© 2001 Heron Publishing—Victoria, Canada
Variation in water relations characteristics of terminal shoots of Port-Orford-cedar (Chamaecyparis lawsoniana) seedlings
Donald B. Zobel (1), Lee Riley (2), Jay H. Kitzmiller (3) and Richard A. Sniezko (2)
1. Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA / 2. Dorena Genetic Resources Center, USDA Forest Service, Cottage Grove, OR 97424, USA / 3. Pacific Southwest Region, USDA Forest Service, Chico, CA 95928, USA / Received August 31, 2000
Summary
We measured water relations attributes of the terminal shoots of 3-year-old Port-Orford-cedar (Chamaecyparis lawsoniana (A. Murr.) Parl.) seedlings that represented its geographic range. Pressure–volume curves were developed and osmotic potentials
at full (Ψsf) and zero turgor (Ψsz), relative water content at zero turgor, and an index of tissue elasticity (IE) were calculated for 38 families during early,
mid- and late summer at an inland nursery, and for 12 of these families during mid- and late summer at a coastal nursery.
Compared with other conifer species, Ψsz was high (–1.4 to –1.5 MPa) and declined in seedlings at both nurseries as the season progressed. Both IE and osmotic amplitude
(Ψsf – Ψsz) increased during the season. Osmotic potential at zero turgor was lower and osmotic amplitude greater in seedlings at the
inland nursery than at the coastal nursery. Correlations of water relations attributes with geographic location of the seed
sources were weak and usually not significant. High elevation southern sources exhibited smaller differences in Ψsz between nurseries than low elevation northern sources. The small differences in water relations attributes among sources
and between nurseries suggest that some may be of marginal physiological importance; however, sources that produced larger
seedlings appeared to be less desiccation tolerant. We conclude that, when moving genotypes during reforestation, decisions
based on patterns in tree size and timing of growth will account for these small differences in water relations.
Keywords:
desiccation tolerance, genetic variation, osmotic potential, phenotypic variation, relative water content, seasonal variation,
tissue elasticity.
