The Proteaceous Pistil: Morphological and Anatomical Aspects of the Pollen Presenter and Style of Eight Species Across Five Genera

The morphology and anatomy of pollen presenters, styles andpollen of species ofBanksia, Dryandra, Hakea, IsopogonandMacadamiawerestudied. Serial sections of pistils and SEM images of pollenwere quantified to determine whether the low fertility observedin the Proteaceae has a structural basis. Pollen access to thestigma was investigated. There were three types of stigmaticcavity. A groove in which the stigmatic papillae were enclosedwas present inDryandra, BanksiaandHakea. Macadamiahad a groovewith protruding papillae, andIsopogonhad a tube which enclosedthe papillae. Anatomical studies showed the pollen presenterto be structurally complex but overall to have similar internalanatomy across the species studied. The species could be groupedaccording to presence or absence of transfer tissue and presenceor absence of sclerenchyma, but these groups were not mutuallyexclusive. In the pistil there were three structural filtersto pollen tube passage. The first was at the stigma, where pollengrain access could be limited by the diameter or length of thestigmatic groove or the capacity of the pollination chamberin relation to pollen volume. The second and third related toa narrowing of the transmitting tissue tract within the pollenpresenter and in the lower style which could influence pollentube passage to the ovule.Copyright 1999 Annals of Botany Company Proteaceae,Banksia coccinea, Banksia ericifolia, Dryandra formosa, Dryandra nana, Dryandra quercifolia, Hakea bucculenta, Isopogon cuneatus, Macadamia integrifolia,stigmatic cavity, fertility, pollen presenter, structural limitation, stigma, pollen grain, image analysis, transfer tissue.