Underground signals carried through common mycelial networks warn neighbouring plants of aphid attack

Abstract

The roots of most land plants are colonised by mycorrhizal fungi that provide mineral nutrients in exchange for carbon. Here, we show that mycorrhizal mycelia can also act as a conduit for signalling between plants, acting as an early warning system for herbivore attack. Insect herbivory causes systemic changes in the production of plant volatiles, particularly methyl salicylate, making bean plants, Vicia faba, repellent to aphids but attractive to aphid enemies such as parasitoids. We demonstrate that these effects can also occur in aphid-free plants but only when they are connected to aphid-infested plants via a common mycorrhizal mycelial network. This underground messaging system allows neighbouring plants to invoke herbivore defences before attack. Our findings demonstrate that common mycorrhizal mycelial networks can determine the outcome of multitrophic interactions by communicating information on herbivore attack between plants, thereby influencing the behaviour of both herbivores and their natural enemies.

Facilitation between woody and herbaceous plants that associate with arbuscular mycorrhizal fungi in temperate European forests

“…There are several obvious ways through which mycorrhiza can mediate plant coexistence. For example through facilitating the establishment of seedlings, amplifying allelopathic interactions and interspecific negative feedbacks (many of which are reviewed in Hart, Reader, & Klironomos, 2003; but also in more recent literature, e.g., Veiga, Howard, & van der Heijden, 2012; Badikova et al., 2013). Here, we refer to the possibility that donor plants, by providing mycorrhizal access or inoculum to other plants, promote establishment and survival of these target plants, as the “mycorrhizal mediation hypothesis.” To the best of our knowledge, the possibility that mycorrhizas mediate coexistence of plants differing in life forms by this general mechanism has never been tested.…”

A comparison of plants and animals in their responses to risk of consumption

“…However, many plants possess networks of mycorrhizal associates that extend the scale of information acquisition far beyond the extent of that individual's roots, at least tens of meters and probably much farther [62 ]. Information transferred by mycorrhizal networks can allow plants to induce defenses before attack [63,64 ]. We predict that information acquired from mycorrhizal associates comes from a greater distance but is less reliable than information collected by an individual itself; therefore, plants may respond less to these cues.…”

Considerations on Legal and Philosophical Problems in Experimental Botany: The case of plant in vitro cultures

“…66 There are several different ways in which this occurs, such as airborne chemicals, 67 soluble compounds submitted by roots 68 or mycelial networks made by mycorrhizal fungi. 69 The role of an effective signaling system is to warn neighboring plants of herbivores, pathogen attacks, or upcoming drought. 70 In such a way, plants can recognize their kin and generally receive information from the surrounding environment.…”