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McCormick MK, Good KL, Mozdzer TJ, Whigham DF. Shade and drought increase fungal contribution to partially mycoheterotrophic terrestrial orchids Goodyera pubescens and Tipularia discolor. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.1047267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Many photosynthetic plants supplement photosynthetic carbon with fungal carbon, but the mechanisms that govern dependence on mycoheterotrophic carbon are poorly understood. We used exclusion shelters to manipulate water and light availability to plants of the terrestrial orchids Goodyera pubescens and Tipularia discolor. We tracked changes in δ13C from photosynthesis and δ15N acquired from soil-derived inorganic nitrogen versus mycoheterotrophy, along with direct measures of photosynthesis in T. discolor. We hypothesized that shade would increase dependence on mycoheterotrophy compared to reference plants, while drought would decrease both photosynthesis and the abundance of potential mycorrhizal fungi. Drought and shade enriched 13C and 15N in both G. pubescens and T. discolor, compared to control plants, indicating increased fungal contribution to orchid tissues. Physiological measurements of T. discolor leaves showed that dark respiration, water use efficiency, and relative electron transport rate did not vary significantly, but shaded plants had greater quantum efficiency, suggesting they were light-limited. Light saturated photosynthesis of T. discolor leaves was lower in both shaded and drought-treated plants, indicating lower photosynthetic capacity, and likely greater dependence on mycoheterotrophy and corresponding enrichment in 13C and 15N. This study documented changes in orchid dependence on fungal carbon in response to manipulated environmental conditions. Both shade and drought increased the dependence of both orchids on mycoheterotrophically derived carbon and nitrogen.
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Suetsugu K, Matsubayashi J. Foliar chlorophyll concentration modulates the degree of fungal exploitation in a rhizoctonia-associated orchid. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:4204-4213. [PMID: 35312761 DOI: 10.1093/jxb/erac124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 03/18/2022] [Indexed: 06/14/2023]
Abstract
Some green orchids obtain carbon from both mycobionts and photosynthesis at the adult stage. Intriguingly, these orchids can produce albino and, in rare cases, variegated phenotypes. Here, we studied a Platanthera hondoensis population with green, variegated, and albino individuals. Although its closely related Platanthera species are usually associated with non-ectomycorrhizal rhizoctonias, and several studies have failed to find evidence of trophic plasticity in rhizoctonia-associated orchids, variegated and albino P. hondoensis must possess a higher fungal dependency than green P. hondoensis. Therefore, we investigated whether (i) P. hondoensis is associated with non-ectomycorrhizal rhizoctonias and (ii) the degree of mycoheterotrophy (using 13C abundance as a proxy) correlates with the foliar chlorophyll concentration. High-throughput DNA sequencing revealed that all P. hondoensis phenotypes were dominantly associated with a rhizoctonia from Ceratobasidiaceae belonging to a clade distinct from recognized ectomycorrhizal clades. Regression analysis revealed a positive linear relationship between foliar chlorophyll concentration and the degree of mycoheterotrophy. This study strongly suggests that rhizoctonia-associated P. hondoensis can dynamically adjust fungal exploitation in response to photosynthetic carbon levels. Since rhizoctonia is the most common orchid mycorrhizal partner, trophic plasticity may be a widespread adaptive trait in green orchids.
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Affiliation(s)
- Kenji Suetsugu
- Department of Biology, Graduate School of Science, Kobe University, Kobe, Japan
| | - Jun Matsubayashi
- Department of Integrated Science and Engineering for Sustainable Societies, Faculty of Science and Engineering, Chuo University, Tokyo, Japan
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Zahn FE, Lee YI, Gebauer G. Fungal association and root morphology shift stepwise during ontogenesis of orchid Cremastra appendiculata towards autotrophic nutrition. AOB PLANTS 2022; 14:plac021. [PMID: 35673361 PMCID: PMC9167560 DOI: 10.1093/aobpla/plac021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 05/03/2022] [Indexed: 06/15/2023]
Abstract
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.
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Affiliation(s)
- Franziska E Zahn
- Laboratory of Isotope Biogeochemistry, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Universitätsstr. 30, 95440 Bayreuth, Germany
| | - Yung-I Lee
- Department of Life Science, National Taiwan University, Taipei 10617, Taiwan
- Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei 10617, Taiwan
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Whigham D, McCormick M, Brooks H, Josey B, Floyd R, Applegate J. Isotria medeoloides, a North American Threatened Orchid: Fungal Abundance May Be as Important as Light in Species Management. PLANTS 2021; 10:plants10091924. [PMID: 34579457 PMCID: PMC8471007 DOI: 10.3390/plants10091924] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 08/30/2021] [Accepted: 09/10/2021] [Indexed: 11/16/2022]
Abstract
The management of endangered or threatened plant species is difficult if protocols are not developed to propagate species for the purpose of restoration or the enhancement of existing populations. The management of endangered and threatened orchids is especially difficult because of the obligate interactions between orchids and orchid mycorrhizal fungi. Isotria medeoloides is a federally threatened forest-dwelling orchid species with a wide distribution in eastern North America. Seeds have not been successfully germinated and current management is based primarily on using subcanopy thinning to increase light in areas where monitoring demonstrates that populations are declining. We report the results of long-term monitoring efforts, canopy thinning, and orchid mycorrhizal fungus abundance studies at two locations in Virginia. The declining populations responded positively to the experimental and natural thinning of the canopy. At one site, the response was the result of understory canopy thinning. At the second site, the response was due to the natural death of a canopy tree. In light of the dramatic increase in fungal abundance following death of the canopy tree, we propose the Fungal Abundance Hypothesis as an additional approach to the management of endangered plant species. The removal of canopy trees in or adjacent to Isotria populations results in an increase in dead belowground biomass (i.e., roots of the dead canopy tree) that provides substrates for microbial growth, including orchid mycorrhizal fungi, that benefit Isotria.
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Affiliation(s)
- Dennis Whigham
- Smithsonian Environmental Research Center, 647 Contees Wharf Road, Edgewater, MD 21037, USA; (M.M.); (H.B.)
- Correspondence: ; Tel.: +1-443-482-2226
| | - Melissa McCormick
- Smithsonian Environmental Research Center, 647 Contees Wharf Road, Edgewater, MD 21037, USA; (M.M.); (H.B.)
| | - Hope Brooks
- Smithsonian Environmental Research Center, 647 Contees Wharf Road, Edgewater, MD 21037, USA; (M.M.); (H.B.)
| | - Brian Josey
- Center for Environmental Management of Military Lands (CEMML), Colorado State University, Fort A. P. Hill, VA 22427, USA;
| | - Robert Floyd
- Headquarters Department of the Army, Washington, DC 20001, USA;
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Suetsugu K, Matsubayashi J. Subterranean morphology modulates the degree of mycoheterotrophy in a green orchid
Calypso bulbosa
exploiting wood‐decaying fungi. Funct Ecol 2021. [DOI: 10.1111/1365-2435.13864] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- Kenji Suetsugu
- Department of Biology Graduate school of Science Kobe University Kobe Japan
| | - Jun Matsubayashi
- Department of Integrated Science and Engineering for Sustainable Societies Faculty of Science and Engineering Chuo University Tokyo Japan
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Wang D, Jacquemyn H, Gomes SIF, Vos RA, Merckx VSFT. Symbiont switching and trophic mode shifts in Orchidaceae. THE NEW PHYTOLOGIST 2021; 231:791-800. [PMID: 33932029 PMCID: PMC8252101 DOI: 10.1111/nph.17414] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 04/09/2021] [Indexed: 05/15/2023]
Abstract
Mycorrhizal fungi are central to the biology of land plants. However, to what extent mycorrhizal shifts - broad evolutionary transitions in root-associated fungal symbionts - are related to changes in plant trophic modes remains poorly understood. We built a comprehensive DNA dataset of Orchidaceae fungal symbionts and a dated plant molecular phylogeny to test the hypothesis that shifts in orchid trophic modes follow a stepwise pattern, from autotrophy over partial mycoheterotrophy (mixotrophy) to full mycoheterotrophy, and that these shifts are accompanied by switches in fungal symbionts. We estimate that at least 17 independent shifts from autotrophy towards full mycoheterotrophy occurred in orchids, mostly through an intermediate state of partial mycoheterotrophy. A wide range of fungal partners was inferred to occur in the roots of the common ancestor of this family, including 'rhizoctonias', ectomycorrhizal, and wood- or litter-decaying saprotrophic fungi. Phylogenetic hypothesis tests further show that associations with ectomycorrhizal or saprotrophic fungi were most likely a prerequisite for evolutionary shifts towards full mycoheterotrophy. We show that shifts in trophic mode often coincided with switches in fungal symbionts, suggesting that the loss of photosynthesis selects for different fungal communities in orchids. We conclude that changes in symbiotic associations and ecophysiological traits are tightly correlated throughout the diversification of orchids.
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Affiliation(s)
- Deyi Wang
- Naturalis Biodiversity CenterLeiden2332 AAthe Netherlands
- Institute of BiologyLeiden UniversityLeiden2333 BEthe Netherlands
| | - Hans Jacquemyn
- Department of Biology, Plant Conservation and Population BiologyKU LeuvenKasteelpark Arenberg 31, HeverleeLeuven3001Belgium
| | - Sofia I. F. Gomes
- Naturalis Biodiversity CenterLeiden2332 AAthe Netherlands
- Institute of BiologyLeiden UniversityLeiden2333 BEthe Netherlands
| | - Rutger A. Vos
- Naturalis Biodiversity CenterLeiden2332 AAthe Netherlands
- Institute of BiologyLeiden UniversityLeiden2333 BEthe Netherlands
| | - Vincent S. F. T. Merckx
- Naturalis Biodiversity CenterLeiden2332 AAthe Netherlands
- Department of Evolutionary and Population BiologyInstitute for Biodiversity and Ecosystem DynamicsUniversity of AmsterdamAmsterdam1098 XHthe Netherlands
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Giesemann P, Rasmussen HN, Gebauer G. Partial mycoheterotrophy is common among chlorophyllous plants with Paris-type arbuscular mycorrhiza. ANNALS OF BOTANY 2021; 127:645-653. [PMID: 33547798 PMCID: PMC8052919 DOI: 10.1093/aob/mcab003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 01/08/2021] [Indexed: 05/07/2023]
Abstract
BACKGROUND AND AIMS An arbuscular mycorrhiza is a mutualistic symbiosis with plants as carbon providers for fungi. However, achlorophyllous arbuscular mycorrhizal species are known to obtain carbon from fungi, i.e. they are mycoheterotrophic. These species all have the Paris type of arbuscular mycorrhiza. Recently, two chlorophyllous Paris-type species proved to be partially mycoheterotrophic. In this study, we explore the frequency of this condition and its association with Paris-type arbuscular mycorrhiza. METHODS We searched for evidence of mycoheterotrophy in all currently published 13C, 2H and 15N stable isotope abundance patterns suited for calculations of enrichment factors, i.e. isotopic differences between neighbouring Paris- and Arum-type species. We found suitable data for 135 plant species classified into the two arbuscular mycorrhizal morphotypes. KEY RESULTS About half of the chlorophyllous Paris-type species tested were significantly enriched in 13C and often also enriched in 2H and 15N, compared with co-occurring Arum-type species. Based on a two-source linear mixing model, the carbon gain from the fungal source ranged between 7 and 93 % with ferns > horsetails > seed plants. The seed plants represented 13 families, many without a previous record of mycoheterotrophy. The 13C-enriched chlorophyllous Paris-type species were exclusively herbaceous perennials, with a majority of them thriving on shady forest ground. CONCLUSIONS Significant carbon acquisition from fungi appears quite common and widespread among Paris-type species, this arbuscular mycorrhizal morphotype probably being a pre-condition for developing varying degrees of mycoheterotrophy.
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Affiliation(s)
- Philipp Giesemann
- University of Bayreuth, Laboratory of Isotope Biogeochemistry, Bayreuth Center of Ecology and Environmental Research (BayCEER), Bayreuth, Germany
| | - Hanne N Rasmussen
- University of Copenhagen, Institute of Geosciences and Natural Resources, Rolighedsvej, Frederiksberg C, Denmark
| | - Gerhard Gebauer
- University of Bayreuth, Laboratory of Isotope Biogeochemistry, Bayreuth Center of Ecology and Environmental Research (BayCEER), Bayreuth, Germany
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Jacquemyn H, Brys R, Waud M, Evans A, Figura T, Selosse MA. Mycorrhizal Communities and Isotope Signatures in Two Partially Mycoheterotrophic Orchids. FRONTIERS IN PLANT SCIENCE 2021; 12:618140. [PMID: 33633765 PMCID: PMC7901878 DOI: 10.3389/fpls.2021.618140] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 01/18/2021] [Indexed: 05/20/2023]
Abstract
Partial mycoheterotrophy, the ability of plants to obtain carbon from fungi throughout their life cycle in combination with photosynthesis, appears to be more common within the Plant Kingdom than previously anticipated. Recent studies using stable isotope analyses have indicated that isotope signatures in partially mycoheterotrophic plants vary widely among species, but the relative contributions of family- or species-specific characteristics and the identity of the fungal symbionts to the observed differences remain unclear. Here, we investigated in detail mycorrhizal communities and isotopic signatures in four co-occurring terrestrial orchids (Platanthera chlorantha, Epipactis helleborine, E. neglecta and the mycoheterotrophic Neottia nidus-avis). All investigated species were mycorrhizal generalists (i.e., associated with a large number of fungi simultaneously), but mycorrhizal communities differed significantly between species. Mycorrhizal communities associating with the two Epipactis species consisted of a wide range of fungi belonging to different families, whereas P. chlorantha and N. nidus-avis associated mainly with Ceratobasidiaceae and Sebacinaceae species, respectively. Isotopic signatures differed significantly between both Epipactis species, with E. helleborine showing near autotrophic behavior and E. neglecta showing significant enrichment in both carbon and nitrogen. No significant differences in photosynthesis and stomatal conductance were observed between the two partially mycoheterotrophic orchids, despite significant differences in isotopic signatures. Our results demonstrate that partially mycoheterotrophic orchids of the genus Epipactis formed mycorrhizas with a wide diversity of fungi from different fungal families, but variation in mycorrhizal community composition was not related to isotope signatures and thus transfer of C and N to the plant. We conclude that the observed differences in isotope signatures between E. helleborine and E. neglecta cannot solely be explained by differences in mycorrhizal communities, but most likely reflect a combination of inherent physiological differences and differences in mycorrhizal communities.
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Affiliation(s)
- Hans Jacquemyn
- Department of Biology, Plant Conservation and Population Biology, Department of Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Rein Brys
- Research Institute for Forest and Nature, Geraardsbergen, Belgium
| | - Michael Waud
- Department of Biology, Plant Conservation and Population Biology, Department of Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Alexandra Evans
- Department of Biology, Plant Conservation and Population Biology, Department of Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Tomáš Figura
- Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum national d'Histoire naturelle, CNRS, Sorbonne Université, EPHE, Paris, France
- Faculty of Biology, University of Gdańsk, Gdańsk, Poland
| | - Marc-André Selosse
- Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum national d'Histoire naturelle, CNRS, Sorbonne Université, EPHE, Paris, France
- Faculty of Biology, University of Gdańsk, Gdańsk, Poland
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Suetsugu K, Matsubayashi J. Evidence for mycorrhizal cheating in Apostasia nipponica, an early-diverging member of the Orchidaceae. THE NEW PHYTOLOGIST 2021; 229:2302-2310. [PMID: 33118174 DOI: 10.1111/nph.17049] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Accepted: 09/23/2020] [Indexed: 05/12/2023]
Abstract
Most land plants, from liverworts to angiosperms, form mutualistic mycorrhizal symbioses with fungal partners. However, several plants known as mycoheterotrophs exploit fungal partners by reversing the polarity of carbon movement, which usually moves from plant to fungus. We investigated the physiological ecology of a photosynthetic orchid, Apostasia nipponica, which belongs to the first branching group within the Orchidaceae, to improve our understanding of mycoheterotrophic evolution in orchids. The fungal symbionts and nutrition modes of A. nipponica were investigated using molecular barcoding and carbon-13 (13 C) and nitrogen-15 (15 N) measurements, respectively. Community profiling based on a metabarcoding technique revealed that A. nipponica associates with specific Ceratobasidium spp. within ectomycorrhizas-forming clades, whereas isotope analysis revealed that A. nipponica was similar to fully mycoheterotrophic orchids in its 13 C signature and was even more enriched in 15 N than most of the fully mycoheterotrophic orchids that exploit ectomycorrhizal fungi. Our molecular and mass-spectrometric approaches demonstrated, for the first time, that a member of the Apostasioideae, the earliest-diverging lineage of the Orchidaceae, gains carbon through both photosynthesis and fungal cheating (i.e. partial mycoheterotrophy) during the adult stage.
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Affiliation(s)
- Kenji Suetsugu
- Department of Biology, Graduate School of Science, Kobe University, Kobe, Hyogo, 657-8501, Japan
| | - Jun Matsubayashi
- Department of Integrated Science and Engineering for Sustainable Societies, Faculty of Science and Engineering, Chuo University, Bunkyo-ku, Tokyo, 112-8551, Japan
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Suetsugu K, Matsubayashi J, Ogawa NO, Murata S, Sato R, Tomimatsu H. Isotopic evidence of arbuscular mycorrhizal cheating in a grassland gentian species. Oecologia 2020; 192:929-937. [PMID: 32172377 DOI: 10.1007/s00442-020-04631-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 03/05/2020] [Indexed: 01/25/2023]
Abstract
All orchids and pyroloids are mycoheterotrophic at least in the early stage. Many species are predisposed to mycoheterotrophic nutrition even in the adult stage, due to the initial mycoheterotrophy during germination. Although other green plants, such as gentian species, also produce numerous minute seeds, whose germination may depend on fungal associations to meet C demands, physiological evidence for partial mycoheterotrophy in the adult stage is lacking for most candidate taxa. Here, we compared the natural abundances of 13C and 15N isotopes in the AM-associated gentian species Pterygocalyx volubilis growing in high-light-intensity habitats with those of co-occurring autotrophic C3 and C4 plants and AM fungal spores. We found that P. volubilis was significantly enriched in 13C compared with the surrounding C3 plants, which suggests the transfer of some C from the surrounding autotrophic plants through shared AM networks. In addition, the intermediate δ15N values of P. volubilis, between those of autotrophic plants and AM fungal spores, provide further evidence for partial mycoheterotrophy in P. volubilis. Although it is often considered that light deficiency selects partial mycoheterotrophy, we show that partial mycoheterotrophy in AM-forming plants can evolve even under light-saturated conditions. The fact that there have been relatively few descriptions of partial mycoheterotrophy in AM plants may not necessarily reflect the rarity of such associations. In conclusion, partial mycoheterotrophy in AM plants may be more common than hitherto believed.
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Affiliation(s)
- Kenji Suetsugu
- Department of Biology, Graduate School of Science, Kobe University, Kobe, Japan.
| | - Jun Matsubayashi
- Department of Biogeochemistry, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, Japan
| | - Nanako O Ogawa
- Department of Biogeochemistry, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, Japan
| | - Satoe Murata
- Faculty of Science, Yamagata University, Yamagata, Japan
| | - Risa Sato
- Faculty of Science, Yamagata University, Yamagata, Japan
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