Plants and fungi have a complex relationship that ranges from mutualism to parasitism.
In many cases, plants form symbiotic associations with fungi, called mycorrhiza, in which the fungi help the plants absorb nutrients and water from the soil, while the plants provide the fungi with organic carbon.
However, some plants exploit their fungal partners and extract more carbon than they give, or even feed exclusively on fungal carbon without performing any photosynthesis.
These plants are known as mycoheterotrophs.
Understanding how plants feed on fungi is important for studying the ecology and evolution of plant-fungal interactions, as well as their implications for carbon cycling and climate change.
However, measuring the amount of carbon that plants obtain from fungi is challenging, as it requires distinguishing fungal carbon from plant carbon.
One way to do this is to use isotope analysis, which can detect differences in the abundance of carbon atoms with different numbers of neutrons in their nuclei.
These differences reflect the origin and history of the carbon atoms in different organisms.
However, until now, isotope analysis of plant-fungal symbiosis was limited by the availability of fungal samples that could be used as reference values.
Most fungi do not produce fruiting bodies that can be easily collected and analyzed, and extracting fungal tissue from plant roots is difficult and unreliable.
Therefore, a new method was needed to overcome this limitation and enable unrestricted isotope analysis of all types of plant-fungal symbiosis.
A novel method based on compound-specific isotope analysis
Dan Kitwood/Getty Images
A team of researchers led by Prof. Dr. Gerhard Gebauer at the University of Bayreuth has developed a novel method that allows isotope analysis of plant-fungal symbiosis without requiring fungal samples, as per Phys.org.
The method is based on compound-specific isotope analysis (CSIA), which can measure the isotopic composition of individual molecules within a complex mixture.
The researchers focused on a specific molecule called ergosterol, which is a sterol that is found only in fungi and not in plants.
Ergosterol is an essential component of fungal cell membranes and can be extracted from plant tissues using organic solvents.
By measuring the isotopic composition of ergosterol, the researchers could determine the isotopic profile of fungal carbon without having to isolate fungal tissue.
The researchers applied their method to various plant-fungal symbioses, including orchids, heaths, grasses, and ferns.
They compared the isotopic composition of ergosterol with that of bulk plant tissue and found that they were significantly different in most cases.
This difference indicated that the plants obtained carbon from fungi and that the amount of fungal carbon varied among different plant species and habitats.
The researchers also validated their method by comparing it with conventional methods that use fungal fruiting bodies or root samples as reference values.
They found that their method produced consistent and reliable results that agreed well with previous studies.
The new method developed by the researchers is a breakthrough for plant-fungal ecology, as it opens up new possibilities for studying the diversity and dynamics of plant-fungal symbiosis across different ecosystems and scales.
The method can be applied to any type of plant-fungal symbiosis, regardless of whether the fungi produce fruiting bodies or not.
It can also be used to measure other elements besides carbon, such as nitrogen or phosphorus, which are also exchanged between plants and fungi.
The method has several advantages over conventional methods, such as being faster, cheaper, more accurate, and less invasive, and it does not require collecting or destroying fungal samples, which can be rare or endangered.
Moreover, the method also does not require growing plants or fungi under controlled conditions, which can alter their natural isotopic profiles, and it can provide new insights into how plants feed on fungi and how this affects their physiology, ecology, and evolution.
Revealing how plant-fungal symbiosis responds to environmental changes, such as climate change, land use change, or pollution is also possible with this method.
Lastly, it can thus contribute to a better understanding and conservation of plant-fungal biodiversity and ecosystem functioning.
