Figure 4.9 Dimorphic root system of a six-year-old Banksia prionotes tree growing in Western Australia in a deep sand. The trunk (T) is connected through a swollen junction (J) to the root system which comprises a dominant sinker root (S) with smaller sinkers (S2). A system of lateral roots (L) emerge horizontally from the junction, some bearing smaller sinker roots (arrows). Other laterals give rise to cluster roots (CR). (W.D. Jeschke and J.S. Pate, J Exp Bot 46: 907-915, 1995).