The proteaceous pistil: Morphological and anatomical aspects of the pollenpresenter and style of eight species across five genera

The morphology and anatomy of pollen presenters, styles and pollen of speci es of Banksia, Dryandra, Hakea, Isopogon and Macadamia were studied. Serial sections of pistils and SEM images of pollen were quantified to determine whether the low fertility observed in the Proteaceae has a structural basis . Pollen access to the stigma was investigated. There were three types of s tigmatic cavity. A groove in which the stigmatic papillae were enclosed was present in Dryandra, Banksia and Hakea. Macadamia had a groove with protru ding papillae, and Isopogon had a tube which enclosed the papillae. Anatomi cal studies showed the pollen presenter to be structurally complex but over all to have similar internal anatomy across the species studied. The specie s could be grouped according to presence or absence of transfer tissue and presence or absence of sclerenchyma, but these groups were not mutually exc lusive. In the pistil there were three structural filters to pollen tube pa ssage. The first was at the stigma, where pollen grain access could be limi ted by the diameter or length of the stigmatic groove or the capacity of th e pollination chamber in relation to pollen volume. The second and third re lated to a narrowing of the transmitting tissue tract within the pollen pre senter and in the lower style which could influence pollen tube passage to the ovule. (C) 1999 Annals of Botany Company.