Drought resistance among genotypes of Port-Orford-cedar (Chamaecyparis
lawsoniana (A. Murr.) Pan., Cupressaceae) seedlings was evaluated both in the field and
in the greenhouse. Field water potentials (��) of 5-year-old seedlings were measured at
two high-elevation plantation sites where summer drought occurs. Measurements of ��
were compared to survival two years prior at the same site. The north coastal breeding
zone 1 had significantly lower mid-day �� and lower survival than the southern interior
breeding zone 6. Percent survival at 3 years was significantly correlated with mid-day ��.
A second assessment of drought resistance was performed in the greenhouse on 1-0
seedlings. Root growth potential (RGP) was measured in the winter under non-stress
conditions and following a drought in the summer. Differences among breeding zones
were opposite in pattern from outplanting measurements of survival and water potential;
therefore, RGP may not be a good predictor of drought resistance or survival among
different genotypes within a single species. Low-elevation, coastal families had greater
root growth than inland, high elevation sources. Greater root growth occurred in
seedlings with more shoot mass. Little regional specialization in RGP across the species'
range was indicated as there was greater variation among families than among breeding
zones. In the summer RGP test following drought, only the two extremes of the range
were evaluated; both north coastal and southern interior families showed decreased root
growth compared to the winter RGP under non-stress conditions. Despite significantly
higher predawn �� in inland, high elevation families, lower elevation coastal families had
significantly more roots. Change in chlorophyll fluorescence yield measured on foliage
of droughted plants was positively correlated with the absolute value of predawn ��;
however, it was not a sensitive predictor of predawn �� (R��=0.06) at the levels used in
this study. Lower levels of �� may be necessary to produce severe stress to damage Port-Orford-cedar foliage. / Graduation date: 2003
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/31702 |
| Date | 18 October 2002 |
| Creators | Sharpe, Jodie M. |
| Contributors | Zobel, Donald B. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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