Evelin Pfeifer

Developmental morphology of Ledermanniella bowlingii (Podostemaceae) from Ghana

Abstract. Ledermanniella (c. 44 species) is the largest podostemoid genus in Africa. This paper deals with the structure and development of the Ghanaian species Ledermanniella bowlingii (J.B. Hall) C. Cusset (subgenus Ledermanniella). Characters typical for L. bowlingii include: green ribbon-like roots with exogenous lateral roots and endogenous shoots up to 120 cm; most leaves 3–7 times forked, with intrapetiolar stipules; flowers solitary or in clusters, borne on elongate stems or directly on roots; each flower bud inverted within a spathella; flowers unistaminate; tricolpate pollen in dyads; ovary mainly unilocular but bilocular at the base due to a rudimentary septum; mature capsule with eight ribs, 1.0–1.8 mm long, containing 12–34 seeds, dehiscing by two equal valves; capsule stalk with pedicel (10 mm) and gynophore (2 mm); silica bodies absent in all plant parts. Several characters of L. bowlingii are described here for the first time. The paper shows that accurate morphological analyses of African Podostemaceae are badly needed.

How to get off the mismatch at the generic rank in African Podostemaceae

The Podostemaceae are highly enigmatic plants which are restricted to submerged river-rock habitats. The availability of new material of nine taxa from continental Africa prompted this new study. Five species belonging to the genera Dicraeanthus, Leiothylax, Letestuella, Macropodiella, and Stonesia and another four species of the large genera Inversodicraea sensu stricto and Ledermanniella sensu stricto have been analysed for the first time. New anatomical and developmental data are described and illustrated by use of microtome sections and scanning electron microscopy. In parallel, phylogenetic analyses of all available sequence data of African Podostemaceae have been conducted using three plastid markers (matK, trnD-trnT, rpoB-trnC). Inversodicraea cf. bosii appears basal within the continental African clade. The remaining taxa are distributed in three, rather poorly supported, major clades which are consistent with their morphology: (1) the Inversodicraea clade is characterised by stem scales and contains members of the former Ledermanniella subg. Phyllosoma with either pollen-monads or dyads; (2) the Ledermanniella-Monad group consisting of Leiothylax, Letestuella, Macropodiella, Stonesia, and Ledermanniella species—all taxa without stem scales but showing pollen as single grains, with Monandriellalinearifolia being basal to this clade; (3) the Ledermanniella-Dyad clade including Djinga, Dicraeanthus, and Ledermanniella species without stem scales but with pollen dyads. To reduce the polyphyly of Ledermanniella sensu lato (i.e. sensu C. Cusset) we propose restricting Ledermanniella to the species of the former subgenus Ledermanniella, resurrecting Monandriella as monotypic genus, and accepting the genus name Inversodicraea for members of Ledermanniella subg. Phyllosoma.

Gunnera herteri – developmental morphology of a dwarf from Uruguay and S Brazil (Gunneraceae)

Abstract.New morphological and developmental observations are presented of Gunnera herteri (subgenus Ostenigunnera) which is, according to molecular studies, sister to the other species of Gunnera. It is an annual dwarf (up to 4 cm long) whereas the other Gunnera spp. are perennial and slightly to extremely larger. External stem glands are combined with channels into the stem cortex serving as entrance path for symbiotic Nostoc cells. Young stem zones show globular regions of cytoplasm-rich cortex cells, prepared for invasion by Nostoc. The leaf axils contain 2–5 inconspicuous colleters (glandular scales) which can be taken as homologous to the more prominent scales of G. manicata (subg. Panke) and G. macrophylla (subg. Pseudogunnera). Foliage leaves of G. herteri have tooth-like sheath lobes which may be homologous to stipules. Adult plants have extra-axillary inflorescences arising from leaf nodes. The main stem is interpreted as a chain of sympodial units, each one consisting of a leaf and an extra-axillary inflorescence. This “sympodium hypothesis” may be also valid for other species of Gunnera. Each globular inflorescence of G. herteri contains several female flowers and 2–7 stamens at the top, perhaps equalling a single male flower. There are neither bracts nor bracteoles. The ovary is inferior, bicarpellary and unilocular. Its single hanging ovule develops into a dry and endosperm-rich seed.

Comparative morphology of Cladopus (including Torrenticola, Podostemaceae) from East Asia to north-eastern Australia

Cladopus (with 12 or less species) is an Asian and Australian genus of Podostemaceae–Podostemoideae. They are haptophytes that grow in rivers. The developmental morphology and anatomy of Cladopus austro-osumiensis Y.Kadono & N.Usui, C. austrosatsumensis Koidzumi, C. chinensis Chao, C. japonicus Imamura and C. queenslandicus [Domin] C.D.K. Cook & Rutish. (syn. Torrenticola queenslandica [Domin] Domin ex Steenis) are studied by scanning electron microscope and microtome. The architecture of the examined species fits with the bauplan known from other Asian Podostemoideae. Rosulate shoots arise in zigzag patterns or as opposite pairs from narrow or broad green ribbons which may be interpreted as adhesive creeping roots. Cladopus is the only podostemaceous genus known with both endogenous and exogenous lateral roots along the mother root. Exogenous lobes (which may develop into daughter roots) are next to the sites of root-borne shoots which, finally, give rise to terminal flowers. Cladopus species have the following features (synapomorphies) in common: (1) leaves on older and reproductive shoots with one or two median, long filaments (caducous) and 1–4 lateral short lobes (persistent) on either side of the leaf, which are called stipules; (2) spathella (i.e. mantle-like flower cover) with an apical two-tipped papilla; (3) spathella splitting more or less circumscissilely; (4) capsules globose or nearly so, smooth or with three faint ribs per valve.

Developmental morphology of branching flowers in Nymphaea prolifera

Nymphaea and Nuphar (Nymphaeaceae) share an extra-axillary mode of floral inception in the shoot apical meristem (SAM). Some leaf sites along the ontogenetic spiral are occupied by floral primordia lacking a subtending bract. This pattern of flower initiation in leaf sites is repeated inside branching flowers of Nymphaea prolifera (Central and South America). Instead of fertile flowers this species usually produces sterile tuberiferous flowers that act as vegetative propagules. N. prolifera changes the meristem identity from reproductive to vegetative or vice versa repeatedly. Each branching flower first produces some perianth-like leaves, then it switches back to the vegetative meristem identity of the SAM with the formation of foliage leaves and another set of branching flowers. This process is repeated up to three times giving rise to more than 100 vegetative propagules. The developmental morphology of the branching flowers of N. prolifera is described using both microtome sections and scanning electron microscopy.

Stonesia ghoguei, Peculiar Morphology of a New Cameroonian Species (Podostemaceae, Podostemoideae)

Abstract The traditional circumscription of the genus Stonesia G. Taylor (Podostemaceae, Podostemoideae) includes three species restricted to western tropical Africa. Here, a new species, S. ghoguei E. Pfeifer & Rutishauser, is described, which represents the first Cameroonian member of the genus. There are another three Stonesia species restricted to western tropical Africa (Guinea and Sierra Leone). The genus Stonesia is characterized by capsule valves with five or seven ribs each, with the ribs nearest the sutures shorter and not reaching the ends of valves. This unique pattern is shared with the two Madagascan genera Endocaulos C. Cusset and Paleodicraeia C. Cusset. Molecular (matK) data indicate that this capsule pattern is homoplastic, occurring in Madagascar and (with Stonesia) in tropical Africa. Various characters of Stonesia (including S. ghoguei) are also found in other African podostemoids. These include flower buds inverted in the sac-like spathella; crustose roots or broad ribbons with exogenous root lobes (daughter roots); stems usually simple (rarely branched), up to 10(–40) cm long; flowers arising primarily from endogenous buds inside the stem cortex in S. ghoguei and S. fascicularis G. Taylor; and leaves repeatedly forked into narrow segments, with epiphyllous flowers arising from the clefts of these forks in S. ghoguei and S. heterospathella G. Taylor. Unlike the western African Stonesia species, S. ghoguei has pollen mainly released in monads (not only dyads), one stamen per flower with two lateral tepals (not two stamens with three tepals), and unilocular ovaries (not bilocular ones).