Stigma and Style Morphology in Relation to Taxonomy and Breeding Systems in Eucalyptus and Angophora (Myrtaceae)

Abstract

The stigma and style of 94 species of Eucalyptus and two species of Angophora were studied by scanning electron microscopy and/or light microscopy. All species had papillate stigmas and a stylar canal of varying length. Angophora species had mop-like stigmas with long papillae that were very similar in appearance to those of the red bloodwood group of the Corymbia, e.g. E. gummifera. The spotted gum group of the Corymbia had mop-like stigmas with short papillae and the yellow bloodwoods had tapered stigmas. The latter group was also charaderised by an extremely thick cuticle on the outer surface of the style, over 100 µm in thickness in E. watsoniana. All species in Blakella had tapered stigmas with a lobed surface and relatively few short papillae. The stylar canal had no cuticle in E. papuana. Eudesmia is a variable subgenus with E. erythrocorys unusual in having long multicellular papillae. Most Symphyomyrtus species had blunt or pinhead-shaped lobed stigmas with a heavily cutinised stylar canal. E. deglupta and E. microcorys did not conform to this pattern and had mop-shaped stigmas with long papillae. Monocalyptus species had blunt stigmas with few papillae and hollow styles and appeared to form a cohesive group.

On the basis of stigma and style morphology Angophora is more similar to Corymbia than to Blakella. E. deglupta and E. microcorys are distinct from other Symphyomyrtus species studied. E. trachyphloia and E. jacobsiana are more similar to E. gummifera than to E. watsoniana or other yellow bloodwoods.