“…basic units of the phenotype; Serebrovsky, 1925;Lynch, 2011; for discussion, see York et al, 2013) enhance phosphorus acquisition, including root architectural phenes for topsoil foraging , such as shallow root growth angles Ho et al, 2005), increased basal root whorl number (Lynch and Brown, 2012;Miguel et al, 2013), and adventitious rooting (Miller et al, 2003); phenes to enhance soil exploitation, including root hair length and density (RHL/D; Bates and Lynch, 2000a, 2000bMa et al, 2001a;Gahoonia and Nielsen, 2004;Yan et al, 2004) and phosphorus-solubilizing root exudates (Ryan et al, 2001); mycorrhizal symbioses (Smith and Read, 2008); and phenes that reduce the metabolic cost of soil exploration , such as root etiolation and root cortical aerenchyma (Fan et al, 2003;Lynch, 2010, 2011). It is probable that interactions among these phenes are important in determining the phosphorus acquisition of integrated phenotypes.…”