Floral Morphology of Eucalyptus melliodora A. Cunn. ex Schau. And Comparisons With Other Eucalypt Species

Abstract

The important phases of floral development in E. melliodora from bud initiation to anthesis and style abscission are documented by means of scanning electron micrographs. Thirteen phases of bud development from first indication of operculum abscission to style abscission are presented, as well as the timing and duration of each phase. Anther dehiscence commences prior to flower opening and no pollen grains were observed on flowers 2 days after opening. Secondary transportation of pollen after deposition is possible. Nectar secretion did not commence until after pollen was shed and the stigma became receptive. Although individual flowers were protandrous, there was some overlap within a single inflorescence between pollen shed and the 'wet stigma' phase, suggesting that geitonogamy was possible. The style did not increase in length following anthesis, a common feature in Eucalyptus, leaving the stigma in close proximity with the anthers. There was a graduation in filament length from the outer to inner whorls. The innermost anthers produced the most pollen grains while the outermost were staminodal.

There was considerable difference between the number of stamens (71-312), staminodes (0-83) and pollen grains per anther (643-1790) found in the six species examined. Stamen length in all species increased across the staminophore from 1.82-6.99 mm in the inner whorl to 4.84-12.61 mm in the outer whorl.