© 2007 Heron Publishing—Victoria, Canada
Temperature effects on wood anatomy, wood density, photosynthesis and biomass partitioning of Eucalyptus grandis seedlings
D. S. Thomas (1, 2, 3), K. D. Montagu (4, 5) and J. P. Conroy (1)
1. Centre for Horticulture and Plant Sciences, University of Western Sydney, Locked Bag 1797 South Penrith, NSW 1797, Australia / 2. Present address: Forests NSW, Plantation Improvement, Land management and Technical Services, PO Box J19 Coffs Harbour Jetty,
NSW 2450, Australia / 3. Corresponding author (danet@sf.nsw.gov.au) / 4. State Forests of NSW, Research and Development Division, PO Box 100 Beecroft, NSW 2119, Australia / 5. Present address: Cooperative Research Centre for Irrigation Futures, c/o School of Environment and Agriculture, University
of Western Sydney, Locked bag 1797 South Penrith, NSW 1797, Australia / Received January 20, 2006; accepted March 11, 2006; published online November 1, 2006
Summary
Wood density, a gross measure of wood mass relative to wood volume, is important in our understanding of stem volume growth,
carbon sequestration and leaf water supply. Disproportionate changes in the ratio of wood mass to volume may occur at the
level of the whole stem or the individual cell. In general, there is a positive relationship between temperature and wood
density of eucalypts, although this relationship has broken down in recent years with wood density decreasing as global temperatures
have risen. To determine the anatomical causes of the effects of temperature on wood density, Eucalyptus grandis W. Hill ex Maiden seedlings were grown in controlled-environment cabinets at constant temperatures from 10 to 35 °C. The
20% increase in wood density of E. grandis seedlings grown at the higher temperatures was variously related to a 40% reduction in lumen area of xylem vessels, a 10%
reduction in the lumen area of fiber cells and a 10% increase in fiber cell wall thickness. The changes in cell wall characteristics
could be considered analogous to changes in carbon supply. Lumen area of fiber cells declined because of reduced fiber cell
expansion and increased fiber cell wall thickening. Fiber cell wall thickness was positively related to canopy CO2 assimilation rate (Ac), which increased 26-fold because of a 24-fold increase in leaf area and a doubling in leaf CO2 assimilation rate from minima at 10 and 35 °C to maxima at 25 and 30 °C. Increased Ac increased seedling volume, biomass and wood density; but increased wood density was also related to a shift in partitioning
of seedling biomass from roots to stems as temperature increased.
Keywords:
biomass partitioning, CO2 assimilation, fiber cell, photosynthesis, xylem vessel.
