Cluster roots are extremely specialized root structures that are formed as bottlebrush-like clusters of small rootlets with limited growth, which emerge along the lateral roots (Fig. 1) in many species of the Proteaceae (Dinkelaker et al., 1995; Shane & Lambers, 2005). Members of this family comprise sclerophyllous shrubs and trees, representing a major component of the flora in Western Australia and South Africa. Apart from c. 1600 species within the Proteaceae, clustered root structures are also formed ...