School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemVegetative propagation of Acacia melanoxylon R. Br. through root cuttings( 2000)A method of vegetative propagation of Acacia melanoxylon using root cuttings was trialed to identify the best treatment combinations. Ten individual trees from three distinct provenances were selected. The other factors were pre-treatments including hormones and season of collection of root cuttings. Provenances were from near Canberra and the East Gippsland and the Otways region of Victoria. The different media trialed included a commercial propagation mix, sand, and a mixture of perlite and vermiculite. Five different pre-treatments were investigated to determine if they boosted the number of shoots produced from a root cutting. The whole trial was repeated over four seasons in one year. Results showed that the provenance varied significantly in the number of shoots produced from root cuttings. One medium (Burnley Mix) also gave significantly better results than the other two media. One of the pretreatments the hormone (IBA) retarded shoot growth significantly. Season of collection had the most significant impact on shoot production. Cuttings set in autumn produced more than twice as many shoots as the cuttings set in the other seasons. A histological investigation was undertaken to determine the origin of the shoots. It was found that the cells originated from the vascular cambium region of the root sections. This thesis has demonstrated that mature Acacia melanoxylon trees can be vegetatively propagated successfully and produce morphologically juvenile plants. The method if further refined could produce the consistent results required to allow commercial propagation of Acacia melanoxylon.
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ItemComparisons of the morphology and physiology of cuttings and seedlings of Eucalyptus globulus( 1994)Eucalyptus globulus subspecies globulus is widely planted for pulp production. It is propagated by cuttings for tree improvement and mass deployment. Development of cuttings and related seedlings was compared to test whether vegetative propagation affects growth adversely. A clone bank was developed from seed and the two best-rooting clones from each of five families compared with seedlings from the same families under optimal, controlled water stress, and field conditions. Cuttings had similar height growth but lower diameter growth rates than seedlings under all conditions. Even under optimal conditions, the morphology of the root systems of cuttings differed from that of seedlings, and cuttings partitioned less biomass to their roots. In all comparisons clones of each family performed similarly to the mean of all cuttings, but variability was high within most clones. Shoot physiology of cuttings and seedlings was similar under optimal and water stressed conditions, but the total water use of cuttings was less than that of seedlings under sub-optimal water availability. Water relations of both plant types were preconditioned by reduced watering frequency; preconditioned cuttings died at higher residual water contents than seedlings, or cuttings watered optimally. Comparisons under field conditions were precluded by early mortality of most seedlings, but the growth and development of the cuttings was monitored for more than one year. Height growth was highly variable within clones and the uniformity expected of clonal plantations was not achieved. Root systems of cuttings and seedlings were fundamentally different. High levels of deformity were observed in the root-shoot junctions of cuttings. These deformities, which imply poor development and instability for seedlings, were not necessarily deleterious for cuttings at 13 months. Accumulated evidence suggested that the root systems of cuttings had poorer uptake and transport capacities. Anatomical examination of the root-shoot junctions showed that the vascular systems were highly distorted. The contortions probably increase resistance in the vascular pathway both by increasing its length and physical resistance. The lack of uniformity within clones was probably due to varying quality of the root systems and suggests the propagation system was inadequate. However, the presence of some individuals which grew similarly to seedlings suggests the propagation system might be modified to produce such plants. In conclusion, it is premature to plant cuttings of Eucalyptus globulus widely until the propagation system is better understood and improved. Long-term monitoring of field plantings is required to evaluate fully the effect of root system morphology and to define the optimal root system for cuttings.