The significance of the leaf epidermis in the taxonomy of the Combretaceae. V: The genus Cimbretum subgenus Cacoucia in Africa

The anatomy of the leaf epidermis of 49 of the approximately 65 African species of Combretum subgenus Cacoucia is described. This is discussed in relation to the taxonomy of the subgenus, particularly its sectional classification. Of the 17 sections which have been describrd, Campylogyne is now referred to the genus Quisqualis, Argyrotricha is referred to Combretum subgenus Combretum , and Angolensia, Grandiflora, Mweroensia, Parvula and Trichopetala are included with other sections. Combretum grandidieri is referred to the genus Calopyxis . In general the leaf epidermis of speries of subgenus Cacoucia is of far lower taxonomic value than in subgenus Combretum .     

The significance of the leaf epidermis in the taxonomy of the Combretaceae.

The value of the leaf epidermis, particularly of the glandular trichomes, in the identification and classification of Combretum subgenus Combretum in the African continent is assessed. The peltate hairs ('scales'), found in every species of this subgenus, show a wide range of anatomy and have proved extremely valuable in assessing taxonomic relationshipS. In general, differentiation by these means is at the sectional level, and the species are treated under the 22 sections now recognized in Africa. It may be concluded that the systematic value of the scales is at least as great as that of any other organ in the subgenus, and in a great number of cases valuable indications have been obtained for the first time. In an appendix three new sections are described.     

Taxonomy and variation of Vulpia ciliata Dumort.

The arguments lor the conspecificity of the tetraploid taxa in Vulpia section Vulpia sensu Cotton & Stace are discussed.     

A classification of stomatal types

In 1950 Metcalfe & Chalk showed the need for new technical terms 'devoid of taxonomic or ontogenetic implications' to replace those of Vesque. Their new terms and some others, proposed by Metcalfe and Stace, are now generally used. All previous classifications of stomatal types included only those of Angiosperms and Gymnosperms. The eight new forms described in this and a previous paper (Van Cotthem, 1968) include five known only from the Filices and bring the number of known stomatal types to 15, of which two have been subdivided.     

The inhibition of Clostridium chauvoei (jakari strain) neuraminidase activity by methanolic extracts of the stem barks of Tamarindus indicus and Combretum fragrans

The inhibition of neuraminidase from Clostridium chauvoei (jakari strain) with partially purified methanolic extracts of some plants used in Ethnopharmacological practice was evaluated. Extracts of two medicinal plants, Tamarindus indicus and Combretum fragrans at 100-1000 microg/ml, both significantly reduced the activity of the enzyme in a dose-dependent fashion (P < 0.001). The estimated IC50 values for Tamarindus indicus and Combretum fragrans were 100 and 150 microg/ml respectively. Initial velocity studies conducted, using fetuin as substrate revealed a non-competitive inhibition with the Vmax significantly altered from 500 micromole min(-1) mg(-1) to 240 micromole min(-1) mg(-1) and 340 micromole min(-1) mg(-1) in the presence of Tamarindus indicus and Combretum fragrans respectively. The KM remained unchanged at 0.42 mM. The computed Index of physiological efficiency was reduced from 1.19min(-1) to 0.57min(-1) and 0.75min(-1) with Tamarindus indicus and Combretum fragrans as inhibitors respectively.     

A new species of Combretum section Ciliatipetala (Combretaceae) from southern Africa, with a key to the regional members of the section

Combretum stylesii O.Maurin, Jordaan & A.E.van Wyk, a liana or slender tree with scrambling branches from the Tugela River Valley (KwaZulu-Natal), South Africa, is described. Molecular data supports its placement in subgenus Combretum section Ciliatipetala with its closest relative Combretum edwardsii. The new species differs from C. edwardsii in having, amongst others, a single mature leaf form, leaves softly textured, with whitish hairs, often with drooping habit, shorter leaf petioles (less than 5 mm), and less complex 8-celled leaf scales. A key to the species and infraspecific taxa of section Ciliatipetala in the Flora of southern Africa region is provided.     

The sweet jelly of Combretum lanceolatum flowers (Combretaceae): a cornucopia resource for bird pollinators in the Pantanal, western Brazil

 The pollination biology of the neotropical scandent shrub Combretum lanceolatum was studied in the seasonally-flooded Pantanal region in western Brazil. This plant bears horizontally oriented inflorescences, whose yellowish green flowers begin to expand at dusk and are fully open at dawn. Instead of fluid nectar the flowers produce sweet gelatinous secretion in form of pellets. The glandular complex of the flower is composed of the inner wall of the receptacle and its tubular extension, being equivalent to the nectariferous disk of the nectar-producing species within the genus. The jelly is produced at night, contains mannan and is imbibed by free hexoses. It originates by swelling and disintegration of the inner wall, after contact with the nectar generated concomitantly in the mesophyll. Combretum lanceolatum is unique within the genus in its production of jelly pellets instead of liquid nectar. A new term, the jelly-flower, is proposed for flowers with this kind of reward. The pellet is not replaced once removed by a bird, and thus resembles a fruit in its availability to consumers, another unique feature that distinguishes this species within the genus. The jelly pellets offered by the many flowered branches attract a great diversity of bird visitors (28 species from eight families), which feed on this copious food resource and pollinate the flowers. The most effective pollinators probably are thrushes, tanagers, and orioles. Flocking parakeets and macaws sometimes feed on the petals, thus acting as flower plunderers. Combretum lanceolatum presents a high fruit set under natural conditions, which likely favours its spreading and becoming a weed species. Received July 11, 2000 Accepted November 18, 2000     

Generic and infrageneric nomenclature of annual Poaceae: Poeae related to Vulpia and Desmazeria

The 26 generic and 63 infrageneric names which have been applied to the approximately 47 species belonging to the Vulpia–Desmazeria group of annual Poaceae: Poeae are listed, together with their bibliographic, nomenclatural and typological details. A synopsis of the classification of this group adopted by the author, involving twelve genera and five extra sections, follows, and includes a new combination at the sectional level: Vulpia sect. Apalochloa (Dumort.) Stace. Although not closely related to this group of grasses, the genus Sclerochloa is included as it has been very widely confused taxonomically, nomenclaturally and typographically with Scleropoa.     

The Inhibition of Clostridium chauvoei (Jakari strain) Neuraminidase Activity by Methanolic Extracts of the Stem Barks of Tamarindus indicus and Combretum fragrans

The inhibition of neuraminidase from Clostridium chauvoei (jakari strain) with partially purified methanolic extracts of some plants used in Ethnopharmacological practice was evaluated. Extracts of two medicinal plants, Tamarindus indicus and Combretum fragrans at 100–1000 μg/ml, both significantly reduced the activity of the enzyme in a dose-dependent fashion (P < 0.001).

The estimated IC₅₀ values for Tamarindus indicus and Combretum fragrans were 100 and 150 μ/ml respectively. Initial velocity studies conducted, using fetuin as substrate revealed a non-competitive inhibition with the V_max significantly altered from 500 μmole min^?1 mg^?1 to 240μmole min^?1 mg^?1 and 340 μmole min^?1 mg^?1 in the presence of Tamarindus indicus and Combretum fragrans respectively. The K_M remained unchanged at 0.42 mM. The computed Index of physiological efficiency was reduced from 1.19 min^?1 to 0.57 min^?1 and 0.75 min^?1 with Tamarindus indicus and Combretum fragrans as inhibitors respectively.     

BOOK REVIEWS

Book reviewed in this article:
New Flora of the British Isles. Clive Stace. 1,226 pp., 149 black-and-white illustrations.
Flowering Earth. Donald Culross Peattie. xii + 260 pp., 7 wood-engravings by Paul Landacre.
The English Garden Abroad. Charles Quest-Ritson. 232 pp., many black-and-white and colour illustrations.     

Effect of Water Potential and Temperature on the Germination of Four Species of African Savanna Trees

The germination responses of seeds from the African tree speciesColophospermum mopane, Combretum apiculatum, Acacia tortilisand Acacia karroo under varying regimes of temperature and waterstress (induced by incubation in PEG 8000) are reported Withthe exception of Combretum (at –0.14 and –0.29 MPa)and Colophospermum (at –0.29 MPa), incubation in PEG decreasedthe maximum achieved germination percentage (90–100% forall species), but did not extend the germination lag (exceptin Combretum) or affect the time required to reach maximum germinationCombretum and Colophospermum were found to germinate under thewidest range of temperatures and water potentials, for example,as strongly negative as –1.0 MPa at 20 and 30 °C,respectively These seeds also showed greater or equivalent hypocotylelongation in PEG solutions creating potentials of –0.14,–0.29 or –0.51 MPa when compared with seeds germinatedin water, indicating an additional stress adaptation Acaciaspecies showed progressive reduction in germination rates andradicle elongation in response to decreasing water potentialExperiments giving pre-imbibition treatments in water priorto transfer to PEG solutions showed that both Acacia speciesgerminated at approximately 90% if given such pre-treatmentand less than 10% if transferred directly to PEG It is concludedthat the most stress-adapted species studied are Colophospermummopane and Combretum apiculatum, a finding generally correlatedwith the growth habit of these trees Colophospermum mopane, Combretum apiculatum, Acacia tortilis, Acacia karroo, germination, water stress, Zimbabwe     

Sugars in the gut of the sandfly Phlebotomus orientalis from Dinder National Park, Eastern Sudan

The sandfly Phlebotomus orientalis Parrot (Diptera: Psychodidae) is the vector of visceral leishmaniasis in eastern and Upper Nile regions of Sudan, where vector infection rates of over 7% have been reported. Sugars are known to be important for development of the parasite and for increasing the survival and oviposition rates of several species of sandflies. In the present study we have analysed the sugars present in the guts of individuals and groups of male and female P. orientalis and compared these with sugars from several potential local plant sources: Acacia seyal, Balanites aegyptiaca and Combretum kordofanum. The distribution of these trees in Sudan is closely correlated with that of P. orientalis. Only 20% of individually analysed female sandflies had significant amounts of sugars present suggesting that P. orientalis either digest their sugar meal quickly or do not require regular sugar meals. Interestingly, the sugars present in the males were significantly different to those found in the females, indicating that they had fed on different sugar sources. There was evidence that fruit sugars from Balanites aegyptiaca, Combretum kordofanum and aphid or coccid honeydew are utilized by male and female P. orientalis. There was evidence to indicate that female P. orientalis feeds directly on honeydew. There was no evidence to indicate that direct feeding on leaves is a typical source for the sugar meal. There was no melizitose and only a very small amount of turanose present in the male, suggesting that honeydew was not an important sugar source for males.     

Conserving montane willow scrub on Ben Lawers NNR

Summary

The paper describes the status of surviving montane willow scrub on or adjacent to Ben Lawers NNR, referring to eight species of willow and juniper. Most of these have no viable future on the Reserve. The evidence and reasons for decline are discussed, and the conservation work initiated since 1987 described, including its rationale and the associated objective problems. Intervention with fencing and planting is intended to test the feasibility of restoring a viable scrub community, with the proximate objective of reestablishing seed-producing populations of the respective species. The long term and uncertain nature of the work is discussed. Plant names used are according to Stace (1991).     

The significance of the leaf epidermis in the taxonomy of the Combretaceae

The epidermal anatomy, with special reference to the glandular trichomes, is surveyed in the Asian species of the genus Combretum. Emphasis is laid on the value of such characters in reviewing the sectional classification of the genus. It is concluded that sections Quadrangulares, Squamosae, Tetragonocarpus and Flagrocarpeae should be amalgamated to form an enlarged section Tetragonocarpus. It is also likely that sections Quisqualoides, Ovalifoliae and Dasystachyeae , and sections Decandra'e and Kaloëdron , should be amalgamated.     

Composition of the gum from Combretum paniculatum and four other gums which are not permitted food additives.

Only three gum exudates are permitted for pharmaceutical and food use by international regulatory authorities, viz. gum tragacanth (Asiatic Astragalus spp.), gum karaya (Sterculia spp.) and gum arabic [Acacia senegal (L.) Willd.], but a wide range of other tree exudates is used for a variety of uses in their countries of origin. This paper presents analytical data for the gum exudates from Atalaya hemiglauca, Cassine aethiopica, Combretum paniculatum, Sclerocarya birrea, and Pseudocedrela kotschyi. These gums may have local technological applications, but are not recommended for addition to foodstuffs.     

Linking riparian vegetation types and fluvial geomorphology along the Sabie River within the Kruger National Park, South Africa

Vegetation types were studied in relation to the fluvial geomorphology along the mixed bedrock‐alluvial Sabie River within the Kruger National Park, Mpumalanga, South Africa. Six vegetation types were identified using TWINSPAN analysis, namely: Phragmites mauritianus , Phyllanthus reticulatus , Breonadia salicina , Combretum erythrophyllum , Diospyros mespiliformis and Spirostachys africana vegetation types. Spirostachys africana and Diospyros mespiliformis vegetation types were found to occur predominantly on the stable, infrequently flooded macro‐channel banks, while the remaining four vegetation types were found almost exclusively along the more geomorphically and hydrologically dynamic macro‐channel floor. The degree of bedrock or alluvial influence was identified as being an integral factor in the distribution of the four macro‐channel floor vegetation types at both the morphological unit and the channel type scale. The geomorphological continuum from the bedrock influenced bedrock anastomosing channel types, to mixed anastomosing and pool‐rapid channel types, to the fully alluvial braided channel types, is reflected in the change in species composition from Breonadia salicina vegetation type, to Phyllanthus reticulatus and Phragmites mauritianus vegetation types, to Combretum erythrophyllum vegetation types, respectively. Given the vegetation/fluvial geomorphology links established, changes in vegetation composition are proposed in response to scenarios of geomorphological change as a result of progressive sedimentation.     

A contribution to the rust flora (Uredinales) of southern Africa,with an emphasis on Namibia

Five new rust species are described and hitherto unknown spore states for the following seven species are reported: Puccinia desertorum on Evolvulus alsinoides, Uromyces comptus on Merremia bipinnatipartita, Puccinia halsei on Acacia hereroensis, Ravenelia transvaalensis on Acacia mellifera, Puccinia abutili on Abutilon angulatum, on Abutilon cf. austroafricanum, and on Abutilon cf. rehmannii, Puccinia lycii on Lycium sp. and Puccinia turgida on Lycium europaeum and on Lycium cf. oxycarpum. We also examined Uredo combreticola on Combretum cf. engleri, on Combretum hereroense, and on Combretum zeyheri, Puccinia afra on Lycium sp., and Uredopeltis cf. chevalieri on Grewia flavescens. All mentioned rust fungi are described in detail and are shown by line drawings. Selected species are illustrated with SEM-photographs. Part 220 in the series “Studies in Heterobasidiomycetes” from the Botanical Institute, University of Tübingen     

A New Species of the Genus <Emphasis Type="Italic">Steatococcus</Emphasis> Ferris, 1921 (Homoptera,Coccinea: Margarodidae) with Some Additions to the Fauna of the Republic of Mali

Steatococcus hystrixsp. n. (Margarodidae s. l.), collected in Mali on the stem of Combretum glutinosum Perrottet, 1828, is described and illustrated. A widely distributed Afrotropical soft scale (Coccidae) species, Udinia catori (Green, 1915), is recorded for Mali for the first time. Additional locality data are provided for another Afrotropical soft scale, Pulvinaria tenuivalvata (Newstead, 1911).