A simplified process-based model simulating growth and water use in forest plantations was utilised to predict the growth of Pinus elliottii in South African forest plantations. The model is called 3-PG (Physiological Principles in Predicting Growth) and predicted the growth of trees by simulating physiological processes that determine growth and water use, and the way trees are affected by the physical conditions to which they are subjected, and with which they react. Pinus elliottii growth data recorded in 301 sample stands around South Africa were sourced from forestry companies. A selection procedure reduced the number of stands to 44, where 32 were used to parameterise 3-PG and 12 were reserved for testing the final model parameters. This was accomplished by matching model output to observed data. All stand simulations were initialised at age four years and continued to the maximum age of recorded growth. A provisional set of parameter values provided a good fit to most stands and minor adjustments of the specific leaf area (σ), which was assigned a value of 5 m2.kg-1, were made, bringing about an improved fit. The predictions of mean DBH, Height, and TPH were relatively good, achieving R2 of 0.8036, 0.8975, and 0.661 respectively, while predictions of stem volumes were worse (R2 =0.5922, n=32). The 3-PG model over-predicted DBH in 20 stands, while modelled volume predictions improved substantially in thinned stands (R2 =0.8582, n=14) compared to unthinned stands (R2 =0.3456, n=18). The height predictions were generally good producing an R2 =0.8975. The final set of 3-PG parameter values was then validated against growth data from the 12 independent stands. The predictions of mean DBH, Height, and TPH were relatively good, achieving R2 of 0.8467, 0.7649, and 0.9916 respectively, while predictions of stem volumes were worse (R2 =0.5766, n=12). The results of this study demonstrated the potential for 3-PG to respond to many growth factors and to predict growth and water use by trees with encouraging realism. Patterns of changing leaf area index (L) over time, responses to drought, and annual evaporation patterns all look realistic. Consequently, 3-PG is judged to have potential as a strategic forestry tool. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Thesis (PhD(Agric) (Horticulture))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Branch architecture is the position and length of lateral shoots along a main axis, and is dependant on competitions (dominance) among meristems and lateral shoots. In areas with inadequate winter chilling, branch architecture is altered, the dynamics of which are poorly understood. The aim of this work was to better understand the dynamics underlying plant architecture. In the first part of the study, the dynamics of apple branch architecture were characterized for two cultivars, Golden Delicious and Granny Smith, in areas with differing degrees of inadequate winter chilling (a warm area and a cool area). In an additional study, progeny of a mapped ‘Telamon’ (columnar habit) and ‘Braeburn’ (normal habit) population were used to quantify branch architecture in an effort to develop quantitative trait loci (QTLs) for branching habit. Although branch architecture could be quantified, it was difficult to relate these to known qualitative branching habits, as the columnar gene is dominant and limited the number of progeny that were not columnar. With the exception of organogenesis in the season preceding growth, acrotonic tendencies (number of growing laterals, lateral length, fruit set) were not related to temporal (primigenic) dominance of the distally located buds or flowers within an axis. In the warm area, both relative time of budburst and flowering among buds within an axis did depict a loss of acrotony (positional dominance of the distally located buds and shoots within an axis). The first buds to burst and flower in the warm area had the greatest ability to grow out and set fruit, respectively, regardless of position within the shoot, implicating a role for primigenic dominance when chill unit accumulation was inadequate. Overall, temporal (primigenic) dominance in the warm area, and positional dominance (acrotony) in the cool area dictated lateral outgrowth and development. / AFRIKAANSE OPSOMMING: Takargitektuur verwys na die posisie en lengte van laterale lote soos dit oor die hoofas versprei voorkom. Dit is afhanklik van kompetisie (dominansie) tussen meristeme en laterale lote. In areas met onvoldoende winterkoue word takargitektuur verander, maar die dinamika van hierdie veranderinge word nog nie goed verstaan nie. Die doel van hierdie navorsing was om die onderliggende dinamika wat plantargitektuur beïnvloed beter te verstaan. In die eerste deel van die studie is die dinamika van appeltakargitektuur van twee cultivars Golden Delicious en Granny Smith, in twee areas met verskillende mate van onvoldoende winterkoue bestudeer (’n warm en ’n koel area). In ’n verdere studie is die nageslag van ‘n ‘Telemon’ (kolomgroeiwyse) en ‘Braeburn’ (normale groeiwyse) kruising gebruik om takargitektuur te kwantifiseer. Dit is gedoen in ’n poging om kwantitatiewe eienskapslokusse vir vertakking te ontwikkel. Alhoewel takargitektuur kwantifiseer kon word, was dit moeilik om dit in verhouding te bring met kwalitatiewe vertakkingspatrone daar die kolomgroeiwyse-geen dominant is en die aantal indiwidue in die nageslag wat nie ’n kolomgroeiwyse gehad het nie beperk was. Met die uitsondering van organogenese in die seisoen wat groei voorafgaan, is akrotoniese neigings (aantal laterale lote, laterale lootlengte, vrugset) nie beïnvloed deur tydelike (primigeniese) dominansie van distale knoppe of blomme binne ’n as nie. In die warm area het beide relatief tot knopbreek en blomtyd binne ’n assestelsel die verlies aan akrotonie beskryf (posisionele dominansie van distale knoppe en lote in assestelsel). Die eerste knoppe wat bot en blom in die warm area het die beste vermoë om te groei en vrugte te set, onafhanklik van hul posisie. Dit impliseer die rol van primigeniese dominansie wanneer ’n gebrek aan winterkoue ervaar word. Algemeen gesien was dit tydelike (primigeniese) dominansie in warm areas en posisionele dominansie (akrotonie) in die koeler area wat lateraal bot en ontwikkeling bepaal het.

This study examined the effects of replicating woodland soil surface horizonation on the nutrient status of underlying soils and the initial establishment and growth of trees. A total of 283 container grown trees were planted in a bufferzone around a future landfill site. Control amendments consisted of an 8 cm layer (0.5 m3) of wood chips applied in a circular area of 4.6 m2 around the trees' planting pit. For the treatment, a 2.5 cm layer of composted biosolids (0.15 m3 or 80 Mg/ha) was applied in a circular area of 4.6 m2 around the trees' planting pit followed by an 8 cm layer (0.5 m3) of wood chips. The results indicate that the replication of woodland soil surface attributes using composted biosolids can significantly improve the nutrient status of underlying soil. Some significant effects were seen under control conditions, too. However, the effects on tree establishment and growth parameters were, for the most part, not statistically significant.

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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.

In South Africa, Eucalyptus trees are used for many processed wood products (e.g. paper) and in the mining industry. Priorities in Eucalyptus breeding programmes include selection of varieties that are fast growers, insect and disease resistant, have appropriate wood characteristics and can grow in a wide variety of environmental conditions. Cold-tolerant cultivars of E. saligna and of E. grandis have been bred and selected in Australia and South Africa, respectively for use in cold regions of Natal Midlands and North Eastern Cape. However, the production of large numbers of such cultivars for planting out in a commercial scale is being impaired by slow growth rate, low regeneration time and poor rooting ability of cuttings from these trees. Consequently, methods of in vitro propagation of cold-tolerant clones were investigated. Axillary buds were induced and subjected to a variety of multiplication, elongation and rooting media. The optimised protocol for the production of shoots from axillary buds was: bud induction medium comprising of MS supplemented with 20 grl sucrose and 10 grl agar for 1-2 weeks, multiplication medium comprising of MS supplemented with 0.1 mgrl biotin, 0.1 mgrl calcium pantothenate, 0.2 mgrl benzyladenine phosphate, 20 grl sucrose and 3.5 grl Gelrite for 4 weeks, elongation medium for 4-6 weeks comprising of MS medium supplemented with 0.1 mgrl biotin, 0.1 mgrl calcium pantothenate, 0.35 mgr' NAA, 0.1 mgr' kinetin, 0.1 mgrl IBA, 20 grl sucrose and 3.5 gr1 Gelrite. Production of plantlets via somatic embryogenesis was also investigated but hampered because of high rates of contamination as pieces of mature leaves were used as exp1ants. Ongoing breeding programmes are aimed at obtaining hybrids of Eucalyptus that are cold tolerant. The hybrid progeny then need to be screened for cold-tolerance. However, a major problem in the selection of cold-tolerant clones is that diagnosis can only be undertaken by assessing the field performance of the genotypes under various environmental conditions. In this regard, a protocol for 1D gel electrophoresis was developed for Eucalyptus species with the view to use it for the detection of cold-tolerant stress proteins. Leaf material from both non-cold tolerant and cold-tolerant clones was used. Well-resolved gels that focused on the comparison' between protein profiles of cold-susceptible and cold-tolerant clones before and after period of cold stress were obtained. The findings of this study showed that two polypeptides, one in the lower molecular region of 14.3-20.1kD and another of a higher molecular weight in the region of 116.4-170 kD were observed after cold acclimation. These changes in polypeptide profiles were observed in cold-tolerant E. grandis x nitens (GN1) and E. saligna (AS 184, AS 196 and TS 15) but not in a non-cold tolerant species E. grandis (TAG 731). These polypeptides may have an important role in the cellular adaptation to cold temperatures. It is suggested that this method may be used as a diagnostic tool for screening cold tolerance on Eucalyptus cultivars. / Thesis (M.Sc.)-University of Natal, Durban, 1996.

Climate change, induced by increases in the concentration of greenhouse gases in the atmosphere, can affect the growth and community structure of ecosystems in two ways. Firstly directly through changes in atmospheric concentration of CO2, and secondly indirectly through changes in temperature and rainfall. The aim of the present investigation was to test the effect of elevated CO2 and altitude-related temperature differences on the growth of two species of Acacia that form important components of the vegetation of KwaZulu-Natal. Plants of Acacia sieberana and Acacia nilotica were grown in chambers at elevated (700 pll-1) and ambient (350 IJW1) CO2 with and without rhizobial inoculation. Both treatments (elevated CO2 and the presence of rhizobial inoculation) stimulated growth and branching. A. nilotica was the most responsive to both elevated CO2 level and inoculation. Inoculated plants showed greater increases in mass and height than uninoculated plants. While elevated CO2 had a significant effect on plant mass, height and leaf area accumulation, other factors, such as species type and rhizobial inoculation had a somewhat greater influence on the short term mass accumulation under elevated CO2 , Significant differences existed between the average percentage leaf nitrogen for the two species (P < 0.001), and for inoculated and uninoculated plants (P < 0.005). There were no significant differences in photosynthetic rates (A) at any internal CO2 concentration (Cj) between plants grown in elevated CO2 compared to those grown under ambient conditions. When photosynthesis was plotted against C, (A/CJ, the initial slopes of the graphs for both A. sieberana and A. nilotica were shallower for plants grown in elevated CO2 , compared to plants grown in ambient conditions , indicating a decreased Rubisco concentration at low C, and greater nitrogen use efficiency. At higher C; A. sieberana continued to have lower A in plants grown at elevated CO2 levels suggesting an inability to regenerate RuBP or the possible accumulation of soluble carbohydrates. A. nilotica grown in elevated CO2 had a slightly increased Pj regeneration capacity at higher CO2 concentrations. While the A/Cj results demonstrate that CO2 ·has a minor effect on photosynthesis, growth responses indicated otherwise. This is a result often reported and indicates the importance of measuring as many parameters as is possible to determine actual plant responses to elevated CO2 levels. In the field experiment, the effect of temperature was studied by transplanting twenty plants of each species at three different elevations in the Drakensberg at Cathedral Peak. Plant height, mass, condition and finally survivorship were measured . All of these attributes decreased as elevation increased. Plants growing at the highest elevation all died back prior to winter while those growing at lower elevations grew throughout the experimental period. Results suggest that elevation and hence temperature are important factors controlling Acacia distribution. If the greenhouse gas induced increases in temperature occur as predicted, and the estimated latitudinal migration rates of 30-100km per decade are required for species to remain within their current climatic envelopes, it is expected that the structure and appearance of vegetation in the Drakensberg will change markedly with global warming . The presence or absence of Rhizobia in the soil will further complicate this. Those plants that have access to the elevated nitrogen levels as a result of these root nodule bacteria will have a distinct advantage over competitors growing without them. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.

Although Eucalyptus species are indigenous to Australia, they have been successfully cultivated in South Africa, where they are mainly used in the mining and paper industries. With the explosion in these industries it has been necessary to increase Eucalyptus plantations, often into areas which experience frost and chilling temperatures. To combat this, high yielding Eucalyptus species able to cope with these conditions would be desirable. The ability to rank species according to their chilling tolerance will enhance decisions as to the suitability of species for use in the field. To this aim, two biochemical and two biophysical parameters were chosen to investigate and characterise Eucalyptus nitens, E. smithii, E. macarthurii, E. grandis and E. grandis x nitens (GNI026). Ranking of these species in terms of chilling tolerance did not appear possible using the data from the biochemical parameters (proline concentration and glutathione reductase activity), but the biophysical parameters (fluorescence characteristics and onset of temperature of melt) gave results comparable to those obtained in field trials using these species. Fluorescence characteristics were particularly useful in assessing the chilling tolerance of the species in question. Fluorescence is the recommended technique for further studies as it is relatively inexpensive, rapid, does not require destructive sampling and can be used in both the laboratory and field. / Thesis (M.Sc.)-University of Natal, 1993.