17 November 2017

Could fungi determine which plants survive, and which don’t?

Relationships between plants and fungi are important and more complex than previously thought, influencing the ability of ecosystems to adapt to impacts such as climate change.

Hiding below ground: connecting plants with the soil

Fungi often grow hidden underground, with the mushrooms that we eat the only visible part. Some fungi are particularly special, living in the roots of plants and exchanging nutrients which help both to grow – these are called mycorrhizal fungi and they form mycorrhizas (meaning fungal roots). Most of the world’s plants such as vegetables, flowering plants and trees need these special fungi to survive.

My colleagues at Kew and Imperial College and I are studying the relationship between plants and these fungi in the European Alps, as the fungi help pioneer plants to establish after changes to the environment. Mycorrhizal fungi influence these ecosystems' resilience to environmental change, which is the ability to overcome or recover from stresses such as increasing temperatures. This research helps us understand how alpine plants, with the help of fungi, might be able to cope with events such as climate change. So, how many of these fungi are there and what role do they play in determining plant survival?

The fruits and roots of the fungal world

Mushrooms and truffles are the fruits of the fungal world, distributing their spores (similar to seeds) and finding new places to grow. But mushrooms are just the tip of the iceberg, with most of the fungal body underground and made up of numerous tiny filaments which connect to plant roots.

Fungi need sugars from plants for growth, while plants need nutrients and water from the soil which fungi help to collect. In this way, plants and fungi work symbiotically together in a win:win relationship, helping to extend the area that plants have for taking up nutrients and water by several metres. The association is so important that it affects the survival and competitiveness of many plant species, and therefore whole ecosystems. Only when conditions are favourable do fungi form mushrooms that we can see, but the rest of the time they remain and grow belowground.

Not all fungi are equal

From our work so far, and the work of others, we know that mycorrhizal fungi vary hugely – not just in how they look, but also in how they work. Some are good at collecting and sharing nitrogen, which is critical for plants to produce food from the sun, while others are great at transferring water over long distances to plants – useful during droughts. How species of plants and fungi determine whether a partnership is formed, and how many partnerships they create, is still little understood.

What is clear is that we need to know the function, diversity and distribution of different mycorrhizal fungi to understand the resilience of plants, and therefore ecosystems, to adapt to or recover from environmental change.

Plant and fungal relationships in the Alps

Despite the importance of mycorrhizal fungi in alpine ecosystems, many of them remain undocumented or undescribed. Funded by the Winton (Harding) Alpine Plant Conservation & Research Programme, we have been studying their diversity and distribution, as well as the impact the plants they associate with and the physical environment have on their survival and success. During two consecutive summers, we have studied the fungal associations of hundreds of individuals of three alpine plants including dwarf willow, mountain avens and alpine bistort, across five countries in the Alps. We have collected thousands of mycorrhizas that we will identify through DNA techniques.

Our early results show that alpine plants associate with hundreds of species of fungi. This tells us that mycorrhizal fungi are very diverse despite the more extreme environmental conditions at high elevations in the Alps, ensuring plant survival in harsh and changing conditions. What is even more interesting is that the fungi most common below ground, and most likely to affect plant survival, are difficult to find above ground. This is important because only by looking at the roots of these plants, at their mycorrhizas, can we determine the diversity and importance of these fungi in alpine ecosystems.

There is much more to find out about alpine plant and fungal communities, models for understanding pioneer communities. However, it is clear that fungi play a key role in plant success and survival which is important for emerging threats such as climate change. With the ever more advanced molecular techniques available to us, we are certain to discover more about these fascinating and crucial relationships.

Find out more about the Plant-fungal interactions in Alpine ecosystems project.