landscape and biotic controls on soil respiration in a semiarid savanna

Characterisation of the heat stable proteome of thedesiccation tolerant form of the resurrection fernMohria caffrorum

A.T. Gill, J.M. Farrant, M.S. RafudeenDepartment of Molecular and Cell Biology, University of CapeTown, Private Bag X3, Rondebosch 7701, South Africa

Desiccation tolerant plants have the capacity to lose most oftheir cellular water (more than 95%), equilibrate their internalwater potential with that of the surrounding dry air, and thenresume normal metabolic function after rehydration (Gaff,1971). There is limited information on mechanisms of veg-etative desiccation tolerance in pteridophytes, but a recent studyon the resurrection fern Mohria caffrorum has shown that thisspecies is desiccation tolerant and desiccation sensitive in thedry and rainy seasons respectively (Farrant et al., 2008). Pre-liminary one dimensional sodium dodecyl sulphate - poly-acrylamide gel electrophoresis (1-D SDS PAGE) showed thatthe desiccation tolerant form produced several new heat stableproteins, which were not present in the sensitive form, upondehydration. The current study was undertaken to further char-acterise the heat stable proteome of this species by use of 2-DPAGE in order to identify proteins that might play a protectiverole against water deficit stress. Preliminary results indicate thatat least 4 new proteins were made and 33 are up-regulated inresponse to drying in the desiccation tolerant variant of this fern.These are being analysed using Bio-Rad PDQuest analysissoftware and sequenced using MALDI TOF MS. This data willbe presented.

doi:10.1016/j.sajb.2009.02.143

Molecular and morphological studies reveal new subspecieswithin southernAfricanPachycarpusE.Mey. (Apocynaceae:Asclepiadoideae)

M. Glen, A. Nicholas, J. Lamb, A. ShuttleworthSchool of Biological and Conservation Sciences, University ofKwaZulu-Natal, PO Box 1781, Forest Hills 3624, South Africa

Recent specimens of Pachycarpus collected at Highflats(South Africa, KwaZulu-Natal) suggest that these populationsmay have arisen due to hybridisation between P. asperifoliusand P. scaber. In order to test this hypothesis and at the sametime propose a rational classification for the Highflats' popu-lations it was decided to do an extensive morphological in-vestigation complimented by and integrated with gene sequencestudies; using the nuclear ribosomal ITS region. Molecular dataunfortunately remains equivocal on the exact evolutionaryrelationships and distinctness of the Highflats' populations;however, morphological studies confirm the hybrid status of thistaxon and suggest that it should be described as a new subspeciesof P. scaber, viz. subsp. acidostelma. In the process of thisinvestigation, it was observed that there were some major

morphological differences between the northern and southernpopulations of P. asperifolius. It was found that, although themolecular data was largely unresolved, there was a substantialgenetic difference (0.37%) within the ITS region betweennorthern and southern populations of P. asperifolius. Thus it wasdecided that the northern populations of P. asperifoliusbe recognized as a distinct subspecies, viz. subsp. validus(resurrecting an older specific name for this taxon).

doi:10.1016/j.sajb.2009.02.144

Carbon accumulation, competition and capillaroid roots:The role of the restiad species Empodisma minus in NewZealand mire development

T.A. Hodgesa, G.L. Rapsona, L. Schipperb, B. ClarksoncaEcology Group, Institute of Natural Resources, MasseyUniversity, Palmerston North, New ZealandbEarth and Ocean Sciences Department, University of Waikato,Hamilton, New ZealandcLandcare Research, Hamilton, New Zealand

Van Breeman (1995) reviewed how Sphagnum, as an eco-system engineer of northern hemisphere mires, creates anacidic, nutrient poor and slowly permeable peat due to specificmorphological, physiological and organo-chemical properties.This process can change the ecology of fens (high-nutrient, wetmires) so that they become bogs (low nutrient mires with driersurfaces), the so-called fen-bog transition. Peat accumulation inmires results in increasing reliance upon nutrient release fromdecomposing litter and ombrotrophic inputs. Species best ableto compete in this low nutrient environment possess morpho-logical adaptations to increase nutrient capture, or traits whichminimise nutrient losses (low tissue nutrient levels, high leaflongevity and high nutrient resorption prior to abscission).Observations and experimental studies in both the glasshouseand field support the construction of an Ecosystem Engineeringmodel similar to that proposed for Sphagnum for the dev-elopment of Empodisma minus (Restionaceae) dominated miresin New Zealand.

doi:10.1016/j.sajb.2009.02.145

Landscape and biotic controls on soil respiration in asemiarid savanna

S.M. Jacobsa, K.B. Mantlanab, R.J. NaimancaDepartment of Conservation Ecology and Entomology,Stellenbosch University, Private Bag X1, Matieland 7602,South AfricabClimate Change and Bio-adaptation Division, South AfricanNational Biodiversity Institute, Kirstenbosch Research Centre,Private Bag X7, Claremont 7735, Cape Town, South Africa

433SAAB Annual Meeting Abstracts

cSchool of Aquatic and Fishery Sciences, University ofWashington, Box 355020, Seattle WA 98195, United States

Soil respiration is an important process that contributessignificant amounts of carbon to global atmospheric carbonstocks and carbon cycling; however, little is known about thefactors that control soil respiration in semiarid savanna such asfound in many parts of Sub-Saharan Africa. We investigated therate of soil respiration and the abiotic and biotic factorscontrolling this process in a granitic savanna in Kruger NationalPark, South Africa. We found catenal processes, more preciselysoil moisture, to be more closely related to the rate of soilrespiration than changes in plant cover due to herbivoreactivities. Riparian zones, consistently wetter than elsewherein the catena, showed higher soil respiration rates than uplandareas, both in the wet and dry season. During the wet season wealso found significantly higher soil respiration rates in theuplands in areas beneath the canopy of trees compared to openareas, again due to elevated soil moisture levels. We concludethat soil moisture, rather than soil temperature is the strongercontrol on soil respiration in this semiarid savanna, and thatbecause of this riparian zones make an outsize contribution tosoil CO2 emissions.

doi:10.1016/j.sajb.2009.02.146

Leaf micromorphology and anatomy of Cryptolepis(Apocynaceae, Periplocoideae) in southern Africa

L. Joubert, R.L. VerhoevenDepartment of Plant Sciences, University of the Free State, POBox 339, Bloemfontein 9300, South Africa

The genus Cryptolepis R.Br. consists of 31 species and iswidespread throughout Africa, the island Socotra, India, southernChina, Malaysia and Ceylon. In southern Africa six Cryptolepisspecies occur as slender, woody climbers or low growing shrubs.Five of the six species inhabit sub-tropical forests or savannah,and only one species is found in the semi-desert regions towardsthe west of southern Africa. Floral characteristics are generally oflittle taxonomic value in the genus since variation among thedifferent species is small. Consequently vegetative characteristicsare most often used for species identification. The aim of thepresent investigation was to identify diagnostic characteristics ofthe leaf anatomy and epidermal surface of the six southernAfricanCryptolepis species. The results show that a combination of thesecharacteristics is effective for distinguishing all the Cryptolepisspecies in southern Africa. Diagnostic characteristics of leafanatomy and micromorphology include the isobilateral or dor-siventral arrangement of the parenchyma, amphistomatic or hy-postomatic arrangement of the stomata and the occurrence of waxplatelets, striations and papillae on the epidermal surface.

doi:10.1016/j.sajb.2009.02.147

Antifungal activity of Psychotria capensis leaf extracts

L. Kafuaa, Q. Kritzingera, A. HusseinbaDepartment of Plant Science, University of Pretoria, Pretoria0002, South AfricabChemistry of Medicinal Plants Department, National Re-search Centre, Dokki, Cairo, Egypt

Cowpea (Vigna unguiculata) is an indigenous Africanlegume crop of nutritional importance for many small-scalefarmers and rural communities in sub-Saharan Africa. However,these seeds, as with other grain and legume crops, are sus-ceptible to fungal infection under sub-optimum storage con-ditions. Some fungi, including Aspergillus and Fusarium spp.,produce mycotoxins which can adversely affect the health ofanimals and humans if ingested. The control of these fungi withbiological extracts is currently attracting a great deal of atten-tion. Psychotria capensis (Rubiaceae) is an evergreen shrub,which has been used for gastric complaints. Other Psychotriaspecies are known for their antimalaria, anti-emetic andantimicrobial activity. The aim of this study was to investigatethe antifungal activity of P. capensis leaf extracts againstfumonisin producing Fusarium species and to isolate potentialactive compounds. The antifungal activity of 16 major fractionswas conducted by a direct bioassay on TLC plates. The plateswere developed with dichloromethane and methanol (20:2) andthereafter sprayed with spore suspensions of F. proliferatumand F. verticillioides. From the 16 major fractions tested, twofractions showed activity and three pure compounds were iso-lated. Two of the compounds have been identified as β-sitosteroland a carotenoid derivative. These compounds will be tested theirfor antifungal activity.

doi:10.1016/j.sajb.2009.02.148

Vegetation classification of the proposed Heritage Park,North-West Province, South Africa

M. la Grange, K. Kellner, S.S. Cilliers, A.R. GötzeSchool of Environmental Sciences and Development, North-West University, Private Bag X6001, Potchefstroom 2520, SouthAfrica

The proposed Heritage Park will link the Pilansberg NationalPark and the Madikwe Game Reserve with a corridor ofapproximately 170 000 ha. Currently this area is bordered by 38rural villages and is used by these communities for livestockgrazing and crop production. High poverty levels exist and anyform of socio-economic development will increase the liveli-hoods of the rural communities. Due to the tourism demand, thechallenge is to create a conservation area for eco-tourism, whichcould lead to better job opportunities. The area is also known forits archaeological importance. For effective development andmanagement, scientific studies need to be conducted. Thisproject, which focuses on vegetation classification, forms the

434 SAAB Annual Meeting Abstracts