ABSTRACT
Roots were an early development in plant life, evolving on land during the Devonian Period, 416 million to 360 million years ago (Gensel et al. 2001; Raven and Edwards 2001; Kenrick 2002; Boyce 2005). is was a time of enormous change, which witnessed the evolution of forest ecosystems from an earlier diminutive herbaceous vegetation of small rootless and leaess plants (Gensel and Edwards 2001; Gensel 2008; Meyer-Berthaud et al. 2010). From the outset, symbiotic associations with fungi were important (Taylor et al. 2004; Strullu-Derrien and Strullu 2007; Bonfante and Genre 2008), and it is clear that mycorrhizae and plant roots have coevolved in many dierent ways (Brundrett 2002; Wang and Qiu 2006; Taylor et al. 2009a). Roots combined with a fully integrated vascular system were essential to the evolution of large plants, enabling them to meet the requirements of anchorage and the acquisition of water and nutrients (Boyce 2005). Beginning in the Middle Devonian (ca 392 Ma), the earliest forest ecosystems already displayed an astonishing diversity of rooting systems encompassing extinct forms and others that are comparable in many ways to those of modern tree ferns and gymnosperms (Driese et al. 1997; Algeo and Scheckler 1998; Soria and Meyer-Berthaud 2004; Stein et al. 2007). e combined weight of evidence from both fossils and living plants demonstrates that once plants made the transition to the land, rooting organs evolved in a piecemeal fashion independently in several dierent clades, rapidly acquiring and extending functionality and complexity.
