Relationships Between Fire Response, Morphology, Root Anatomy and Starch Distribution in South-west Australian Epacridaceae

Selected epacrids (92 species in 15 genera) were examined withrespect to fire response type, morphology, root anatomy andstarch storage. Seeders, 75% of the species investigated, possesseda single main stem and a small root system with lateral rootswhich in most cases did not spread beyond the shoot canopy.Resprouter species were generally multi-stemmed with large lignotuberousroot stocks. Certain seeder and resprouter species were intermediatein form and showed small root systems and basally branched mainstems. Amounts of starch in roots of seeders (1.9±0.5mgstarch gd.wt per root) were much less than in resprouters (14.1±3.3)whereas amounts in shoots were similar (1.9±0.5 and 1.6±0.6mgstarch gd.wt per shoot, respectively). Starch storage in rootswas mostly confined to rays of xylem parenchyma and inter-rayxylem parenchyma and the greater storage capacity of resprouterswas generally due to broader rays. Growth zones in root xylemranged from clear, verifiable annual rings, as in many seederspecies, to indistinct growth zones, typical of many resprouterspecies. Shoot:root dry weight ratios were higher in seedersthan resprouters. The study suggests that speciation withinthe Epacridaceae into seeder and resprouter forms involved divergentdifferentiation in terms of morphology, shoot:root dry weightratio root storage of starch. Seeder; starch storage; growth rings; growth zones; south-west Australia; resprouter; Epacridaceae