Figure - available from: Frontiers in Plant Science
This content is subject to copyright.
Gynoecium of Monotremoideae. Potarophytum riparium, serial cross-sections through mature gynoecium. (A) Receptacle below the ovary. (B) Basal part of synascidiate zone, ovary base. (C,D) Synascidiate zone, level of ovule attachment. (E) Transition to symplicate zone. (F) Distal part of ovary, symplicate zone. Note open ventral slits. (G) Ovary roof with triradial canal in its center, symplicate zone. (H) Basal part of style with triradial canal, symplicate zone. (I) Style surrounded by stamens, (a)symplicate zone. (J) Distal part of style below stigma, level above stamens, asymplicate zone. Vb, homocarpellous ventral bundle; *, synventral bundle. Scale bars = 200 mkm in panels (A–F) and 100 mkm in panels (G–J).
Source publication
The family Rapateaceae represents an early-divergent lineage of Poales with biotically pollinated showy flowers. We investigate developmental morphology and anatomy in all three subfamilies and five tribes of Rapateaceae to distinguish between contrasting hypotheses on spikelet morphology and to address questions on the presence of nectaries and gy...
Similar publications
Cyperaceae is a widespread family composed of two subfamilies, Mapanioideae and Cyperoideae. As opposed to the dimerous Mapanioideae spicoid inflorescences, Cyperoideae flowers are known for their typical trimerous Bauplan, however, morphological variation is reported in each floral whorl. This wide range of variation is challenging, mainly regardi...
Citations
... In the other families of the order, they either do not occur or are septal nectaries, as in Bromeliaceae (Sajo et al., 2004). Some species of Rapateaceae display an unusual type of gynoecial (non-septal) nectary represented by a secretory epidermis at the gynoecium base (Koblova et al., 2022). Although the development of the nectariferous stylar appendages in Xyridaceae (Stützel, 1990) occurs similarly to what we describe here for the nectariferous branches of Leiothrix, in Xyridaceae the dorsal carpellary bundles branch to vascularize the stigma (Oriani & Scatena, 2012). ...
Leiothrix differs from other genera of Eriocaulaceae by having pistillate flowers with nectariferous and stigmatic branches that diverge at different heights on the style and staminate flowers with free or fused petals. To understand the ontogenetic processes that result in these morphological variations, we studied the development and floral vasculature in six species of the genus. In pistillate flowers, the nectariferous branches, which are in a carinal position, correspond to the apex of the carpels, whereas the stigmatic branches, in a commissural position, are formed by the marginal tissues of the carpels and initiate later than the nectariferous branches. The upper margins of the carpels elongate, forming a tubular structure that raises the stigmatic branches; the greater its development, the greater the distance between the stigmatic and nectariferous branches. In staminate flowers, the fusion of the petals appears to be post-genital in the median and apical portions and congenital in the more basal portion. Despite the differences in floral development, Leiothrix shares the same pattern of floral vasculature with other genera of Eriocaulaceae, exhibiting a central vascular plexus in the receptacle from which a single trace diverges for each sepal, petal and stamen. The staminodes are not vascularized. The dorsal carpellary bundles supply the nectariferous branches, but the ventral carpel bundles are reduced and are not involved in the supply of the ovules and stigmas. The differences in the height of insertion of the nectariferous branches are probably the result of selective pressure exerted by different groups of pollinating insects. Our hypothesis is that species in which the nectariferous branches are inserted below the stigmatic branches, and are therefore less accessible, exhibit a more specialized pollination system. The absence of nectariferous branches in L. angustifolia indicates secondary loss probably associated with spontaneous geitonogamy.
The phenomenon of heterochrony, or shifts in the relative timing of ontogenetic events, is important for understanding many aspects of plant evolution, including applied issues such as crop yield. In this paper, we review heterochronic shifts in the evolution of an important floral organ, the carpel. The carpels, being ovule-bearing organs, facilitate fertilisation, seed, and fruit formation. It is the carpel that provides the key character of flowering plants, angiospermy. In many angiosperms, a carpel has two zones: proximal ascidiate and distal plicate. When carpels are free (apocarpous gynoecium), the plicate zone has a ventral slit where carpel margins meet and fuse during ontogeny; the ascidiate zone is sac-like from inception and has no ventral slit. When carpels are united in a syncarpous gynoecium, a synascidiate zone has as many locules as carpels, whereas a symplicate zone is unilocular, at least early in ontogeny. In ontogeny, either the (syn)ascidiate or (sym)plicate zone is first to initiate. The two developmental patterns are called early and late peltation, respectively. In extreme cases, either the (sym)plicate or (syn)ascidiate zone is completely lacking. Here, we discuss the diversity of carpel structure and development in a well-defined clade of angiosperms, the monocotyledons. We conclude that the common ancestor of monocots had carpels with both zones and late peltation. This result was found irrespective of the use of the plastid or nuclear phylogeny. Early peltation generally correlates with ovules belonging to the (syn)ascidiate zone, whereas late peltation is found mostly in monocots with a fertile (sym)plicate zone.
