Thesis (Ph. D.)--University of Western Sydney, Hawkesbury, 1995. / Includes bibliographical references (p. 177-188).

Thesis (doctoral)--Friedricks-Universität Halle-Wittenberg, 1914. / Includes bibliographical references (p. [54]).

No description available.

Thesis (PhD) -- Stellenbosch University, 1984. / No abstract available

Thesis (MScAgric)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The effect of shoot heterogeneity on vegetative and reproductive growth parameters, vine physiology and grape composition was investigated in a ShirazlRichter 99 vineyard. Comparisons between underdeveloped (typically shorter and less ripened at véraison) and normally developed shoots in both shaded (non-manipulated) and well-exposed (manipulated) canopies were made. Compared to underdeveloped shoots, normal shoots had a larger total leaf area, due to the higher occurrence of secondary shoots as well as larger leaves on primary and secondary shoots. Since the photosynthetic activity of the leaves from normal shoots was higher than those from underdeveloped shoots, higher levels of carbohydrates were produced and stored in the former. Starch was more evenly distributed over the length of the whole shoot in normally developed shoots compared to underdeveloped shoots. Normally developed shoots were longer and thicker in diameter than underdeveloped shoots. The larger clusters of the normally developed shoots are evidence of their more favourable total leaf area per gram berry mass. Berries from the normally developed shoots were smaller at five weeks after véraison than those from underdeveloped shoots, displaying a higher skin to pulp ratio and therefore higher anthocyanin and total phenolic extraction potential for winemaking. The smaller clusters and fewer berries per cluster found for the underdeveloped shoots indicate an imbalance between vegetative and reproductive growth initiated during the vegetative growth phase and continued during the ripening period. The peculiar absence of statistically significant differences in grape composition between normally and underdeveloped shoots indicates that assimilates needed for berry ripening of the latter originated in organs other than the leaves [e.g. from adjacent normal shoots and the rest of the permanent structure of the vine (cordon, trunk, roots)]. The larger differences in berry size that occurred between shoot types in the shaded compared to the well-exposed canopies may be evidence for this. The photosynthetic activity of shoots was lower in shaded than in exposed canopies. The total carbohydrate production of the normal shoots in shaded canopies seemed insufficient to supply in the ripening needs of the shoot itself, their own clusters as well as the ripening of stem tissue and clusters of the underdeveloped shoots in the canopy. This is illustrated by the lower levels of starch that accumulated in the normal shoots from shaded compared to that of exposed canopies. Vine shoot heterogeneity clearly leads to visible and physiological imbalances that would impact negatively on grape and wine quality as well as production costs and should therefore be avoided on any terroir. / AFRIKAANSE OPSOMMING: In hierdie studie is die effek van heterogene lootontwikkeling in die lower van 'n ShirazlRichter 99 wingerd ondersoek. Vergelykings is getref tussen normale en onderontwikkelde lote in beskadude en blootgestelde lowers ten opsigte van hul vegetatiewe en reproduktiewe groeieienskappe, fisiologiese aktiwiteit en druifsamestelling en -gehalte. 'n Groter totale blaaroppervlak het by die normaalontwikkelde lote voorgekom as gevolg van die groter aantal sekondêre lote en groter primêre en sekondêre blare. Aangesien die blare van die normaal ontwikkelde lote fotosinteties meer aktief was as dié van onderontwikkelde lote, het die eersgenoemde lote groter hoeveelhede koolhidrate geproduseer en gestoor. Styselopberging het meer eweredig oor die lengte van die normale lote plaasgevind. Laasgenoemde lote was ook heelwat langer en dikker in deursnee as die onderontwikkelde lote. Die gunstiger totale blaaroppervlak per korrelmassa verhouding van die normale lote is duidelik weerspieêl in die groter trosse, terwyl die kleiner korrels (en dus die groter dop:pulp verhouding) op 'n groter potensiaal vir kleur- en fenolekstraksie tydens die wynbereidingsproses dui. Die kleiner trosse en kleiner aantal korrels per tros wat by die onderontwikkelde lote gevind is, dui op 'n wanbalans tussen die vegetatiewe en reproduktiewe groei van die loot wat tydens die vegetatiewe groeifase van die wingerdstok geïnisieer is en tydens die rypwordingsperiode voortgesit is. Die vreemde afwesigheid van enige statisties betekenisvolle verskille in druifsamestelling tussen die normale en onderontwikkelde lote dui daarop dat die verbindings wat vir die rypmaking van trosse op onderontwikkelde lote aangewend is, waarskynlik van ander wingerdorgane (bv. naasliggende lote, kordonarms, stam, wortels) as die spesifieke loot se blare afkomstig was. Die waarneming dat die korrelgroottes van normale en onderontwikkelde lote meer van mekaar verskil het in die beskadude as blootgestelde lowers, kan moontlik as bewys hiervoor dien. Die fotosintetiese aktiwiteit van beide loottipes was laer in die skaduryke lowers. Die koolhidrate wat deur normaalontwikkelde lote in skadu-Iowers geproduseer is, was oênskynlik onvoldoende vir die rypmaking van die loot self, die spesifieke loot se trosse, asook die trosse en lootweefsel van naasliggende onderontwikkelde lote. Hierdie bewerings word gerugsteun deur die laer vlakke van styselakkumulasie wat by die normale lote in beskadude lowers gevind is. Aangesien heterogene lootontwikkeling en -groei duidelike sigbare en fisiologiese wanbalanse in die wingerdstok tot gevolg het wat negatief op druifsamestelling, wyngehalte en produksiekoste inwerk, behoort dit in kommersiêle wingerde vermy te word.

Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT:Six experiments, five in the glasshouse and one in the field near Nelspruit, were carried out to ascertain the effect of factors related to shoot die-back, and of water treatments on the growth and physiological responses of Pterocarpus angolensis seedlings. The study was undertaken to broaden the knowledge and understanding of the phenomenon of shoot die-back in order to enhance our ability to regenerate the species. The following experiments were carried out (a) Assessment of biomass accumulation; anatomical characteristics of the shoot apical meristem; foliar, stem and root concentration of micro- and macronutrients associated with each phenophase, (b) Effect of seedling age and seed source on the occurrence of shoot die-back under field conditions; (c) Water treatment effects on ChI. afluorescence traits of£'. angolensis seedlings obtained by assessing the fluorescence yield of photosynthetic samples subjected to dark- and light-adaptation; (d) Genetic variation in shoot die-back and other traits of sixteen halfsib families of £.. angolensis from Malawi, Namibia and Zambia grown over two die-back seasons. Experiments conducted revealed the following 1. Patterns of growth observed in phenophases are indicators of seasonal changes in annual biomass allocation to the shoot and root. Phenophases such as leaf loss and stem senescence, whether shoot die-back occurs completely or not, are directly related to the decline in above-ground biomass and declined rate of increase in root biomass respectively. Leaf flush, expansion and maturation result in increased biomass accumulation whilst shoot die-back has a minimal downregulatory effect on root biomass accumulation compared to the shoot. Shoot dieback is not sudden, therefore from the first day of germination, seedlings synchronise growth and development with the occurrence of shoot die-back. 2. Phenophasic concentration of foliar N, Ca and Mg, stem Fe and Cu and root concentrations of P, K, Mg, Fe and B are associated with shoot die-back. Patterns of mineral nutrient concentration obtained in foliage and roots but to a lesser extent in the stem, may be related to nutrient remobilisation during shoot dieback. Higher relative mineral nutrient changes during leaf yellowing and shoot die-back may be an indication of the removal of significant volumes of mobile nutrients from senescing tissues. 3. The volume of the shoot apex of E. angolensis remains constant during different phenophases which points to seasonal uniformity in the size of the apical dome. Changes in phenology associated with declined growth, or shoot die-back, is revealed through declined cell number in the tunica which is a reflection of declined mitotic activity. 4. Shoot die-back occurs in all seedlings from nursery stock planted under field conditions and all seedlings of up to two years experience complete shoot dieback. Shoot die-back takes place irrespective of seed source or the age of nursery stock that is planted. Survival after the first shoot die-back is normally low. Water treatments had no significant effect on the function of PSIJ reaction centres of P. angolensis nursery seedlings. In the case of both dark- and light-adapted leaves, water treatment had no significant effect on the measured Chi. a fluorescence parameters or the calculated parameters (specific activities, phenomenological fluxes, structure-function and performance indexes and drivingforces). 5. Water treatments affect the shape of ChI. a fluorescence transients of lightadapted compared to that of dark-adapted photosynthetic samples of E. angolensis. No significant water treatment effect was obtained for extracted and technical Chi. afluorescence parameters, specific fluxes, quantum efficiencies and phenomenological fluxes. Quantum yield, relative electron transport and quantum yield limitation, de-excitation rate constants, structure-function, performance indexes and driving forces were also not significantly different across water treatments.6. Genetic variation was observed to exist among 16 halfsib families from Malawi, Namibia and Zambia. High heritabilities were obtained for shoot die-back and other traits, indicating that shoot die-back is genetically controlled. The trait is passed from parents to offspring and it is highly probable that it occurs, throughout its natural range, in all seedlings. Since shoot die-back is genetically programmed, it remains crucial to the ability of a seedling to regenerate in the following rainy season / AFRIKAANSE OPSOMMING:Ses eksperimente, vyf in die glashuis en een in die veld naby Nelspruit, is uitgevoer om die effek van faktore wat verwant is aan die terugsterwing van lote op saailinge, sowel as om die effek van waterstres op die groei en fisiologiese responsies van Pterocarpus angolensis saailinge, te ondersoek. Die studie is ondemeem om die kennis en begrip aangaande die regenerasie-dinamika van die spesies te verbeter. Die volgende eksperimente is uitgevoer: (a) Evaluering van die effek van jisiologiese veranderings op biomassa; blaar-, stam- en wortelkonsentrasies van spoor- en makro-voedingselemente, en anatomiese eienskappe van die apikale meristeem van die lote. (b) Effek van saailingouderdom en saadbron op die voorkoms van lootterugsterwing onder veldtoestande. (c) Waterbehandelingseffekte op Chi. ajluorisensie eienskappe van ,e. angolensis saailinge wat verkry is deur die jluorisensie te evalueer van fotosintesemonsters wat aan donker- en lig-adaptasies onderwerp is. (d) Genetiese variasie in loot-terugsterwing en ander groei-eienskappe van 16 halfsib families van ,e. angolensis vanaf Malawi, Namibia en Zambia wat gekweek is oor twee terugsterj-seisoene. Die eksperimente het die volgende aan die lig gebring: 1. Groeipatrone waargeneem gedurende die fenofases is indikatore van seisoenale veranderings in jaarlikse biomassa allokasies aan die loot en die wortels. Fenofases soos blaarverlies en lootafsterwing, ongeag of loot-terugsterwing volledig is of nie, is direk verwant aan die afname in bogrondse biomassa en afnemende tempo van toename in wortelbiomassa respektiewelik. Bottende blare, vergroting en rypwording van blare lei tot toenemende biomassa akkumulasie terwyl loot-terugsterwing 'n minimale afskalende effek op akkumulasie van wortelbiomassa het in vergelyking met die van die loot. Loot-terugsterwing is nie skielik, met ander woorde vanaf die eerste dag van ontkieming sinchroniseer saailinge groei en ontwikkeling met die voorkoms van loot-terugsterwing. 2. Fenofase konsentrasies van en veranderings in blaar N en Ca en loot Fe, asook veranderings in waargenome wortel N, K, Ca, Mn, Cu, Zn en B is sterk geassosieer met loot-terugsterwing. Patrone van minerale voedingselementkonsentrasies wat in blare en wortels, en in minder mate in die loot, verkry is, mag direk verwant wees aan hermobilisering van voedingselemente gedurende loot-terugsterwing. Hoe relatiewe minerale voedingselementveranderings gedurende die vergeling van blare en lootterugsterwing mag 'n indikasie wees van die verwydering van betekenisvoUe hoeveelhede mobiele nutriente vanaf sterwende weefsel. 3. Die volume van die groeipunt van r. angolensis bly konstant gedurende verskillende fenofases wat dui op seisoenale uniformiteit in die grootte van die apikale koepel. Veranderings in fenologie ge-assosieer met afnemende groei, of loot-terugsterwing, word gerejlekteer deur afnemende selgetaUe in die tunika wat dui op afnemende mitotiese aktiwiteit. 4. VoUedige loot-terugsterwing kom voor in aUe saailinge vanaf die kwekery wat in die veld geplant word tot op die ouderdom van twee iaar. Dit kom voor angeag van saadbron of ouderdom van saailinge ten tye van planting. Oorlewing na aanvanklike loot-terugsterwing is normaalweg laag. 5. Water behandelings het geen beduidende effek op die funksie van PSII reaksiesentra van r. angolensis kewekery-saailinge gehad. Vir beide donker- en lig-aangepaste blare is geen beduidende waterbehandelingseffek verkry vir waargenome ChI. a jluoresensie parameters of die berekende parameters (spes ifieke aktiwiteite, jenomenologiese jlukse, struktuur-funksie-indekse, "perjormance-indekse oj" driving forces" ). 6. Genetiese variasie tussen 16 halfsibfamilies vanaf Malawi, Namibie en Zambie is verkry vir loot-terugsterwing en ander groei-eienskappe. Dit dui op genetiese beheer van terugsterwing en dat die eienskap oorerjbaar is, en waarskynlik in die hele natuurlike verspreidingsgebied van die spesies in aUe saailinge voorkom. Aangesien loot-terugsterwing gene ties geprogrammeer is, is dit noodsaaklik vir die vermoe van die plant om in die volgende reenseisoen te regenereer.

Partial rootzone drying (PRD) is an irrigation management technique designed to reduce water use in grapevines without a decline in yield, thereby increasing water–use efficiency (measured as t/ML) (WUE). The principle of PRD is to keep part of the root system at a constant drying rate to produce soil-derived signals to above–ground plant organs to induce a physiological response. Major PRD effects include a reduced canopy size and greatly increased WUE with possible improvements in fruit quality. Although we have a good understanding of the hormonal physiology of PRD, little is known on the effect of PRD on partitioning of C, N and inorganic ions such as K. This thesis broadens our knowledge on the effects of PRD on grapevine field performance, growth and dry matter accumulation as well as its effects on physiology and biochemistry. In field experiments over 3 seasons, PRD reduced water use in grapevines without a significant decline in yield. PRD effects included reduced shoot growth and greatly increased WUE. Field–grown Cabernet Sauvignon, where the PRD grapevines were irrigated at half the control rate, and Shiraz where the PRD grapevines were irrigated at same rate as controls, confirmed that PRD is not simply an irrigation strategy that applies less water, rather it alters the way in which the plant responds to its environment, e.g. PRD alters the sensitivity of the stomatal response to atmospheric conditions and significantly influence enzymes that regulate nutrient accumulation and partitioning. PRD did not change the total amount of carbon and nitrogen on a whole plant basis. However, it caused a significant partitioning of carbon and nitrogen towards trunk, roots and fruit at the expense of shoot growth. This change in partitioning occurred as a result of altered activity of the enzymes controlling the assimilation of carbon and nitrogen. PRD significantly reduced nitrate reductase (NR) activity in grapevine leaves, which catalyses the first step in the assimilation of nitrate irrespective of the amount of water applied. The reduction in NR activity is correlated with the development of the PRD cycle and the associated reduction in stomatal conductance. PRD also significantly altered grapevine sucrolytic enzyme activity that regulate source:sink relationships. PRD showed transient increases in leaf sucrose phosphate synthase (SPS) activity (formation of sucrose) compared to control, but significantly reduced leaf neutral invertase (sucrose cleavage) and leaf starch content in both field and potted experiments. This may indicate an increased photosynthetic capacity and a reduction in its sink strength for sucrose in favor of organs such as fruit and roots. This hypothesis was reinforced by the fact that berries showed significantly higher levels in glucose and fructose early in the season. Berry sugar content and Brix at harvest however was unaffected. Although PRD had no significant effect on berry characteristics at harvest such as Brix and pH, it occasionally reduced per berry K+ content and increased total amino acid concentration that may lead to positive outcomes for wine quality. PRD–treated grapevine roots on the 'wet'– and 'drying'–sides differed greatly in enzyme activity and osmolality. PRD significantly increased osmolality in both wet and drying roots by increasing total osmolyte concentration that may facilitate the movement of water from wet to dry roots. The increases in osmolality were also associated with increased free polyamine production (spermidine and spermine) in PRD roots that may be related to increased root growth and density. / Thesis (Ph.D.)--School of Agriculture and Wine, 2005.

In South Africa, clonal forestry of Eucalyptus and its hybrids has been implemented to increase the productivity on existing forestry lands and marginal sites and to facilitate the production of desired fibre types for timber processing operations. The cold-tolerant Eucalyptus grandis x E. nitens hybrids have produced consistently high yields, and are propagated clonally with limited success via a macro-cutting system currently in use for other hybrid species. The heart of vegetative propagation operations is the clonal hedge and its management, and nutrition in particular, is an important element of any vegetative propagation programme. However, achieving and sustaining an optimum nutritional balance in macrohedges is difficult in practice and, in order to accurately predetermine the optimum plant nutrition required all year round and to ensure optimal levels of rooting, a more controllable nutrient environment is essential. Hydroponics may facilitate this control of nutrition. At the same time it may be possible to manipulate the system to determine accurately what levels of each nutrient may contribute to the highest rooting and more importantly allow forest nursery managers to maintain those levels in a practical manner. The main aims of the present work were to obtain and compare cuttings and rooting yields from hydro-ramets in different hydroponic substrates and systems and to investigate the possible roles of essential nutrients on those parameters. Modified Nutrient Film Technique (NFT), ebb-and-flow and aeroponic tables were used in this study. The former consisted of eight individual gutters, allowing for eight different substrates to be tested simultaneously. One gutter was set up as an unmodified NFT table and the other seven gutters had gravel, Leca, peat, perlite, perlite: vermiculite mix, Rockwool® and sand as substrates; all were supplied with the same nutrient solution. Three commercial clones were used throughout these trials: GN107, GN156 and NHOO. Rooting results and data from plant elemental analyses indicated that certain elements (Ca, Cu, Zn, Mn and B) appeared to play a more important role in rooting than others (N, P, K, Mg, Na and Fe). It was also found that when comparing the hydroponic systems, the substrate and / or method of irrigation affected the availability and uptake of different nutrients, which in turn affected the rooting of coppice collected from those ramets. The rooting performance of coppice from the eight different substrates tested in the NFT system was compared. Within each of the four harvests undertaken, both clone and substrate had a significant effect on the rooting performance. However, when the four harvests were compared, only harvest number/time had a significant effect on the rooting performance of the cuttings derived from the hydro-hedges . For both the ebb-and-flow and aeroponics systems (where there was no substrate), only the clone had a significant effect on the rooting performance. In addition to this, the plants from the ebb-and-flow system produced the highest number of cuttings to be placed overall (7.9 cuttings per mother plant per harvest) while those from the gravel substrate had the highest rooting percentage overall (26.9 %). When combining these two factors into a success rate, the perlite substrate rated highest (1.7 rooted cuttings per mother plant per harvest). From a cost efficiency perspective, perlite was the most cost effective substrate, as it required the least initial capital outlay to produce one million rooted clones per year from a hydroponics system (R6 533 655). The plants in the perlite substrate also produced the highest number (6 700) of rooted cuttings per year from 1 000 mother plants with a low cost per plant (R2.33 per rooted plant). / Thesis (M.Sc.)-University of KwaZulu- Natal, Durban, 2004.

Hybrid clones of the fast-growing Eucalyptus grandis and cold-tolerant E. nitens (GN clones) have been identified by the South African Forestry Industry as being highly suitable for plantations in cold-dry marginal areas. However, one of the main problems regarding their propagation is the difficulty in rooting of cuttings, both in vitro and ex vitro. The aims of this investigation, therefore, were (1) to develop widely applicable and efficient in vitro rooting system(s) for these commercially important clones, and (2) to assess some physiological characteristics of the roots produced. Adventitious shoots (15-20 mm in length) were obtained (l0 shoots/explant) from axillary buds on Murashige and Skoog's (MS) medium containing 0.01 mg.l-1 NAA, 0.01 mg.l-1 IBA and 0.2 g.l-1 FAP. The effect of various medium components, as well as modification of culture environment on in vitro rooting, were investigated. The highest rooting frequencies in clones GN121 (75%) and GN107 (65%) were achieved on l/4 MS with additional 0.22 g.l-1 CaCl2..2H2O and 0.18 g.1-1 MgS04.7H2O, 0.1 mg.l-1 IBA, 0.1 mg.l-1 biotin, 0.1 mg.l-1 calcium pantothenate, 15 g.1-1 sucrose and 4 g.l-1 Gelrite. Best culture conditions were an initial 72-hours dark incubation followed by a 16-hours day/8-hours night photoperiod at a PPFD of 37 µmol.m-2.s-1 and 23°C day/21°C night for seven days, after which the PPFD was increased to 66 µmol.m-2.s-1 at 27°C day/21°C night for 18 days. Towards the development of a more widely applicable in vitro rooting protocol for GN clones, the use of Agrobacterium rhizogenes strains was investigated. Production of transgenic roots was observed on carrot discs and shoots from seedlings of Eucalyptus grandis and E. nitens, but not on shoots of GN clones. Therefore, a method needs to be established for the successful transfer and integration of the Ri plasmid of Agrobacterium into the hybrid plant genome for induction of transgenic roots. The quality of roots produced in vitro and from cuttings was assessed by examination of root anatomy and hydraulic characteristics. Adventitious roots were prepared for measurement of hydraulic conductivity by detopping explants, then filtered, acidified distilled water was drawn through undisturbed potted root systems under partial vacuum, causing no damage to the roots. Initial studies showed that tissue culture-derived roots exhibited a higher specific root mass hydraulic conductivity than those derived from cuttings (6.46 x 10-6 vs. 3.06 X 10-6 g.kPa-1.s-1.g-1 dry root), probably due to root architecture. Curves relating vulnerability to water potential were constructed and both types of roots showed vulnerability to cavitation at high water potentials. Differences were also observed in staining reactions (safranin and fastgreen) which might suggest differences in presence and level of secondary metabolites in these roots at the juvenile stage. Applications of the developed protocols and future research strategies are discussed. / Thesis (M.Sc.)-University of Natal, Durban, 1999.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 185-200). Also available on the Internet.