Navorsing op die gebied van die sosiale wetenskappe*

In Hollands is die woord scientia vertaal met wetenskap, wat sowel die natuur- as die geesteswetenskappe insluit, waardeur die woordsy oorspronklike betekenis behou. Die neiging bestaan om die Engels science met wetenskap in Afrikaans te vertaal, waarmee dan eintlik die natuurwetenskap bedoel word

Suid-Afrika se dilemma: Uitdagings en geleenthede*)

U ontvang vanaand almal sertifikate wat as bewys sal dien dat u ’n graad verwcrf het na volgehoue studie van minstens drie jaar. U moes baie toetse en ’n hele aan- tal eksamens slaag. Hierdie eksamens en evalueringstoetse is telkens gestel om u kennis te meet, naamlik die kennis wat u veronderstel was om van die bepaalde vak te verwerf het. En u het finaal gestaag: u het daardie veronderstelde kennis, inderdaad verwerf. Nou kom die groot vraag, seker die allerbelangrikste vraag wat ek vanaand aan u kan stel: wat gaan u met die verworwe kennis maak? Inderdaad ja, u het na die Universiteit gekom om u voor te berei vir die lewe. U wil as u hiervandaan vertrek (om dit nou maar gewoonweg te stel) toeberei wees om “ ’n lewe te gaan maak” , vir uself ’n lewe te gaan verdien. Is ek reg, of wil u, as u hiervandaan vertrek, die kennis wat u verwerf het gaan aanwend in diens van andere, d.w.s. van u naaste, die volk van wie u lid is, die land waarin u woon en wat ons almal liefhet

Waarom universiteitsopleiding?

Wanneer ons die vraag „Waarom universiteitsopleiding?” stel en ’n antwoord daarop wil vind, kan die vraag uit vele gesigspunte benader word. Die doel en taak van die universiteit kan byvoorbeeld die tema van die antwoord wees en die klem kan op die vormingstaak van die universiteit geplaas word. Daar kan aangetoon word dat dit die taak van die universiteit is om die student tot volwaardige volwassenheid te voer; dat die leiers van móre die studente van vandag is en dat dit van besondere belang is dat die universiteit sal meehelp om die student as religieus-sedelike persoonlikheid te vorm deur die skepping van gunstige toestande daartoe

Skeppende denke of vermoë

Ons leef in ’n tyd van ongeëwenaarde ontwikkeling en spesialisasie. A1 m eer w ord van deskundiges op verskillende terreine gebruik gemaak om die toekom s op haas elke fase van die lewe te beplan. So sterk is die behoefte aan beplanning dat in die R.S.A. onlangs ’n D epartem ent van Beplanning ingestel is

Possible role of fungi in negatively affecting fruit-set in avocados

Poor fruit set continues to be a major problem in the avocado industry in South Africa. In the past this was estimated to have caused a loss of income of millions of rands. In this investigation the role of fungi on the pistils of avocado cultivars after pollination was examined. Pollinated pistils of avocado cultivars ‘Pinkerton’, ‘Ryan’, ‘Hass’, ‘Fuerte’ and ‘Nabal’ were removed twenty-four hours after the first anthesis (female stage), for detection and isolation of fungi. Germinating conidia were seen on the surface of stigma adjacent to the germinated pollen grains. A number of dematiaceous fungi were isolated from the pistils and the most important species were identified.When a drop of the spore suspension of the most frequently isolated fungi was inoculated on the stigmas of emasculated flowers after hand pollination, a high rate of abscission was observed. Thus some of these fungi appear to have played a significant role which resulted in greater abscission of flowers

A note on auxotelic cones and basitonic branching in Encephalartos

A male cone of Encephalartos longifolius (Jacq.) Lehm. with four normal euphylls at its apex was found on a plant in a Pretoria garden. This phenomenon is discussed in relation to branching patterns in cycads

Seed development of Ornithogalum dubium, with special reference to fertilization and the egg apparatus

The ovule of Ornithogalum dubium is anatropic, bitegmic and crassinucellate. The integuments are biseriate. Starch grains occur in the outer integument, the funicule and in the intercellular space surrounding the embryo-sac. The embryo-sac development is of the Polygonum type. The synergids are conspicuous and contain a large filiform apparatus. Fertilization is porogamic and occurs 24h after pollination. The pollen tube enters the egg apparatus in the region of an intercellular space between the micropylar ends of the synergids. Sperm cells in the pollen tube appear to be released through small protuberances of the pollen tube. Migration of the sperm cell to the egg cell is possibly through a gap in the wall between the egg cell and the receptive synergid. Changes in the synergids occur only after a pollen tube has entered the receptive synergid. Changes occurring in the persistent synergid suggest that this cell may be involved in the nutrition of the pro-embryo up to the eight-cell pro-embryo stage. Syngamy is of the post-mitotic type. The first division of the zygote is transverse. The basal cell gives rise to the multicellular suspensor, and the terminal cell to the embryo. The endosperm is of the Helobial type

Comparative immune-profiling of three cattle breeds infested with Rhipicephalus microplus and Ixodes ricinus-infested BALB/c mice

Ticks and tick-borne diseases have a negative impact on the quality and quantity of livestockderived products. As such, effective control strategies against these parasites are needed. Currently, acaricides are the most widely used control mechanism against ticks but due to the increase in resistance to these chemicals, new control strategies, like vaccination, need to be developed and improved. In cattle, increasing the understanding of the basic underlying variation in immunological responses to tick infestation may constitute the basis of improved tick control strategies in the future. While the identification of protective antigens is essential, the final formulation of vaccines is pivotal in the efficacy of a future vaccine. As such, increasing the understanding of the basic underlying variation in immunological responses to tick infestation may constitute the basis of improved tick control strategies in the future. Chapter 2 describes the differential regulation of T and B-lymphocyte subsets in the skin and lymph nodes amongst three cattle breeds as potential mediators of immune-resistance to Rhipicephalus microplus tick. This study has been the first to describe in detail the in vivo immune responses in lymph nodes of cattle following Rhipicephalus microplus infestation, attachment and continued feeding. To further compliment this study, Chapter 3 provides a temporal analysis of the bovine lymph node transcriptome during cattle tick (Rhipicephalus microplus) infestation. Here a detailed description on the specific transcriptional processes in the lymph nodes of Bonsmara cattle is given. These processes include: (1) Leukocyte recruitment to the lymph node via chemokines and chemotaxis, (2) Trans-endothelial and intranodal movement on the reticular network, (3) Active regulation of cellular transcription and translation in the lymph node (including leukocyte associated cellular regulatory networks) and (4) Chemokine receptors regulating the movement of cells out of the lymph node. In addition to studying the immune response in cattle, the viability of a mouse model was used for basic immune profiling during tick feeding and vaccination in Chapter 4. Here an in vivo evaluation of Ixodes ricinus induced effects on T and B-cell maturation in the spleen and lymph nodes of BALB/c mice is given.Thesis (PhD)--University of Pretoria, 2018.GeneticsPhDUnrestricte

Ultrastructure of the stigma and style of Mangifera indica L.

The stigma of Mangifera indica L. is non-papillate and wet, with the style semi-solid. The exudate of the stigma and style is of the mixed type and is transported from vesicles in the secretory cells, via plasmatubules, to the surrounding cell walls. Cell walls of the transmitting tissue of the stigma and style are bilayered. The outer wall layer is typically reticulate and the exudate accumulates between the loosely woven wall fibrils. At the base of the style a specialized obturator, the ponticulus, facilitates the direct passage of the growing pollen tubes towards the embryo sac

The structure of the seed of Mangifera indica L. and notes on seed characters of the tribe Mangifereae (Anacardiaceae)

The anatropous, unitegmic and pachychalazal mango ovule develops into the campylotropous, pachychalazal seed. The undifferentiated seed coat is of dual origin, developing from the integument as well as from the pachychalaza. The term ‘peritesta’ is suggested for the peripheral, band-like integumentary part of the seed coat. The major saddle-shaped chalazal part is associated with a tanniniferous hypostase. The discussion includes the anatomy and histochemistry of the seed. The pachychalazal seed with undifferentiated seed coat probably characterizes the tribe Mangifereae. After consideration inter alia of seed characters, it is concluded that, according to generally accepted criteria, the Anacardiaceae is phylogenetically one of the more advanced forest families