Thesis (Ph.D.) --Murdoch University, 2004. / Thesis submitted to the Division of Science and Engineering. Includes bibliographical references (leaves 171-185).

Thesis (PhD(Agric))--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Little is understood regarding flowering in the genus Protea. The information available on inflorescence initiation and development in the family Proteaceae was reviewed and discussed. A number of experiments were conducted to investigate inflorescence initiation and development, and their manipulation for commercial production, in selected Protea cultivars, in the Western Cape, South Africa (33°S, Protea species can be allocated into groups according to similar times of flower initiation and of harvest. The stages occurring during flower initiation, and their synchrony relative to shoot growth were investigated for three cultivars, viz. Protea cv. Carnival (P. compacta x P. neriifolia), Protea cv. Lady Di (P. compacta x P. magnifica) and Protea cv. Sylvia (P. eximia x P. susannae), when flower initiation occurred on the spring growth flush. For all three cultivars the spring flush was preformed and enclosed in the apical bud before spring budbreak. During elongation of the spring flush the apical meristem produced floral primordia which differentiated into involucral bracts. After completion of the spring flush meristematic activity continued, to produce floral bracts with florets in their axils. The three cultivars showed differences and similarities in the time of budbreak, and the rates of shoot growth, appendage formation and flower development. The presence of mature leaves on an over-wintering shoot is essential for inflorescence initiation on the spring growth flush of 'Carnival'. Inflorescence initiation in 'Carnival' started at spring budbreak, and production of involucral bracts occurred concurrently with spring flush elongation. Shoots were defoliated at different degrees of severity at intervals from pre- to post- spring budbreak. Total defoliation applied earlier than 6-7 weeks before spring budbreak prevented flowering. Defoliation closer to spring budbreak affected characteristics of the spring flush and the inflorescence subtended by the spring flush. Effects were most marked following total defoliation and diminished with less severe treatments imposed by partial defoliation. Total defoliation applied before spring budbreak resulted in slower inflorescence development and lead to later anthesis. Defoliation treatments applied after completion of spring flush elongation had no effect on either vegetative or reproductive spring growth. The requirement for mature overwintering leaves to effect inflorescence initiation in 'Carnival' suggests that environmental factors, such as low temperature and daylength may play an inductive role. Shoots were in the induced state and committed to flowering 6-7 weeks before spring budbreak. A change in source size and position subsequent to different severalties of defoliation in 'Carnival' lead to reduced dry mass accumulation and altered partitioning. Mature leaves on the overwintering shoot supported growth of the spring flush and the early stages of inflorescence development. When these leaves were removed by total defoliation dry mass accumulation in the spring flush was reduced. A hierarchy of priorities between competing sinks was revealed by defoliation during growth of the spring flush and concomitant inflorescence development: formation of involucral bracts> leaf growth> stem elongation. Dry mass accumulation of the inflorescence subtended by the spring flush was supported by the spring flush leaves and was only indirectly affected by defoliation. Treatments which resulted in the production of a weaker spring flush lead to a reduction in dry mass accumulation of the inflorescence. Different severalties of partial defoliation, whereby either upper or lower leaves were removed from a shoot, indicated that the position of leaves relative to the active sink is more important, with respect to source availability, than the number of leaves on the shoot. Mature overwintering leaves are essential in 'Lady Di' for shoots to achieve the induced state for flowering; and are also crucial to the early stages of inflorescence initiation. Defoliation applied before formation of involucral bracts was complete prevented flowering. Defoliated shoots either remained vegetative or produced inflorescences which aborted. Reserve carbohydrates in the stem and leaves of overwintering shoots were low, and early growth and development of both the spring flush and inflorescence were, therefore, supported by current photosynthates from the overwintering leaves. Likewise, reserve carbohydrates available in the flowering shoot were insufficient to account for the dry mass increase during the major portion of growth of the spring flush and inflorescence. This rapid increase in dry mass occurred after elongation of the spring flush was complete and was supported by current photosynthates from the leaves of the spring flush. Defoliation treatments that did not prevent inflorescence initiation, had no effect on inflorescence development, and flowering time of 'Lady Di' was not delayed by defoliation. 'Sylvia' has an open window for inflorescence initiation and can initiate flowers throughout the year. Despite the 'open window' inflorescences are initiated more readily on the spring flush, when it is subtended by one or more overwintering shoots. This may be the expression of a facultative response to inductive conditions for which 'Carnival' and 'Lady Di' have an obligate requirement. The date of pruning affected flowering time of 'Sylvia' by influencing on which flush inflorescence initiation occurred, and the harvest could be manipulated to fall within the optimum marketing period for export to Europe. Flowers initiated on the spring flush reach anthesis in January and February; on the first summer flush predominantly in April and May; on the second summer flush in July and August; and on the autumn flush in November and December. Thus, shoots harvested within the optimum marketing period (September to February) initiated inflorescences on the autumn and spring flushes. Due to the readiness of shoots to initiate inflorescences on the spring flush many shoots harvested in January and February (following initiation in the previous spring) were short and were rendered unmarketable. For commercial production pruning in July is recommended. Long flowering stems will be harvested in October to November of the following year. Since the vegetative and reproductive cycles necessary to produce inflorescences on long stems span more than a year, a biennial cropping system is recommended. / AFRIKAANSE OPSOMMING: Bloeiwyse-inisiasie en -ontwikkeling, en die manipulasie daarvan, van geselekteerde cultivars van die genus Protea. Min word verstaan van blomvorming in die genus Protea. Die beskikbare inligting oor die bloeiwyse-inisiasie en -ontwikkeling in die familie Proteaceae is nagegaan en bespreek. 'n Aantal eksperimente is uitgevoer waarin geselekteerde Protea cultivars van die Wes-Kaap, Suid-Afrika (33°S, 19°0) se bloeiwyse-inisiasie en -ontwikkeling, asook die manipulasie daarvan vir kommersiële produksie ondersoek is. Protea spesies kan in groepe ingedeel word op grond van blominisiasietye en oestye wat ooreenstem. Die verskillende stadiums van blominisiasie en hulle sinchronisering relatieftot stingelgroei is ondersoek vir drie kultivars, naamlik Protea cv. Carnival (P. compacta x P. neriifolia), Protea cv. Lady Di (P. compacta x P. magnifica) en Protea cv. Sylvia (P. eximia x P. susannae) tydens blominisiasie op die lentegroeistuwing. By al drie die kultivars was die lentegroeistuwing reeds gevorm en omsluit in die apikale knop voor die lente-knopbreking. Gedurende die verlenging van die lentegroeistuwing het die apikale meristeem blomprimordia, wat in bloeiwyseomwindselskutblare gedifferensieer het, geproduseer. Na voltooiing van die lentegroeistuwing, het meristematiese aktiwiteit voortgeduur en blomskutblare met blommetjies in hulle oksels is gevorm. Die drie kultivars het verskille en ooreenkomste vertoon tydens die periode van knopbreking, asook in die tempo van stingelgroei, aanhangselformasie en blomontwikkeling. Die teenwoordigheid van volwasse blare op 'n oorwinteringstingel is noodsaaklik vit bloeiwyse-inisiasie op die lentegroeistuwing van 'Carnival'. Bloeiwyse-inisiasie in 'Carnival' het met lente-knopbreking begin en die produksie van bloeiwyseomwindselblare het gelyktydig met lentegroeistuwing verlenging plaasgevind. Stingels is met tussenposes, van voor tot na die lente-knopbreking, en met verskillende grade van felheid, ontblaar. Algehele ontblaring vroeër as 6-7 weke voor die lente-knopbreking het blomvorming verhoed. Ontblaring nader aan die lenteknopbreking het 'n invloed gehad op die eienskappe van die lentegroeistuwing asook die bloeiwyse gedra deur die lentegroeistuwing. Die effek was die duidelikste sigbaar by algehele ontblaring en het verminder namate die behandeling minder fel geword het by gedeeltelike ontblaring. Algehele ontblaring wat voor die lente-knopbreking gedoen is, het gelei tot stadiger bloeiwyse-ontwikkeling en later antese. Ontblaringsbehandelings wat na die voltooiing van die lentegroeistuwing verlenging toegepas is, het geen effek op die vegetatiewe of die reproduktiewe lentegroei gehad me. Die nodigheid van volwasse oorwinteringsblare vir bloeiwyse-inisiasie in 'Carnival' dui daarop dat omgewingsfaktore soos lae temperature en daglengte 'n induktiewe rol kan speel. Stingels was in die geïnduseerde toestand en verbind tot blomvorming 6-7 weke voor die lente-knopbreking. 'n Verandering in oorspronggrootte en -posisie as gevolg van verskille in die felheid van ontblaring by 'Carnival', het gelei tot verminderde droë-massa-akkumulasie en veranderde verdeling. Volwasse blare op die oorwinteringstingel het die groei van die lentegroeistuwing en die vroeë stadiums van bloeiwyse-ontwikkeling ondersteun. Toe hierdie blare verwyder is in 'n algehele ontblaring, het die droë-massa-akkumulasie in die lentegroeistuwing verminder. 'n Hiërargie van prioriteite tussen kompeterende sinke is blootgelê tydens ontblaring gedurende die lentegroeistuwing en saamlopende bloeiwyse-ontwikkeling: vorming van bloeiwyse-omwindselblare > blaargroei > stamverlenging. Droë-massa-akkumulasie van die bloeiwyse onderspan deur die lentegroeistuwing is ondersteun deur die blare van die lentegroeistuwing en is slegs op 'n indirekte wyse deur ontblaring geaffekteer. Behandelings wat tot die produksie van 'n swakker lentegroeistuwing gelei het, het tot 'n vermindering in die droë-massaakkumulasie van die bloeiwyse gelei. Verskille in die felheid van gedeeltelike ontblaring, waartydens óf die boonste óf die onderste blare van 'n stingel verwyder is, het aangetoon dat die posisie van die blare relatief tot die aktiewe sink belangriker is, met betrekking tot die beskikbaarheid van die oorsprong, as die aantal blare op die stingel. By 'Lady Di' is volwasse oorwinteringsblare noodsaaklik VIr stingels om die geïnduseerde stadium van blomvorming te bereik en hulle is ook van die uiterste belang in die vroeë stadiums van bloeiwyse-inisiasie. Waar ontblaring gedoen is voordat die vorming van bloeiwyse-omwindsel voltooi was, het blomvorming nie plaasgevind nie. Ontblaarde stingels het ófvegetatief gebly ófbloeiwyses geproduseer wat geaborteer het. Reserwe-koolhidrate in die stam en blare van die oorwinteringstingels was laag en die vroeë groei en ontwikkeling van beide die lentegroeistuwing en die bloeiwyse is dus deur die bestaande fotosintate van die oorwinteringsblare onderhou. Net so was die reserwe-koolhidrate beskikbaar in die blomdraende stingels nie voldoende om die toename in droë massa gedurende die grootste deel van die groei van die lentegroeistuwing en die bloeiwyse te verklaar nie. Hierdie vinnige toename in droë massa het plaasgevind nadat die verlenging van die lentegroeistuwing voltooi was en is deur die bestaande fotosintate van die blare van die lentegroeistuwing onderhou. Ontblaringsbehandelings wat nie bloeiwyse-inisiasie verhoed het nie, het geen effek op bloeiwyse-ontwikkeling gehad nie en die blomtyd van 'Lady Di' is nie deur ontblaring vertraag nie. 'Sylvia' beskik oor 'n oop venster vir bloeiwyse-inisiasie en kan regdeur die jaar blomme inisieer. Ten spyte van die 'oop venster', word bloeiwyses tog meer geredelik in die lentegroeistuwing geïnisieer, wanneer dit deur een of meer van die oorwinteringstingels gedra word. Dit mag die uitdrukking wees van 'n fakultatiewe respons op induktiewe toestande wat vir 'Carnival' en 'Lady Di' 'n verpligte vereiste is. 'Sylvia' se blomtyd is deur die snoeidatum geaffekteer omdat die snoeidatum 'n invloed gehad het op die keuse van by watter groeistuwing bloeiwyse-inisiasie plaasgevind het. Die oestyd kon gemanipuleer word om binne die optimum bemarkingstydperk vir uitvoer na Europa te val. Blomme wat op die lentegroeistuwing geïnisieer is, bereik antese in Januarie en Februarie; dié wat op die eerste somergroeistuwing geïnisieer is, bereik antese hoofsaaklik in April en Mei; dié wat op die tweede somergroeistuwing geïnisieer is, bereik antese in Julie en Augustus en dié wat op die herfsgroeistuwing geïnisieer is, bereik antese in November en Desember. Stingels wat in die optimum bemarkingsperiode (September tot Februarie) geoes is, het dus bloeiwyses op die herfs- en lente-groeistuwings geïnisieer. As gevolg van die gereedheid van stingels om bloeiwyses op die lentegroeistuwings te inisieer, was baie van die stingels wat in Januarie en Februarie geoes is, kort en kon nie bemark word nie. Vir kommersiële doeleindes word snoei in Julie aanbeveel. Lang blomdraende stingels sal in Oktober en November van die volgende jaar geoes word. Aangesien die vegetatiewe en reproduktiewe siklusse wat nodig is om bloeiwyses met lang stingels te produseer oor meer as fn jaar strek, word fn tweejaarlikse oesinsamelingstelsel aanbeveel.

Ph.D. (Botany) / Please refer to full text to view abstract

Phytophthora cinnamomi Rands is a common and devastating pathogen of cultivated proteas worldwide. Webb (1997) described a Sudden Death plant disease of proteas in Western Australia (WA) protea plantations. Proteas that suffer the syndrome display symptoms such as stunted growth, wilting, chlorosis and often death. In the current study, a number of protea plantations in the southwest of WA were visited to quantify the extent that P. cinnamomi was attributing to deaths of cultivated proteas. The survey indicated that P. cinnamomi is the major cause of Sudden Death in proteas. A range of other fungi (Fusarium, Botryosphaeria, Pestalotiopsis, Alternaria) and pests (nematodes, mealy bug, scale insects) were also identified to be contributing to protea death and decline in WA plantations. In many cases the factors contributing to protea disease appeared complex, with a range of physical factors or nutritional imbalances commonly associated with these pathogens and pests. As P. cinnamomi was the major cause of death of cultivated proteas the remainder of the experiments described in this dissertation investigated its control in horticultural plantings. Biofumigation has the potential to become an important technique in an overall integrated management approach to P. cinnamomi. In this thesis, biofumigation refers to the suppression of pathogens and pests by the incorporation of Brassica plants into the soil. Two biofumigants (Brassica juncea (L.) Czern., B. napus L.) were screened for their effect on the in vitro growth of five common Phytophthora species (P. cinnamomi, P. cactorum (Lebert & Colin) Schroeter., P. citricola Sawada, P. cryptogea Pethyb. & Laff. and P. megasperma Drechsler). Growth was determined by the measuring dry weight and radial growth of vegetative hyphae. B. juncea was found to be superior in its suppressive effect compared to B. napus. There was also significant variation in the sensitivity of the Phytophthora species to the suppressive effects of the biofumigants. P. cinnamomi was the most sensitive of the five species investigated. Where the rates of the biofumigant were sufficient to suppress growth of Phytophthora, the suppressive effect was mostly fungicidal. To determine how B. juncea and B. napus affect the infective ability and survival of P. cinnamomi, their effects on sporangia and chlamydospores production in soil was investigated in vitro. P. cinnamomi colonised Miracloth discs were added to soil amended with the two Brassica species, before being removed every two days over an eight day period for the determination of sporangia production, chlamydospore production and infective ability. Only the soils amended with B. juncea significantly reduced sporangia production in P. cinnamomi. Both Brassica species increased the percentage of aborted or immature sporangia and reduced the infective ability of the pathogen. Neither Brassica species had any effect on zoospore release or chlamydospore production in P. cinnamomi. Soil cores and soil leachate were collected from biofumigant-amended field soils to determine the inoculum potential and infective ability of the pathogen under glasshouse conditions. Amending the soil with both Brassica species had an immediate suppressive effect on the inoculum potential and infective ability of the P. cinnamomi. However, after this initial suppression there was a gradual increase in the recovery of the pathogen over the monitoring period of four weeks. To determine if the suppression would result in decreased disease incidence in a susceptible host, Lupinus angustifolius L. seeds were planted in the biofumigant amended soil. B. juncea amended soils reduced the disease incidence of P. cinnamomi by 25%. B. napus had no effect on disease incidence in L. angustifolius. Although the current study had demonstrated that biofumigants could suppress the growth, sporulation and infection of P. cinnamomi, it was unclear if this would equate to a reduction in disease incidence when applied in the field. A field trial was conducted on a protea plantation in the southwest of Western Australia that compared biofumigation with B. juncea to chemical fumigation (metham sodium) and soil solarisation. The three soil treatments were used in an integrated management approach to control P. cinnamomi that included the use of a hardwood compost, mulch and water sterilisation. All treatments were monitored during their application to ensure the treatments were conducted successfully. The three soil treatments significantly reduced the recovery of the pathogen and the infective ability of the pathogen to a soil depth of 20 cm. Metham sodium was the most suppressive soil treatment and soil solarisation was the least suppressive treatment. Only the metham sodium treatment resulted in a significant reduction in the incidence of root rot in Leucadendron salignum P.J. Bergius x laureolum (Lam.) Fourc (c.v. Safari Sunset) over the monitoring period of three years. Another field trial was conducted on the same protea plantation to compare the effectiveness of B. juncea and B. napus, without the use of other control strategies, to reduce the incidence of P. cinnamomi infection of Leucadendron Safari Sunset. The concentration of isothiocyanates was monitored for seven days after the incorporation of the biofumigants. Although both Brassica species reduced the recovery and infective ability of the pathogen, neither biofumigant reduced the incidence of root rot in Leucadendron Safari Sunset. In conclusion, P. cinnamomi is the most common and devastating pathogen in WA protea plantations. The current study demonstrated that P. cinnamomi is sensitive to the suppressive nature of biofumigants. Biofumigants can suppress the in vitro growth, sporulation, infective ability of P. cinnamomi and reduce the incidence of the disease caused by the pathogen in the glasshouse. Of the two Brassica species investigated, B. juncea was superior in its ability to control P. cinnamomi compared to B. napus. When applied in the field, biofumigation using B. juncea was found to be more suppressive that soil solarisation, but not as effective as metham sodium.

Thesis (MSc)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The aim of this study was to elucidate the control of flowering in Protea spp. The main factor that makes studying flowering in this diverse genus so challenging is the fact that most Protea spp. and their commercial hybrids have very dissimilar flowering times. The carbon input into floral organ formation and support is expensive as flowers from Protea spp are arranged in a very large ‘flowerhead’ (50 mm by 130 mm for ‘Carnival’) that can take up to two months to develop fully. Therefore the carbon needed for structural formation, metabolic respiration and the sugar-rich nectar production make these structures extremely expensive to form and maintain. Protea is a sclerophyllous, woody perennial shrub with a seasonal flush growth habit. The leathery leaves (source tissue) produce most of the carbon needed for support and growth of the new leaves, roots and flowers (sink tissue). In the case of expensive structures, such as the inflorescences, remobilization from stored reserves, probably from underground storage systems, can be observed for structural development and maintenance. At all times the flush subtending the apical meristem or florally developing bud provides the largest proportion of carbon for support of the heterotrophic structures. Protea apical meristems stay dormant during the winter months, but BA (benzyl adenine, 6-benzylaminopurine) application to the apical meristem of the Protea hybrid ‘Carnival’ has shown to be effective in the release of dormancy and subsequently shift flowering two months earlier than the natural harvesting time. BA is thought to shift source/sink relationships by stimulating the remobilization of carbon to the resting meristem. Although no direct evidence was found for this in our assay, possible reasons for a weak assay are discussed. This study combined physiological research with the use of molecular tools. An homologue of the Arabidopsis thaliana meristem identity gene, LEAFY, was identified in Proteaceae. PROFL (PROTEA FLORICAULA LEAFY) is expressed in both vegetative and reproductive meristems as well as leaves. PROFL expression in leaves may have an inhibitory effect on vegetative growth, as the expression was high at the same time as the expression in the apical meristem increased marking the transition to reproductive growth. In perennial species such as Protea, the availability of carbon is thought to be the main factor controlling floral development. Possible mechanisms of control may be through the direct control of meristem identity genes such as PROFL through sugar signaling. BA did not have a direct effect on PROFL expression although the expression pattern was one month in advance when compared to the natural system. PROFL expression seems to be consistent with that found for other woody perennial species and would therefore be a convenient marker for floral transition. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die inisiëring van blomvorming in Protea spp. te ondersoek. Die verskil in blomtyd tussen Protea spp. en hul kommersieel ontwikkelde hibriede maak die studie van hierdie genus ‘n groot uitdaging. Die groot hoeveelheid koolstof wat benodig word vir blomvorming in Protea is hoofsaaklik as gevolg van die grootte (50 mm by 130 mm vir ‘Carnival’) van die blomkop waarin individuele blomme geranskik is. Hierdie blomkoppe kan tot 2 maande neem om volwassenheid te bereik. Die koolstof benodig vir strukturele ontwikkeling, metaboliese respirasie en produksie van suiker-ryke nektar maak die vorming van hierdie structure ongelooflik duur. Protea is ‘n bladhoudende, houtagtige bos met ‘n seisoenale groeipatroon. Die leeragtige blare voorsien die grootste hoeveelheid koolstof vir die ontwikkelende blare, wortels en blomme. Koolstof vir die ontwikkeling en ondersteuning van die groot stukture soos die blomkoppe word gedeeltelik deur die huidige fotosinfaat voorsien en bewyse vir die remobilisasie van gestoorde koolstof, heel waarskynlik vanaf ondergrondse stukture, is gevind. Die blare van die stemsegment wat die apikale meristeem of ontwikkelende blom dra, voorsien altyd die grootse hoeveelheid koolhidrate aan die ontwikkelende struktuur. Die apikale meristeme van Protea bly dormant gedurende die winter maande, maar applikasie van BA (bensieladenien, 6-bensielaminopurien) aan die apikale meristeme van die Protea hibried ‘Carnival’ verbreek dormansie en die blomtyd van hierdie gemanipuleerde plante is daarom twee maande vroeër as die natuurlike oestyd. Daar word gespekuleer dat BA applikasie aan die apikale meristeem die hoeveelheid koolstof wat na die dormante meristeem gestuur word verhoog wat dan die dormansie verbreek. Hierdie studie beproef ongelukkig hierdie hipotese swak en redes hiervoor word bespreek. In hierdie studie word fisiologiese analises met molekulêre studies gekombineer. ‘n Meristeem identiteits gene wat homologie wys met LEAFY (LFY) in Arabidopsis thaliana (Arabidopsis), PROFL (PROTEA FLORICAULA LEAFY), is in Proteaceae geïdentifiseer. PROFL word uitgedruk in reproduktiewe meristeme so wel as die vegetatiewe meristeme en blare. PROFL uitdrukking in blare mag dalk ‘n inhiberende effek hê op die vorming van nuwe blare, omdat die uitdrukking hoog was op die selfde tyd as wat blominisiëring plaasgevind het in die apikale meristeem. Die transisie tot reproduktiewe groei word gekenmerk deur ‘n verhoging in PROFL uitdrukking in die apikale meristeem. In meerjarige plante soos Protea spp word daar verwag dat die teenwoordigheid van voldoende koolstof die oorskakeling na reproduktiewe groei inisieer. Dit mag wees deur die direkte aksie van suikers met gene soos PROFL wat die finale skakel na reproduktiewe groei beheer. Alhoewel BA applikasie geen direkte effek gehad het op PROFL uitdrukking nie, was die blomtyd met twee maande vervroeg. PROFL uitdrukking was vergelykbaar met die uitdrukking van LFY homoloë in ander houtagtige, meerjarige plante en kan gebruik word as ‘n merker vir blominisiëring in Protea spp.

Dissertation (PhD(Agric))--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: Advancement of the flowering time of Protea cv. Carnival by approximately three months, without compromising the product quality, was achieved by the application of 6- benzyladenine-containing plant growth regulators to three-flush shoots in autumn. This earlier flowering time coincides favourably with the prime European marketing period (November-January). The percentage three-flush shoots initiating an inflorescence following the brush application of the 6-benzyladenine (BA)-containing regulators, ABG- 3062 (active ingredient: BA 2% w/w) and Accel® (active ingredients: BA 1.8% w/w; gibberellins A4A7 0.18% w/w) on dormant terminal buds, increased with later application dates and flowering percentages as high as 90% was achieved. No inflorescences were initiated on flushes induced by Promalin® (active ingredients: BA 1.8% w/w; gibberellins A4A7 1.8% w/w). Phenological phase progression of green point, flush expansion and inflorescence development of 'Carnival' shoots as induced by BA was calculated to have base temperatures of 8°C, 6°C and 1°C respectively. The days required from application of the BA-containing growth regulator until green point stage increased progressively over the six consecutive treatment dates in autumn (14 March - 22 May 2003). In contrast, the days required to complete inflorescence development decreased with each successive treatment date. The days required between the respective stages were mostly negatively correlated with temperature, except for the phase 'green point to flush expansion', where the relationship was unclear. For three-flush shoots of eight-year old plants, between 13-57, 39-65 and 121-177 days were required to reach green point, to achieve full flush expansion following green point and to complete inflorescence after flush expansion respectively. BA application enhanced budbreak in most dormant shoots, irrespective of plant age, BA concentration, decreasing temperature over time or shoot characteristics. However, twoflush shoots treated in late May had low budbreak and hence low flowering percentages. Shoots varied considerably in their responsiveness to BA treatments. BA application (500mg·L-1) as MaxCelTM (active ingredients: BA 1.9% w/w) to terminal buds alone of mature three-flush shoots from less vigorous growing plants resulted in the highest flowering percentages. Applications were most effective when applied to the terminal bud in the dormant state or up to the ‘green point’ stage. Shoot characteristics such as flush length, leaf area, shoot dry mass, number and proximity of the leaves to the terminal bud were all positively correlated with the propensity of shoots to initiate inflorescence under BA induction. Terminal flush intercalation shoot diameter (>7mm) was identified as the most important variable influencing the likeliness of flowering and can effectively serve as a nondestructive estimation of a shoot's propensity to flower. The presence of developing inflorescences or possible floral inhibiting factors derived from the previous flowering season is suggested to be inhibitory to inflorescence initiation following BA application. Synchronisation of shoot growth by pruning plants in late winter appears to be an essential step to ensure high percentages inflorescence initiation with BA treatment the following autumn. The use of BA as a management tool to control flowering times in Protea for better market opportunities is shown to hold considerable commercial potential. / AFRIKAANSE OPSOMMING: Protea cv. Carnival se blomtyd is met ongeveer drie maande vervroeg sonder om produkkwaliteit prys te gee. Hierdie vervroegde blomtyd wat gunstig saam val met die optimale Europese bemarkingstyd van November-Januarie is bewerkstelling deur die herfstoediening van 6-bensieladenien-bevattende plantgroei-reguleerders op lote bestaande uit drie groeistuwings. Die persentasie lote met drie groeistuwings wat 'n bloeiwyse geïniseer het na 'n kwas-aanwending met die 6-bensieladenien (BA)-bevattende groeireguleerders, ABG-3062 (aktiewe bestandeel: BA 2% w/w) en Accel® (aktiewe bestandele: BA 1.8% w/w; gibberellins A4A7 0.18% w/w), het toegeneem met latere behandelingsdatums en blompersentasies so hoog as 90% is behaal. Geen bloeiwyses is geïnisieer op groeistuwings wat deur Promalin® (aktiewe bestandeel: BA 1.8% w/w; gibberellins A4A7 1.8% w/w) teweeggebring is nie. Basis temperature van 8°C, 6°C en 1°C respektiewelik is bereken vir fenologiese fasevordering vanaf groeireguleerder toediening tot by groenpunt, groeistuwing-voltooing en bloeiwyse-ontwikkeling van 'Carnival' lote soos geïnduseer deur BA. Die dae wat benodig was vanaf toediening van die BA-toediening totdat groenpunt stadium bereik is, het progressief toegeneem oor die ses opeenvolgende herfsbehandelingsdatums (14 Maart-22 Mei 2003). In teenstelling met bostaande, het die vereiste aantal dae om bloeiwyseontwikkeling te voltooi afgeneem met elke opeenvolgende behandelingsdatum. Die aantal dae wat benodig was vir die onderskeie fases was meestal negatief gekorreleer met temperatuur, behalwe vir die fase 'groenpunt tot groeistuwing-voltooing', waar die verhouding onduidelik was. Vir lote van agt-jaar-oue plante met drie groeistuwings was tussen 13-57, 39-65 en 121-177 dae respektiewelik benodig om groenpunt te bereik, volledige groeistuwingverlenging te bewerkstellig en om bloeiwyse-ontwikkeling wat volg na groeistuwing verlenging, te voltooi. BA-toediening het knoprusbreking bevorder in die meeste dormante lote, ongeag plant ouderdom, BA konsentrasie, afname in temperatuur met tyd of loot eienskappe. Lote met twee groeistuwings wat laat in die herfs behandel is, het egter lae rusbreking en dus gevolglik ook lae blompersentasies getoon. Lote varieer aansienlik in hul reaksie op BA behandeling. BA toediening (500mg·L-1) as MaxCelTM (active ingredients: BA 1.9% w/w) op die terminale knop van afgeharde lote met drie groeistuwings en afkomstig van minder groeikragtige plante het tot die hoogste blompersentasies gelei. Die effektiwiteit van die behandeling was die hoogste met toedienings aan dormante terminale knoppe tot en met groenpuntstadium. Loot eienskappe soos groeistuwinglengte, blaaroppervlakte, loot droë massa, asook die aantal en nabyheid van die blare relatief tot die terminal knop was almal positief gekorreleerd met die vermoë van die loot om 'n blom te inisisieer in reaksie op BA induksie. Terminale groeiverstuwing interkalasie-lootdikte (>7mm) is geïdentifiseer as die belangrikste veranderlike wat die vermoë om te kan blom kan beïnvloed en kan gebruik word as 'n nie-destruktiewe voorspeller vir blom-inisiasie. Die teenwoordigheid van ontwikkelende bloeiwyses of potensiële blom-inhiberende faktore aanwesig in die loot na die vorige blomperiode, word moontlik beskou om inhiberend te wees vir BA-geïnduseerde blom-inisiasie. Sinchronisering van lootgroei deur die snoei van plante in laat-winter blyk krities te wees om 'n hoë blompersentasie met BA behandeling te verseker in die daaropvolgende herfs. Die aanwending van BA as 'n bestuurstegniek om die blomtyd van Protea te posisioneer vir beter bemarkingsgeleenthede toon aansienlike kommersiële potensiaal.

Dissertation (PhD (Agric))--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Leaf blackening is a particular problem limiting vase life and marketability of Protea cut flowers. This research investigated suppression of Protea leaf blackening with a specific focus on Protea cv. Sylvia (P. eximia x P. susannae) cut flowers. Leaf blackening decreased significantly with decreasing storage temperatures m 'Sylvia' proteas and this was attributed to lower respiration rate and conservation of carbohydrate. Low storage temperatures were beneficial in short term handling procedures encountered during airfreight. However, use of low temperatures alone during the longer sea freight period was unsatisfactory in either maintaining or extending 'Sylvia' protea vase life. Cooling of 'Sylvia' proteas under vacuum significantly suppressed leaf blackening and was of greater benefit than forced air cooling. Although removal of the uppermost leaves delayed leaf blackening in short term storage no significant benefit was found for longer storage periods. Girdling directly beneath the 'Sylvia' protea flowerhead significantly reduced leaf blackening and in combination with low storage temperatures (O°C) enabled a significant extension in both storage and vase life of 'Sylvia' proteas. 'Sylvia' proteas did not exhibit a climacteric respiration peak during 96 h storage at O°C. Exposure to ethylene did not increase Protea leaf blackening or have a detrimental effect on vase life of either proteas or pincushions evaluated. No beneficial response to sucrose supplementation was found in 'Sylvia' proteas. Analysis of the sugar content of both flowerhead and leaves indicated that glucose supplementation might be of benefit and was investigated. Holding solutions of 2.5 % glucose significantly extended vase life due to a significant reduction in leaf blackening. Vase life was terminated due to flowerhead collapse instead of leaf blackening for the first time in 'Sylvia' protea cut flowers. Vase life was significantly extended by 2:3% glucose pulse solutions and leaf blackening significantly suppressed with increasing glucose pulse concentration. Solution uptake was facilitated by use of high intensity PAR lights in the early morning and was attributed to increased stomata opening and a consequent increase in both transpiration and glucose solution uptake. The faster uptake of glucose solutions in shoots harvested in the afternoon was attributed to higher shoot temperatures and consequent transpiration rate to those harvested in the morning. There was a significant reduction in uptake time with increasing pulse temperature, which enabled vacuum cooling to be performed earlier further benefiting storage and vase life extension. Enclosure of 'Sylvia' proteas in polyethylene (PE) lined cartons did suppress leaf blackening in non-pulsed shoots. However, this had no practical significance on useful vase life, which was terminated at this point due to excessive leaf blackening. Water loss appears to have a minimal influence on 'Sylvia' protea leaf blackening. Shading at four and three weeks prior to harvest coincided with a period of significant flowerhead dry mass increase. It is thought that shading at this point, concurrent with an increased carbohydrate demand by the developing flower head resulted in a temporary limitation in carbohydrate supply resulting in the appearance of preharvest leaf blackening. It would appear that proteas do not store large quantities of carbohydrate. Although accentuating winter light conditions by shading did result in a decrease in carbohydrate content the fact that carbohydrate content was already low precluded shading from having a significant impact on postharvest leaf blackening. The finding that glucose was beneficial in extension of both storage and vase life of 'Sylvia' proteas directed research into its use for other Protea and Leucospermum cut flowers. Significant differences in the response to glucose supplementation were found in both Protea and Leucospermum (pincushions). The significant difference in sensitivity to glucose concentration in 'Pink Ice' proteas (phytotoxic at 2:4%) and 'Susara' proteas (no apparent toxicity), in conjunction with a lack of response in 'Cardinal' proteas, a hybrid from the same parents as 'Sylvia' indicates the need to direct future research to individual cultivars. Glucose supplementation had no beneficial effect on vase life of 'Scarlet Ribbon' and 'Tango' pincushions, whilst significantly extending vase life of 'Cordi', 'Gold Dust', 'High Gold' and 'Succession' pincushions. / AFRIKAANSE OPSOMMING: Blaarverswarting is 'n spesifieke probleem wat die vaasleeftyd en die bemarkbaarheid van Protea snyblomme beperk. In hierdie navorsing is ondersoek ingestel na die onderdrukking van Protea blaarverswarting met spesifieke fokus op die snyblomme van die kv. Sylvia (P. eximia x P. susannae). Die voorkoms van blaarverswarting by 'Sylvia' het merkbaar afgeneem tydens die verlaging van bergingstemperature. Hierdie afname is toegeskryf aan 'n laer respirasietempo en die behoud van koolhidrate. Lae bergingstemperature in die korttermyn hantering van die produk tydens lugvrag was voordelig. Die gebruik van lae temperature, slegs tydens die langer verskeepingsperiode, was egter onbevredigend vir vaasleeftyd verlenging en onderhoud van 'Sylvia' protea. Die afkoeling van 'Sylvia' proteas onder vakuum het blaarverswarting in 'n groot mate onderdruk en het beter resultate gelewer as geforseerde lugverkoeling. Alhoewel die verwydering van die heel boonste blare blaarverswarting by korttermynopberging vertraag het, het dit geen merkbare voordele vir langer bergingsperiodes ingehou nie. Ringelering direk onder die blomkop van die 'Sylvia' protea het blaarverswarting aansienlik verminder, en saam met lae bergingstemperature (O°C) het dit 'n merkbare verlenging in beide die bergingstyd en die vaasleeftyd van 'Sylvia' proteas teweeggebring. 'Sylvia' proteas het geen klimakteriese respirasiekruin tydens 'n bergingsperiode van 96 uur teen O°C getoon nie. Blootstelling aan etileen het nie die Protea blaarverswarting laat toeneem of 'n nadelige effek op die vaasleeftyd van die proteas of speldekussings wat geevalueer is, gehad nie. Geen voordelige reaksie op sukrose-byvoeging is in 'Sylvia' proteas gevind nie. 'n Analise van die suikerinhoud van beide die blomkoppe en die blare het aangetoon dat 'n glukose-byvoeging moontlik voordelig kon wees, en hierdie aspek is ondersoek. Met stooroplossings van 2,5 % glukose is die vaasleeftyd aansienlik verleng omdat daar 'n merkbare afname in blaarverswarting was. Vir die eerste keer in die geval van die 'Sylvia' protea, het die vaasleeftyd van die snyblomrne tot 'n einde gekom omdat die blornkoppe uitmekaar gebreek het en nie omdat blaarverswarting ingetree het nie. Die vaasleeftyd is aansienlik verleng met ~ 3% glukose-pulsoplossings, en blaarverswarting is merkbaar onderdruk met die verhoging van hierdie oplossings se glukosekonsentrasie. Die opname van die oplossings is gefasiliteer deur hoe intensiteit PAR (fotosinteties-aktiewe radiasie) ligte vroeg in die oggend, en is toegeskryf daaraan dat meer huidmondjies oopgegaan het. Dit het gelei tot 'n toename in transpirasie en 'n toename in die opname van die glukose-oplossing. Die feit dat glukose-oplossings vinniger opgeneem is deur lote wat in die middag geoes is, is toegeskryf daaraan dat loottemperature dan hoer is as soggens en gevolglik lei tot 'n vinniger transpirasietempo. Daar was 'n merkbare afname in die opnametyd wanneer die temperatuur van die pulsoplossings verhoog is. Vakuumafkoeling kon dus vroeer toegepas word, wat 'n verlenging in bergingstyd en vaasleeftyd tot gevolg gehad het. Verpakking van 'Sylvia' proteas in kartonne wat met poli-etileen uitgevoer is, het blaarverswarting van lote wat nie aan pulsering onderwerp is nie, onderdruk. Hierdie maatreel het egter geen praktiese waarde met betrekking tot vaasleeftyd nie; die vaasleeftyd het tot 'n einde gekom as gevolg van omvangryke blaarverswarting. Dit lyk asof waterverlies weinig invloed het op die blaarverswarting van' Sylvia' proteas. Die vermoede bestaan dat lae koolhidraatvlakke proteas ontvanklik maak vir blaarverswarting. Alhoewel die beklemtoning van winterligtoestande deur beskaduwing gelei het tot 'n afname in koolhidraatinhoud, was hierdie inhoud reeds laag en blaarverswarting na die oes is nie beinvloed nie. Beskaduwing tydens die vier en drie weke voor oestyd het saamgeval met 'n tydperk van aansienlike toename in die droe massa van die blomkop. Die vermoede bestaan dat beskaduwing tydens hierdie fase, saam met die toename in die ontwikkelende blomkop se behoefte aan koolhidrate, aanleiding gegee het tot 'n tydelike beperking in koolhidraatvoorraad wat die voorkoms van blaarverswarting voor die oes tot gevolg gehad het. Die bevinding dat glukose voordelig is vir die verlenging van beide die bergingstyd en die vaasleeftyd van 'Sylvia' proteas het die navorsing gerig om ook ondersoek in te stel na die gebruik daarvan vir ander Protea en Leucospermum snyblomme. Merkbare veranderinge is gevind in die reaksie op glukosebyvoegings in beide Protea en Leucospermum (speldekussings). Die opmerklike verskil in sensitiwiteit vir glukosekonsentrasie in 'Pink Ice' proteas (fitotoksies by ~ 4%) en 'Susara' proteas (geen klaarblyklike toksisiteit), saam met 'n gebrek aan reaksie by 'Cardinal' proteas, 'n hibried van dieselfde ouers as 'Sylvia', dui aan dat verdere navorsing op individuele kultivars toegespits sal rnoet word. Glukosebyvoegings het geen voordelige uitwerking op die vaasleeftyd van 'Scarlet Ribbon' en 'Tango' speldekussings gehad nie, terwyl dit die vaasleeftyd van 'Cordi', 'Gold Dust', 'High Gold' en 'Succession' speldekussingkultivars merkbaar verIeng het.

M.Sc. (Botany) / Please refer to full text to view abstract

<p><font face="Times New Roman"> <p align="left">This mini-thesis seeks to interrogate the interplay between memory and documentation in the process of exhibition-making by a looking at the preparation for and mounting of the exhibition, Museum. This will be achieved by looking at the institutional methodologies employed by the Museum in dealing with ex-residents of District Six, their memories and artefacts in the heritage practice of a Museum as a forum. This practice was put into effect as the District Six Museum engaged ex-residents of other locations of removal.</p> </font></p>

<p><font face="Times New Roman"> <p align="left">This mini-thesis seeks to interrogate the interplay between memory and documentation in the process of exhibition-making by a looking at the preparation for and mounting of the exhibition, Museum. This will be achieved by looking at the institutional methodologies employed by the Museum in dealing with ex-residents of District Six, their memories and artefacts in the heritage practice of a Museum as a forum. This practice was put into effect as the District Six Museum engaged ex-residents of other locations of removal.</p> </font></p>