Mycoheterotrophic Plants Research Articles

What are the genomic consequences for plastids in a mixotrophic orchid (Epipactis helleborine)?

The chloroplast (plastid) controls carbon uptake, so its DNA sequence and function are highly conserved throughout the land plants. But, for those that have alternative carbon supplies, the plastid genome is susceptible to mutations in the photosynthetic genes and overall size reduction. Fully mycoheterotrophic plants receive organic carbon from their fungal partner, do not photosynthesize, and also do not exhibit green coloration (or produce substantial quantities of chlorophyll). Epipactis helleborine (L.) Crantz exhibits all trophic modes from autotrophy to full mycoheterotrophy. Albinism is a stable condition in individuals of this species and does not prevent them from producing flowers and fruit. Here we assemble and compare the plastid genome of green and albino individuals. Our results show that there is still strong selective pressure in the plastid genome. Therefore, the few punctual differences among them, to our knowledge, do not affect any normal photosynthetic capability in the albino plant. These findings suggest that mutations or other genetically controlled processes in other genomes, or environmental conditions, are responsible for the phenotype.

Mycorrhizal communities of two closely related species, Pyrola subaphylla and P. japonica, with contrasting degrees of mycoheterotrophy in a sympatric habitat.

Mycoheterotrophic plants typically form associations with a narrow range of mycorrhizal fungi. Consequently, mycorrhizal specialization is often considered to be an important step in mycoheterotrophic evolution. However, it remains unclear whether such specialization is likely to occur in plants of the genus Pyrola, which are generally associated with fungi in multiple ectomycorrhizal families. Here, we investigated the mycorrhizal communities of a nearly fully mycoheterotrophic Pyrola species (Pyrola subaphylla), a closely related partially mycoheterotrophic Pyrola species (Pyrola japonica), and a co-occurring autotrophic ectomycorrhizal tree, Quercus crispula, which is their potential carbon source, in a cool-temperate Japanese forest. High-throughput DNA sequencing revealed that numerous common ectomycorrhizal OTUs interact with the two Pyrola species and Q. crispula, thereby providing an opportunity to exploit a certain amount of carbon from common mycorrhizal networks. In addition, not only P. japonica but also P. subaphylla exhibited exceptionally high alpha mycobiont diversity, with 52 ectomycorrhizal OTUs belonging to 12 families being identified as P. subaphylla mycobionts and 69 ectomycorrhizal OTUs in 18 families being detected as P. japonica mycobionts. Nonetheless, the beta mycobiont diversity of P. subaphylla and P. japonica individuals was significantly lower than that of Q. crispula. Moreover, the beta mycobiont diversity of P. subaphylla was found to be significantly lower than that of P. japonica. Therefore, despite their seemingly broad mycorrhizal interactions, the two Pyrola species (particularly P. subaphylla) showed consistent fungal associations, suggesting that mycorrhizal specialization may have developed during the course of mycoheterotrophic evolution within the genus Pyrola.

Improved de novo Assembly of the Achlorophyllous Orchid Gastrodia elata.

Achlorophyllous plants are full mycoheterotrophic plants with no chlorophyll and they obtain their nutrients from soil fungi. Gastrodia elata is a perennial, achlorophyllous orchid that displays distinctive evolutionary strategy of adaptation to the non-photosynthetic lifestyle. Here in this study, the genome of G. elata was assembled to 1.12 Gb with a contig N50 size of 110 kb and a scaffold N50 size of 1.64 Mb so that it helped unveil the genetic basics of those adaptive changes. Based on the genomic data, key genes related to photosynthesis, leaf development, and plastid division pathways were found to be lost or under relaxed selection during the course of evolution. Thus, the genome sequence of G. elata provides a good resource for future investigations of the evolution of orchids and other achlorophyllous plants.

IDENTIFICATION OF MYCOHETEROTROPHIC PLANTS (Burmanniaceae, Orchidaceae, Polygalaceae, Tiuridaceae) IN NORTH SUMATRA, INDONESIA

The majority of mycoheterotrophic herbs live in shady and humid forest. Therefore, the types of mycoheterotrophic plant are very abundant in tropical areas. One of the areas in Indonesia with the tropics is North Sumatera province. Unfortunately, the information about the species of mycoheterotrophic in North Sumatra is still limited. The objective of the research was to figure out the types of mycoheterotrophic plants in North Sumatra. The study was conducted in August until October 2019 in several areas of the Natural Resources Conservation Hall (BBKSDA) of North Sumatra province, the nature Reserve and nature Park. The research sites covered Tinggi Raja Nature Reserve, Dolok Sibual-Buali Nature Reserve, Sibolangit Tourist Park and Sicike-Cike Natural Park. In conducting sampling, the method used was through exploration or cruising method. The list of mycoheterotrophic plant species presented in this study consisted of their scientific names, synonyms, descriptions, distributions, and ecological information. A total of 9 species of mycoheterotrophic plants (4 families) in Sumatra have been found. As for the family Burmanniaceae, there are three species Burmannia championii, Burmannia lutescens, Gymnosiphon aphyllus. On the other hand, as for the Orchidaceae, there are 4 species, such as Didymoplexis pallens, Eulophia zollingeri, Galeola lindleyana, Gastrodia verrucosa while for the Poligalaceae and Tiuridaceae family, simply one type is found: Epirixanthes elongata and Sciaphila Secundiflora, respectively.

Molecular evidence supports simultaneous association of the achlorophyllous orchid Chamaegastrodia inverta with ectomycorrhizal Ceratobasidiaceae and Russulaceae

BackgroundAchlorophyllous orchids are mycoheterotrophic plants, which lack photosynthetic ability and associate with fungi to acquire carbon from different environmental sources. In tropical latitudes, achlorophyllous forest orchids show a preference to establish mycorrhizal relationships with saprotrophic fungi. However, a few of them have been recently found to associate with ectomycorrhizal fungi and there is still much to be learned about the identity of fungi associated with tropical orchids. The present study focused on mycorrhizal diversity in the achlorophyllous orchid C. inverta, an endangered species, which is endemic to southern China. The aim of this work was to identify the main mycorrhizal partners of C. inverta in different plant life stages, by means of morphological and molecular methods.ResultsMicroscopy showed that the roots of analysed C. inverta samples were extensively colonized by fungal hyphae forming pelotons in root cortical cells. Fungal ITS regions were amplified by polymerase chain reaction, from DNA extracted from fungal mycelia isolated from orchid root samples, as well as from total root DNA. Molecular sequencing and phylogenetic analyses showed that the investigated orchid primarily associated with ectomycorrhizal fungi belonging to a narrow clade within the family Ceratobasidiaceae, which was previously detected in a few fully mycoheterotrophic orchids and was also found to show ectomycorrhizal capability on trees and shrubs. Russulaceae fungal symbionts, showing high similarity with members of the ectomycorrhizal genus Russula, were also identified from the roots of C. inverta, at young seedling stage. Ascomycetous fungi including Chaetomium, Diaporthe, Leptodontidium, and Phomopsis genera, and zygomycetes in the genus Mortierella were obtained from orchid root isolated strains with unclear functional role.ConclusionsThis study represents the first assessment of root fungal diversity in the rare, cryptic and narrowly distributed Chinese orchid C. inverta. Our results provide new insights on the spectrum of orchid-fungus symbiosis suggesting an unprecedented mixed association between the studied achlorophyllous forest orchid and ectomycorrhizal fungi belonging to Ceratobasidiaceae and Russulaceae. Ceratobasidioid fungi as dominant associates in the roots of C. inverta represent a new record of the rare association between the identified fungal group and fully mycoheterotrophic orchids in nature.

Use of radiocarbon for assessing the mycorrhizal status of mycoheterotrophic plants

ABSTRACT Mycoheterotrophic plants are non-photosynthetic plants that obtain nutrients from fungi. Even though most of these plants are associated with the mycorrhizal partners of surrounding photosynthetic plants, recent studies have suggested that some mycoheterotrophic orchids indirectly obtain carbon from decaying organic matter through associations with saprotrophic fungi. However, such suggestions have been based primarily on indirect evidence, such as the 13C and 15N abundances of fungi and plants. It was recently reported that some mycoheterotrophs yield elevated Δ 14C values, owing to the indirect acquisition of 14C-enriched bomb carbon from dead wood. The approach was based on the anthropogenic change of Δ 14C values; atmospheric CO2 were globally elevated by nuclear weapons testing in the 1950s and early 1960s, but have steadily declined since its peak after the atmospheric nuclear test ban treaty of 1963. The study has provided novel evidence that mycoheterotrophic plants can exploit both mycorrhizal and saprotrophic fungi. We suggest that the radiocarbon analysis is also useful for investigating the nutritional modes of mixotrophic plants as well as for investigating whether the recruitment of wood-decaying fungi into novel mycorrhizal partnerships preceded the evolution of full mycoheterotrophy.

Degradation of key photosynthetic genes in the critically endangered semi-aquatic flowering plant Saniculiphyllum guangxiense (Saxifragaceae)

BackgroundPlastid gene loss and pseudogenization has been widely documented in parasitic and mycoheterotrophic plants, which have relaxed selective constraints on photosynthetic function. More enigmatic are sporadic reports of pseudogenization and loss of important photosynthesis genes in lineages thought to be fully photosynthetic. Here we report the complete plastid genome of Saniculiphyllum guangxiense, a critically endangered and phylogenetically isolated plant lineage, along with genomic evidence of reduced chloroplast function. We also report 22 additional plastid genomes representing the diversity of its containing clade Saxifragales, characterizing gene content and placing variation in a broader phylogenetic context.ResultsWe find that the plastid genome of Saniculiphyllum has experienced pseudogenization of five genes of the ndh complex (ndhA, ndhB, ndhD, ndhF, and ndhK), previously reported in flowering plants with an aquatic habit, as well as the surprising pseudogenization of two genes more central to photosynthesis (ccsA and cemA), contrasting with strong phylogenetic conservatism of plastid gene content in all other sampled Saxifragales. These genes participate in photooxidative protection, cytochrome synthesis, and carbon uptake. Nuclear paralogs exist for all seven plastid pseudogenes, yet these are also unlikely to be functional.ConclusionsSaniculiphyllum appears to represent the greatest degree of plastid gene loss observed to date in any fully photosynthetic lineage, perhaps related to its extreme habitat specialization, yet plastid genome length, structure, and substitution rate are within the variation previously reported for photosynthetic plants. These results highlight the increasingly appreciated dynamism of plastid genomes, otherwise highly conserved across a billion years of green plant evolution, in plants with highly specialized life history traits.

Mitochondrial genome of the nonphotosynthetic mycoheterotrophic plant Hypopitys monotropa, its structure, gene expression and RNA editing.

Heterotrophic plants—plants that have lost the ability to photosynthesize—are characterized by a number of changes at all levels of organization. Heterotrophic plants are divided into two large categories—parasitic and mycoheterotrophic (MHT). The question of to what extent such changes are similar in these two categories is still open. The plastid genomes of nonphotosynthetic plants are well characterized, and they exhibit similar patterns of reduction in the two groups. In contrast, little is known about the mitochondrial genomes of MHT plants. We report the structure of the mitochondrial genome of Hypopitys monotropa, a MHT member of Ericaceae, and the expression of its genes. In contrast to its highly reduced plastid genome, the mitochondrial genome of H. monotropa is larger than that of its photosynthetic relative Vaccinium macrocarpon, and its complete size is ~810 Kb. We observed an unusually long repeat-rich structure of the genome that suggests the existence of linear fragments. Despite this unique feature, the gene content of the H. monotropa mitogenome is typical of flowering plants. No acceleration of substitution rates is observed in mitochondrial genes, in contrast to previous observations in parasitic non-photosynthetic plants. Transcriptome sequencing revealed the trans-splicing of several genes and RNA editing in 33 of 38 genes. Notably, we did not find any traces of horizontal gene transfer from fungi, in contrast to plant parasites, which extensively integrate genetic material from their hosts.

Plastome of the mycoheterotrophic eudicot Exacum paucisquama (Gentianaceae) exhibits extensive gene loss and a highly expanded inverted repeat region.

Mycoheterotrophic plants are highly specialized species able to acquire organic carbon from symbiotic fungi, with relaxed dependence on photosynthesis for carbon fixation. The relaxation of the functional constraint of photosynthesis and thereby the relaxed selective pressure on functional photosynthetic genes usually lead to substantial gene loss and a highly degraded plastid genome in heterotrophs. In this study, we sequenced and analyzed the plastome of the eudicot Exacum paucisquama, providing the first plastid genome of a mycoheterotroph in the family Gentianaceae to date. The E. paucisquama plastome was 44,028 bp in length, which is much smaller than the plastomes of autotrophic eudicots. Although the E. paucisquama plastome had a quadripartite structure, a distinct boundary shift was observed in comparison with the plastomes of other eudicots. We detected extensive gene loss and only 21 putative functional genes (15 protein-coding genes, four rRNA genes and two tRNA genes). Our results provide valuable information for comparative evolutionary analyses of plastomes of heterotrophic species belonging to different phylogenetic groups.

Physisporinus is an important mycorrhizal partner for mycoheterotrophic plants: Identification of mycorrhizal fungi of three Yoania species

Improved understanding of mycorrhizal diversity in mycoheterotrophic (MH) plants is a key element of studies that investigate their evolution. MH plants are completely dependent on their mycorrhizal fungi for carbon. Mycorrhizal fungi of the MH genus Yoania (Orchidaceae), which is distributed in East Asia, have yet to be identified. We identified the mycobionts of three Japanese Yoania species, Y. amagiensis, Y. flava, and Y. japonica, by sequencing the internal transcribed spacer regions of nuclear ribosomal DNA. The sequences obtained were assigned to five operational taxonomic units (OTUs), among which four belonged to the genus Physisporinus (Meripilaceae, Polyporales) and one to Thelephoraceae. Yoania flava and Y. japonica were specifically associated with a single OTU of Physisporinus, while Y. amagiensis was associated with four Physisporinus OTUs. A phylogenetic analysis showed that fungal sequences from species of two other MH orchid genera, Cyrtosia and Galeola, also belonged to Physisporinus and were closely related to the Yoania mycobionts. This is the first study to report that (i) wood-rotting Physisporinus fungi form mycorrhizae with plant species, and (ii) have an important role in orchid mycoheterotrophy.

Morpho-anatomical differences among mycoheterotrophic Afrothismia spp. (Thismiaceae) indicate an evolutionary progression towards improved mycorrhizal benefit

Achlorophyllous, mycoheterotrophic plants depend on their mycorrhizal fungi for 100% of their carbon supply. Hence, there is strong evolutionary pressure towards a well-organized functioning of the association from the plant’s perspective. Members of the mycoheterotrophic genus Afrothismia have evolved elaborate fungal colonization patterns allowing a sustained benefit from external fungal penetration events. On the basis of anatomical details of the root-shoot systems of A. korupensis and A. hydra, we elucidate an evolutionary progression between the comparatively simple mycorrhizal pattern in A. gesnerioides and the so far most complex mycorrhiza in A. saingei. We detected two major advancements: (1) two species, A. korupensis and A. saingei, use the fungus itself as energy storage, replacing starch depositions used by A. gesnerioides and A. hydra, and (2) the morphological complexity of hyphal forms in plant tissue compartments increases from A. gesnerioides to A. saingei. We discuss the omitting of starch metabolism as well as the morpho-anatomical differences as an evolutionary fine-tuning of the compartmented mycorrhizal organization in Afrothismia. Our results support the idea of a taxonomic distinction between Afrothismia and other Thismiaceae.

Mycoheterotrophic plants living on arbuscular mycorrhizal fungi are generally enriched in 13C, 15N and 2H isotopes

Abstract Fully mycoheterotrophic plants are thought to obtain carbon exclusively from their root‐associated fungal partners. The general enrichment of these plants in the heavy isotopes 13C and 15N suggests that fungi are the main nutrient source for these plants. Yet, the majority of studies have targeted mycoheterotrophic plants associated with ectomycorrhizal, orchid mycorrhizal and saprotrophic fungi, while mycoheterotrophic plants living on arbuscular mycorrhizal fungi remain understudied. Here, we sampled 13 species of arbuscular mycorrhizal fully mycoheterotrophic plants from five families and co‐occurring autotrophic reference plants growing in forests of tropical South America, tropical South East Asia and temperate Australasia. We measured stable isotope natural abundances (δ13C, δ15N, δ2H and δ18O), determined total nitrogen concentrations and used high‐throughput DNA sequencing to characterize the arbuscular mycorrhizal fungal communities associated with the sampled mycoheterotrophic plants. We observed a general enrichment in 13C and 15N isotopes across mycoheterotrophic plant families and geographic regions. We confirm cases where no 15N enrichment is present, but we show that in general arbuscular mycoheterotrophic plants are enriched in 15N. Moreover, we demonstrate for the first time that these plants are significantly enriched in 2H but not in 18O in relation to their autotrophic references. The fungal communities targeted by the mycoheterotrophs mainly consist of Glomeraceae and show strong association with the isotopic signatures and geographic origin of the plants. Synthesis. Our findings enlarge the limited knowledge on the multi‐element stable isotopic signatures of mycoheterotrophic plants living on arbuscular mycorrhizal fungi. We show that these plants are enriched in 13C and 2H as expected due to their mycoheterotrophic nutrition, and that in general they are also enriched in 15N, despite some exceptions. Variation in stable isotope signatures is likely influenced by plant taxonomy, geography and fungal community composition.

Evidence for newly discovered albino mutants in a pyroloid: implication for the nutritional mode in the genus Pyrola.

PremiseDifficulties in comparing extremely divergent features in fully mycoheterotrophic plants with those in closely related chlorophyllous plants have complicated attempts to reveal the evolutionary patterns and processes of fully mycoheterotrophic plants. Albino mutants of partially mycoheterotrophic plants, generally observed in Orchidaceae, have provided an ideal model for investigating the evolution of mycoheterotrophy within similar genetic backgrounds. In 2018, we found a putative albino population of Pyrola (Ericaceae). Here we aimed to reveal the identity of the albino pyroloid and confirm its fully mycoheterotrophic status.MethodsTo reveal the putative albino pyroloid's identity, we examined its morphology and sequenced its chloroplast DNA. In addition, we assessed the trophic status of the putative albino pyroloid by analyzing chlorophyll fluorescence, chlorophyll concentration, and natural 13C and 15N abundances.ResultsWe identified albino individuals as P. japonica—otherwise a partially mycoheterotrophic species. We confirmed their albino status by their considerably lower chlorophyll fluorescence and concentrations than those of sympatrically occurring chlorophyllous plants. 13C abundance in the albino individuals was significantly higher than in the green individuals of P. japonica.ConclusionsThis first report of albino mutants from partially mycoheterotrophic species in angiosperms other than orchids will play a valuable role in further studies focused on mycoheterotrophy. For instance, their δ 13C and δ 15N values represent a reference for fully mycoheterotrophic plants in Pyrola. Our findings also indicate the strong dependence of some leafy Pyrola species on fungal C during their entire life cycle.

<p><strong><em>Sciaphila kozushimensis </em></strong><strong>(Triuridaceae), a new mycoheterotrophic plant from Kozu Island, Izu Islands, Japan, based on morphological and molecular data</strong></p>

A new species of Sciaphila (Triuridaceae), S. kozushimensis Suetsugu, is described from Kozu Island, Izu Islands, Japan. The new species is similar to S. tosaensis in having unisexual flowers (the female towards the base of the rachis), perianth-segments without any appendages and club-shaped style that is as long as or slightly exceeds ovary in the flowering stage. However, it is distinguishable by smaller male flowers, wide and acuminate male perianth segments and somewhat dissimilar perianth segments. An illustration and molecular analysis based on ITS sequences of the new species are provided. A key to the Japanese Sciaphila is also provided for identification of these rare mycoheterotrophic plants.

Cheating in arbuscular mycorrhizal mutualism: a network and phylogenetic analysis of mycoheterotrophy

Although mutualistic interactions are widespread and essential in ecosystem functioning, the emergence of uncooperative cheaters threatens their stability, unless there are some physiological or ecological mechanisms limiting interactions with cheaters. In this framework, we investigated the patterns of specialization and phylogenetic distribution of mycoheterotrophic cheaters vs noncheating autotrophic plants and their respective fungi, in a global arbuscular mycorrhizal network with>25000 interactions. We show that mycoheterotrophy evolved repeatedly among vascular plants, suggesting low phylogenetic constraints for plants. However, mycoheterotrophic plants are significantly more specialized than autotrophic plants, and they tend to be associated with specialized and closely related fungi. These results raise new hypotheses about the mechanisms (e.g. sanctions, or habitat filtering) that actually limit the interaction of mycoheterotrophic plants and their associated fungi with the rest of the autotrophic plants. Beyond mycorrhizal symbiosis, this unprecedented comparison of mycoheterotrophic vs autotrophic plants provides a network and phylogenetic framework to assess the presence of constraints upon cheating emergences in mutualisms.

The First Plastid Genome of the Holoparasitic Genus Prosopanche (Hydnoraceae).

Plastomes of parasitic and mycoheterotrophic plants show different degrees of reduction depending on the plants’ level of heterotrophy and host dependence in comparison to photoautotrophic sister species, and the amount of time since heterotrophic dependence was established. In all but the most recent heterotrophic lineages, this reduction involves substantial decrease in genome size and gene content and sometimes alterations of genome structure. Here, we present the first plastid genome of the holoparasitic genus Prosopanche, which shows clear signs of functionality. The plastome of Prosopanche americana has a length of 28,191 bp and contains only 24 unique genes, i.e., 14 ribosomal protein genes, four ribosomal RNA genes, five genes coding for tRNAs and three genes with other or unknown function (accD, ycf1, ycf2). The inverted repeat has been lost. Despite the split of Prosopanche and Hydnora about 54 MYA ago, the level of genome reduction is strikingly congruent between the two holoparasites although highly dissimilar nucleotide sequences are observed. Our results lead to two possible evolutionary scenarios that will be tested in the future with a larger sampling: 1) a Hydnoraceae plastome, similar to those of Hydnora and Prosopanche today, existed already in the most recent common ancestor and has not changed much with respect to gene content and structure, or 2) the genome similarities we observe today are the result of two independent evolutionary trajectories leading to almost the same endpoint. The first hypothesis would be most parsimonious whereas the second would point to taxon dependent essential gene sets for plants released from photosynthetic constraints.

Some mycoheterotrophic orchids depend on carbon from dead wood: novel evidence from a radiocarbon approach.

Mycoheterotrophic plants depend entirely on fungal associations for organic nutrients. While most mycoheterotrophic plants are associated with the mycorrhizal partners of surrounding green plants, some mycoheterotrophs are believed to obtain carbon from decaying litter or dead wood by parasitising saprotrophic fungi, based on culture experiments and 13 C and 15 N isotopic signatures. The carbon age (the time since carbon was fixed from atmospheric CO2 by photosynthesis) can be estimated by measuring the concentration of 14 C arising from the bomb tests of the 1950s and 1960s. Given that mycorrhizal fungi obtain photosynthate from their plant partners, and saprotrophic wood-decaying fungi obtain carbon from older sources, radiocarbon could represent a new and powerful tool to investigate carbon sources of mycoheterotrophic plants. We showed that the Δ14 C values of mycoheterotrophs exploiting ectomycorrhizal fungi were close to 0‰, similar to those of autotrophic plants. By contrast, the Δ14 C values of mycoheterotrophs exploiting saprotrophic fungi ranged from 110.7‰ to 324.8‰, due to the 14 C-enriched bomb carbon from dead wood via saprotrophic fungi. Our study provides evidence supporting that some mycoheterotrophic orchids depend on forest woody debris. Our study also indicates that radiocarbon could be used to predict the trophic strategies of mycoheterotroph-associated fungal symbionts.

A New Record Mycoheterotrophic Plant in Bukit Barisan Grand Forest Park, North Sumatra, Indonesia

Mycoheterotrophic plants are unique plants because these plants do not have leaves (chlorophyll) and get their nutrients from a symbiotic relationship with fungi. In some recent literature, Mycoheterotrophic can be also called holomycotrophic plants. The purpose of this study was to determine the mycoheterotrophic plant species in the Bukit Barisan Grand Forest Park, North Sumatra. The purpose of this research is to know the type of mycoheterotrophic plant in Bukit Barisan Grand Forest Park, North Sumatra, Indonesia. This research was conducted in August 2019 in Bukit Barisan Grand Forest Park, North Sumatra, Indonesia. In conducting plant sampling the method used is the exploration or roaming method. Identification of mycoheterotrophic plants based on morphological characteristics in the form of habitus, stems, flowers, roots and matched using literature then lists the species of mycoheterotrophic plants presented in this study consisting of scientific names, synonyms, descriptions, distributions, ecological information. The results of field exploration found 3 species in two mycoheterotrophic plant families, Burmaniaceae and Orchidaceae. The Burmaniaceae family consists of 1 type of Burmannia lutescens Becc. While the Orchidaceae family consists of two species, among others, the Epipogium roseum (D. Don) Lindl. and Gastrodia siamensis Rolfe ex Downie. 3 mycoheterotrophic plants became a new record for the Forest Park of Bukit Barisan Sumatra Utara because previously there was no data on the plant.

Isolation and identification of plant growth-promoting bacteria from rhizomes of Arachnitis uniflora, a fully mycoheterotrophic plant in southern Chile

Fully mycoheterotrophic plants have attracted attention due to their ability to obtain carbon and mineral nutrients directly from fungal hyphae. However, research on bacteria associated with full mycoheterotrophs is limited. This study identifies rhizosferic and endophytic bacteria associated with A. uniflora rhizomes and analyzes their ability to produce microbial metabolites of various functions. Eight bacterial OTUs were revealed, and their potential roles in plant-growth promotion and antimicrobial activities were demonstrated. These findings suggest that root-system associated bacteria can be considered as essential microorganisms for growth and development of fully mycoheterotrophic plants.

First Record of Ategmic Ovules in Orchidaceae Offers New Insights Into Mycoheterotrophic Plants.

The number of integuments found in angiosperm ovules is variable. In orchids, most species show bitegmic ovules, except for some mycoheterotrophic species that show ovules with only one integument. Analysis of ovules and the development of the seed coat provide important information regarding functional aspects such as dispersal and seed germination. This study aimed to analyze the origin and development of the seed coat of the mycoheterotrophic orchid Pogoniopsis schenckii and to compare this development with that of other photosynthetic species of the family. Flowers and fruits at different stages of development were collected, and the usual methodology for performing anatomical studies, scanning microscopy, and transmission microscopy following established protocols. P. schenckii have ategmic ovules, while the other species are bitegmic. No evidence of integument formation at any stage of development was found through anatomical studies. The reduction of integuments found in the ovules could facilitate fertilization in this species. The seeds of P. schenckii, Vanilla planifolia, and V. palmarum have hard seed coats, while the other species have seed coats formed by the testa alone, making them thin and transparent. P. schenckii, in contrast to the other species analyzed, has a seed coat that originates from the nucellar epidermis, while in other species, the seed coat originates from the outer integument.