Interspecific and Intergeneric Pistil–Pollen Compatibility of Banksia coccinea (Proteaceae)

Abstract

Interspecific and intergeneric pollen-tube growth was investigated using controlled hand pollinations of Banksia coccinea R.Br., 35 species of Banksia L.f., and three species of the related genus Dryandra R.Br. Currently, the relationship between B. coccinea and other species groups within Banksia is unclear. Some species supported no germination of B. coccinea pollen, some supported normal pollen-tube growth and others produced pollen-tube abnormalities including thickened walls, bulbous swellings, directionless growth, burst tips and branched tubes. Control of pollen-tube growth in the pistil was imposed in the pollen presenter and upper style. There was no significant reciprocal effect on pollination success in the lower style. The results of pollen-tube compatability in the lower style indicated that B. coccinea has a closer affinity to the section Oncostylis, than the section Banksia where it is currently placed. Intergeneric crosses of B. coccinea with Dryandra species resulted in some compatibility, with one cross having low numbers of pollen-tubes in the pollen presenter and upper style region. These results indicate a close relationship between Banksia and Dryandra, which are sister genera in the tribe Banksiae, family Proteaceae.