Will new research necessitate a rewrite of biology texts? Green plants collect carbon using fungi

In biology classes around the world, students learn that green plants nourish themselves solely by photosynthesis, a process in which plants use solar energy to convert water and atmospheric carbon dioxide into oxygen and sugars. Apparently, things aren’t quite so simple. The conventional understanding has been contested by a recent Danish-German study conducted at the University of Copenhagen and University of Bayreuth.

Some plants also collect vital carbon by way of fungi living in their roots, fungi that are part of a vast underground network of fungi — the Wood Wide Web. Plants use these fungi to collect a significant amount of their carbon from other plants while performing photosynthesis.

It is pretty controversial that some green plants do not live entirely from their own photosynthesizing, but in fact get carbon from other plants by way of fungi. At the same time, the result helps to underscore the incredible influence of fungi on our ecosystems. 

May apply to 40 percent of all green plant species

So far, researchers have demonstrated that there is a transfer of carbon from fungi in herb-paris (Paris-quadrifolia) and white anemone. The findings open up the possibility that roughly 40% of all plant species have their own photosynthesis supplemented by carbon compounds transmitted via fungi to their roots. This estimate is based on the fact that the type of fungal symbiosis (mycorrhiza) that herb-paris and white anemone have is very common and found in roughly 40% of all green plant species.

Several years ago, Hanne N. Rasmussen came up with the idea that green plants with a certain type of fungal symbiosis gather carbon from their cohabitation with fungi. She shelved the idea due to a lack of experimental results to back it up.

"The long and established understanding is that green plants feed solely on their own photosynthesis," says Hanne N. Rasmussen.  

Unable to escape her idea, she introduced it to a German colleague, whose interest was piqued. Together, they launched a study to reveal the origin of the carbon found in the leaves in a number of common forest floor herbs, including herb-paris and white anemone. The new knowledge gained from their study has caused a stir in the scientific world.

Orchids are unorthodox

For many years the researcher has been working with orchids, where it has been established that orchid plants supplement photosynthesis with carbon from fungi via their roots. The new study reveals that orchids are not as unique as once thought. However, while orchids are rare and have a special type of fungal symbiosis, the new findings apply to much more common and widespread plant species, such as white anemone, together with a nearly omnipresent type of mycorrhiza. It reverses our conception of the interrelationship of plants in nature.

The research results are based on analyses of stable isotopes in collaboration with the laboratory for isotope biogeochemistry at the Bayreuth Center for Ecology and Environmental Research (BayCEER).

The study, Discreet heterotrophs: green plants that receive fungal carbon through Paris-type arbuscular mycorrhiza is published as a letter in New Phyotologist: https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.16367