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Item Phase change, flowering and postharvest characteristics of Metrosideros excelsa (Myrtaceae) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Biology at the Institute of Molecular BioSciences, Massey University, Palmerston North, New Zealand(Massey University, 2001) Henriod, Robert E.The development of Metrosideros excelsa (pohutukawa) as an ornamental crop has been limited by a lack of knowledge on the cultural requirements and underlying physiological processes associated with: (a) vegetative phase change (maturation) following micropropagation, (b) the environmental control of flowering, and (c) the postharvest characteristics of the cut-flower. These three concerns were addressed in this thesis. First, plantlets of M. excelsa that had undergone rejuvenation following micropropagation, were subjected to shoot and root restriction treatments to accelerate vegetative phase change. Leaves of shoot-restricted, single-stemmed plants became progressively more adult with increasing node position, whereas root restriction reduced root growth but did not accelerate vegetative phase change. In single-stemmed plants, light saturated maximum rate of photosynthesis and leaf carbon isotope discrimination decreased within increasing node position. However, carbon isotope composition in leaves of these plants diverged away from those exhibited by leaves of adult plants, possibly reflecting physiological changes resulting from altered source/sink relations. Second, the effects of photoperiod, temperature and irradiance on floral initiation and development were examined in M. excelsa by manipulating these parameters in controlled and greenhouse environments. M. excelsa responded as a facultative short-day plant with maximum flowering occurring following a 15 weeks cool (mean 15° C) short-day (10 h) inductive treatment. An irradiance of 567 µmol m-2 s-1 during induction provided the optimal conditions for floral primordial growth and subsequent flower development. Buds initially 2.0-3.0 mm in diameter had the highest probability of becoming floral, whilst those less than 2.0 mm in diameter were more likely to remain vegetative or to not break. Finally, the postharvest characteristics of M. excelsa as a cut flower were assessed. Generally, holding solution treatments containing sucrose extended vase life, whereas those containing HQC (applied alone or as a pulse) were detrimental. Cut flowers were sensitive to exogenous ethylene and pre-treatment with inhibitors of ethylene action (STS and 1-MCP) conferred significant protection. This thesis has contributed significantly to furthering our understanding and knowledge of cultural and physiological factors that underlie vegetative phase change, flowering and vase life characteristics in flowers of M. excelsa.Item Quantitative markers of phase change, and modelling the size and complexity of trees : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Biology at the Institute of Molecular BioSciences, Massey University, Palmerston North, New Zealand(Massey University, 2001) Sismilich, MilošQuantitative markers of ontogenetic phase change were sought to track the restoration of the adult state in plants of Metrosideros excelsa (pohutukawa) that had been rejuvenated by micropropagation (plantlets). The potential markers of leaf carbon isotope discrimination and tree architecture were examined in association with leaf morphology for plantlets, and juvenile and adult plants at a range of temperatures (32/24, 24/16 and 16/8 ଌ day/night). Changes in leaf morphology of plantlets and juvenile plants that were indicative of vegetative phase change were associated with a decrease in carbon isotope discrimination. Phase change, judged by these two markers, occurred most rapidly at 24/16 ଌ and in plantlets faster than in juvenile plants. Adult plants showed long-term stability. It was hypothesised that phase change could be quantified by changes in plant growth rate, expressed through canopy topological size and complexity parameters. A model of tree architecture (the Metrosideros Model) was developed that would allow tree size and 2D structural complexity to be recorded and analysed quantitatively. A further hypothesis was that juvenile plants and plantlets must attain a certain size and/or structural complexity before passing to the adult state and this was evaluated using the Metrosideros Model. Dynamics of growth and structural change were examined using both non-linear and linear analyses. The Metrosideros Model was successfully tested, confirming the hypothesis of quantitative differences between juvenile plants, plantlets and adult plants in structural complexity and branching patterns. The model was able to separate parameters of plant size from those of structural complexity. Complexity was indicative of ontogenetic state, and tracked the progress of phase change in juvenile plants and plantlets independently of temperature. Adult plant parameters of structural complexity, as δ13C, also remained stable at all temperatures. On the other hand, the growth rate of size parameters was not associated with phase change, but was responsive to temperature. It was concluded that while leaf morphology, carbon isotope discrimination and crown architecture can be used to track phase change, each relates to a program of change that might occur largely independently of others. Crown architecture was less affected by temperature than were leaf characteristics, and was, therefore, the most reliable marker of phase change of those studied.