Homology and functions of inner staminodes in Anaxagorea javanica (Annonaceae)

Inner staminodes are widespread in Magnoliales and present in Anaxagorea and Xylopia, but were lost in the other genera of Annonaceae and have no counterparts in derived angiosperms. The coexistence of normal stamens, modified stamens and inner staminodes in Anaxagorea javanica is essential to understand the homology and pollination function of the inner staminodes. Anaxagorea javanica was subjected to an anatomical study by light and scanning electron microscopy, and the chemistry of secretions was evaluated by an amino acid analyser. Inner staminodes have a secretory apex, but do not have thecae. They bend towards either tepals or carpels at different floral stages, and function as a physical barrier preventing autogamy and promoting outcrossing. At the pistillate phase, the exudates from the inner staminodes have high concentration of amino acid, and provide attraction to pollinating insects; while abundant proline was only detected in stigmas exudates, and supply for pollen germination. Modified stamens have a secretory apex and one or two thecae, which are as long as or shorter than that of the normal stamens. As transitional structures, modified stamens imply a possible degeneration progress from normal stamens to inner staminodes: generating a secretory apex first, shortening of the thecae length next and then followed by the loss of thecae. The presence of modified stamens together with the floral vasculature and ontogeny imply that the inner staminodes are homologous with stamens.

Floral structure in Thismia (Thismiaceae: Dioscoreales): new insights from anatomy, vasculature and development

Thismia is characterized by an exceptionally complicated floral morphology that is currently not understood properly. In the taxonomic literature, descriptive rather than morphological terms are often applied to parts of the flower in Thismia, relating to the general appearance of the floral organs instead of their precise homologies. Precise understanding of the floral structure is complicated by the rarity of Thismia spp. and the paucity of appropriate material. Here we provide a comprehensive study of reproductive organs of three Thismia spp. (T. annamensis, T. javanica and T. mucronata) including the first investigation of inflorescence architecture and early floral development in Thismiaceae. We found a hitherto unknown diversity of the reproductive shoots in the genus, manifested in the number of floral prophylls (two or three, in contrast to a single prophyll in the vast majority of monocots) and in the branching plane resulting in two distinct inflorescence types, a drepanium and a bostryx. We report the non-acropetal sequence of initiation of floral whorls (with stamens being the last elements to initiate), never previously described in monocots, and the gynoecium composed of completely plicate carpels, also a rare feature for monocots. Floral vasculature is relatively uniform in Thismia, but significant interspecific differences are found in tepal innervation, including the number of tepal traces; some of these differences are not immediately related to the external tepal morphology. We argue that the annulus, which acts as a roof of the hypanthium, possesses an androecium nature and represents congenitally fused bases of stamen filaments. We describe the stamens as laminar structures, which are also shortly tubular in the distal part of the supraconnective with the adaxial tubular side forming a skirt-like appendage. Finally, the placentas, which are column-like when mature, are initially parietal, becoming secondarily similar to free-central placentas through schizogenous separation from the ovary wall.

Floral vasculature and its variation for carpellary supply inAnthurium(Araceae, Alismatales)

Introduction and AimsAnthuriumis the largest genus of Araceae, with 950 species distributed in the neotropics. Despite the great diversity of the genus, the knowledge of its floral vasculature is based on observations in only two species, viz.A. denudatumandA. lhotzkyanum, with remarkable variation in vascular carpellary supply: carpels are either vascularized by ventral bundles alone or by reduced dorsal bundles in addition to the ventral ones. Our main objective is to test this peculiar variation through a detailed anatomical study of the floral vasculature in taxa belonging to some sections ofAnthuriumdesignated as monophyletic groups in recent phylogenies.MethodsWe compare the floral vasculature of 20 neotropical species belonging to distinct sections ofAnthurium, using both light and confocal laser scanning microscopies.ResultsThe number and position of vascular bundles are constant within the tepals and stamens, regardless of the species and sections studied. However, the gynoecium vasculature exhibits variation between species belonging to the same or different sections. Our results reveal two patterns of vasculature: carpels vascularized by synlateral bundles alone (Pattern A) and carpels vascularized by both dorsal and synlateral bundles (Pattern B). Pattern A is shared by the majority of species studied here and corroborates the previous data in the literature. Pattern B occurs in three species:A. affine(Anthuriumsect. PachyneuriumseriesPachyneurium),A. obtusumandA. scandens(Anthuriumsect.Tetraspermium), described here for the first time for the genus.ConclusionsThe variation in the supply to the carpels inAnthuriumis corroborated here. However, our results in addition to those from the available literature suggest the existence of three patterns (A, B and C) of carpellary vasculature. Based on the recent phylogeny ofAnthuriumit is possible to notice that the three patterns of carpellary vasculature occur in representatives of Clade B and deserve to be investigated in a larger number of species. Pattern A could be a plesiomorphy for the genus and the occurrence of dorsal bundles could be a derived character. Our data contributes to the taxonomy and to the understanding of the floral evolution of the largest neotropical genus of Araceae.

Relationships of Plumiereae (Apocynaceae). III. Based on floral vasculature

The study of the floral anatomy of some common Indian species of the tribe <i>Plumiereae (Apocynaceae)</i> supports the conclusions derived from the study of chromosomes and secondary xylem, which are: (1) <i>Holarrhena</i> are distinct from Ervatamia and should be placed in <i>Alostoniinae</i> (Schumann, 1895) and not under <i>Tabernaemontaninae</i> (Bentham and Hooker, 1876). (2) Different subtribes possess distinctive features; and, therefore, the classification into subtribes is justified. (3) <i>Tabernaemontaninae</i> are the most primitive subtirbe from which the others can be derived. (4) <i>Alstoniinae</i> are heterogeneous and are composed of different evolutionary lines. (5) The genus <i>Plumeria</i> stands isolated in tribe <i>Plumiereae</i> and needs separation as a new taxon.

Floral vasculature and trichomes of common Indian Scrophulariaceae

The floral anatomy of 24 species of <i>Scrophulariaceae</i> was studied. The results show that although, clear anatomical bases to differentiate taxa are absent, the Pennell classification of subfamilies is strongly supported.