Dormancy, cold hardiness and height growth were examined in four poplar clones exposed to four temperature conditions (13.5ºC/8.5ºC, 18.5ºC/3.5ºC, 18.5ºC/13.5ºC and 23.5ºC/8.5ºC day/night temperatures) under short photoperiod. The selected clones were WP-69 (Okanese)- early acclimation, Walker and Katepwa - intermediate acclimation, and Prairie Sky- late acclimation. Changes in physical water properties and mobility within the vascular tissue region, vascular transition region into the axillary bud and the upper axillary bud were assessed during endodormancy development using Magnetic Resonance Microimaging (MRMI). <p>In summary:<br>a) There were distinct differences between poplar clones during dormancy induction in response to temperature. For example, Katepwa, Walker and WP-69 clones became endodormant but Prairie Sky did not enter endodormancy. Endodormancy development and cold acclimation in WP-69 were less affected by temperature than Katepwa and Walker suggesting that genotypic variation exists in response to temperature change.<p>b) Growth cessation, not endodormancy, was a prerequisite for cold acclimation since cold hardiness increased in Prairie Sky in the absence of endodormancy. However, increases in endodormancy coincided with increase in cold hardiness in other clones.<p>c) Low night temperatures (18.5ºC/3.5ºC) delayed endodormancy development and cold acclimation in all clones compared to the warm night temperature treatment (18.5ºC /13.5ºC). Night temperature was negatively correlated with time to growth cessation, and cold hardiness and positively correlated with dormancy development. Changes in night temperature may affect time to growth cessation, subsequently altering timing of cold acclimation and endodormancy development since growth cessation appeared to be a prerequisite for both processes. <p>d) ADC (Apparent Diffusion Coefficient), an indicator of water mobility within living tissues, was negatively correlated with endodormancy induction. Specifically, the transition region of vascular tissue between the stem and the lower axillary bud showed the highest correlation with endodormancy development. By contrast, decreases in T1 relaxation times, an indicator of biophysical water properties, were inconsistent with changes in endodormancy levels in axillary buds. Thus, ADC appears to correspond more closely with endodormancy development than changes in T1 relaxation times. <p>It is apparent that temperature impacts dormancy development in hybrid poplar. Underlying changes in water appear to correspond with changes in endodormancy. Under future warming scenarios, genotypes such as WP 69 (Okanese) that are less sensitive to temperature and maintain a consistent, endodormancy induction pattern, may be better fit to changing climates.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-12272007-170130 |
| Date | 02 January 2008 |
| Creators | Kalcsits, Lee Anthony |
| Contributors | Silim, Salim, Kendall, Edward J., Hucl, Pierre J., Fennell, Anne, Coulman, Bruce E., Bai, Yuguang, Tanino, Karen |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-12272007-170130/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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