Bio Louis Nyananyo

Pollen morphology in thePortulacaceae (Centrospermae)

Pollen of 110 species from 18 genera in thePortulacaceae has been examined by light and scanning electron microscopy, and a representative number by transmission electron microscopy. Three basic pollen types were found: 3-colpate with thick tectum and foot layer with prominent unbranched columellae and an extremely thin endexine; pantoporate with thick tectum and foot layer with branched columellae enclosing pores and an endexine that is one to two layers thick; pantocolpate with thin tectum and foot layer with broad, short unbranched columellae and an inconspicuous endexine. All pollen types, however, have a spinulose and tubuliferous/punctate ektexine. Also, all the genera except three,Calandrinia H.B.K.,Montia L. andTalinumAdanson are stenopalynous. There is, however, no absolute correlation between pollen morphology and geographical distribution, although both the major centre of palynological diversity and the majority of all species with tricolpate grains occur in South America.

Leaf anatomical studies in thePortulacaceae (Centrospermae) with regards to photosynthetic pathways

A total of 112 species in 18 genera in thePortulacaceae were investigated anatomically for the presence or absence of the chlorenchymatous bundle sheath cells around the vascular bundles: C4 or Kranz anatomy. Twenty species in only one genus,Portulaca L. of all the taxa investigated possesses the C4 or Kranz anatomy. All others have the C3 anatomy.

A survey of leaf flavonoids in the portulacaceae

Abstract A survey of 26 species in 12 genera of the Portulacaceae showed the presence of flavonoids in 24, and their absence in two, Hectorella caespitosa Hooker fil. and Lyallia kerguelensis Hooker fil. Of the 24 positive species, 16 are reported for the first time. In all 24 however, flavonols and flavones did not occur together suggesting that this dichotomy might be useful for classification at and below the generic level in the Portulacaceae, e.g. the genera Silvaea Philippi (syn. Philippiamara Kuntze), Ceraria Pearson & Stephens and Portulacaria Jacquin which were previously grouped together on palynological characteristics have now been shown to differ in their leaf flavonoids, subsidiary cells of the stomata and geographical location: Silvaea possesses flavones and is endemic to South America, while Ceraria and Portulacaria possess flavonols and are endemic to Africa. The dichotomy also occurs below the generic level. In Calandrinia H.B.K. and Portulaca L. the dichotomy amongst their species is supported by other new taxonomic characters from cytology, palynology, pubescence of surfaces, type of subsidiary cells surrounding the leaf stomata and seed morphology recently elucidated by the author.

The systematic significance of seed morphology and anatomy in the Portulacaceae (Centrospermae)

Nyananyo B. L. (1988): The systematic significance of seed morphology and anatomy in thePortulacaceae (Centrospermae).—Folia Geobot. Phytotax., Praha, 23: 275–279.—The seeds of 115 species in eighteen genera of the familyPortulacaceae were examined with the scanning electron microscope. Longitudinal sections of seeds of representatives of all the genera were examined with the light microscope. Two broad groups based on shape of the seeds, ornamentation of the external surface of their testa, and the position of the embryo relative to the endosperm were recognised. The first group comprising three genera:Anacampseros L.,GrahamiaGillies andTalinopsisA. Gray, have seeds which are pyriform with wings and trichomes, and an embryo that is more or less parallel to the endosperm, while the second of fifteen genera:Calandrinia H.B.K.,CalyptridiumNuttall,CalyptrothecaGilg,CerariaPearson etStephens,Claytonia L.,LenziaPhilippi,LewisiaPursh,LyalliaHooker fil.,Montia L.,Portulaca L.,PortulacariaJacquin,SilvaeaPhilippi,TalinellaBaillon,TalinumAdanson, andWangeriniaFranz, are reniform without wings and with an embryo that is horse-shoe shaped around the endosperm.

Notes on the reproductive biology ofPortulaca L. (Portulacaceae) in Nigeria

Nigerian species ofPortulaca: P. grandifloraHooker,P. oleracea L. andP. quadrifida L. combine inbreeding, outbreeding and vegetative propagation in the wild and in the oultivation. Observations have shown that the anthers ofPortulaca species dehisces before the flower bud opens, and are usually ripe at the time the stigmas are receptive. This enhances self-fertilization.

A new nomenclatural combination inPortulacaceae (Centrospermae)

Examination of type specimens of the monotypic genera,Grahamia (G. bracteata) andTalinaria (T. palmeri) together with detailed palynological, morphological and seed anatomical evidence have shown that these two species are very similar. These two genera are subsequently grouped into one genus,Grahamia. A new combination,G. palmeri is now proposed.

Palynology ofTelfairia L. (Cucurbitaceae)

Okoli B. E. etNyananyo B. L. (1988): Palynology ofTelfairia L. (Cucurbitaceae).—Folia Geobot. Phytotax., Praha, 23: 281–283.—Scanning and transmission electron microscopic studies were carried out on the pollen of the two species ofTelfairia, T. pedata(Sims.) Hooker andT. occidentolisHooker fil. Pollen grains in both species are spheroidal, tricolporate and tectate. The extexine is finely reticulate. The tectum, foot layer and columellae are all well developed. Significant differences of taxonomic value do not exist in the structure of the pollen of the two species.

Identification of the Genus Phyllanthus (Family Phyllanthaceae) in Southern Nigeria Using Comparative Systematic Morphological and Anatomical Studies of the Vegetative Organs

Five species of Phyllanthus L. Family Phyllanthaceae occurring in Southern Nigeria, P. amarus Schum and Thonn, P. urinaria Linn., P. odontadenius Mull-Arg., P. niruroides Mull-Arg. and P. muellerianus (O. Ktze) Excell were compared using the morphology and anatomy with the view to adding to increasing the systematic lines of evidence and providing a more natural clarification than the existing one. The foliar and floral morphology of these species were described while the anatomical characteristics of the leaf, stem and root are valuable characters in delimiting the species. The results obtained from the studies showed that species of Phyllanthus have different attributes in their vascular characteristics that could be used together with other existing systematic evidence in clarifying the confusion in identifying these plants. Evidence from the nature of the palisade parenchyma in the mesophyll, nature of the collenchyma, sclerenchyma and vascular bundles are presented and discussed with their values in the systematic positions of these plants. A dichotomous bracketed key to the identification of the species studied is provided.