Regulatory mechanisms of flowering in Sturt's desert pea ('Swainsona formosa')

Abstract

'Swainsona formosa' (G.Don) J. Thompson (Sturt's desert pea) is an Australia native legume which has potential as an ornamental pot plant and is also suitable for hanging baskets and as a cut flower. Accurate identification of the timing and control of growth stages is critically important in making management decisions for floricultural crops. One of the impediments to the commercialisation of 'S. formosa' as a pot plant is its inability to produce flowers under low light conditions. The apical meristems of 'S. formosa' were investigated by stereomicroscopy and scanning electron microscopy to identify flowering time and stages of floral development. Conversion from the vegetative to the reproductive stages began within 40 to 46 days after seed germination for axillary branches and 46 to 52 days for central stems. The order of floral organ initiation within each whorl is unidirectional, except for the petal whorl, which is simultaneous; the flower is organised into five whorls and shows a pentamerous arrangement of sepals and petals, ten stamens in two whorls and a central carpel. This is the first description of the complete floral ontogeny of a member of tribe Galegeae in papilionoid legumes.