Plants have their own underground network with each other, but how do they use it?
Thomas Scott, postdoctoral researcher in evolutionary theory at the University of Oxford, digs in to find out.
Thomas Scott is a postdoctoral researcher in evolutionary theory at the University of Oxford. In his research, he uses mathematical models to tackle questions about the evolution of adaptation, especially social behaviors, and the resolution of evolutionary conflicts. His work has been recognized by an Early Career Investigator Award from the American Society of Naturalists.
Plants ‘Eavesdrop’ on Fungal Networks
Land plants can be connected to a complex, underground fungal network known popularly as ‘the wood wide web.’ Networks emerge because mycorrhizal fungi form symbiotic partnerships with plant roots, through which the plants receive nutrients and the fungi receive carbon. It’s been demonstrated that plant resources and information can be transmitted through the fungal network and be used by other plants.
Previous studies have found that, if a plant is attacked by a herbivore or pathogen, this often leads to other plants connected to the same fungal network upregulating their defence mechanisms. However, it hasn’t been clear whether plants being attacked by herbivores actively signal through this network, to warn others to activate their defences.
Active signalling between plants appears to contradict evolutionary theory, which suggests that this kind of behaviour would only be favoured when it provides a benefit to both the sender and the receiver of the signal. This presented a conundrum – why should a plant being attacked send signals to warn its neighbours?
My coauthors and I investigated this using mathematical models. We found that it’s extremely unlikely that plants would be evolutionarily selected to warn their fellows of impending attack. The reason for this is that plants compete with neighbours for resources such as sunlight and nutrients, and so don’t benefit from helping neighbouring competitors.
Our mathematical models challenge the idea that plants behave altruistically, and suggest that we need to consider alternative hypotheses for why neighbouring plants upregulate their defence mechanisms when one is attacked. One possibility is that plants release an involuntary cue that they can’t suppress, which other plants eavesdrop on. Another possibility is that fungi monitor their plant partners, detect when one has been attacked, and then warn the other plants in their network.
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This research was recently published in Proceedings of the National Academy of Sciences: “The evolution of signaling and monitoring in plant–fungal networks” https://www.pnas.org/doi/abs/10.1073/pnas.2420701122
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