Evolution of Plant Rooting Systems

Abstract The evolution of rooting systems was essential for the diversification of land plants enabling plants to uptake essential water and nutrients and providing stable anchorage for ever‐larger herbaceous plants and subsequently the advent of trees. To understand how roots evolved, it is essential to combine studies of both fossil and living plants, and by doing this, we can identify three major steps in rooting system evolution. First, during land plant evolution, there was a switch between the primary rooting systems of plants from rhizoid‐based systems developing on the gametophyte stage of the life cycle, to specialised roots that developed on the sporophyte stage. Second, roots evolved independently in the two major lineages of vascular plants, lycophytes and euphyllophytes. Third, root evolution in the lycophyte lineage occurred in a gradual fashion from rhizoid‐based systems, through specialised rooting axes finally to roots. Key Concepts The evolution of roots was essential for the evolution of plant life and also made major changes to the Earth system. Early diverging bryophytes develop a rhizoid‐based rooting system on their free‐living gametophyte stage. The common ancestor of vascular plants is predicted to develop a rhizoid‐based rooting system on both the sporophyte and gametophyte generation. Plant roots evolved independently in the lycophytes and euphyllophyte lineage. Exceptionally well‐preserved fossils from the 407 million‐year‐old Rhynie chert shed light on the stepwise evolution of plant roots in the lycophyte lineages.