Figure 1.

Evolution among major vascular plant lineages and its relation to root meristem organization. (A) Hypothesis of root evolution in vascular plants. Both major extant vascular plant lineages, lycophytes and euphyllophytes, have been hypothesized to independently evolve roots. Based on [3,4,6,15,16,17,18]. (B) Schematic representation of cell layer organization and stem cell niches in different described roots from extant vascular plants (Table S1). Meristem diversity has been extensively assessed across flowering plants, but not in other lineages. Color lines covering the roots, correspond to color patterns represented in A. The different RAM morphologies showed in Figure 1B were obtained from published articles. The scientific name of each species, its plant lineage and the corresponding reference can be found in Table S1 in Supplementary Materials. [19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39].