy followed by interval surgery in patients with stage IIIB to IVB epithelial ovarian cancer, using global real-world data. Secondary objectives included evaluation of progression-free survival and the influence of race, post-operative complications, and residual disease. METHODS:SUROVA is a retrospective, international cohort study involving patients treated between 2018 and 2019 across 174 centers in 55 countries. Patients underwent primary surgery or received neoadjuvant chemotherapy followed by interval surgery, per institutional protocols. Propensity score matching was based on 7 baseline variables: age, race, Eastern Cooperative Oncology Group performance status at diagnosis, CA125 level at diagnosis, FIGO (International Federation of Gynecology and Obstetrics) stage IV disease, presence of ascites, and final tumor grade. Cox regression models with time-dependent effects and interaction terms were applied. A clinical risk calculator was developed and internally validated. RESULTS:A total of 3286 patients had a mean age of 60.0 years (SD 12); 2978 (90.6%) had high-grade serous carcinoma, and 795 (24.7%) presented with FIGO stage IV disease. A total of 1666 patients (50.7%) underwent primary cytoreductive surgery, and 1620 (49.3%) received neoadjuvant chemotherapy. The median follow-up duration was 43.8 months (interquartile range; 22.6-59.3). After propensity score matching (n=1524), overall survival was similar between groups (67.2 vs 65.0 months; HR 1.002, 95% CI 0.85 to 1.18, p=.98). Outcomes differed by ethnicity, residual disease, and post-operative complications. Post-operative complications (28%) significantly worsened survival (66 vs 46 months; HR 1.5, 95% CI 1.2 to 1.9, p<.001), especially among patients undergoing primary surgery (73 vs 46 months; HR 1.85, 95% CI 1.43 to 2.37, p<.001). The most favorable outcomes were observed among patients with primary surgery, complete resection, and no complications, with median overall survival not reached (HR 1.25, 95% CI 1.12 to 1.40, p<.001). CONCLUSIONS:Although overall survival was similar between groups, treatment effects differed by ethnicity, residual disease, and complications. Post-operative complications were associated with significantly worse survival, particularly among patients undergoing primary surgery, while the best outcomes were achieved in those who had primary surgery with complete resection and no complications.

Fully mycoheterotrophic (FMH) orchids rely entirely on mycorrhizal fungi for carbon and nutrients, with tropical Asian FMH orchids typically associating with saprotrophic fungi, though some known relationships also with ectomycorrhizal fungi, leaving much to learn about their fungal partners. Didymoplexis belongs to tribe Gastrodieae, which represents one of the largest fully mycoheterotrophic orchid lineages. Although mycorrhizal associations of its sister genus Gastrodia have been relatively well-studied, those of Didymoplexis remain largely unexplored. Here, we used molecular barcoding to analyze fungal associations and stable isotope analysis to elucidate the nutritional strategies of Didymoplexis micradenia, Didymoplexis pallens, and Didymoplexis siamensis in subtropical and tropical forests across Taiwan. In Didymoplexis pallens and Didymoplexis micradenia, most fungal partners were litter-decaying fungi (Mycena, Clitocybula, Marasmius, Gymnopus) with smaller contributions from ectomycorrhizal and rhizoctonia fungi. In Didymoplexis siamensis, ectomycorrhizal fungi dominated, particularly Sebacinales, however, with additional associations with wood-decaying Delicatula. The pattern of carbon and nitrogen isotope enrichments found for the three Didymoplexis species was in the typical range known for fully mycoheterotrophic orchids associated with litter- or wood-decaying fungi. 15N enrichments of all investigated Didymoplexis species distinguished from fully mycoheterotrophic orchids associated with ectomycorrhizal fungi. Despite its ectomycorrhizal association, Didymoplexis siamensis was weakly enriched in 15N and more enriched in 13C than found for exclusively ectomycorrhizal fully mycoheterotrophic orchids. Thus, Didymoplexis siamensis covered its carbon and nitrogen demand obviously through the additional association with wood-decaying Delicatula. These findings enhance our understanding of the diverse fungal associations and physiological ecology of Didymoplexis species in subtropical and tropical ecosystems.

The prevalence and potential functions of common mycorrhizal networks, or the ‘wood-wide web’, resulting from the simultaneous interaction of mycorrhizal fungi and roots of different neighbouring plants have been increasingly capturing the interest of science and society, sometimes leading to hyperbole and misinterpretation. Several recent reviews conclude that popular claims regarding the widespread nature of these networks in forests and their role in the transfer of resources and information between plants lack evidence. Here we argue that mycoheterotrophic plants associated with ectomycorrhizal or arbuscular mycorrhizal fungi require resource transfer through common mycorrhizal networks and thus are natural evidence for the occurrence and function of these networks, offering a largely overlooked window into this methodologically challenging underground phenomenon. The wide evolutionary and geographic distribution of mycoheterotrophs and their interactions with a broad phylogenetic range of mycorrhizal fungi indicate that common mycorrhizal networks are prevalent, particularly in forests, and result in net carbon transfer among diverse plants through shared mycorrhizal fungi. On the basis of the available scientific evidence, we propose a continuum of carbon transfer options within common mycorrhizal networks, and we discuss how knowledge on the biology of mycoheterotrophic plants can be instrumental for the study of mycorrhizal-mediated transfers between plants. In this Perspective, Vincent Merckx and colleagues discuss an important but overlooked aspect of mycorrhizal interactions, mycoheterotrophy, in the context of recent arguments about the importance of these interactions to forest functioning.

Background and Aims The earliest-diverging orchid lineage, Apostasioideae, consists only of two genera: Apostasia and Neuwiedia. Previous reports of Apostasia nipponica indicated a symbiotic association with an ectomycorrhiza-forming Ceratobasidiaceae clade and partial utilization of fungal carbon during the adult stage. However, the trophic strategy of Neuwiedia throughout its development remains unidentified. To further improve our understanding of mycoheterotrophy in the Apostasioideae, this study focused on Neuwiedia malipoensis examining both the mycorrhizal association and the physiological ecology of this orchid species across various development stages. Methods We identified the major mycorrhizal fungi of N. malipoensis protocorm, leafy seedling and adult stages using molecular barcoding. To reveal nutritional resources utilized by N. malipoensis, we compared stable isotope natural abundances (δ13C, δ15N, δ2H, δ18O) of different developmental stages with those of autotrophic reference plants. Key Results Protocorms exhibited an association with saprotrophic Ceratobasidiaceae rather than ectomycorrhiza-forming Ceratobasidiaceae and the 13C signature was characteristic of their fully mycoheterotrophic nutrition. Seedlings and adults were predominantly associated with saprotrophic fungi belonging to the Tulasnellaceae. While 13C and 2H stable isotope data revealed partial mycoheterotrophy of seedlings, it is unclear to what extent the fungal carbon supply is reduced in adult N. malipoensis. However, the 15N enrichment of mature N. malipoensis suggests partially mycoheterotrophic nutrition. Our data indicated a transition in mycorrhizal partners during ontogenetic development with decreasing dependency of N. malipoensis on fungal nitrogen and carbon. Conclusions The divergence in mycorrhizal partners between N. malipoensis and A. nipponica indicates different resource acquisition strategies and allows various habitat options in the earliest-diverging orchid lineage, Apostasioideae. While A. nipponica relies on the heterotrophic carbon gain from its ectomycorrhizal fungal partner and thus on forest habitats, N. malipoensis rather relies on own photosynthetic carbon gain as an adult, allowing it to establish in habitats as widely distributed as those where Rhizoctonia fungi occur.

Chlorophyllous plants exhibiting partial mycoheterotrophy obtain carbon through mycorrhizal interactions in addition to photosynthesis. In arbuscular mycorrhizal (AM) plants, the Paris-morphotype (i.e. hyphal coils) is considered essential for mycoheterotrophic carbon gains. Numerous tree species in tropical lowland forests form this morphotype, and under light- and nutrient-limitation, additional carbon gain would be beneficial. However, if seedlings of woody species in the understory of tropical lowland forests exhibit partial mycoheterotrophy remains unexplored. Here we (a) examined the AM morphotype (Paris- or Arum-type) in seedlings of 41 tropical woody species, and (b) to determine if any of the target Paris-type species are partially mycoheterotrophic, we compared their multi-element stable isotope natural abundance (13C, 2H, 18O, 15N) with neighbouring autotrophic non-Paris-type reference seedlings. About 50% of the investigated species (and 80% of the genera) exhibited the Paris-type, expanding the number of tropical plant genera with Paris-type AM. Enrichment in 13C, but not in 18O in target compared with neighbouring reference plants indicated partial mycoheterotrophy in seedlings of 6 of the 21 investigated Paris-type AM species. Our results indicate for the first time that carbon gain through mycoheterotrophy occurs in seedlings of AM tropical tree species. In tropical forests, partial mycoheterotrophy during seedling establishment may confer so far unrecognised ecological advantages influencing seedling recruitment and ecosystem dynamics.Read the free Plain Language Summary for this article on the Journal blog. Las plantas clorof & iacute;licas que presentan micoheterotrofia parcial obtienen carbono mediante fotos & iacute;ntesis e adicionalmente a travez de interacciones con hongos micorrizos. En las plantas con micorriza arbuscular (MA), el morfotipo Paris (es decir, con espirales hifales) se considera esencial para micoheterotrofia. Numerosas especies arb & oacute;reas en bosques tropicales forman este morfotipo y, en condiciones de limitaci & oacute;n de luz y nutrientes, la ganancia adicional de carbono ser & iacute;a beneficiosa. Sin embargo, si pl & aacute;ntulas de especies le & ntilde;osas en el sotobosque de bosques tropicales de tierras bajas exhiben micoheterotrofia parcial, permanece inexplorada. En este studio (a) examinamos el morfotipo MA (tipo Paris o Arum) en pl & aacute;ntulas de 41 especies le & ntilde;osas tropicales, y (b) para determinar si algunas de las especies con MA tipo Paris presentan micoheterotrofia parcial, comparamos su abundancia natural de is & oacute;topos estables multielementos (13C, 2H, 18O, 15N) con pl & aacute;ntulas de referencia vecinas aut & oacute;trofas (sin MA tipo Paris). El 50 % de las especies investigadas (y el 80 % de los g & eacute;neros) presentaban el tipo Paris. El enriquecimiento en 13C, pero no en 18O indic & oacute; micoheterotrofia parcial en pl & aacute;ntulas de 6 de las 21 especies investigadas de MA de tipo Paris. Nuestros resultados sugieren por primera vez que la ganancia de carbono a trav & eacute;s de la micoheterotrofia ocurre en pl & aacute;ntulas de especies de & aacute;rboles tropicales con MA. En bosques tropicales, la micoheterotrofia parcial en las pl & aacute;ntulas puede conferir ventajas ecol & oacute;gicas hasta ahora no reconocidas que influyen el establecimiento de pl & aacute;ntulas y la din & aacute;mica del ecosistema. Chlorophyllhaltige Pflanzen, die partiell mykoheterotroph sind, nehmen Kohlenstoff zus & auml;tzlich zur Photosynthese auch & uuml;ber Mykorrhiza-Interaktionen auf. Bei arbuskul & auml;r mykorrhizierten (AM) Pflanzen gilt der Paris-Morphotyp (mit characteristischen Hyphenwindungen) als Voraussetzung f & uuml;r eine mykoheterotrophe Kohlenstoffaufnahme. Dieser Morphtyp tritt in zahlreichen Baumarten in tropischen Tieflandw & auml;ldern auf und unter Licht- und N & auml;hrstoffbeschr & auml;nkungen im Unterwuchs k & ouml;nnte eine zus & auml;tzlicher Kohlenstoffaufnahme f & uuml;r S & auml;mlinge einen & ouml;kologischen Vorteil darstellen. Ob partielle Mykoheterotrophie bei S & auml;mlingen tropischer Baumarten auftritt, wurde allerdings noch nicht erforscht. In dieser Studie haben wir (a) den AM-Morphotyp (Paris- oder Arum-Typ) in S & auml;mlingen von 41 tropischen Holzarten untersucht, und (b) um festzustellen, ob von den Zielarten mit Paris-Typ einige partielle Mykoheterotrophie aufweisen, haben wir deren nat & uuml;rlichen stabile Isotopen-H & auml;ufigkeits-Signaturen (13C, 2H, 18O, 15N) mit benachbarten autotrophen Referenzs & auml;mlingen ohne Paris-Typ verglichen. 50 % der untersuchten Arten (und 80 % der Gattungen) wiesen den Paris-Typ der AM auf. Eine Anreicherung an 13C, aber nicht an 18O in den Zielpflanzen im Vergleich zu den benachbarten Referenzpflanzen deutet auf partielle Mykoheterotrophie in S & auml;mlingen von 6 der 21 untersuchten verholzten Arten vom Paris-Typ hin. Unsere Ergebnisse geben zum ersten Mal einen deutlichen Hinweis, dass S & auml;mlinge tropischer AM-Baumarten durch Mykoheterotrophie Kohlenstoff aufnehmen. In tropischen W & auml;ldern k & ouml;nnte partielle Mykoheterotrophie w & auml;hrend der Etablierung von S & auml;mlingen bislang unerkannte & ouml;kologische Vorteile mit sich bringen, welche die Rekrutierung von S & auml;mlingen und die Dynamik des & Ouml;kosystems beeinflussen.

Der Erhalt der Fertilität ist für einen erheblichen Anteil der Patientinnen mit einer Zervixkarzinom von Bedeutung. Wird die Erkrankung in einem sehr frühen Stadium diagnostiziert und ist eine Radiochemotherapie verzichtbar, so kann ein fertilitätserhaltendes Konzept zur Behandlung zur Anwendung kommen, ohne die onkologische Sicherheit zu gefährden. Im vorliegenden Artikel werden die Möglichkeiten des Fertilitäts- und Organerhalts bei Zervixkarzinom in Abhängigkeit vom jeweiligen Stadium dargestellt.

Stable isotope signatures of fungal sporocarps have been instrumental in identifying carbon gains of chlorophyllous orchids from a fungal source. Yet, not all mycorrhizal fungi produce macroscopic sporocarps and frequently fungi of different taxa occur in parallel in orchid roots. To overcome this obstacle, we investigated stable isotope signatures of fungal pelotons extracted from orchid roots and compared these data to the respective orchid and reference plant tissues. Anoectochilus sandvicensis and Epipactis palustris represented specialized or unspecialized rhizoctonia-associated orchids. Epipactis atrorubens and Epipactis leptochila are orchids considered ectomycorrhiza-associated with different preferences for Basidio- and Ascomycota. 13 C enrichment of rhizoctonia pelotons was minor compared with plant tissues and significantly lower than enrichments of pelotons from ectomycorrhizal Epipactis species. 15 N values of pelotons from E. leptochila and E. atrorubens showed similar patterns as known for respective sporocarps of ectomycorrhizal Ascomycota and Basidiomycota, however, with an offset towards lower 15 N enrichments and nitrogen concentrations. Our results suggest an explicit fungal nutrition source of orchids associated with ectomycorrhizal fungi, whereas the low 13 C enrichment in rhizoctonia-associated orchids and fungal pelotons hamper the detection of carbon gains from fungal partners. 15 N isotopic pattern of orchids further suggests a selective transfer of 15 N-enriched protein-nitrogen into orchids.

Preservation of fertility is important for a significant proportion of patients with cervical cancer. If the disease is diagnosed at an early stage and chemoradiotherapy is not necessary, a fertility-preserving treatment concept can be used without jeopardizing oncological safety. In the following article, the possibilities of fertility and organ preservation in cervical cancer patients depending on the stage of disease are described.

Deforestation and subsequent land-use conversion has altered ecosystems and led to negative effects on biodiversity. To ameliorate these effects, nitrogen-fixing (N2-fixing) trees are frequently used in the reforestation of degraded landscapes, especially in the tropics; however, their influence on ecosystem properties such as nitrogen (N) availability and carbon (C) stocks are understudied. Here, we use a 30-y old reforestation site of outplanted native N2-fixing trees (Acacia koa) dominated by exotic grass understory, and a neighboring remnant forest dominated by A. koa canopy trees and native understory, to assess whether restoration is leading to similar N and C biogeochemical landscapes and soil and plant properties as a target remnant forest ecosystem. We measured nutrient contents and isotope values (δ15N, δ13C) in soils, A. koa, and non-N2-fixing understory plants (Rubus spp.) and generated δ15N and δ13C isoscapes of the two forests to test for (1) different levels of biological nitrogen fixation (BNF) and its contribution to non-N2-fixing understory plants, and (2) the influence of historic land conversion and more recent afforestation on plant and soil δ13C. In the plantation, A. koa densities were higher and foliar δ15N values for A. koa and Rubus spp. were lower than in the remnant forest. Foliar and soil isoscapes also showed a more homogeneous distribution of low δ15N values in the plantation and greater influence of A. koa on neighboring plants and soil, suggesting greater BNF. Foliar δ13C also indicated higher water use efficiency (WUEi) in the plantation, indicative of differences in plant-water relations or soil water status between the two forest types. Plantation soil δ13C was higher than the remnant forest, consistent with greater contributions of exotic C4-pasture grasses to soil C pools, possibly due to facilitation of non-native grasses by the dense A. koa canopy. These findings are consequential for forest restoration, as they contribute to the mounting evidence that outplanting N2-fixing trees produces different biogeochemical landscapes than those observed in reference ecosystems, thereby influencing plant-soil interactions which can influence restoration outcomes.

Since the first discovery of unique carbon (C) and nitrogen (N) isotope signatures in fungal fruiting bodies (Gebauer & Dietrich, 1993; Gleixner et al., 1993), natural abundances of stable isotopes have been extensively used to identify the nutritional dynamics of fungi (Mayor et al., 2009). Assigning ecological roles of fungi is essential to determine the role of individual taxa in nutrient cycling and forest ecology. The use of isotope natural abundances in forest ecosystems has been crucial in distinguishing fungi with two main modes of life: ectomycorrhizal and saprotrophic fungi (Henn & Chapela, 2001). Within saprotrophic fungi, isotope natural abundances further allow the identification of the substrates used (Kohzu et al., 1999). Dual isotope analyses of the δ13C and δ15N values consistently indicate a differentiation in isotopic signatures between ectomycorrhizal and saprotrophic fungi within and among ecosystems (Henn & Chapela, 2001; Taylor et al., 2003; Trudell et al., 2004; Mayor et al., 2009). These signatures have been shown to reflect the ecophysiology of fungi and demonstrate that fungi that can utilize organic nitrogen exhibit higher δ15N than those fungi restricted to mineral nitrogen sources (Gebauer & Taylor, 1999; Lilleskov et al., 2002). Still, the ability to distinguish fungal nutritional modes has been long restricted to fungi that produce macroscopic sporocarps, such as mushrooms, due to their large mass which allows for physical measurements. Thus, for many fungi, particularly those associated with plant roots that do not form evident fruiting bodies, isotope natural abundances of fungal hyphae are scarce. Besides ectomycorrhizal fungi, isotope natural abundances are known for sporocarp-forming ericoid (e.g. Hobbie & Hogberg, 2012) and orchid-associated nonrhizoctonia saprotrophic fungi (e.g. Ogura-Tsujita et al., 2009). Yet, values of δ13C and δ15N are poorly known for arbuscular mycorrhizal fungi (but see e.g. Courty et al., 2011; Suetsugu et al., 2020, for isotope values of fungal spores), and the orchid-associated fungi known as ‘rhizoctonia’ in natural conditions. Recently, Klink et al. (2020) obtained the δ13C and δ15N of arbuscular mycorrhizal hyphae isolated from roots of a grass and a legume, inoculated in experimental conditions, thereby providing an efficient method to extract hyphae from roots. Using this method with a few modifications, here, we measured the isotope natural abundances δ13C and δ15N of naturally occurring arbuscular mycorrhizal (Fig. 1a–c) and orchid-associated hyphae (Fig. 1d–f) directly from roots (see Supporting Information Methods S1). To obtain hyphae of arbuscular mycorrhizal fungi, we selected two species of fully mycoheterotrophic plants: Thismia megalongensis C. A. Hunt, G. Steenbee. & V. Merckx and Sciaphila megastyla Fukuy. & T. Suzuki. Mycoheterotrophs are achlorophyllous plants that obtain carbon from their associated fungal partners (Leake, 1994; Merckx, 2013). Species in the plant genus Thismia have been demonstrated to be highly specialized on narrow lineages of Glomeromycotina fungi (Gomes et al., 2017; Merckx et al., 2017), while species of Sciaphila tend to associate with a wider phylogenetic diversity within the fungal subphylum (Merckx et al., 2012; Suetsugu & Okada, 2021). For fungi associated with orchid roots, we selected two chlorophyllous partially mycoheterotrophic orchid species, known to associate with rhizoctonia symbionts, Orchis militaris L. and Ophrys insectifera L., for which both isotope natural abundances and Sanger sequencing of the root-associated fungi have been performed previously (Schweiger et al., 2018). To be able to compare isotope values across sampling sites, the δ values of C and N stable isotope abundances were normalized by calculating enrichment factors (ε; see Methods S1). The enrichment factors ε13C and ε15N were significantly different between the fungal hyphae, mycoheterotrophic and reference plants for both T. megalongensis and S. megastyla (Fig. 1g; Table 1). For both species, ε13C was not distinguishable between the mycoheterotrophs and respective fungal hyphae, while ε15N was significantly different between mycoheterotrophs and fungi for S. megastyla, and marginally significant for T. megalongensis (Fig. 1; Table 1). In relation to the reference plants, the fungi extracted from both mycoheterotrophic species were significantly enriched in ε13C, and fungi from S. megastyla were marginally significantly depleted in ε15N. Similarly, both mycoheterotrophic plants were enriched in ε13C although only significantly for T. megalongensis. This indicates that the ε13C of fungal hyphae drives the 13C enrichment of arbuscular mycorrhizal fully mycoheterotrophic plants, and there seems to be a difference in nitrogen source between T. megalongensis and S. megastyla-associated fungi. Each mycoheterotrophic plant species is associated with nonoverlapping fungal clades within the Glomeromycotina (Fig. 2a). Sciaphila megastyla harboured fungi belonging to the genera Dominikia, Kamienskia and two unidentified amplicon sequence variants, while the fungi in the roots of T. megalongensis belonged exclusively to the genus Rhizophagus, supporting a specialization on fungal interactions of different degrees between these plant lineages (Gomes et al., 2020; Suetsugu & Okada, 2021). The enrichment factors ε13C and ε15N were generally significantly different between fungal hyphae, orchids and reference plants for both O. militaris and O. insectifera (Fig. 1h; Table 1). Both ε13C and ε15N were significantly different between orchid leaves and hyphae for O. militaris, while for O. insectifera, only ε13C was significantly higher in the hyphae in comparison with the plant tissue (Fig. 1; Table 1). In both orchid species, fungal hyphae were significantly enriched in ε13C, and in O. insectifera fungi were also enriched in ε15N in relation to the reference plants. The fungal hyphae extracted from the two orchid species were only weakly enriched in ε13C in comparison with reference plants and far less enriched in 13C than tissues of ectomycorrhizal fungi reported previously (Mayor et al., 2009). This observation is consistent with previous findings of absence of 13C enrichment in fully mycoheterotrophic protocorms of O. militaris, which were also associated with rhizoctonia fungi by Schweiger et al. (2018). Interestingly, in that study, protocorms of O. insectifera were somewhat enriched in 13C. We detected most sequenced reads obtained from root pieces to belong to the fungal order Helotiales. Fungi in the genus Ilyonectria were also detected, concordant with previous observations of these orchid species collected at the same site (Schweiger et al., 2018). Both Helotiales and Ilyonectria were present in the roots of both orchid species and, as far as we know, have an unknown ecological function. Helotiales have also been detected in the species studied in Zahn et al. (2023). In addition, we detected rhizoctonia fungi belonging to the families Ceratobasidiaceae, Serendipitaceae and Thelephoraceae in the roots of O. insectifera, and to the families Ceratobasidiaceae and Thelephoraceae in the roots of O. militaris (Fig. 2b). One orchid individual of O. militaris presented a high relative abundance of Ceratobasidiaceae, and another of Thelephoraceae in their roots. We cannot exclude that Tulasnellaceae are underrepresented in our data influenced by the primers used (Vogt-Schilb et al., 2020), as these taxa have been shown to be present in O. insectifera roots (Schweiger et al., 2019). Besides rhizoctonia fungi, we also found fungi known to form ectomycorrhizas (according to FungalTraits; Põlme et al., 2020), such as Sebacina (Sebacinaceae), Amphinema (Atheliaceae), Hebeloma and Hymenogaster (Hymenogastraceae) in two O. insectifera individuals. In terms of isotope signatures, no apparent differences were observed between individual samples where rhizoctonia fungi are present and those where Helotiales are predominant, and neither in relation to the plant material between specimens. Yet, a larger sample size would be needed to properly evaluate this. While ε13C values of hyphae are within the same range as found for the respective plant tissues of the AM mycoheterotrophic plants, as expected, ε15N values of the hyphae were considerably lower than ε15N of the respective plant tissues. This relative 15N depletion of hyphae in comparison with plant tissue was also observed for the two orchid species. One could wonder whether this depletion is either due to potential loss of hyphal content during extraction considering that nitrogen in chitin is depleted in 15N by c. 10‰ in comparison with fungal protein (Taylor et al., 1997; Hobbie & Hogberg, 2012) or due to a selective transport of 15N-enriched protein-derived compounds from fungal to plant tissues. Similarly, Zahn et al. (2023) show an equal depletion in 15N of hyphae extracted from two rhizoctonia-associated orchid species and for identically extracted hyphae from ectomycorrhiza-associated orchid roots an even larger depletion in 15N in relation to orchid leaves. In addition, the N concentrations of the extracted fungal hyphae of both T. megalongensis (2.25 ± 0.53 mmol gdw−1) and S. megastyla (2.18 ± 0.42 mmol gdw−1) were not distinguishable from those of the mycoheterotrophic plant tissues (1.95 ± 0.28 and 1.88 ± 0.45 mmol gdw−1 respectively), in congruence with Klink et al. (2020), while reference plants presented lower N concentrations (1.36 ± 0.44 and 1.17 ± 0.19 mmol gdw−1 for each set respectively) in relation to both fungal hyphae (T. megalongensis: Z = 2.772, P = 0.008, and S. megastyla: Z = 3.231, P = 0.002) and mycoheterotrophic plants (T. megalongensis: Z = 2.140, P = 0.032 and S. megastyla: Z = 2.710, P = 0.007). The N concentrations between fungal hyphae (1.19 ± 0.23 mmol gdw−1 for O. militaris and 1.64 ± 0.17 mmol gdw−1 for O. insectifera), orchids (1.74 ± 0.07 and 2.19 ± 0.17 mmol gdw−1 respectively) and reference plants (1.62 ± 0.76 and 1.79 ± 0.79 mmol gdw−1 for each set respectively) were not statistically different for both orchid species. In Zahn et al. (2023), the fungal hyphae extracted from rhizoctonia-associated orchids were also nondistinguishable from reference plants, while for one species (Anoectochilus sandvicensis), fungal hyphae had significantly lower N concentration than the orchid leaves. The arbuscular mycorrhizal diversity in the roots of the mycoheterotrophic plant species did not overlap between T. megalongensis and S. megastyla, and the fungal enrichment in ε15N was variable between plant species. The association with different fungal genera, in addition to local soil nitrogen availability, could have contributed to the differences in ε15N between species. Further studies are required to assess the source of variation and generality of isotope values among arbuscular mycorrhizal fungi. In the orchid-associated fungi, the fungal composition was variable between individual specimens, yet without reflection on the isotopic values of the extracted hyphae. The absence of differences in fungal isotopic values may indicate an artefact on the integration of both techniques. The apparent dominance of specific fungal groups in the roots could reflect spatial segregation of fungi, as a small piece of root was used for sequencing, while for the hyphal extraction, the remainder of the root system was used. Furthermore, ectomycorrhizal fungi were detected in two individuals of O. insectifera, while rhizoctonia fungi were detected in three individuals. The presence of ectomycorrhizal fungi in the roots of some rhizoctonia-associated orchids is commonly reported in the literature (e.g. Jacquemyn et al., 2021), yet it remains to be demonstrated whether these fungi indeed establish a mycorrhizal symbiosis with the orchid, in a sporadic or constant way during the orchid development, or represent endophytic fungi as it has been shown in typical nonmycorrhizal hosts (Schneider-Maunoury et al., 2020). Nevertheless, we cannot exclude those ectomycorrhizal fungi found in the roots of O. insectifera to be responsible for the slight enrichment in 13C and 15N of the hyphae extracted from O. insectifera in comparison with O. militaris. However, these isotopic differences are rather small and are not seen in the leaves of these two species, that is there appears to be no major plant matter gain from these ectomycorrhizal fungi. In addition, our results reveal that sporadic appearance of ectomycorrhizal fungi in orchids hitherto classified as rhizoctonia-associated does obviously not affect their isotope signature. Zahn et al. (2023) present further isotope signatures and diversity of root-associated fungi of orchids associated with ectomycorrhizal fungi. The assessment of fungal diversity often comprises a qualitative snapshot of a fraction of the root system, and although different fungal species or guilds may contribute differently to nutrient uptake at multiple occasions, we still lack a solid framework to quantify the contribution of each of these fungi to fungal–plant matter exchange. By contrast, isotopic abundance data are a temporal and spatial integrator (Dawson et al., 2002) over all fungal–plant matter exchange processes without providing direct information about the role of the individual potential fungal players, which is less sensitive to occasional changes in carbon or nitrogen supply. To the best of our knowledge, we reveal for the first-time isotope signatures of hyphae of arbuscular mycorrhizal fungi in mycoheterotrophic plants and, together with Zahn et al. (2023), of fungal pelotons present in chlorophyllous orchids in relation to the plant tissues from their roots. Arbuscular mycorrhizal hyphae have isotope signatures that allow a significant distinction in ε13C abundance in relation to reference plants. Subsequently, hyphae resemble the ε13C of the mycoheterotrophic plants, suggesting that these mycoheterotrophs gain carbon from the detected fungi. For the orchid-associated fungi, hyphae are only slightly enriched in 13C in relation to both reference and orchid plants, remaining unclear whether these orchids gain C from the associated fungi based on these results. However, the significant enrichment in 15N of hyphae or orchid leaves indirectly indicates a partial mycoheterotrophic matter gain by these orchids. Our study appeals to a careful interpretation when integrating root-associated fungal diversity and isotope natural abundances considering their inherent ecological significance as each method contains fundamentally different categories of information. Still, the combination of both approaches is greatly valuable and contributes to understand complex patterns in plant–fungal interactions, for example considering spatial and temporal fungal colonization in roots, and both advantages and caveats of each technique should be considered in the subsequent interpretation of ecological patterns. Finally, including the isotopic signatures of root-associated fungi in the context of mycorrhizal symbiosis contributes to a direct observation of fungal participation to organic matter gain of the plant. The authors thank Christine Tiroch, Carina Bauer and Petra Eckert (BayCEER – Laboratory of Isotope Biogeochemistry) for skilful technical assistance with stable isotope abundance measurements, and also Johanna Pausch for allowing to use her laboratory for fungal extractions. Financial support was provided by an EMBO short-term fellowship to SIFG. The authors acknowledge the authorization by the Regierung von Oberfranken to collect samples of protected orchid species. Open Access funding enabled and organized by Projekt DEAL. None declared. SIFG and GG designed the research and collected the orchid material. PG and SK guided the fungal hyphal extraction by SIFG. CH and KS collected the arbuscular mycorrhizal plant material. GG supervised the isotope abundance analyses. SIFG performed the molecular analysis, analysed the data, and together with GG wrote the manuscript. All authors commented and approved the final version of the manuscript. Isotope abundance data are available in the Supporting Information. Raw sequencing data are available in GenBank/SRA under project number PRJNA966927. Methods S1 Methods used in this paper. Table S1 Isotope raw data and identity of reference plants at genus level. Please note: Wiley is not responsible for the content or functionality of any Supporting Information supplied by the authors. Any queries (other than missing material) should be directed to the New Phytologist Central Office. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

The stable N and O isotope composition of soil and soil‐respired N 2 O is increasingly measured, yet a solid theoretical framework for interpreting the data remains to be developed. Here, the physical processes that affect soil N 2 O and its isotopes are embedded in a diffusion/reaction model. Numerical experiments are compared to data to demonstrate how various soil processes influence depth profiles and surface fluxes of soil N 2 O, δ 15 N N2O , and δ 18 O N2O . Model predictions and data suggest that the isotope composition of the net N 2 O soil flux, in soils that have N 2 O consumption, is a function of the net flux rate, and the isotope differences between the atmosphere and the biological source. Asymptotically large negative or positive δ 15 N flux and δ 18 O flux values occur as the net soil N 2 O flux approaches zero from positive or negative flux rates, respectively. This implies that the isotopic imprint of soil fluxes on the global atmospheric N 2 O pool is more variable than previously suggested. Additionally, the observed isotope values in static flux chambers are possibly complicated by the fact that consumption fluxes increase as the concentration in the chambers increases. This work reveals that even simple chamber flux measurements may possess isotope effects imparted by consumption during the chamber measurement and suggests ways to experimentally test this possibility. Additionally, simple methods to estimate depth‐dependent net production/consumption and its isotope effects are suggested. However, understanding the gross rates of the production and consumption of soil N 2 O remains an elusive goal.

Orchid mycorrhiza forms unique symbiotic associations between members of the Orchidaceae and multiple ecological guilds of fungi. Because orchids associate with a wide variety of fungi with different ecological functions, they represent an ideal study system to address fundamental questions about the evolution and ecophysiology of mycorrhizal symbiosis. Although it is well established that shifts in mycorrhizal associations are linked to transitions in plant trophic mode, it remains unclear what ecological drivers promote these evolutionary changes. Here, we investigated mycorrhizal communities and isotope signatures across six populations of the terrestrial orchid Neottia ovata growing under contrasting light conditions in temperate Europe. We hypothesized that plants growing in forests would associate with different mycorrhizal fungi than plants occurring in grasslands and that the limited light availability in forests leads to a higher contribution of fungi to the carbon budget of orchids. Our results showed that N. ovata predominantly associated with rhizoctonia fungi of the family Serendipitaceae in both habitats, but plants in forests also recruited ectomycorrhizal fungi. Root communities highly resembled soil communities and variation in root communities was significantly related to habitat type and edaphic factors. In contrast, isotope signatures (C-13, N-15, H-2 and O-18) and N concentration showed no significant relationship with habitat type. In addition, both C-13 and H-2 were not significantly correlated to habitat's light availability. Although it has been suggested that the presence of a wide variety of ectomycorrhizal fungi in root communities of orchids can serve as a precursor for evolutionary shifts to partial mycoheterotrophy (mixotrophy), the presence or absence of ectomycorrhizal fungi did not substantially influence the isotope signatures of N. ovata. These results indicate that rhizoctonia fungi played the major functional role in C and nutrient supply and that ectomycorrhizal fungi did not substantially contribute to the carbon budget of the plants. Read the free Plain Language Summary for this article on the Journal blog.

Temperate grasslands exhibit strong spatial and temporal variation in water regimes. Thus, grassland plants experience potentially stressful water regimes, which may influence their tissue silicon (Si) and nitrogen (N) concentrations. Plant Si and N concentrations play important ecological roles in temperate grasslands, for example, by influencing plant performance and herbivory, yet comparisons of species' responses to a broad range of water regimes, including drought, waterlogging and flooding, are lacking. We conducted a mesocosm experiment with 10 temperate grassland species of two life-forms (grasses and forbs) exposed to four different soil water regimes (drought, a benign control, waterlogged and flooded conditions), and analysed their Si and N concentrations. Grasses showed lower Si concentrations under drought and flooding compared to the benign control and the highest concentrations emerged under waterlogging. Overall, plant Si responses of grasses were more uniform, while in forbs, responses varied both in direction and magnitude across species. For N concentrations, all species and life-forms showed the highest concentrations under drought compared to the benign control, while half of the species exhibited decreasing concentrations under waterlogging and/or flooding. The water regimes, especially waterlogging and flooding, induced changes in species rankings of plant Si and N concentrations, with stronger shifts in forbs than in grasses. Our results indicate that spatial and temporal variation of water regimes may influence plant Si and N concentrations in temperate grassland species. Plant Si responses to water regimes might be highly species-specific in forbs but more similar in grasses, whereas plant N responses are likely to be relatively uniform across species and life-forms. The strong plasticity in plant Si and N concentrations we observed might have pervasive consequences for ecological processes, such as herbivory. Read the free Plain Language Summary for this article on the Journal blog.

The chlorophyllous, terrestrial orchid Cremastra appendiculata from East Asia is unique concerning its fungal mycorrhiza partners. The initially mycoheterotrophic protocorms exploit rather specialized non-rhizoctonia saprotrophic Psathyrellaceae. Adult individuals of this orchid species are either linked to Psathyrellaceae being partially mycoheterotrophic or form mycorrhiza with fungi of the ubiquitous saprotrophic rhizoctonia group. This study provides new insights on nutrition mode, subterranean morphology and fungal partners across different life stages of C. appendiculata. We compared different development stages of C. appendiculata to surrounding autotrophic reference plants based on multi-element natural abundance stable isotope analyses (δ13C, δ15N, δ2H, δ18O) and total N concentrations. Site- and sampling-time-independent enrichment factors of stable isotopes were used to reveal trophic strategies. We determined mycorrhizal fungi of C. appendiculata protocorm, seedling and adult samples using high-throughput DNA sequencing. We identified saprotrophic non-rhizoctonia Psathyrellaceae as dominant mycorrhizal fungi in protocorm and seedling rhizomes. In contrast, the roots of seedlings and mature C. appendiculata were mainly colonized with fungi belonging to the polyphyletic assembly of rhizoctonia (Ceratobasidium, Thanatephorus and Serendipitaceae). Mature C. appendiculata did not differ in isotopic signature from autotrophic reference plants suggesting a fully autotrophic nutrition mode. Characteristic of orchid specimens entirely relying on fungal nutrition, C. appendiculata protocorms were enriched in 15N, 13C and 2H compared to reference plants. Seedlings showed an intermediate isotopic signature, underpinning the differences in the fungal community depending on their subterranean morphology. In contrast to the suggestion that C. appendiculata is a partially mycoheterotrophic orchid species, we provide novel evidence that mature C. appendiculata with rhizoctonia mycobionts can be entirely autotrophic. Besides an environmentally driven variability among populations, we suggest high within-individual flexibility in nutrition and mycobionts of C. appendiculata, which is subject to the ontogenetic development stage.

QR-Codescannen&Beitragonline lesen Das Endometriumkarzinom galt viele Jahreals eineErkrankungälterer Patientinnen, die operativ gut behandelbar ist und sich durch eine relativ gute Prognose auszeichnet. Dies mag erklären, weshalb das Endometriumkarzinom lange Zeit weniger im Focus klinischer Studien zur Optimierung der Therapiestrategien stand. Während die Prognose zumindest früher Stadien tatsächlich als vergleichsweise gut zu bezeichnen ist, so ist bei der fortgeschrittenen oder metastasierten ErkrankungdasmittlereÜberlebenkurz, und die wissenschaftlich in klinischen Studien gut evaluierten Behandlungsmöglichkeiten sind sehr begrenzt. Weltweit ist in den letzten Jahren eine deutliche Zunahme der Inzidenz des Endometriumkarzinoms zu verzeichnen, sodass das Endometriumkarzinom inzwischen die vierthäufigste Krebserkrankung bei Frauen darstellt, was die Notwendigkeit zur Optimierung und Standardisierung der Therapiestrategien unterstreicht.

BACKGROUND AND AIMS:While isotopic enrichment of nitrogen (15N) and carbon (13C) is often used to determine whether carnivorous plant species capture and assimilate nutrients from supplemental sources such as invertebrate prey or mammal excreta (heterotrophic nutrition), little is known about how successful the different strategies deployed by carnivorous plants are at obtaining supplemental nutrition. The collection of mammalian faeces by Nepenthes (tropical pitcher plants) is the result of a highly specialized biological mutualism that results in heterotrophic nitrogen gain; however, it remains unknown how effective this strategy is in comparison to Nepenthes species not known to collect mammalian faeces. METHODS:We examined how isotopic enrichment varied in the diverse genus Nepenthes, among species producing pitchers for invertebrate capture and species exhibiting mutualisms for the collection of mammal excreta. Enrichment factors were calculated from δ15N and δ13C values from eight Nepenthes species and naturally occurring hybrids along with co-occurring reference (non-carnivorous) plants from three mountain massifs in Borneo: Mount Kinabalu, Mount Tambuyukon and Mount Trus Madi. RESULTS:All Nepenthes examined, except N. edwardsiana, were significantly enriched in 15N compared to co-occurring non-carnivorous plants, and 15N enrichment was more than two-fold higher in species with adaptations for the collection of mammal excreta compared with other Nepenthes. CONCLUSIONS:The collection of mammal faeces clearly represents a highly effective strategy for heterotrophic nitrogen gain in Nepenthes. Species with adaptations for capturing mammal excreta occur exclusively at high elevation (i.e. are typically summit-occurring) where previous studies suggest invertebrate prey are less abundant and less frequently captured. As such, we propose this strategy may maximize nutritional return by specializing towards ensuring the collection and retention of few but higher-value N sources in environments where invertebrate prey may be scarce.

Background and Aims Previous carbon stable isotope (C-13) analyses have shown for very few C-3-hemiparasites utilizing C-4- or CAM-hosts the use of two carbon sources, autotrophy and heterotrophy. This C-13 approach, however, failed for the frequently occurring C-3-C-3 parasite-host pairs. Thus, we used hydrogen stable isotope (H-2) natural abundances as a substitute for C-13 within a C-3-Orobanchaceae sequence graded by haustoria complexity and C-3-Santalaceae. Methods Parasitic plants and their real or potential host plants as references were collected in Central European lowland and alpine mountain meadows and forests. Parasitic plants included the xylem-feeding holoparasite Lathraea squamaria parasitizing on the same carbon nutrient source (xylem-transported organic carbon compounds) as potentially Pedicularis, Rhinanthus, Bartsia, Melampyrum and Euphrasia hemiparasites. Reference plants were used for an autotrophy-only isotope baseline. A multi-element stable isotope natural abundance approach was applied. Key Results Species-specific heterotrophic carbon gain ranging from 0 to 51 % was estimated by a H-2 mixing-model. The sequence in heterotrophic carbon gain mostly met the morphological grading by haustoria complexity: Melampyrum- < Rhinanthus- < Pedicularis-type. Conclusion Due to higher transpiration and lower water-use efficiency, depletion in C-13, O-18 and H-2 compared to C-3-host plants should be expected for tissues of C-3-hemiparasites. However, H-2 is counterbalanced by transpiration (H-2-depletion) and heterotrophy (H-2-enrichment). Progressive H-2-enrichment can be used as a proxy to evaluate carbon gains from hosts.

Human land use is of growing concern for island ecosystems. Besides direct impacts on biodiversity, land uses can alter the functioning and structure of ecosystems. Central to this are impacts on food webs. The release of additional nutrients from human origin, habitat homogenization, or environmental filtering due to human land use can change the diet of individual consumer species (i.e., their trophic niches) and the distribution and overlap of trophic niches within a food web. However, it remains largely unclear whether the effects on food web properties vary between the different and predominant human land uses present on islands. Here, we investigated the impact of two dominant human land uses on small oceanic islands (i.e., urban and tourism development) and tested if and how different land uses on islands affect food web structure. To disentangle human land uses, we investigated islands, which were either privately owned by a tourist facility (i.e., exclusively tourism land use) or experienced urban development from the local population (i.e., urban land use), or remained uninhabited, serving as reference sites free of direct land use. Using stable isotope analysis, we show that isotope signature, trophic (isotopic) niches, and overall food web properties of the investigated island invertebrate communities were significantly changed under both land use regimes. While trophic diversity was reduced and trophic niche widths increased under tourism land use, the investigated food webs showed reduced trophic diversity at the food web base and a more uneven trophic niche distribution under urban land use. In summary, these findings show that different human land uses can have contrasting impacts on oceanic island food webs. As oceanic islands experience rapidly growing human land conversion, our results indicate that they may also face increasing yet unpredictable long-term changes in food web dynamics.