VARIATIONS IN ECOPHYSIOLOGICAL AND MORPHOLOGICAL ATTRIBUTES IN PROVENANCES AND FAMILIES OF COROMBIA CITRIODORA SUBSP. VARIEGATA

Tejan, Abdul Gassimu (2006). VARIATIONS IN ECOPHYSIOLOGICAL AND MORPHOLOGICAL ATTRIBUTES IN PROVENANCES AND FAMILIES OF COROMBIA CITRIODORA SUBSP. VARIEGATA PhD Thesis, School of Integrative Biology , University of Queensland.

       
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Author Tejan, Abdul Gassimu
Thesis Title VARIATIONS IN ECOPHYSIOLOGICAL AND MORPHOLOGICAL ATTRIBUTES IN PROVENANCES AND FAMILIES OF COROMBIA CITRIODORA SUBSP. VARIEGATA
School, Centre or Institute School of Integrative Biology
Institution University of Queensland
Publication date 2006
Thesis type PhD Thesis
Supervisor Dr David Yates
Abstract/Summary Attainment of targets for timber production and greenhouse gas reduction requires the establishment of large areas of forest plantations, particularly in the less densely populated tropical and subtropical areas. In Australia, most of the proposed plantations will be hardwood species, particularly species of Eucalyptus. Relatively little is known of the requirements of different hardwood species in plantation as up to now their supplies have come from native forests. Studies have shown that eucalypts growing under different environmental conditions exhibit considerable morphological and physiological variations. However the selection of appropriate taxa for specific environments is hindered by the lark of information available on the physiological responses of different species to environmental variables. The current study investigated the variation in morphological and physiological attributes between and within families and provenances of Corymbia citriodora subsp. variegata (CCV) in terms of their adaptability and suitability to different environments. The study was carried out in two phases. The first phase entailed provenance trials in standard glasshouses to determine variations in growth habits, morphological and physiological attributes of seedlings of two Corymbia citriodora subsp. variegata provenances and a hybrid of C.torelliana and C. variegata (CT x CV). Each provenance was tested for speed and completeness of germination, post germination survival, photosynthesis, transpiration, leaf area, stem extension, water use efficiency and drought tolerance. There were no significant differences in speed of germination but differences were observed in growth rates and leaf dimensions among the provenances. Differences in photosynthetic characteristics were evident between and within provenances and between watered and unwatered treatments. Differences in net photosynthesis A, stomatal conductance to water vapour, transpiration rate and water use efficiency (WUE) were observed among the provenances and hybrid. Although differences in WUE among the provenances were related to their natural habitats, they exhibited a great degree of plasticity. More detailed studies were conducted in temperature-controlled glasshouses where the significant effects of different temperature and watering regimes on the responses of different populations were observed. In general stomatal control between and within the provenances was related to atmospheric evaporative demand in response to VPD, soil water status and leaf temperature. There was evidence of visible injury to leaves and apical meristems of the CCV provenances particularly after temperatures rose above 45°C in the compartments following a power failure that lasted more than 12 hours. The second phase was a two-part field study of the provenances in plantations established under different management regimes and in different environments. The first part entailed a pilot study comparing two provenances (Woondum and Presho) from the two extremes of the CCV rainfall gradient in the expectation that they might exhibit differences in water use efficiency. Another provenance (Richmond Range) was included in the second part because of its rapid growth in early trials. This provenance, like Woondum, originated from a high rainfall area. Field measurements of gas exchange, chlorophyll fluorescence, leaf water potential of the three provenances and soil water content were taken over a period of two years at two trial sites, namely, Tiaro (25° 46’ 30” S 152° 38’E) with a mean rainfall of 1295 mm yr¯¹ and Lilydale (27° 30’ 15” S 152o 15’ 3” E) with a rainfall of around 839 mm yr¯¹. Comparative physiological responses across sites showed statistically significant differences among provenances and between seasons. Photosynthetic rates, fluorescence yields and quantum efficiencies were higher at the Tiaro than the Lilydale site and the Woondum provenance showed slightly higher values of these attributes than the other provenances. Irrespective of site, all the provenances studied showed the typical diurnal pattern of variation of water potential (Ψ). There was a gradual decrease from predawn (Ψ pd) optimum values to reach minimum values at midday (Ψ md) and recovery began in the late afternoon. A similar trend was observed in the photosynthetic efficiencies of the sample populations. Significant correlations between leaf to air vapour pressure deficit (VPD), stomatal conductance to water vapour (gs), transpiration (E), leaf temperature (Tleaf) and net photosynthesis (A) were strongest at Lilydale, indicating that these variables were important factors underlying environmentally induced differences in productivity between the sites.

 
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