Floral morphology and pollination system in the native Australian perennial pasture legume Cullen australasicum (syn. Psoralea australasica)

Abstract

Cullen australasicum (syn. Psoralea australasica) is a native perennial legume with potential in the low-rainfall wheatbelt of southern Australia. The objective of this study was to investigate the reproductive biology of C. australasicum utilising five accessions. Glasshouse and field pollination experiments were conducted in Adelaide, South Australia. Floral morphology, stigma receptivity and pollen : ovule ratios were determined. Pollen tube growth and stigma morphology were examined using fluorescence and scanning electron microscopes. Glasshouse pollination studies indicated that four of the accessions showed the need for an external tripping agent to bring about pollination and that hand-tripping was the most efficient method. A scanning electron microscopy study revealed there are two types of stigmas in this species. Stigma receptivity was significantly lower at the early bud stage before anther dehiscence. The results show that C. australasicum is a self-compatible species comprising accessions with a wide range of outcrossing potential.