Ecophysiological traits that vary in response to water stress, and that exhibit significant genotypic variation in Pinus radiata, may reveal a differentiation between genotypes in their ability to respond to and function under water-limitation. Where the genotypic variation of these ecophysiological traits is also genetically correlated with tree growth, they improve the understanding of the genetic variation in growth under water limitation in this species. Ultimately they could be used as selection criteria for improved growth in water-limited environments. The objectives of the thesis were to identify ecophysiological traits in Pinus radiata that responded significantly to water stress; to assess the genotypic variation of those ecophysiological traits in P. radiata; and to determine the genetic correlation between those genetically variable ecophysiological traits and growth. / The thesis assessed the genotypic variation in ecophysiological response to water stress in Pinus radiata, and the genetic correlation between ecophysiological response and growth. These assessments were carried out in seedlings in the glasshouse, in 10 year-old trees in two field trials, and in increment cores of three field trials. / The response of Pinus radiata to water stress was exhibited in a wide range of ecophysiological traits, including growth, respiration, gas exchange, carbon isotope discrimination, chlorophyll fluorescence and osmotic adjustment. Gas exchange and carbon isotope discrimination were not genetically variable in response to water stress, despite significant treatment effects. Some of the other ecophysiological traits, including chlorophyll fluorescence, respiration in growing tissues and osmotic adjustment, did exhibit significant genetic variation under water stress, suggesting some genetic plasticity in P. radiata in response to water stress. However, there were few significant genetic correlations between any of these ecophysiological traits and growth traits, and none of them were demonstrated to be suitable selection criteria for genetic improvement of growth under water stress. / The thesis concludes that genetic variation in ecophysiological response to water stress is limited in P. radiata, and that the growth response to water stress was remarkably homogeneous between genotypes, despite there otherwise being significant genetic variation in growth that was unrelated to water stress. These findings were consistent across several trials and degrees of water stress, in both seedlings and mature trees. They are an important contribution to discussion of the appropriate balance of genetic improvement and silviculture in the optimum management of P. radiata in water-limited environments or under a drying climate, particularly as they are in contrast to results of studies of other Pinus spp such as P. pinaster or P. elliottii x caribaea in growth response to water stress has been shown to be genetically variable.
| Identifer | oai:union.ndltd.org:ADTP/269978 |
| Date | January 2008 |
| Creators | Rowell, Douglas Murray |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
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