Key Takeaways
- Researchers from Chiba University and Kobe University found that Gentiana squarrosa, a small flowering plant in the Gentianaceae family, receives carbon through arbuscular mycorrhizal (AM) fungal networks in addition to photosynthesis.
- The study, led by Professor Masahide Yamato, was published in Volume 36 of the journal Mycorrhiza on May 28, 2026.
- Researchers grew G. squarrosa seedlings alongside C3 or C4 companion plants in a U-shaped pot system, using a fine nylon mesh that let fungal mycelium pass between roots while blocking direct root contact.
- Seedlings connected to C4 companion plants showed significantly higher carbon-13 levels than those connected to C3 companions, supporting carbon transfer through fungal networks.
- The findings confirm partial mycoheterotrophy in G. squarrosa and suggest AM fungal networks may act as a broader pathway for carbon exchange between plants.
Chiba University Researchers Trace Carbon Transfer in Gentiana squarrosa
Researchers from Chiba University and Kobe University have found experimental evidence that Gentiana squarrosa Ledeb., a small flowering plant in the Gentianaceae family, obtains carbon through underground fungal networks in addition to photosynthesis. The study, led by Professor Masahide Yamato of Chiba University's Graduate School of Education, was published in Volume 36 of the journal Mycorrhiza on May 28, 2026.
The research team also included Moe Sasuga from the Graduate School of Education at Chiba University, Keito Shimabukuro from the Faculty of Education at Chiba University, Ryota Kusakabe from the Graduate School of Horticulture at Chiba University, and Kenji Suetsugu from the Department of Biology, Graduate School of Science at Kobe University.
How Mycorrhizal Networks Support Plant Nutrition
Underground mycorrhizal networks, sometimes called the “wood-wide web,” connect plant roots to fungi that help plants draw nutrients from soil in exchange for carbon compounds made through photosynthesis. These fungal links can also connect neighboring plants of different species. Some plants rely partly or fully on this exchange for carbon, a process known as mycoheterotrophy, which may matter most for plants growing in shaded, low-light conditions.
Detecting this carbon exchange has been difficult in arbuscular mycorrhizal fungi, the most common type of mycorrhizal fungi, because the carbon isotope signatures of these fungi often closely match those of their host plants.
Testing Carbon Transfer with a U-Shaped Pot System
To trace carbon movement, the team paired G. squarrosa seedlings with either C3 or C4 companion plants, which naturally carry different amounts of carbon-13. The pairs were grown in a U-shaped pot system where a fine nylon mesh separated the two plants' roots but allowed fungal mycelium to pass through.
“Specifically, if carbon transfer occurs through AM fungal connections, the carbon-13 isotope ratio should be higher in G. squarrosa seedlings grown with a C4 companion plant than in those grown with a C3 companion plant,” explains Prof. Yamato.
Chiba University Study Confirms Partial Mycoheterotrophy
The results matched that hypothesis: shoot carbon-13 levels in G. squarrosa were significantly higher when seedlings were paired with a C4 companion plant than with a C3 companion. Among plants grown with a C4 companion, shoot growth was also positively linked to carbon-13 levels, suggesting the fungal carbon transfer supported growth under the tested conditions. Together, the results point to partial mycoheterotrophy in G. squarrosa, meaning the plant draws on both photosynthesis and fungal symbiosis for its carbon supply.
Implications for Future Research
The Chiba University-led team said its pot system could be applied to other plant species to check for similar carbon transfer through AM fungi.
“The U-shaped pot cultivation experimental system developed in this study will enable us to verify the presence or absence of carbon transfer between plants via AM fungi in various plant species. If confirmed in diverse plants, the hyphal network may not simply be a pathway for nutrient absorption but may also function as a site for ‘energy distribution' where carbon compounds move between plants,” says Prof. Yamato.
The study is titled “Partial mycoheterotrophy in the arbuscular mycorrhizal Gentiana squarrosa (Gentianaceae) demonstrated by coculture assays using C3 and C4 plants” and appears in the journal Mycorrhiza (DOI: 10.1007/s00572-026-01271-6).
