Leaf epicuticular wax and cuticle ultrastructure of four Eucalyptus species and their hybrids

Leaf epicuticular wax and cuticle ultrastructure were assessed in four eucalypt species Eucalyptus platypus, Eucalyptus spathulata, Eucalyptus yalatensis and Eucalyptus viridis, and in their interspecific hybrid progeny. In parent species, epicuticular wax appeared as digitate-edged platelets. Leaves of E. yalatensis showed parallel-stacked platelets and abundant surface wax cover, while other species showed random or parallel-oriented platelets forming a less dense cover. Distinct cuticular papillae were evident on E. yalatensis leaves but not in the other species. Leaf surfaces of E. platypus and E. spathulata were indistinguishable. Epistomatal cavities were present in all species and were lined with digitate-edged platelets, except for those in E. viridis leaves, which contained amorphous wax. Subsurface cuticular channels connecting epistomatal cavities were detected in some species. The wax and cuticle morphology of E. spathulata x E: yalatensis and E. spathulata x E: viridis hybrids indicated maternal, paternal, intermediate, and transgressive modes of inheritance. Hybrids from reciprocal crosses between E. spathulata and E. platypus were similar and indistinguishable from the parents.