Floral anatomy of Paepalanthoideae (Eriocaulaceae, Poales) and their Nectariferous structures

BACKGROUND AND AIMS: Eriocaulaceae (Poales) is currently divided in two subfamilies: Eriocauloideae, which comprises two genera and Paepalanthoideae, with nine genera. The floral anatomy of Actinocephalus polyanthus, Leiothrix fluitans, Paepalanthus chlorocephalus, P. flaccidus and Rondonanthus roraimae was studied here. The flowers of these species of Paepalanthoideae are unisexual, and form capitulum-type inflorescences. Staminate and pistillate flowers are randomly distributed in the capitulum and develop centripetally. This work aims to establish a floral nomenclature for the Eriocaulaceae to provide more information about the taxonomy and phylogeny of the family. METHODS: Light microscopy, scanning electron microscopy and chemical tests were used to investigate the floral structures. KEY RESULTS: Staminate and pistillate flowers are trimerous (except in P. flaccidus, which presents dimerous flowers), and the perianth of all species is differentiated into sepals and petals. Staminate flowers present an androecium with scale-like staminodes (not in R. roraimae) and fertile stamens, and nectariferous pistillodes. Pistillate flowers present scale-like staminodes (except for R. roraimae, which presents elongated and vascularized staminodes), and a gynoecium with a hollow style, ramified in stigmatic and nectariferous portions. CONCLUSIONS: The scale-like staminodes present in the species of Paepalanthoideae indicate a probable reduction of the outer whorl of stamens present in species of Eriocauloideae. Among the Paepalanthoideae genera, Rondonanthus, which is probably basal, shows vascularized staminodes in their pistillate flowers. The occurrence of nectariferous pistillodes in staminate flowers and that of nectariferous portions of the style in pistillate flowers of Paepalanthoideae are emphasized as nectariferous structures in Eriocaulaceae.     

On the morphological position of Paepalanthus subgenus Psilandra (Eriocaulaceae)

Paepalanthus subgen. Psilandra comprises two species known only from the type collections. The aim of this study is to evaluate their unique floral morphology within a given phylogenetic context and its implications for taxonomy. Flowers of both species were analyzed, described, and photographed using a digital microscope. Taxonomically relevant characters were mapped on previous molecular phylogenies. The flowers of both species fit the Paepalanthoideae pattern and are quite similar to each other. The petals of the pistillate flowers, although free, show evidence of previous fusion in the middle. The free condition is interpreted to be secondary, probably because of the handling of the specimens or to the current developmental stage. Character mapping indicates that both species share floral features with Syngonanthus but not with Paepalanthus. Therefore, based on the median fusion of the pistillate flower petals, absence of floral bracts, petals of the pistillate flower being shorter than the sepals, simple stigmas in the commissural position, the pedicellate pistillate flower, and the glabrous petals and sepals, we transfer P. subgen. Psilandra to synonymy of Syngonanthus sect. Syngonanthus and combine both species in this genus.     

Embryology ofEriocaulon setaceum (Eriocaulaceae)

Eriocaulon setaceum can be characterized by: young microsporangium wall with epidermis, endothecium (with fibrous thickenings), and glandular tapetum (uninucleate cells); pollen grains 3-celled, spiraperturate; embryo sac development according to the Polygonum type and with antipodal cyst; endosperm nuclear; embryo small, with incipient differentiation into cotyledonary and epicotylary loci; seed coat mainly from the inner layers of the integuments; pericarp 2-layered and membranous. Embryologically, theEriocaulaceae are nearer to theXyridaceae than to otherFarinosae. Their elevation to the rank of an order,Eriocaulales, therefore appears justified.     

拟鹅观草属3种植物的核型研究

对禾本科小麦族拟鹅观草属物种Pseudoroegneria geniculata、P.geniculata ssp.scythica和P.geniculata ssp.pruinifera的核型进行了研究.结果显示:P.geniculata和P.geniculata ssp.scythica为四倍体物种,P.geniculata ssp.pruinifera为六倍体物种;P.geniculata、P.geniculata ssp.scythica和P.geniculata ssp.pruinifera的核型公式分别为2n=4x=28=18m(2sat)+10sm(2sat)、2n=4x=28=28m(2sat)和2n=6x=42=36m(6sat)+6sm(2sat);P.geniculata和P.geniculata ssp.pruinifera为2A核型,而P.geniculata ssp.scythica为1A核型.研究表明:3种植物的核型存在差异;P.geniculata ssp.pruinifera的核型为首次报道,其核型明显不同于P.geniculata和P.geniculata ssp.scythica.     

A Morphogenetic Approach to the Embryogeny of Indotristicha (Podostemaceae)

Embryogenesis in Indotristicha ramosissima presents a uniqueinstance where exomorphic development marches ahead of endomorphicdifferentiation. Embryonic key centres of metabolic activitysuch as the epiphysis, the hypophysis and the cotyledonary lociare recognized largely by their topographical positions ratherthan on histological characteristics. The growth of the cotyledonsis also atypical in that an arc of protodermal and the subjacenthypodermal cells at the apex of the appendage become involvedin the attainment of the mature size and form. A postulate ispresented which recognizes the interaction of two sets of factorsin embryogenesis: one responsible for the attainment of theexomorphic contour and the other for endomorphic differentiation. Indotristicha ramosissima (Wight) van Royen, Podostemaceae, embryogeny, morphogenesis     

A new species of Eriocaulon (Eriocaulaceae) from Ethiopia

Eriocaulon crassiusculum sp. nov. is described from the Kefa province in southwestern Ethiopia. Illustrations are provided for habit as well as details of flowers (including pollen) and seeds. The new species is most closely related to E. transvaalicum , a widespread species in southern and eastern Africa.     

Eriocaulon peninsulare (Eriocaulaceae) - a new species from India

Eriocaulon peninsulare, a new species allied to E.sexangulare from Anshi National Park, Karnataka is described and illustrated.