AJOL: South African Journal of Botany: VOLUME 68 ISSUE 3 (2002) Abstracts

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South African Journal of Botany

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VOLUME 68 ISSUE 3 (2002)
Abstracts

South African Journal of Botany 2002, 68: 283–298

Minireview

The genus Pyramimonas (Prasinophyceae) from southern African inshore waters

RN Pienaar* and SD Sym

School of Animal, Plant & Environmental Sciences, University of the Witwatersrand, Private Bag 3 WITS, Johannesburg 2050, South Africa

* Present Address: Deputy Vice Chancellor (Academic: Internal), University of the Witwatersrand, Private Bag 3 WITS, Johannesburg 2050, South Africa

* Corresponding author, e-mail: [email protected]

Received 2 August 2002, accepted 4 August 2002

Some seventeen species of the genus Pyramimonas from southern African inshore waters were encountered, isolated and cultured. Only two of these had been found in this locality prior to this study, and four were new to science. Details of their features observable at the light and electron microscope level were recorded and used in a cladistical analysis which yielded two most parsimonious trees. Most ultrastructural features were found to be useful, with the exception of the eyespot groupings suggested by Hori et al. (1995), which are afforded additional attention. The subgenera Pyramimonas and Punctatae are not resolved and appear basal. The cladogram supports the notion of very advanced vestigiferans whose sister group interestingly is formed by the trichocystin cluster of P. grossii/P. cirolanae. The results are compared with a cladogram derived from molecular data, and possible evolutionary trends are presented.

South African Journal of Botany 2002, 68: 299–303

Priority ranking scheme for Red Data plants in Gauteng, South Africa

MF Pfab

Gauteng Department of Agriculture, Conservation, Environment and Land Affairs, PO Box 8769, Johannesburg 2000, South Africa

Corresponding author, e-mail: [email protected]

Received 11 June 2001, accepted in revised form 6 September 2001

The Gauteng Department of Agriculture, Conservation, Environment and Land Affairs is often faced with the necessity of priority setting for the distribution of limited resources. As conservation action cannot be targeted simultaneously to all 32 Red Data plant taxa in the province of Gauteng, a hierarchical priority ranking scheme was developed using criteria reflecting species distribution, current conservation status and factors of threat. The current top five Red Data plant taxa in Gauteng are Khadia beswickii, Delosperma macellum, Ceropegia decidua subsp. pretoriensis, Delosperma purpureum and Delosperma gautengense. The resulting priority list will be used to distribute resources for the development of long-term monitoring programmes and extensive ecological and population studies for priority taxa. The priority ranking scheme forms the basis of a departmental policy to assist with the evaluation of development applications and environmental impact assessments affecting Red Data plant taxa in Gauteng. The scheme will also be used as a factor in setting priority conservation areas for future conservation action in the province.

South African Journal of Botany 2002, 68: 304–307

Passerina quadrifaria (Thymelaeaceae): a new species from the southern Cape and Little Karoo in South Africa

CL Bredenkamp^1* and AE van Wyk²

¹ National Botanical Institute, Private Bag X101, Pretoria 0001, South Africa

² HGWJ Schweickerdt Herbarium, Department of Botany, University of Pretoria, Pretoria 0002, South Africa

* Corresponding author, e-mail: [email protected]

Received 23 February 2001, accepted in revised form 5 October 2001

Passerina L. is an endemic southern African genus, with the exception of two species that have outliers in eastern Africa. The genus comprises about 20 species and four subspecies. P. quadrifaria Bredenkamp and Van Wyk is a new species occurring in the Karoo Mountain, Langeberg and Southeastern phytogeographic centres of the Cape Floristic Region. It is most closely related to P. comosa C.H.Wright as the leaves and bracts of both species are abaxially hairy. The most obvious diagnostic feature of the new species is the distinct four-ranked appearance of the leaves, which are decussate, imbricate, sessile and spreading at an angle of ±45º. The species have complementary nonoverlapping ranges, P. comosa occurring from the Kamiesberg of the Northern Cape Province to the Roggeveld, Witteberg and Klein Swartberg mountain ranges of the Western Cape Province, whereas P. quadrifaria is restricted to mountain ranges of the southern Cape and western parts of the Eastern Cape Province. There are two morphological forms of P. quadrifaria, the first form corresponding to the general species description and a second form with slightly longer internodes, smaller leaves and the apices of the bracts more rounded. As the leaves of these two forms are anatomically identical, they are not given formal taxonomic status.

South African Journal of Botany 2002, 68: 308–311

Daubenya alba (Hyacinthaceae, tribe Massonieae), a new species from the Roggeveld, Northern Cape Province

AM van der Merwe and EM Marais*

Department of Botany, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa

* Corresponding author, e-mail: [email protected]

Received 24 October 2001, accepted in revised form 29 November 2001

Daubenya alba A.M. van der Merwe, from the edge of the Roggeveld escarpment in the Northern Cape Province, is described as a new species. It resembles D. capensis (Schltr.) A.M. van der Merwe & J.C. Manning in leaf shape, floral structure and the presence of a staminal tube, but is distinguished by its delicate white to pale lilac flowers and lack of a staminal disc.

South African Journal of Botany 2002, 68: 312–321

Classification of estuaries in the Ciskei and Transkei regions based on physical and botanical characteristics

BM Colloty, JB Adams* and GC Bate

Department of Botany, University of Port Elizabeth, PO Box 1600, Port Elizabeth 6000, South Africa

* Corresponding author, e-mail: [email protected]

Received 9 May 2001, accepted in revised form 3 December 2001

For the first time a comprehensive botanical survey has taken place in the Ciskei and Transkei estuaries, Eastern Cape Province, South Africa. In total 54 plant species were found in the 92 estuaries surveyed. These plants could be divided into the following five habitat complexes; reed and sedge beds (23 species), salt marsh (20 species), mangrove forest (4 species), macroalgal assemblages (3 species) and swamp forest (4 species). Ordination showed that salinity and depth were important in influencing the distribution of species. Salinity separated salt marsh from reed and sedge species and depth separated mangrove and associated species (e.g. Zostera capensis, Halophila ovalis and Acrostichum aureum) from reed and sedge species.

Based on the plant species composition the estuaries could be divided into those that were permanently open versus those that were temporarily open/closed. The characteristic habitat complexes for the permanently open estuaries were intertidal salt marsh and mangrove forest. This region is a transition between the warm temperate and subtropical biogeographic zones and both permanently open and temporarily open/closed estuaries showed divisions at the Great Kei and Mngazana estuaries. In permanently open estuaries mangrove forest occurred north of the Great Kei Estuary and swamp forest north of the Mngazana Estuary. In temporarily open/closed estuaries reed and sedge beds occurred north of the Great Kei River and swamp forest, reed and sedge beds occurred north of the Mngazana Estuary where they replaced the salt marsh. The temporarily open/closed estuaries in the Ciskei were characterised by salt marsh and macroalgae. Submerged macrophytes such as Ruppia cirrhosa and Potamogeton pectinatus were also common. Salt marsh occurred because of high water column salinity and wide intertidal and supratidal zones. These estuaries were characterised by seawater washing into the estuary over the berm at the mouth and thus had high salinity. The variation in physical environment, changes in climate and transition between biogeographic regions has resulted in regions of high biodiversity. Mangrove, salt marsh and swamp forest species are found in the same region.

South African Journal of Botany 2002, 68: 322–326

Amatoxins and phallotoxins in indigenous and introduced South African Amanita species

HE Hallen1*, GC Adams2 and A Eicker3

¹ Michigan State University, Department of Plant Biology, East Lansing, MI 48824–1312, USA

² Michigan State University, Department of Plant Pathology, East Lansing, MI 48824–1312, USA

³ University of Pretoria, Department of Botany, Pretoria 0002, South Africa

* Corresponding author, e-mail: [email protected]

Received 24 July 2001, accepted in revised form 12 December 2001

The production of lethal amatoxins and phallotoxins in species of Amanita from South Africa was investigated by HPLC (High Performance Liquid Chromotography) analyses. The indigenous mushrooms Amanita foetidissima and A. pleropus tested negative for production of these toxins. Several introduced species were analysed; of these, A. phalloides var. phalloides, A. phalloides f. alba and A. reidii contained amatoxins and phallotoxins. Despite reports of rapid degradation of phallotoxins upon drying, phallotoxins and amatoxins were both readily detectable in dried herbarium specimens up to 17 years old. Previous reports of phallotoxins in A. rubescens were not substantiated.

South African Journal of Botany 2002, 68: 327–332

Pathogenicity of Phytophthora and Pythium species associated with citrus root rot in South Africa

BOZ Maseko* and TA Coutinho

Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria 0002, South Africa

* Corresponding author, e-mail: [email protected]

Received 22 October 2001, accepted in revised form 12 December 2001

Root rot is a serious disease problem facing the citrus industry in South Africa. Pythiaceous fungi, especially Phytophthora spp., are well known causal agents of root diseases in citrus orchards and nurseries. In contrast, little is known regarding the role played by Pythium spp. in the development of citrus root rot. This is despite their abundance in the rhizosphere of diseased citrus trees. In this study, we isolated and identified a large collection of Phytophthora and Pythium spp. obtained from diseased citrus trees as well as from rhizosphere soil. Pathogenicity was tested using a rapid screening technique. A subset of the most pathogenic Phytophthora and weakly pathogenic Pythium isolates were further inoculated into commercial citrus rootstocks, Rough Lemon and Troyer Citrange. All Phytophthora isolates were found to be pathogenic on citrus fruit and rootstocks. Significant differences in pathogenicity were, however, found amongst the different Phytophthora isolates tested. Pythium spp. were found to be either avirulent or only weakly pathogenic. Results obtained indicate that Pythium spp. are not serious pathogens of citrus and probably do not play a significant role in the development of citrus root rot.

South African Journal of Botany 2002, 68: 333–341

Optimising heavy metal adsorbance by dried seaweeds

SA Nigro, WA Stirk* and J van Staden

Research Centre for Plant Growth and Development, University of Natal, Pietermaritzburg, P/Bag X01, Scottsville 3209, South Africa

* Corresponding author, e-mail: [email protected]

Received: 15 March 2001, accepted in revised form 14 January 2002

Industrialisation has resulted in large-scale production of anthropogenic pollutants, particularly heavy metals. Existing industrial techniques for the purification of waste water are expensive. A cheaper alternative may be `bioremoval', that is, the accumulation and concentration of pollutants from aqueous solutions using biological material.

The adsorption of copper, zinc and cadmium using two dried seaweeds Ecklonia maxima and Laminaria pallida (order Laminariales) and Kelpak waste (also made from Ecklonia maxima), a byproduct from the manufacture of the seaweed concentrate Kelpak, were investigated under laboratory conditions, to determine some factors affecting heavy metal adsorption. Ion adsorption from single and mixed metal ion solutions of 10mgl^-1 and 100mgl^-1 containing copper, zinc and cadmium were tested at various temperatures and pH. Optimum adsorption occurred at pH 3 and pH 7 and Kelpak waste had equal or superior adsorption ability to dried Ecklonia maxima and Laminaria pallida, particularly for copper. Optimum adsorption occurred at temperatures of 20ºC and 30ºC. Heavy metal adsorption trends by the individual seaweed biosorbent remained constant regardless of the species of anion present. Drying of the experimental material (fan air and oven drying at 85ºC) prior to adsorption cycles resulted in more efficient ion uptake, particularly after additional rehydration. Heavy metal uptake was monitored over a number of semi-continuous adsorption cycles, using the same biomasses. Ion uptake was the most efficient after 2–4 adsorption cycles.

South African Journal of Botany 2002, 68: 342–348

New records of marine benthic algae for the Mozambican coast, collected at Inhaca Island

E Coppejans*, F Leliaert and T Schils

Research Group Phycology, Department of Biology, Ghent University, Krijgslaan 281, S8, 9000 Ghent, Belgium

* Corresponding author, e-mail: [email protected]

Received 30 July 2001, accepted in revised form 14 January 2002

Thirteen taxa of Rhodophyta, Phaeophyta and Chlorophyta are reported for the first time from Inhaca Island: Gelidiopsis repens, Solieria robusta, Tricleocarpa cylindrica, Dictyota humifusa, Padina boergesenii, Sargassum crassifolium, Stoechospermum polypodioides, Caulerpa microphysa, Cladophora catenata, C. coelothrix, C. vagabunda, Rhizoclonium africanum, Udotea indica. All of these species are new records for Mozambique, Cladophora catenata is recorded for the first time in the Indian Ocean. The seaweed flora of Inhaca Island now totals 224 taxa, including 73 genera of Rhodophyta (120 species), 15 genera of Phaeophyta (28 species) and 28 genera of Chlorophyta (35 species, some of which have several varieties).

South African Journal of Botany 2002, 68: 349–356

The effect of activated charcoal and auxins on root formation by hypocotyl segments of Daucus carota

M Pan and J van Staden*

Research Centre for Plant Growth and Development, School of Botany and Zoology, University of Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa

* Corresponding author, email: [email protected]

Received 20 August 2001, accepted in revised form 18 January 2002

The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) by activated charcoal (AC) from methanol and aqueous solutions was determinated using HPLC. The level of the added 2,4-D decreased in both methanol and aqueous solutions in the presence of 1% AC. About 68% and 61% of the added 2,4-D was adsorbed respectively by AC (1.0%) from these two sources. In vitro rooting of hypocotyl segments of Daucus carota using AC and the auxins 2,4-D, _-naphthaleneacetic acid (NAA) and indole-3-acetic acid (IAA) was investigated. Rooting occurred when 7-day-old seedling hypocotyl segments were placed on Murashige and Skoog medium supplemented with 1.0mgl^-1 2,4-D in the presence of AC, and 0.5mgl^-1 NAA or IAA. Hypocotyl segments did not produce roots on the 2,4-D-containing medium in the absence of AC. Hypocotyl segments produced roots polarly on the NAA or IAA-containing media in the presence of activated charcoal. No-polarity of root formation was observed on media supplemented with NAA or IAA without AC. Different responses of hypocotyl segments to various levels of 2,4-D (0mgl^-1, 0.5mgl^-1, 1.0mgl^-1, 3.0mgl^-1, 5.0mgl^-1, 8.0mgl^-1 and 10.0mgl^-1) were observed on media supplemented with 0.02%, 0.1% and 0.5%AC. Root number per hypocotyl segment decreased in the NAA or IAA-containing media in the presence of AC. However, root number per hypocotyl segment, on the media supplemented with NAA or IAA, increased when the segments were pre-cultured on MS medium supplemented with 2,4-D (1.0mgl^-1) for 2–3 days. When hypocotyl segments were pre-cultured on a 2,4-D-containing MS medium for 5 days, embryos emerged from the segments directly on the medium supplemented with AC.

South African Journal of Botany 2002, 68: 357–361

Forest tree and fern species as indicators of an unnatural fire event in a southern Cape mountain forest

LH Watson* and MJ Cameron

Department of Nature Conservation, Port Elizabeth Technikon, Saasveld Campus, Private Bag X6531, George 6530, South Africa

* Corresponding author, e-mail: [email protected]

Received 14 March 2001, accepted in revised form 21 January 2002

Afromontane forests in the southern Cape are typically surrounded by fire prone fynbos. Although the impact of fire on fynbos has been extensively studied, little is known about the impact of fire on adjacent forest. Fire swept through a mountain forest in the southern Cape in 1996. Our study indicated that this fire was one of at least two fires that influenced the recent history of this forest; the other fire was probably the great fire of 1869. We consider the latter fire typical of fires that burn mountain forest and suggest a return period for these fires of between a 100 and 200 years. In contrast to the 1869 fire, evidence from our study suggests that the 1996 fire was unprecedented in the recent history of the forest. This fire changed a large proportion of Ocotea bullata in the margin from single stemmed to multi-stemmed trees and reduced the number of Cyathea capensis in the margin by 68%. Using these species as indicators, we argue that similar fires will reduce the structure and diversity of mountain forests as a whole. The 1996 fire was fuelled by abnormally high fuel loads associated with surrounding pine plantations and mountain fynbos invaded by woody aliens. Given that large areas of mountain fynbos are invaded by woody aliens, that large areas of the southern Cape are afforested and that global climate change is likely to lead to an increase in the conditions favouring intense fires, we consider effective management of Afromontane mountain forests essential.

South African Journal of Botany 2002, 68: 362–369

Effects of pre-planting treatments on the initial establishment success of indigenous grass seedlings planted into a degraded Aristida junciformis-dominated grassland

R Wiseman¹, CD Morris²* and JE Granger¹

¹ School of Applied Environmental Sciences, University of Natal, Private Bag X01, Scottsville 3209, South Africa

² Range and Forage Institute,Agricultural Research Council, Private Bag X01, Scottsville 3209, South Africa

* Corresponding author, e-mail: [email protected]

Received 15 December 2000, accepted in revised form 21 January 2001

The effects of various manipulations to facilitate the establishment of indigenous grasses planted into degraded Aristida junciformis subsp. junciformis-dominated grassland were investigated. Four treatments — complete clearing, a single spring burn, applications of Roundup^®, and undisturbed (control) — were applied to replicated plots, with half of each plot mown before planting. Themeda triandra and Tristachya leucothrix seedlings were planted into each plot. Post-planting survival of the planted seedlings was uniformly high (>80%), except in the poisoned, unmown plots where residual herbicide appears to have significantly lowered seedling survival (<35%). Seedling mortality over the remainder of the growing season and through winter was low (<10%). Seedlings planted into swards killed with herbicide had a greater basal area and more tillers than did those planted amongst living adult plants. However, basal cover of the sward in the poisoned plots a year after planting was significantly lower (<6%) than in other treatments (14–19%). The cost of implementing pre-planting treatments and planting the seedlings was high and the method is labour-intensive. It is therefore recommended that a pre-planting burn, which temporarily reduces the vigour of the surrounding sward and is economically viable, be applied before planting, and that the cost and effectiveness of strip-planting be investigated.

South African Journal of Botany 2002, 68: 370–375

Threatened plants of Gauteng, South Africa

MF Pfab¹* and JE Victor²

¹ Gauteng Department of Agriculture, Conservation, Environment and Land Affairs, PO Box 8769, Johannesburg 2000, South Africa

² National Herbarium, National Botanical Institute, Private Bag X101, Pretoria 0001, South Africa

* Corresponding author, e-mail: [email protected]

Received 20 September 2001, accepted in revised form 19 February 2002

The Red Data List status of threatened plants of Gauteng, South Africa is presented. This includes evaluations using categories and criteria adopted by the IUCN in 1994 and updated in 2000 for assessing the risk of extinction. A total of 23 taxa were found to be threatened, nine are Data Deficient and 33 former Red Data taxa are not threatened with extinction. The major threat to the continuing persistence of threatened plants in Gauteng is urban development. Recommendations for the conservation of these species are made, and suggestions are given for research needs on certain taxa for which inadequate information is available.

South African Journal of Botany 2002, 68: 376–381

Senescence activity in extracts from fruiting Bidens pilosa plants

AM Zobolo^1,2 and J van Staden*¹

¹ Research Centre for Plant Growth and Development, School of Botany and Zoology, University of Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa

² Science Faculty, University of Zululand, Private Bag X1001, Kwadlangezwa 3886, South Africa

* Corresponding author, e-mail: [email protected]

Received 30 January 2002, accepted in revised form 1 May 2002

Senescence activity of extracts from the leaves of Bidens pilosa was determined using Rumex and bean plants as bioassay systems. Ethanolic extracts of non-senescent and senescent leaves were chromatographed (TLC) using a solvent system of benzene : ethyl acetate : acetic acid 50:5:2 (v/v). Fraction 1 (R_f0.0–0.1) from both non-senescent and senescent leaves, eluted with methanol, induced senescence of bean leaves in the light. In Fractions that were eluted with ethyl acetate, senescence-inducing activity was detected from non-senescent but not from senescent leaf extracts, using the bean explant bioassay. This senescence activity was not detected in Fraction 1 but in Fractions 3 (R_f 0.1–0.25), 4 (R_f 0.25–0.35), 6 (R_f 0.6–0.7) and 7 (R_f 0.9–1.0). On the TLC plates, Fractions 3 and 4 co-chromatographed with abscisic acid and 4-chloroindole acetic acid respectively. The results suggest that plant extracts contain senescence factors which operate during the active terminal phase of growth, in the presence of light.

South African Journal of Botany 2002, 68: 382–385

Short Communication

Seedling establishment characteristics of Paeonia ostii var. lishizhenii

H Wang¹ and J van Staden*

* Research Centre for Plant Growth and Development, School of Botany and Zoology, University of Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa

¹ Present address: College of Plant Sciences, Beijing Forestry University, Beijing, 100083, China, e-mail: [email protected]

* Corresponding author, e-mail: [email protected]

Received 14 June 2001, accepted in revised form 3 October 2001

The viability of Paeonia ostii var. lishizhenii seed used in this investigation was around 85% when tested under optimum conditions of tissue culture. Seedling establishment embodied radicle protrusion and breaking of epicotyl dormancy. The seed coat, an endosperm extract, and GA₃ significantly influenced embryo emergence. The seed coat is not an appreciable barrier to water uptake but exhibited a degree of mechanical resistance. Both the coat and endosperm extract inhibited germination. Removal of the radicle end of the testa and soaking in GA₃ (100–200mgl^-1) promoted radicle growth at 15ºC. Epicotyl dormancy was broken by soaking seeds in GA₃ or maintaining excised embryos on Woody Plant Medium containing 1mgl^-1 GA₃. Chilling at 5ºC for 30 days was required to break epicotyl dormancy of emerged embryos. The seed structures surrounding the embryos impose mechanical and chemical restraints on germination. The embryo itself appears to be lacking growth promoters as exogenous GA₃ promoted epicotyl growth.

South African Journal of Botany 2002, 68: 386–388

Short Communication

Tannins, saponins and calcium oxalate crystals from Nigerian species of Boerhavia L. (Nyctaginaceae)

HO Edeoga* and CI Ikem

Department of Biological Sciences, Federal University of Agriculture, Umudike PMB 7267, Umuahia — Abia State, Nigeria

* Corresponding author, e-mail: [email protected]

Received 24 July 2001, accepted in revised form 19 October 2001

Three species of Boerhavia from southern Nigeria have been screened phytochemically. The presence of tannins and saponins are being reported for the first time in B. coccinea and B. erecta whereas the report of these substances in B. diffusa corroborates previous reports. The nature of calcium oxalate crystals in the roots and stems of B. diffusa and B. erecta could be utilised for the characterisation of these plants. The oxalate crystals were present around the regions of the cortex of the stem but were localised almost in every tissue of the root. Tannins and saponins were isolated from the tissues (leaves, stems and roots) of these plants hence the significance of these findings remains an area of further investigations as far as the chemical constituents of these plants are concerned.

South African Journal of Botany 2002, 68: 389–392

Short Communication

Mycelial compatibility groups of Sclerotium rolfsii in South Africa

AJ Cilliers^1*, ZA Pretorius² and PS van Wyk¹

¹ Agricultural Research Council, Private Bag X1251, Potchefstroom 2520, South Africa

² Department of Plant Pathology, University of the Free State, PO Box 339, Bloemfontein 9300, South Africa

* Corresponding author, e-mail: [email protected]

Received 27 August 2001, accepted in revised form 22 October 2001

Sclerotium rolfsii, the causal organism of stem rot or southern blight of groundnut, is widely distributed and has been reported to cause disease in over 500 plant species throughout the world and at least 30 in South Africa. The disease is a problem in most groundnut producing areas in South Africa and no efficient control strategy has yet been developed in this country. Previous studies on the fungus have indicated that diversity within populations of S. rolfsii can be defined by placing isolates into mycelial compatibility groups (MCGs). A total of 121 S. rolfsii isolates were collected from 15 localities and seven plant species throughout South Africa and paired against each other. Thirteen MCGs were identified, some containing isolates from the same host plant or geographic area, suggesting a possible relationship between MCG and host plant or locality. Other MCGs, however, contained isolates from a variety of hosts from various localities. The population of the fungus in South Africa is diverse, with vague associations between MCG, host and geographical distribution.

South African Journal of Botany 2002, 68: 393–396

Short Communication

Disruptive effects of exogenous proline on chloroplast and mitochondrial ultrastructure in Arabidopsis leaves

PD Hare, WA Cress and J van Staden*

Research Centre for Plant Growth and Development, School of Botany and Zoology, University of Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa

* Corresponding author, e-mail: [email protected]

Received 11 September 2001, accepted in revised form 24 December 2001

A dose-dependent damage to chloroplastic and mitochondrial ultrastructure was observed in 21-day-old Arabidopsis thaliana seedlings grown in the presence of millimolar concentrations of exogenous proline. These findings draw into question the widely accepted, although poorly investigated, hypothesis that proline is an inert compatible solute that can be accumulated to high levels with minimal effects on cellular function. The destructive effects of proline on chloroplast ultrastructure may result from feedback inhibition of proline synthesis which causes over-reduction of the photosynthetic electron acceptor pools. Since proline degradation occurs in mitochondria, damage to cristae in plants grown on exogenous proline is proposed to result from elevated rates of mitochondrial electron transport. The resultant increase in levels of reactive oxygen intermediates in these organelles could account for the loss of chloroplast and mitochondrial integrity in plants exposed to exogenous proline.

South African Journal of Botany 2002, 68: 397–400

Short Communication

The first record of Agave celsii var. albicans (Agavaceae), a Mexican plant, in South Africa

GF Smith* and EMA Steyn

Office of the Director: Research and Scientific Services, National Botanical Institute, Private Bag X101, Pretoria 0001, South Africa

* Corresponding author, e-mail: [email protected]

Received 13 September 2001, accepted in revised form 22 January 2002

Agave celsii var. albicans is native to the arid Hidalgo province, Mexico. It is hereby reported from South Africa for the first time. This alien taxon is increasingly being cultivated in the southwestern Cape where it has the potential of becoming part of the naturalised alien flora. In this report the plants are described and illustrated for easy identification.

South African Journal of Botany 2002, 68: 401–403

Short Communication

Pollinium structure in Epistemma: Periplocoideae (Apocynaceae)

RL Verhoeven* and HJT Venter

Department of Plant Sciences, University of the Free State, PO Box 339, Bloemfontein 9300, South Africa

* Corresponding author, e-mail: [email protected]

Received 23 November 2001, accepted in revised form 6 March 2002

The pollinium in Epistemma rupestre H. Huber, an epiphyte from Africa, is described for the first time. The pollinium consists of loosely aggregated pollen-tetrads without any special wall.

South African Journal of Botany 2002, 68: 404–407

Short Communication

Soluble sugars in light-sensitive Grand Rapids lettuce seeds treated with red light, gibberellic acid and a plant-derived smoke extract

AK Jäger and J van Staden*

Research Centre for Plant Growth and Development, School of Botany and Zoology, University of Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa

* Corresponding author, e-mail: [email protected]

Received 20 December 2001, accepted in revised form 16 April 2002

The escape time for far-red light reversal of red light induced germination of light-sensitive Grand Rapids lettuce seeds was determined to be 5h. Levels of soluble sugars were determined during the first 8h of imbibition in seeds treated with red light, gibberellic acid and an aqueous smoke extract all of which stimulate germination of the photoblastic achenes in the dark. Sucrose was the main reserve sugar in the dry seeds; glucose, fructose and rhamnose were also detected. An increase in sucrose was detected 2h after the start of imbibition, lasting 13h. This increase occurred in all treatments, including dark-imbibed control seeds. This suggests that breaking of dormancy is not totally dependent on utilisation of soluble sugars.

South African Journal of Botany 2002, 68: 408–410

Short Communication

The use of plants in traditional medicine: potential genotoxic risks

EE Elgorashi^1,2,3, JLS Taylor^1,2,3, A Maes¹, N de Kimpe²*, J van Staden³ and L Verschaeve¹*

¹ Division ofEnvironmental Toxicology, Flemish Institute for Technological Research (VITO), Boeretang 200, B-2400 Mol, Belgium

² Department of Organic Chemistry, Faculty of Agricultural and Applied Biological Sciences, Ghent University, B-9000 Gent, Belgium

³ Research Centre for Plant Growth and Development, University of Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa

* Corresponding authors, e-mail: [email protected], [email protected]

Received 20 December 2001, accepted in revised form 1 May 2002

Dichloromethane and 90% methanol extracts of different parts of Antidesma venosum, Balanites maughamii, Chaetacme aristata, Croton sylvaticus, Gardenia volkensii, Plumbago auriculata and Spirostachys africana which are commonly used in South African traditional medicine were evaluated for their mutagenic potential. The genotoxicity tests used were the Ames test, micronucleus test, comet assay and VITOTOX^_ test. All species showed mutagenicity or DNA damage in at least one test. The species, organ extracted, extraction solvent and the type of test used, (whether based on bacterial or human cells), could affect the induction of genotoxicity.

South African Journal of Botany 2002, 68: 411–413

Short Communication

Screening of Cenchrus ciliaris L. for biological activity

ME Light, LJ McGaw, SG Sparg, AK Jäger and J van Staden*

Research Centre for Plant Growth and Development, School of Botany and Zoology, University of Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa

* Corresponding author, e-mail: [email protected]

Received 25 February 2002, accepted in revised form 3 May 2002

Cenchrus ciliaris L. (Poaceae) is a commonly occurring perennial grass in South Africa. The underground runners are used in Zulu traditional medicine for ailments including `body pain', menstrual disorders and urinary infections. Water, ethanol and ethyl acetate extracts were prepared from the underground and leaf material of C. ciliaris plants. The extracts were screened for anti-inflammatory activity, antibacterial, anthelmintic and antischistosomial activity. Anti-inflammatory activity was confirmed as shown by the inhibition of prostaglandin synthesis by the ethanol and ethyl acetate extracts in both COX-1 and COX-2 assays. Some antibacterial activity was observed against the Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) at minimal inhibitory concentrations ranging from 0.20–0.78mgml^-1, and against the Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae) at minimal concentrations ranging from 3.13–6.25mgml^-1 for the ethanol and ethyl acetate extracts. Low levels of anthelmintic activity were observed against the test organism Caenorhabditis elegans. No activity was detected in the antischistosomial assay. These results provide evidence for the moderate biological activity of this plant, and could substantiate the use of C. ciliaris in traditional medicine.

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African Journals OnLine South African Journal of Botany

VOLUME 68 ISSUE 3 (2002) Abstracts

African Journals OnLine
South African Journal of Botany

VOLUME 68 ISSUE 3 (2002)
Abstracts