The distribution and systematic relevance of the androecial character oligomery

Localization of the stamens can be approached by a preliminary distinction between two characters, oligomery and polymery, occurring in two different groups of taxa, respectively the oligomerous complex and the polymerous complex. Oligomery is described by four character states standing in a close semophyletic relationship: diplostemony, obdiplostemony, haplostemony and obhaplostemony. Each character state is analysed for its distribution and systematic value. Diplostemony is the synapomorphic character state for the oligomerous line and has arisen once from a polymerous ancestor or in parallel in different lines. Obdiplostemony arises ontogenetically in three different ways. Loss of one whorl leads either to obhaplostemony, or haplostemony; both character states are believed to represent evolutionary steps of no-return. Secondary increases and reductions of the stamens within a whorl are seen as expressions of the intrinsic variability of the character states and should not be homologized with them. Stamen numbers can be increased by the building-up of complex primordia or by secondary receptacular growth. Reductions of stamens affect one or two whorls of stamens and are caused by lack of space, interactions with the gynoecium and zygomorphy. The distribution of the different character states of oligomery is presented on Dahlgrenograms and the androecia of a number of families and their relationships are discussed. The interactions between oligomery and polymery are analysed as guidelines for a global phylogeny of the Magnoliatae.     

Systematic significance of tepal surface morphology in tribes Persicarieae and Polygoneae (Polygonaceae)

In order to improve understanding of the systematic relationships between taxa and of tepal-pollinator and tepal-habitat relationships, a detailed scanning electron microscopy (SEW study of the adaxial tepal surface of 135 taxa belonging to c. 14 genera in the tribes Persicarieae and Polygoneae (Polygonoideae-Polygonaceae) was carried out. The tepal surfaces have revealed some striking differences among the genera studied. Three main patterns of sculpturing and cell shape can be recognized. Type I: mostly rectangular to elongate cells with straight or undulating anticlinal walls; the cuticles smooth or striate in longitudinal direction and often continuous (Persicaria, Bistortu, Aconogonon, Koenigia and some species of Fagopyrum). Type II: irregular tesselated to elongated cells, rarely rectangular with mostly sinuate anticlinal walls; the cuticles rarely with longitudinal striation, but with strong orthogonal to reticulate ridges or striae, often without correlation between cells (Polygonum s.s., Polygonella, Fallopia, Parapteropyrum, Pteropyrum, Atraphaxis and Calligonum). Type III: mostly irregular, mammilliform, papillose cells with either longitudinal tightly pressed or randomly ridged cuticles (some species of Fagotyrum and Oxygonum). The present data generally support the division of Polygoneae and Persicarieae by Ronse Decraene & Akeroyd. The mammilliform, papillate epidermis of tepals in Oxygonum and some Fagopyrum is probably well-adapted to entomophily either as a foothold or even as a light-trap, and also shows some correlation with heterostyly. It is noteworthy that the tepal structure of Polygonella (tesselated form) is highly similar to that of Polygonum s. s. (especially P. sect. Duravia). Cuticular striation alone does not appear to have much systematic value, but has a mechanical function in affording extra strength to the cell walls. Some correlations between the degree/shape of cuticles and the pollination mechanisms or the habitat of each taxon are also briefly discussed. It is concluded that the studied tepal characters can be useful in improving the classification of tribes Persicarieae and Polygoneae, arid give additional support at the infrageneric level.     

The distribution and systematic relevance of the androecial character polymery

RONSE DECRAENE L. P. AND SMETS E. F., 1993. The distribution and systematic relevance of the androecial character polymery . Two characters, viz. oligomery and polymery, have been previously proposed to circumscribe the localization of the androecium. Their distribution is more or less correlated with two groups of taxa: polymery is found in Magnoliidae, Caryophyllidae, Liliatae and part of Hamamelidae; oligomery is found in Dilleniidae, Rosidae, part of Hamamelidae and Asteridae. Polymery can be described by a number of character states, which are presented in a semophyletical scheme. Spiral polyandry, i.e. a multistaminate and spiral androecium, represents the plesiomorphic condition for all Magnoliophytina and is restricted to the polymerous group. Cyclization, induced by an arrangement of the perianth in trimerous whorls and a fractioning of the continuous plastochron, leads to polycycly, i.e. an arrangement of the stamens in numerous cycles; the outer stamens are usually inserted as pairs or in alternation with the inner perianth parts. From this configuration reduction series in different groups result in androecia with a lower number of stamen whorls (such as tetracycly, tricycly, dicycly and (ob)monocycly). The transition from trimery to pentamery induces a derived stamen configuration by the merging of two tepaline whorls and the loss of some stamens. für ther reductions accompanied evolution in trimerous flowers and led to conditions resembling diplostemony as observed in Caryophyllaceae, some Hamamelidaceae and Ranunculaceae. Secondary increases, as well as reductions of stamens within a whorl must be regarded as gradual variations of each character state. Different trends affecting the number and position of the stamens can globally be traced along different lines. Polymery is consistent with other floral characters, such as the nature of perianth, vasculature (axial and cortical systems) and merosity. The androecium of a number of families and their relationships are discussed.     

The systematic relationships of glucosinolate-producing plants and related families: a cladistic investigation based on morphological and molecular characters

A cladistic analysis is performed using 94 morphological and biochemical characters for 42 genera to compare a phylogeny based on morphological data with those obtained using different genes ( rbc L, atp B, 18S RNA, mat K) or their combination with morphological data, and to understand the floral evolution within the expanded Brassicales (Capparales) relative to Sapindales and Malvales. The tree produced with morphological data is congruent with those obtained from macromolecular studies in obtaining a well-supported glucosinolate-producing clade and an expanded Sapindales. The combined analysis of the morphological and molecular characters is generally well resolved with support for many of the relationships. The inclusion of the fossil taxon Dressiantha demonstrates the value of inserting fossil evidence in phylogenetic analyses. However, the fossil appears to be related to the Anacardiaceae and not to the Brassicales. The core Brassicales are well supported by a number of synapomorphies, although the internal position of Tovariaceae and Pentadiplandraceae is not well resolved. Emblingiaceae appears to be related to Bataceae and Salvadoraceae. Several significant morphological characters are mapped on the combined trees and their evolutionary significance is discussed. Within Brassicales and Sapindales several well supported clades can be recognized which merit ordinal or subordinal status, putting the present orders at a higher level; these include: Tropaeolales, Setchellanthales, Batidales, Brassicales (Brassiciflorae), Burserales, Sapindales and Rutales (Sapindiflorae). The present scheme of affinities within the Brassicales corresponds well with a gradual morphological evolution in the order.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 453–494.     

Generic limits in Polygonurn and related genera (Polygonaceae) on the basis of floral characters

In order to investigate the taxonomic value of a number of characters in the elucidation of relationships within the collective genus Polygonum L., and segregate genera Atraphaxis L., Calligonum L., Pteropyrum Jaub. & Spach., Oxygonum Burch., Fagopyrum Mill., Harpagocarpus Hutch. & Dandy and Polygonella Michx., 83 species of the tribe Polygoneae emend. Jaretzky were studied. The following floral characters were examined: stamen number, insertion and external morphology; structure and morphology of the floral nectaries; vasculature and surface morphology of the tepals.
Problems in floral morphology in Polygonaceae are discussed, together with relationships within the Family. The tribal division proposed by Haraldson (1978) is supported, but a new and different delimitation of genera is proposed. The present data support a division of Polygonum L. sensu lato and its related taxa into two tribes: Polygoneae (containing Polygonum L. sensu stricto, Fallopia Adans., Oxygonum Burch., Pteropyrum Jaub. & Sparh., Atraphaxis L. and Calligonum L.), and Persicarieae (containing Fagopyrum Mill., Harpagocarpus Hutch. & Dandy, Persicaria Mill. and Koenigia L.). The genus Reynoutria Houtt. is included as a section of Fallopia Adans.; Bislorta Mill., Aconogonon Reichenb. and Tovara Adans. are included within Persicaria Mill.
A number of new combinations are proposed in Persicaria and Fallopia .     

The impact of receptacular growth on polyandry in the Myrtales

RONSE DECRAENE, L.-P. & SMETS, E., 1991. The impact of receptacular growth on polyandry in the Myrtales. The androecium of the Myrtales shows a wide variation in structure and development, linked with an original diplostemony. The difference between a centrifugal stamen inception in Lythraceae against a centripetal inception in other families has been a major issue in discussing the internal relationships of the Myrtales. The first stamens usually arise as pairs opposite the petals on primary androecial primordia. It is shown that the number of stamens that are initiated and the difference between the direction of development of more stamens are based on the extent of growth of the receptacle after the inception of the primary androecial primordia. In Lagerstroemia indica , receptacular growth takes place between stamens and petals providing room for a centrifugal development. In the Punicaceae and Myrtaceae growth of the receptacle occurs between the androecium and gynoecium, leading to a centripetal development of the stamens. The development of a ring-wall is discussed and a comparison is made with other types of complex polyandry.     

Floral anatomy and systematics of Bretschneidera (Bretschneideraceae)

External morphology and anatomy of the flower and pollen of Bretschneidera sinensis Hemsl. are described to clarify the position of the family Bretschneideraceae relative to the Sapindales and the glucosinolate-producing families. Anatomical and micromorphological characters are investigated and sections are used to understand the structure of the flower. Observation of buds and sections reveal that the flower is obliquely monosymmetric, with the symmetry line running from one petal to a sepal. The upper petal shields the stamens and pistil and becomes positioned apically by the partial resupination of the pedicel. The octomerous androecium is characterized by variable empty positions which are related to the variable insertion of the three carpels. The loss of stamens is linked with a displacement of the remaining stamens. Floral anatomy demonstrates the presence of a nectary extending on the hypanthium from the base of the filaments to the base of the gynoecium. Details of floral anatomy are compared with members of Sapindaceae, Hippocastanaceae, Moringaceae, Akaniaceae, Tropaeolaceae and Capparaceae. Comparison with other characters supports a close relationship with Akaniaceae and Tropaeolaceae in an order Tropaeolales, in concordance with macromolecular results, either at the base of the glucosinolate clade, or in remote connection with the Sapindales. A number of floral anatomical characters with a strong phylogenetic signal are highlighted. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 139 , 29–45.     

Dédoublement revisited: towards a renewed interpretation of the androecium of the Magnoliophytina

RONSE DECRAENE, L. P. & SMETS, E F., 1993. Dedoublement revisited: towards a renewed interpretation of the androecium of the Magnoliophytina. 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.     

Floral Development and Anatomy ofMoringa oleifera(Moringaceae): What is the Evidence for a Capparalean or Sapindalean Affinity?

Floral development and anatomy ofMoringahave been investigatedin the context of the disputed view of a capparalean affinity.Flowers arise in terminal or axillary panicles. Sepals arisesequentially and petals simultaneously. Antepetalous stamensarise simultaneously and precede the antesepalous staminodes,which emerge sequentially. Within their respective whorls, thepetals and stamens become twisted along different orientations.The gynoecium develops as a ring primordium on which three carpellarylobes become demarcated simultaneously. A saccate ovary bearsnumerous ovules on a parietal placentation and is topped bya hollow style. The interpretation of laminal placentation isdenied. Monothecal anthers are formed by the failure of onehalf to initiate. The flowers present a peculiar form of zygomorphyrunning transversally from the petal between sepals 3 and 5to sepal 4. The shape and position of petals and stamens isrelated to a pollen presentation mechanism with bowl-shapedanthers on different levels. The floral anatomy also reflectsthe zygomorphy of the flower. AlthoughMoringashares importantmorphological features with certain members of the Sapindalesand Capparales, differences in ontogeny make a close relationshipwith either Capparales or certain Sapindales appear uncertain.Copyright1998 Annals of Botany Company Moringa,Moringaceae, Capparales, Sapindales, floral ontogeny, floral anatomy.