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Silicon (Si) is now widely recognized to benefit plants through protecting against a range of biotic and abiotic stresses, including herbivory, pathogen attack and climatic fluctuations. But this recognition has been a long time in the making and, like many ecological histories, it links back to Darwin. Silica (SiO 2) phytoliths were identified in dust samples collected by Darwin on the HMS Beagle voyage in 1833; they were sent to Germany and named phytolitharia by Christian Ehrenbeg in 1835 (Piperno 2006). Agricultural researchers were perhaps quicker to recognise the importance of plant silicon than evolutionary biologists or ecologists. A functional role for Si, namely that of protecting crop plants against herbivory, was identified in agricultural systems almost a century ago (McColloch & Salmon 1923) and now Si treatments are routinely applied to protect crops from herbivore attack and increase yields (Keeping & Reynolds 2009; Guntzer, Keller & Meunier 2012; Reynolds et al. 2016). In contrast, relatively less attention was given to the role of Si in ecology, despite some seminal papers predicting its importance (Sangster 1978; Iler 1979; Raven 1983; Parry et al. 1984; Sangster & Hodson 1986; Takahashi, Ma & Miyake 1990; Epstein 1994, 1999). These papers highlighted the high levels of Si in soils, its prominence in many plant families, but a lack of research on its functional roles by experimental plant biologists.

Si research began to re-focus towards ecology in the 1980s, with the pioneering work of McNaughton and Tarrants demonstrating the inducibility of Si defences in response to herbivory (McNaughton 1985; McNaughton et al. 1985 …