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Hugh D. Wilson - One of the best experts on this subject based on the ideXlab platform.

Jurg Schonenberger - One of the best experts on this subject based on the ideXlab platform.

  • early floral development and Androecium organization in the sarracenioid clade actinidiaceae roridulaceae and sarraceniaceae of ericales
    Botanical Journal of the Linnean Society, 2016
    Co-Authors: Stefan D Lofstrand, Maria Von Balthazar, Jurg Schonenberger
    Abstract:

    The early floral development of Actinidia (A. arguta, A. callosa, A. chinensis and A. kolomikta; Actinidiaceae), Saurauia (S. montana, S. oldhamii, S. pittieri and S. subspinosa; Actinidiaceae), Roridula gorgonias (Roridulaceae) and Heliamphora nutans (Sarraceniaceae) was studied comparatively using scanning electron microscopy. Late stages of Androecium development are additionally presented for Clematoclethra scandens (Actinidiaceae), Darlingtonia californica and Sarracenia leucophylla (Sarraceniaceae). Flowers are typically pentamerous and share a number of developmental features: perianth organs emerge in a clockwise or anticlockwise spiral sequence on the floral apex with relatively long plastochrons between successive organs, resulting in conspicuous size differences among perianth organs in early development; the perianth always consists of two differentiated whorls (unlike earlier interpretations of the perianth in Heliamphora); the Androecium is polystemonous in most species and is initiated with leading stamens in alternipetalous positions; successive stamen primordia appear in a lateral succession until a ring‐like structure is formed; and the anthers become inverted shortly before anthesis. Later androecial development differs conspicuously between taxa and further proliferation may be centrifugal, centripetal and/or lateral. For Ericales, unusual features of floral development include: petals initiated in a spiral sequence (but later organized in a whorl) with comparatively long plastochrons between individual petals (except Saurauia); common occurrence of perianth organs in double positions in Actinidiaceae; and anthers that become inverted close to anthesis. The floral development in the sarracenioids is additionally compared with that of other families and clades in Ericales, further emphasizing the highly variable patterns of Androecium development in the order.

  • Early floral development of Pentaphylacaceae (Ericales) and its systematic implications
    Plant Systematics and Evolution, 2014
    Co-Authors: Rui-ju Zhang, Jurg Schonenberger
    Abstract:

    Early floral development of four species from the genera Anneslea, Cleyera, Eurya, and Ternstroemia of Pentaphylacaceae, was studied comparatively using scanning electron microscopy. Together with earlier studies in Euryodendron and Adinandra, 6 out of 12 genera of Pentaphylacaceae have now been studied for their floral development. The usually pentamerous flowers of these taxa share a number of developmental features: the perianth organs appear in a clockwise or anticlockwise spiral sequence on the floral apex with relatively long plastochrons between successive organs, resulting in conspicuous size differences among perianth organs during early developmental stages. The early development of the usually polystemonous Androecium is characterized by an indistinct ring-primordium and a mostly concave floral apex; individual stamens appear subsequently on this ring-primordium. However, further development of the Androecium differs conspicuously among taxa and we describe three main developmental patterns for the family including features such as centripetal stamen whorls and stamens fascicles. Unusual features of floral development and organization of Pentaphylacaceae include: (1) a pronounced spiral sequence of organ appearance during early floral development in perianth and Androecium; (2) the occurrence of paired organs in the corolla and the Androecium of some species; (3) sepals and petals that are positioned opposite from each other in the genera Anneslea and Ternstroemia; and (4) a concave floral apex at the beginning of Androecium development. From a systematic point of view our results clearly support a close relationship between Anneslea and Ternstroemia and also suggest a closer relationship among Adinandra, Cleyera, and Euryodendron on the one hand and between Eurya and Visnea on the other. Further, our developmental study stresses the differences between Pentaphylacaceae and Theaceae, which earlier where thought to form a natural group of plants. While high stamen numbers are achieved via centripetal pattern of stamen formation in the former family, stamens are formed centrifugally in the latter.

  • early floral development and Androecium organization in fouquieriaceae ericales
    Plant Systematics and Evolution, 2005
    Co-Authors: Jurg Schonenberger, A Grenhagen
    Abstract:

    Early floral development with focus on the Androecium was studied with the help of scanning electron microscopy and serial microtome sectioning in Fouquieria columnaris and F. splendens. Perianth organs appear in a spiral pattern on the floral apex. The spiral may be a clockwise or anti-clockwise. The Androecium is best interpreted as two-whorled with all the stamens arranged in a single series. In F. splendens, two or more of the five epipetalous stamen positions are doubled, i.e. they are occupied by stamen pairs. Unusual features in the floral development of Fouquieriaceae include (1) a strong spiral component even in whorled organ categories and (2) a pronouncedly asymmetric floral apex during an early phase of floral development. From a phylogenetic point of view, it seems plausible that the common ancestor of Fouquieriaceae and its sister family Polemoniaceae was characterized by two alternating, pentamerous stamen-whorls.

  • comparative floral development and Androecium structure in malvoideae malvaceae s l
    International Journal of Plant Sciences, 2004
    Co-Authors: Maria Von Balthazar, William S Alverson, Jurg Schonenberger, David A Baum
    Abstract:

    Floral development and Androecium structure were studied in eight genera of the Malvoideae (Malvaceae s.l.). All core Malvoideae (Malvaceae s.s.) share a uniform pattern of floral development and have several characteristic Androecium structures in common. A corolla/Androecium ring wall is formed and subsequently differentiated into five androecial sectors (=primary androecial primordia) that give rise to the Androecium and corolla. Petals are developed at the base of the androecial sectors and are shifted slightly clockwise or counterclockwise relative to the androecial sector. Secondary androecial primordia are initiated centrifugally in two rows on each sector in an alternate pattern. The first secondary androecial primordium is initiated on the opposite side of the androecial sector from the petal. The secondary androecial primordia later subdivide longitudinally and differentiate into functional androecial units, which each have a two‐locular theca with a single longitudinal dehiscence zone. In some ...

Roy E. Gereau - One of the best experts on this subject based on the ideXlab platform.

  • Rubiacearum Americanarum Magna Hama Pars XXVII: Six New Species and a New Taxonomic View of Posoqueria
    Novon, 2011
    Co-Authors: Charlotte M Taylor, Barry Hammel, Roy E. Gereau
    Abstract:

    The Neotropical genus Posoqueria Aubl. (Rubiaceae) has a number of species with an asymmetric Androecium and pollen catapult mechanism and others that apparently lack these features. A new taxonomy based on corolla form and size, the length and symmetry of the filaments, and fruit morphology finds the name P. panamensis (Walp. & Duchass.) Walp. to be a synonym of P. latifolia (Rudge) Roem. & Schult. and distinguishes additional species in southern Central America and northwestern South America, newly described here: P. chocoana C. M. Taylor of wet lowland Panama to northwestern Ecuador has medium-sized corollas, subglobose fruits, corolla lobes of unequal size, and a generally symmetric Androecium that apparently lacks the pollen catapult mechanism; P. correana C. M. Taylor of lowland and premontane Panama has medium-sized corollas, leaf blades that are sharply acute at the apex and densely velutinous abaxially, slightly unequal corolla lobes, and a generally symmetric Androecium that apparently lacks the pollen catapult mechanism; P. costaricensis C. M. Taylor, found in premontane forests in Costa Rica and Panama, has relatively short corollas (for Posoqueria) and a generally symmetric Androecium that apparently lacks the pollen catapult mechanism; P. grandifructa Hammel & C. M. Taylor of lowland Nicaragua and Costa Rica has medium-sized corollas, relatively large, ellipsoid, rough-surfaced, thick-walled fruits, and a generally symmetric Androecium that apparently lacks the pollen catapult mechanism; P. longifilamentosa C. M. Taylor of lowland northwestern Ecuador has relatively long corollas and an asymmetric Androecium with a pollen catapult mechanism, relatively long unequal filaments, and relatively large anthers; and P. robusta Hammel & C. M. Taylor of lowland Nicaragua and Costa Rica has leathery leaves, relatively long corollas with unequal lobes, subglobose leathery fruits, and a symmetric Androecium that apparently lacks the pollen catapult mechanism.

  • Rubiacearum Americanarum Magna Hama Pars XXVII: Six New Species and a New Taxonomic View of Posoqueria
    Novon: A Journal for Botanical Nomenclature, 2011
    Co-Authors: Charlotte M Taylor, Barry Hammel, Roy E. Gereau
    Abstract:

    Abstract.? The Neotropical genus Posoqueria Aubl. (Rubiaceae) has a number of species with an asymmetric Androecium and pollen catapult mechanism and others that apparently lack these features. A new taxonomy based on corolla form and size, the length and symmetry of the filaments, and fruit morphology finds the name P. panamensis (Walp. P. correana C. M. Taylor of lowland and premontane Panama has medium-sized corollas, leaf blades that are sharply acute at the apex and densely velutinous abaxially, slightly unequal corolla lobes, and a generally symmetric Androecium that apparently lacks the pollen catapult mechanism; P. costaricensis C. M. Taylor, found in premontane forests in Costa Rica and Panama, has relatively short corollas (for Posoqueria) and a generally symmetric Androecium that apparently lacks the pollen catapult mechanism; P. grandifructa Hammel P. longifilamentosa C. M. Taylor of lowland northwestern Ecuador has relatively long corollas and an asymmetric Androecium with a pollen catapult mechanism, relatively long unequal filaments, and relatively large anthers; and P. robusta Hammel & C. M. Taylor of lowland Nicaragua and Costa Rica has leathery leaves, relatively long corollas with unequal lobes, subglobose leathery fruits, and a symmetric Androecium that apparently lacks the pollen catapult mechanism.

Erik Smets - One of the best experts on this subject based on the ideXlab platform.

  • Floral Developmental Evidence for the Systematic Relationships of Tropaeolum(Tropaeolaceae)
    Annals of Botany, 2001
    Co-Authors: Louis P. Ronse Decraene, Erik Smets
    Abstract:

    Abstract The floral ontogeny of three species of Tropaeolum was studied using scanning electron microscopy to find morphological evidence for discussing the systematic position of the family. The initiation of the Androecium is highly unusual: there are always eight stamens which arise (1) either in a spiral sequence starting with the stamen opposite sepal four, running in a direction opposite to the sequence of the sepals, and with reversals in the direction of the spiral, or (2) as a sequence of paired and unpaired stamens. The floral symmetry changes twice during the development of the flower, from polysymmetrical at sepal and petal initiation, through oblique monosymmetry at stamen initiation, and ending with median monosymmetry in later developmental stages. The occurrence of median monosymmetry is a late-developmental event and is caused by the initiation of a hypanthial spur, and the unequal growth of the petals and styles. The origin for the unusual sequence of stamen initiation reflects a trend affecting the whole flower which is linked with the changing patterns of floral symmetry. Octandry is enhanced by multiple causes, such as the loss of two stamens in an originally diplostemonous Androecium and the regulating pressure of the gynoecium. The change in symmetry during ontogeny is significant for discussing the systematic position of Tropaeolaceae in comparison with the glucosinolate-producing taxa and the Sapindales. The combination of an Androecium with eight stamens and oblique monosymmetry is either a single event in evolution and links Tropaeolum with the Sapindales, or it has evolved at least twice, once in the Sapindales, and once in a clade comprising Tropaeolaceae, Akaniaceae and Bretschneideraceae. Morphological data support a sister group relationship of the three latter families, which is in line with macromolecular studies.

  • The floral development of Pleuropetalum darwinii, an anomalous member of the Amaranthaceae
    Flora, 1999
    Co-Authors: Louis P. Ronse Decraene, Sergei A. Volgin, Erik Smets
    Abstract:

    Summary The genus Pleuropetalum differs from the Amaranthaceae in its higher stamen and carpel number, coupled with numerous ovules. The floral development of Pleuropetalum darwinii is investigated with the SEM and is compared with the Amaranthaceae and other taxa of the Caryophyllales. Inflorescences are cymose with reduced partial inflorescences. Bracteoles are closely associated with the flower only separated by a short pedicel. Sepal initiation follows a 2/5 sequence but there is an important lag between the first two and the remaining sepals. The Androecium arises on a circular primordium; the first four stamens are initiated as pairs opposite the two outer sepals, and are followed by paired or single stamens opposite the inner sepals. However, the number of stamens can fluctuate, or their sequence may be variable. The gynoecium starts its growth as a ring primordium with a number of apices enclosing a flattened apical dome. In early stages septal tissue can sometimes be observed. The central dome becomes completely subdivided in different sectors on which a large number of coiled ovules arise centrifugally. The development of flower and Androecium shows similarities with other octandrous Caryophyllales, especially Phytolacca. The shared development is interpreted as a primitive feature. A comparison with other Amaranthaceae on the one hand, and with the Caryophyllales on the other shows evidence that a pluristaminate Androecium with outer stamen pairs is plesiomorphic in the Amaranthaceae.

  • pseudodiplostemony and its implications for the evolution of the Androecium in the caryophyllaceae
    Journal of Plant Research, 1998
    Co-Authors: Louis Ronse P Decraene, Erik Smets, Peter Vanvinckenroye
    Abstract:

    The Androecium of the Caryophyllaceae is varied, ranging from a two-whorled condition to a single stamen. A number of species belonging to the three subfamilies, Caryophyl-loideae, Alsinoideae and Paronychioideae have been studied ontogenetically with the SEM to understand their peculiar androecial development in the broader context of the Caryophyllales alliance. Although patterns of initiation are highly variable among species, there are three ontogenetic modes of stamen initiation: all stamens simultaneous within a whorl, the antepetalous stamens simultaneous and the antesepalous sequentially with a reversed direction, or both whorls sequentially with or without a reversed direction. The most common floral (ontogenetic) sequence of the Caryophyllaceae runs as follows: five sepals (in a 2/5 sequence), the stamens in front of the three inner sepals successively, stamens opposite the two outermost sepals, five antepetalous stamens (simultaneously or in a reversed spiral superimposed on the spiral of the antesepalous stamens), five outer sterile (petaloid) organs arising before, simultaneously or after the antesepalous stamens, often by the division of common primordia. A comparison with the floral configurations of the Phytolaccaceae and Molluginaceae indicates that the outer petaline whorl of the Caryophyllaceae corresponds positionally to the alternisepalous stamens of somePhytolacca, such asP. dodecandra. The difference withP. dodecandra lies in the fact that an extra inner or outer whorl is formed in the Caryophyl-laceae, in alternation with the sepals. A comparable arrangement exists in the Molluginaceae, though the initiation of stamens is centrifugal. A comparison of floral ontogenies and the presence of reduction series in the Caryophyllaceae support the idea that the pentamerous arrangement is derived from a trimerous prototype. Petals correspond to sterillized stamens and are comparable to two stamen pairs opposite the outer sepals and a single stamen alternating with the third and fifth sepals. Petals are often in a state of reduction; they may be confused with staminodes and they often arise from common stamenpetal primordia. The antesepalous stamen whorl represents an amalgamation of two whorls: initiation is reversed with the stamens opposite the fourth and fifth formed sepals arising before the other, while the stamens opposite the first and second formed sepals are frequently reduced or lost. Reductive trends are correlated with the mode of initiation of the Androecium, as well as changes in the number of carpels, and affect the antesepalous and antepetalous whorls in different proportions. It is concluded that the Androecium of the Caryophyllaceae is pseudodiplos-temonous and is not comparable to diplostemonous forms in the Dilleniidae and Rosidae. The basic floral formula of Caryophyllaceae is as follows: sepals 5—petals 5 (sterile stamens)—antesepalous stamens 3+2—antepetalous stamens 5 gynoecium 5.

  • dedoublement revisited towards a renewed interpretation of the Androecium of the magnoliophytina
    Botanical Journal of the Linnean Society, 1993
    Co-Authors: Louis Ronse P Decraene, Erik Smets
    Abstract:

    Abstract There has been much controversy about dedoublement in the past. Dedoublement was originally described as a process of doubling of a (stamen) primordium up to two equivalent primordia. Later, it was extended to explain occurrences of higher stamen numbers, even without evidence of a division. Different interpretations from both opponents and protagonists of dedoublement are critically examined and concepts such as negative, positive, serial, lateral and congenital dedoublement are discussed. Some case studies are presented to evaluate the concept of dedoublement. Paired stamens are not necessarily the result of splitting; they can also arise by a spatial shift, connected with the cyclization of a spiral flower. Two smaller stamen primordia replacing a stamen without visible splitting and a primordium dividing ontogenetically into a stamen pair are essentially similar. The morphological difference between both configurations can be explained by the principle of variable proportions. Radial dedoublement and stamen-petal complexes are examples of meristem fusion (absorption) and may be defined by the term 'negative dedoublement' in the sense of Celakovsky (1894). A distinction between 'dedoublement' sensu stricto and 'polygenesis' is proposed.

Eric Smets - One of the best experts on this subject based on the ideXlab platform.

  • Notes on the Evolution of Androecial Organisation in the Magnoliophytina (Angiosperms)
    Botanica Acta, 1998
    Co-Authors: Lp Ronse Decraene, Eric Smets
    Abstract:

    : This paper aims to summarize briefly and to update our ideas about androecial architecture formulated in earlier publications. Ontogenetic evidence of stamen development, viz. the initiation, arrangement and relationship of stamens to other floral morphomes, can be translated into a semophyletic scheme reflecting the phylogeny of the Androecium. The ancestral Androecium is discussed in the light of recent theoriesabout angiosperm phylogeny. Two divergent androecial processes are proposed for the angiosperms starting from a spiral Androecium with a moderate number of stamens. However, transitions exist between spiral polyandry, numerous stamens in whorls, and chaotic polyandry. From an Androecium with several alternating whorls of paired and single stamens, outer stamen pairs are retained following the successive loss of inner stamen whorls. Single stamens instead of pairs occur at the very end of this line and represent a more advanced condition. This line is mostly present in tri- and dimerous flowers. From the same starting point diplostemony (with two alternating whorls of single stamens) originated, again giving rise to various states usually present in pentamerous or tetramerous flowers.

  • A floral ontogenetic investigation of the Hydrangeaceae
    Nordic Journal of Botany, 1997
    Co-Authors: Peter Roels, Lp Ronse Decraene, Eric Smets
    Abstract:

    As a first step towards a broader floral ontogenetic study on Cornales, the flowers of four species of Hydrangeaceae (Deutzia corymbosa, Kirengeshoma palmata, Philadelphus purpurascens and Hydrangea petiolaris) were studied. In Deutzia and Kirengeshoma five sepal primordia are generally initiated, in Philadelphus only four. Sepal initiation in Kirengeshoma shows a tendency to tetramony. Deutzia has a variable sepal initiation. Petal growth was never retarded in the studied species. Initiation of the Androecium in Kirengeshoma, Philadelphus and Hydrangea starts with antesepalous primary primordia, on which secondary primordia are soon formed, leading ultimately to the formation of polystaminate androecia. In Deutzia a diplostemonous Androecium is formed, starting with the initiation of the antesepalous stamen primordia. Gynoecium development is similar in all species studied: on a concave floral apex, a ring meristem is initiated; it develops into a variable number of continuous carpel primordia, while the centripetally growing common margins form the septa. Initiation of the ovule primordia starts halfway up each placenta and extends in an apical, basal and lateral direction. A number of morphological problems are discussed, such as the derivation of tetramery, and evolutionary and developmental trends in the Androecium and gynoecium. Kirengeshoma is well settled in Hydrangeaceae, although its exact position within the family remains uncertain. A sistergroup relationship of Hydrangeaceae with Loasaceae is supported. However, Hydrangeaceae also share features with Saxifragaceae (e.g. similar gynoecium development).

  • evolution of the Androecium in the ranunculiflorae
    Plant Systematics and Evolution, 1995
    Co-Authors: L Ronse P Decraene, Eric Smets
    Abstract:

    Four different evolutionary lines can be recognised for the Androecium of the Ranunculiflorae: (1) a progressive reduction in the number of stamens and stamen whorls. (2) The transformation of the outermost stamens into nectar-leaves or petals. (3) Meristic changes of the flower. (4) Secondary increases in the number of stamens. It is shown that the position and inception of the stamens is valuable to understand relationships of taxa. Ranunculaceae occupy a basal position with the greatest androecial diversity and a reductive trend, linked with a shift from trimery to pentamery and the transformation of the outer stamen pairs into (nectariferous) petals. Berberidaceae and satellite families have androecia with an alternation of trimerous (dimerous) whorls and outer staminodial nectar-leaves. In Papaverales the trimerous flower with a polycyclic Androecium often becomes dimerous and is progressively reduced. Secondary increases occur occasionally in Berberidaceae, Papaveraceae and perhaps Glaucidiaceae.

  • an updated interpretation of the Androecium of the fumariaceae
    Botany, 1992
    Co-Authors: L Ronse P Decraene, Eric Smets
    Abstract:

    A study of the floral development of Dicentra formosa, Corydalis lutea, and Hypecoum procumbens was carried out to better understand the nature of the Androecium in Fumariaceae. Sepals emerge succe...

  • Androecium and floral nectaries of harungana madagascariensis clusiaceae
    Plant Systematics and Evolution, 1991
    Co-Authors: L Ronse P Decraene, Eric Smets
    Abstract:

    The mature flower ofHarungana madagascariensis (Choisy)Poir. has an Androecium of five antipetalous fascicles, consisting of four stamens each. The stamen fascicles alternate with five indented nectary scales. A SEM-study of the floral development, as well as a study of the floral anatomy was carried out to understand whether the nectariferous scales represent staminodia or are receptacular in nature and consequently whether or not the Androecium ofHarungana, and theClusiaceae in general, is originally diplostemonous. The five petals originate by the splitting of petal-stamen complexes. Next the upper part of each complex differentiates basipetally in four stamens. The stamens remain fascicled and are lifted on a long stalk at maturity. Five carpel primordia are initiated united in a low ringwall. The five nectary scales appear after carpel inception and develop an external morphology reminiscent of anthers. The floral anatomy reveals an independent origin of sepal median traces and common sepal lateral traces, free petal traces, stamen fascicle traces and alternating vascular tissue which supplies the nectaries. The petal-stamen complexes are the result of a retardation in petal inception, linked with the absorption of petal tissue into the stamen primordia. The development of the stamen fascicles is discussed; it is suggested that they are of a secondary nature and do not appear as a reduction from a multistaminate Androecium. The external morphology and vascular anatomy of the scales speaks in favour of a staminodial nature. The comparison with some other species of theClusiaceae gives evidence of a diplostemonous ancestry of the Androecium.