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Global Climate Change DigestArchives of the
Global Climate Change Digest

A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999


Item #d99jun7

“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 of trees.

Item #d99jun8

“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.

Item #d99jun9

“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.

Item #d99jun10

“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), 325-330 (1998).

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.

Item #d99jun11

“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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