February 28, 2007
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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FERTILIZATION (JUNE 1999)
Elevated Effects of CO2 Concentrations on Photosynthesis,
Growth, and Reproduction of Branches of the Tropical Canopy Tree Species,
Luehea seemannii Tr. & Planch., C. E. Lovelock et al.,
Plant, Cell and Environment, 22 (1), 49-59 (1999).
In the tropical Luehea, enhanced CO2 increased the rate of
photosynthetic carbon fixation and decreased leaves stomatal
conductance. Leaf area, budding and fruitation, and leaves
nonstructural carbohydrate concentrations were unaffected (although woody
stems nonstructural carbohydrate concentrations were increased).
Other effects that were observed included and increase in leaves
share of total biomass and reduced fruit weight. These results indicate
that atmospheric CO2 increases may change the biomass-allocation patterns
Photosynthetic Acclimation to Long-Term Exposure to Elevated
CO2 Concentration in Pinus radiata D. Don. Is Related to Age of
Needles, M. H. Turnbull et al., Plant, Cell and Environment,
21 (10), 1019-1028 (1998).
The effects of CO2 enrichment on new and one-year-old pine needles was
investigated with trees grown for four years in in open-top chambers. The
one-year-old needles under enhanced CO2 exhibited a photosynthesis rate
that was 17% lower than that of similar needles grown at ambient CO2
concentrations. The emerging needles, however, showed a 63% enhancement of
photosynthesis under CO2 enrichment. Although there was no evidence of
down-regulation after four years of enhanced-CO2 exposure, needles do
become acclimated to the enhancement with age.
Acquisition and Allocation of Carbon and Nitrogen by Danthonia
richardsonii in response to Restricted Nitrogen Supply and CO2
Enrichment, J. L. Lutze and R. M. Gifford, Plant, Cell and
Environment, 21 (11), 1133-1141 (1998).
Under enhanced CO2, wallaby grass exhibited increased net assimilation
rate and leaf-nitrogen productivity; decreased nitrogen concentration,
leaf area, leaf area to root surface ratio, and shoot nitrogen to root
nitrogen ratio; and unchanged nitrogen uptake and root surface area.
Root Hydraulic Conductivity of Larrea tridentata and
Helianthus annuus under Elevated CO2, K. A. Huxman, S. D.
Smith, and D. S. Neuman, Plant, Cell and Environment, 22(3),
With Larrea, the root hydraulic conductivity was unchanged by
increased CO2 concentration, while stomatal conductance and transpiration
decreased and photosynthesis rate increased. Biomass, leaf area, stem
diameter, and root- to-shoot ratio were also unchanged. With Helianthus,
the root hydraulic conductivity was nearly doubled, but there was no
effect on other measured variables. These results indicate that water
uptake and transport are affected in a species- specific manner.
Wood Properties and Ring Width Responses to Long-Term
Atmospheric CO2 Enrichment in Field-Grown Loblolly Pine (Pinus taeda
L.), F. W. Telewski et al., Plant, Cell and Environment,
22 (2), 301-308 (1998).
Wood anatomy, density, and tree-ring width were studied in pine trees
grown at ambient and elevated concentrations of CO2. No differences were
produced in cell wall to cell lumen ratio, density of resin canals, or
ratio of resin-canal cross-sectional area to xylem area. Enhanced CO2
produced significantly wider ring widths and increased the total wood
specific gravity. The most noticeable effect of CO2 enhancement was the
increase in radial growth.
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Index of Abbreviations