Gordon Fain

around the roots of plants, as Nicole van Dam and Harro Bouwmeester report in a review of this fi eld (Trends Plant Sci. (2016) DOI: http://dx.doi. org/10.1016/j.tplants.2016.01.008). Direct investigation of signalling in the rhizosphere is currently focused on communication between plants and their microbial symbionts, as Vittorio Venturi and Christopher Keel report, although the scope could be broadened to include all organisms present (Trends Plant Sci. (2016) DOI: http://dx.doi.org/10.1016/j. tplants.2016.01.005). Plants may send signals to the soil microbiome to recruit benefi cial species or to activate benefi cial traits. In turn, microorganisms may signal to the host plant to activate defences, infl uence metabolism and development, or induce the stress response. Plants are also known to communicate with their neighbours through the entangled root networks. Trees, for instance, can feed their offspring through the roots and keep stumps alive. They can also trade information about threats like drought or diseases. Some forest experts have taken to the expression of the ‘woodwide web’ to characterise this hidden information exchange. Just how it works in detail remains to be explored.