Flowers and inflorescences of the seagrass Posidonia (Posidoniaceae, Alismatales)

Abstract

Our data support a racemose interpretation for the partial inflorescence of Posidonia and the presence of flower-subtending bracts. In common with some other Alismatales, Posidonia has simultaneous development of the flower and its subtending bract and loss of the bract vascular supply accompanied by innervation of the flower by a single vascular strand. The unusual carpel orientation could be an evolutionary reduction of a formerly tricarpellate gynoecium. The ovule of Posidonia is campylotropous and unusual within Alismatales in possessing an integumentary outgrowth.

Morphology ofMaundiasupports its isolated phylogenetic position in the early-divergent monocot order Alismatales

“…A pseudanthial interpretation of the conventional flower of core Alismatales has been criticized on the grounds that the features used in support of this theory can also be found in some monocots belonging to other monocot orders (summarized in Endress, ; see also Lieu, and Buzgo et al ., for case studies in Juncaginaceae). We accept this criticism and follow the euanthial interpretation for flowers of most Alismatales (probably excluding Zannichelliaceae and Cymodoceaceae: Sokoloff, Rudall & Remizowa, ; Remizowa et al ., ).…”

“…Molecular phylogenetic trees suggest that apocarpy and an unstable flower groundplan could be derived rather than ancestral features in core Alismatales (Doyle & Endress, ; Chen et al ., ; Endress & Doyle, ; Remizowa, Sokoloff & Rudall, ; Sokoloff, Remizowa & Rudall, ). The high level of interest in members of core Alismatales has made this group one of the most extensively studied with respect to comparative flower morphology and development (reviewed by Posluszny & Charlton, ; Posluszny, Charlton & Les, ; Remizowa et al ., ). However, a few key taxa remain poorly known, particularly as a result of technical problems in obtaining appropriate plant material.…”

Gynoecial ontogeny of Anthurium: contributions for floral developmental studies in Araceae (Alismatales)

“…Alismatales is one of the basal angiosperm clades (Stevens 2012), whose floral development has been the object of studies focusing particularly on the morphological variety of gynoecia (e.g., Buzgo 2001;Remizowa et al 2010Remizowa et al , 2012Nunes et al 2012). In such studies, the observations on the type of gynoecium closure, either by secretion or postgenital fusion, on the carpel shapes Buzgo 2001), and discussions on whether syncarpy is a plesiomorphic or apomorphic character within monocots are particularly noteworthy (Remizowa et al 2006).…”

Gradual vs. abrupt reduction of carpels in syncarpous gynoecia: A case study from Polyscias subg. Arthrophyllum (Araliaceae: Apiales)

“…In our view, these lobes therefore cannot be interpreted as the morphological tips of individual carpels in a pluricarpellate gynoecium. Irregular apical lobes forming late in development are known in the unicarpellate gynoecia of various other angiosperms such as some Berberidaceae (Endress and Igersheim, 1999) and Posidonia (Posidoniaceae: Remizowa et al, 2012). The case of Metteniusa (Metteniusaceae) is particularly instructive: the five apical lobes of its unilocular gynoecium appear much earlier in development than those of P. diversifolia and can thus plausibly be interpreted as carpel tips (González and Rudall, 2010).…”

“…In angiosperms, monosymmetric flowers (Endress, 1999) typically have a precisely fixed plane of symmetry, most commonly the median plane of a flower. This is why the carpel of unicarpellate flowers normally has a median plane of symmetry (e.g., Eichler, 1875), with the ventral side adaxial or (in a smaller number of taxa—see Swamy and Bailey, 1949; Posluszny et al, 1986; Remizowa et al, 2012) abaxial relative to the flower‐subtending bract. Achlys (Berberidaceae) shows an interesting situation: in spite of chaotic development and an unstable number of stamens, carpel orientation in this genus is relatively stable (Endress, 1989), which may indicate early prepatterning of carpel position in flower development (see also Choob and Penin, 2004).…”