Evolution of the helobial flower

Posluszny, Usher; Charlton, W. A.

doi:10.1016/0304-3770(93)90074-7

Cited by 33 publications

(24 citation statements)

References 64 publications

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“…Weberling (1989;Eichler 1875Eichler /1878 termed this pattern as 'eprophyllate aestivation'; that is, the first two floral organs to develop are positioned as if they were prophylls (two in dicots, one in monocots; Weberling 1989). A developmental presumption in eprophyllate aestivation patterns is that the position at initiation of the first two primordia of a flower is influenced by the position of the preceding organ(s), or that the sequential initiation of an organ from a meristem is influenced by the position of the preceding organ (Hofmeister in Weberling 1989; Eichler 1875-8; termed phyllotactic continuity within a flower by Posluszny 1993). In the case of single flowers in bract axils of Carnarvonia and most other Proteaceae, the organ subtending the flower appears to influence the subsequent initiation of the first floral organs; therefore a more appropriate term would be eprophyllate initiation (Douglas 1994;Douglas & Tucker 1996a, b, in press).…”

Section: Inflorescence and Floral Formmentioning

confidence: 99%

Inflorescence and floral development of Carnarvonia (Proteaceae)

Douglas¹

1996

Telopea

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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.

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Section: Inflorescence and Floral Formmentioning

confidence: 99%

Inflorescence and floral development of Carnarvonia (Proteaceae)

Douglas¹

1996

Telopea

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“…The validity of the outcrossing argument therefore needs to be tested by estimating the importance of sexual reproduction and measuring levels of outcrossing in seagrass populations with different breeding systems. It is also possible that the ancestors of the seagrasses may have been primitively unisexual (Cox & Humphries, 1993;Posluszny & Charlton, 1993;Les & Haynes, 1995;, so that the present high frequency of dioecy does not reflect adaptation to their present environmental niche.…”

Section: Introductionmentioning

confidence: 99%

Genetic uniformity in Amphibolis antarctica, a dioecious seagrass

1996

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Few detailed studies have been published on genetic variation in seagrasses except those on the monoecious Zostera marina L. or the hermaphrodite Posidonia australis Hook. f This paper presents allozyme, RFLP and reproductive biology data on Amphibolis antarctica (Labill.) Sonder & Aschers, one of the 75 per cent of all seagrass species which are dioecious.Collections were made from approximately one-third of the species range in Western Australia. Its only congener, A. gnfflthii (J. M. Black) den Hartog, was collected from one site to provide a comparison. Flowering was observed in 25 per cent of the shoots surveyed and the average sex ratio was 3.8: 1 (F:M) which it has been suggested indicates sexual reproduction. No genetic variation was found within or between populations at 14 allozyme loci. 18S RFLPs and M13 DNA fingerprinting gave few satisfactory results but also did not exhibit any variability. Allozyme variation was observed between A. antarctica and A. griffithii, the only congeneric species. The lack of allozyme and DNA variation within A. antarctica indicates a potentially low level of outbreeding, a highly clonal reproductive system or a very efficient genetic system in A. antarctica. The hypothesis that the dioecious reproductive system evolved in seagrasses to maximize outbreeding and genetic variability, proposed by several authors, is questioned in light of these data.

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“…A strictly defined pedicellar complex of vascular bundles is formed in Acorns, rising from the layer of peripheral spadix vascullature. Alismatids may also form a single complex of va.scular bundles, such as in Juncaginaceae and Potamogetonaceae (Tomlinson, 1982;Posluszny & Charlton, 1993). In Acorns the pedicellar complex simply branches to a hexagonal pattern supplying the stamen-tepal association.…”

Section: Floral Vasculaturementioning

confidence: 98%

“…In Aponogetonaceae vascular bundles form a ring at the base of the flower, and bundles of floral organs originate from several layers of the spadix vasculature (Tomlinson, 1982), similar to Araceae. Independent vascular bundles that do not form a united complex are found in Butomaceae, Alismataceae, and Scheuchzeriaceae (Singh & Sattler, 1972, 1974Tomlinson, 1982;Posluszny & Charlton, 1993).…”

Section: Floral Vasculaturementioning

confidence: 99%

Flower structure and development of Araceae compared with alismatids and Acoraceae

Buzgo¹

2001

Botanical Journal of the Linnean Society

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Floral development of Araceae is compared with that of other basal monocots such as alismatids and Acorus. Flowers of Araceae, Acorus and several alismatids with spicate inflorescences lack a subtending floral bract. In Araceae and some Potamogetonaceae the subtending floral bract is suppressed, and not incorporated into the perianth. This differs from Acorus and some alismatids, where a bract-like median abaxial tepal is formed in the outer perianth whorl (i.e. developmental merger of flower-subtending bract and tepal). In Araceae, Acorus and spicate alismatids flowers develop unidirectionally, correlated with bract reduction. Araceae lack unidirectionality in the outer perianth whorl, in contrast t o Acorus and Juncaginaceae. The transition from trimerous to dimerous flowers in Onintiurn (Araceae) is by accentuation of the unidirectionality of the inner perianth. The gynoecium of Araceae and Acorus is synascidiate. However, in most Araceae the synascidiate portion is shorter than in Acorns, and a distinct basal elongation phase as in Acorus and Juncaginaceae was not found. The perianth and androecium of Lysichiton and Symplocarpus and the gynoecium of Gymnostachys differ from other Araceae and resemble those in Potamogetonaceae. Developmental findings support the isolation of Acorus from Araceae, and show similarities of Araceae with Potamogetonaceae and of Acorus with Juncaginaceae.

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Evolution of the helobial flower

Cited by 33 publications

References 64 publications

Inflorescence and floral development of Carnarvonia (Proteaceae)

Inflorescence and floral development of Carnarvonia (Proteaceae)

Genetic uniformity in Amphibolis antarctica, a dioecious seagrass

Flower structure and development of Araceae compared with alismatids and Acoraceae

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