© 2003 Heron Publishing—Victoria, Canada
Leaf water relations of Eucalyptus cloeziana and Eucalyptus argophloia in response to water deficit
Michael R. Ngugi (1, 2), David Doley (3), Mark A. Hunt (4, 5), Peter Dart (1) and Paul Ryan (4, 5)
1. School of Land and Food Sciences, University of Queensland, St. Lucia, QLD 4072, Australia / 2. Author to whom correspondence should be addressed (m.ngugi@mailbox.uq.edu.au) / 3. Department of Botany, University of Queensland, St. Lucia, QLD 4072, Australia / 4. Queensland Forestry Research Institute, Locked Mail Bag 16, MS 483 Fraser Road, Gympie, QLD 4570, Australia / 5. Cooperative Research Centre for Sustainable Production Forestry, GPO Box 252-12, Hobart, TAS 7001, Australia / Received February 28, 2002; accepted September 20, 2002; published online March 3, 2003
Summary
Leaf water relations responses to limited water supply were determined in 7-month-old plants of a dry inland provenance of
Eucalyptus argophloia Blakely and in a humid coastal provenance (Gympie) and a dry inland provenance (Hungry Hills) of Eucalyptus cloeziana F. Muell. Each provenance of E. cloeziana exhibited a lower relative water content at the turgor loss point, a lower apoplastic water content, a smaller ratio of dry
mass to turgid mass and a lower bulk modulus of elasticity than the single provenance of E. argophloia. Osmotic potential at full turgor and water potential at the turgor loss point were significantly lower in E. argophloia and the inland provenance of E. cloeziana than in the coastal provenance of E. cloeziana. There was limited osmotic adjustment in response to soil drying in E. cloeziana, but not in E. argophloia. Between-species differences in water relations parameters were larger than those between the E. cloeziana provenances. Both E. cloeziana provenances maintained turgor under moderate water stress through a combination of osmotic and elastic adjustments. Eucalyptus argophloia had more rigid cell walls and reached lower water potentials with less reduction in relative water content than either of
the E. cloeziana provenances, thereby enabling it to extract water from dryer soils.
Keywords:
apoplastic water, bulk modulus of elasticity, drought tolerance, leaf anatomy, osmotic adjustment, pressure–volume curves,
subtropics.
