Inflorescence and floral development of Carnarvonia (Proteaceae)

Abstract

749Douglas, Andrew w: (Royal Botanic Gardens, Melbourne, Birdwood Avenue, South Yarra, Victoria, 3141, Australia) 1996. Inflorescence and floral development of Carnarvonia (Proteaceae). Telopea 6(4): 749-774. Carnarvonia araliifolia is an endemic of north-east Queensland and the sole member of the subfamily Carnarvonioideae in Proteaceae. The inflorescence structure is atypical compared to the relatively simple racemiform architecture found in the other taxa of the family (including Grevilleoideae that has flower pairs). There is variability in numbers of flowers on a given axis, irregular branching of inflorescence axes, positions of flowers within an axillary module, numbers of flowers at a node on the principal axes, and the cauliflorous, axillary andlor terminal location of flowering regions on a branch. Carnarvonia has been hypothesized as having shared a common ancestor either with or within Grevilleoideae. Developmental evidence is examined to better define and elucidate the morphogenetic processes involved in the complex architecture of the inflorescence and flowers including the fundamental units of construction within a metameric conceptual framework. Likewise, the developmental evidence is used to examine the hypotheses of morphological derivation of the inflorescence as inferred from phylogenetic hypotheses. The inflorescence structure is interpreted as a paniculiform-raceme although terminal flowers are present on axillary inflorescence branches. There is variation within the developmental programme of the first three metamers of a subunit or axillary inflorescence branch that differs from the variation present in other Proteaceae and an inflorescence branch can vary in the number of flowers that develop. In the terminal flowers of a module, the first tepal is initiated in a position that follows the phyllotactic continuity of each subunit (2/5), the first tepal being initiated in a predictable position based on the position of the preceding bract primordium. The carpel is initiated in a lateral position, closest to both the first initiated stamen and tepal, thus maintaining the phyllotactic continuity in the flower. The ontogenetic events involved in inflorescence development in Carnarvonia clarify its morphological organization and provide morphological evidence of the derivation of the inflorescence form from a single-flowered, perhaps racemiform, ancestor.

A new suprageneric classification of the Proteaceae, with an annotated checklist of genera

“…Secondly, Carnarvonia was placed in its own subfamily by Johnson and Briggs on the grounds that it lacked what they regarded as the most distinctive synapomorphy of their subfamily Grevilleoideae, inflorescences with grevilleoid flower pairs. Douglas (1996), in a detailed study of inflorescence and flower development in Carnarvonia, confirms the complete absence of even a vestige of the development of flower pairs in Carnarvonia. These observations are more consistent with a basal position of Carnarvonia within the Grevilleoideae than membership of the Macadamieae.…”

“…Midgley 1987), morphology (e.g. Douglas 1996), historical biogeography (e.g. Weston & Crisp 1996), anatomy (e.g.…”

Proteaceae

“…Proteaceaous flowers have a single whorl of (usually 4) valvate tepals, each supplied by 1-5 vascular bundles which emerge from a gap in the floral stele. Another possibility is that Proteaceae are primitively dichlamydeous and dimerous, similarly to many other basal eudicots (Soltis et al 2003), and this suggestion is consistent with the decussate pattern of tepal initiation commonly observed (Douglas 1996;Douglas and Tucker 1996b, c). Proteaceae may be primitively monochlamydeous, having diverged from other angiosperms prior to the origin of differentiated sepals and petals.…”

Patterns of angiospermy development before carpel sealing across living angiosperms: diversity, and morphological and systematic aspects

“…18), Carnarvonia araliifolia F.Muell. (Proteaceae) (Douglas, , fig. 53), Abrus precatorius L. (Fabaceae) (Prenner, , fig.…”

“…In the grade of early diverging eudicots above Ranunculales, the ovules are also covered from the beginning of development, as in Sabiaceae (Wanntorp & Ronse De Craene, ), Proteaceae (Douglas, ; Douglas & Tucker, ,b), Nelumbonaceae (Hayes, Schneider & Carlquist, ), Trochodendraceae (Chen et al ., ), Buxaceae (von Balthazar & Endress, ) and Gunneraceae (Rutishauser, Wanntorp & Pfeifer, ). The pattern of carpel closure is unknown in Platanaceae and Myrothamnaceae.…”