Secret growth stimulators

                              

Breaking down the microbiology world one bite at a time


Secret growth stimulators

Fungi…We have a close relationship with them as we love to put them on our pasta or pizza… or find a moldy piece of food now and then. But we are not the only ones with a tight bond. Fungi form symbiotic relationships with more than half of all trees on Earth! They create extensive networks with the roots of the trees and are, thus, called ectomycorrhizal (outside-the-root-cell) fungi, EMF for short. EMF provide trees with delicious, often inaccessible nutrients such as nitrogen, and also protect seedlings from pathogens. And, in return, trees provide tasty carbohydrates.

Hyphae of ectomycorrhizal fungi (EMF) do not penetrate the cells of the root but grow in between the cells. Figure from Wikimedia commons

It is already known that environmental factors such as rain, temperature, and nitrogen availability influence the growth of trees. But so far the influence of EMF communities on trees was very hard to measure because there was not enough data… Until now! 

The team of Mark Anthony and colleagues investigated more than 13,000 trees in 137 locations. In their extensive study, they looked at both environmental factors and the composition of the EMF communities. And, as it turns out, some specific communities were correlated to a three-fold increase in tree growth!

The researchers looked at tree growth in 137 locations in Europe. Image adapted from the original article.

In order to find out which features of the fungal communities were linked to the increased growth, the researchers looked at genes related to nitrogen acquisition, soil organic matter decomposition, and fungal growth. They found communities that could break down inorganic nitrogen compounds, such as nitrate and ammonium, were often attached to the roots of fast-growing trees. Interestingly, these inorganic nitrogen compounds are also used in artificial fertilizers! 

Trees with a microbial community specialized in breaking down organic nitrogen, which is usually found in decaying biomass in the forest soil, were generally growing slower. Processing of organic nitrogen requires a set of special enzymes. The production of these enzymes, and subsequently breaking down the organic compounds, requires more energy from the EMF. This would mean that the EMF are draining more energy from their tree-symbionts, leaving the trees with less energy to dedicate to their own growth. 

Photo by Jimmy Chan on Pexels.com

Another observation from the researchers was that more ‘explorative’ EMF were often correlated with slower tree growth. They found that EMF with a longer or a more extensive network of hyphae were negatively associated with tree growth. Conversely, EMF that are in direct contact with the roots and produce less expanded hyphae were positively associated with tree growth. Again, the cause might be that the adventurous EMF require more energy from the tree in order to grow their hyphae. (If you are interested in fungal growth, learn more about hyphae exploration here, or click here to find out how hyphae avoid geometric obstacles).

How does this research impact the future? Forests are the largest carbon sinks on land. So, if we can regulate their growth by introducing specific fungal communities, we can manage forests to promote carbon storage under a changing climate. 


Link to the original post: Anthony, M.A., Crowther, T.W., van der Linde, S. et al. Forest tree growth is linked to mycorrhizal fungal composition and function across Europe. ISME J (2022). https://doi.org/10.1038/s41396-021-01159-7

Featured image: https://commons.wikimedia.org/wiki/File:Mycorhizes-01.jpg