Anther diversity and function in Verticordia DC. (Myrtaceae)

Anther form and structure across the taxonomic groups in Verticordia were examined. The three anther types which were recognised rectangular, oblong and saccate, accord well with the three subgenera into which the genus has been divided. The sporogenous part of the anther has a fairly typical angiosperm anatomy. However in many species there is a small or large gland in the upper filament/connective which contains lipidic contents. The anatomy of this structure is based on that of the oil glands which are ubiquitous in Myrtaceae primary tissues. However the gland is usually much larger than these and is schizolysigenous in origin. Evolutionary development of the anthers in the genus is related to pollination systems and the development of secondary pollen presentation from the upper style in some groups. Anther glands may have originally had a protective function for the sporogenous tissue. However in different groups the function has changed or the gland has disappeared. In some species in subgenus Chrysoma (which does not have secondary pollen presentation) the gland contents seem to be an additional food source for pollinators. In other groups, with the development of secondary pollen presentation the protective function has become redundant and anther glands have either disappeared or produce contents which have become part of the process of pollen dispersal.