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
FROM VOLUME 2, NUMBER 8, AUGUST 1989
CO2 EFFECTS ON VEGETATION
"Effects of Atmospheric CO2 Enrichment on Root: Shoot Ratios of
Carrot, Radish, Cotton and Soybean," S.B. Idso (U.S. Water Conserv. Lab.,
4331 E. Broadway, Phoenix AZ 85040), B.A. Kimball, J.R. Mauney, Agric.,
Ecosys., Environ., 21(3-4), 293-299, 1988.
Detailed analyses of root:shoot ratios, determined at weekly intervals
during a succession of cropping cycles, show that increased CO2 concentrations
significantly increased the proportions of assimulates allocated to the roots of
radish and carrot. This effect increased the root:shoot ratios of both root
crops by approximately 36% at all stages of plant growth, suggesting a response
to atmospheric CO2 enrichment that is independent of plant size and not caused
by a progressive reduction in nitrogen availability. Cotton and soybean were not
affected by CO2 enrichment.
"Phosphorus Stress Effects on Growth and Seed Yield Responses of
Nonnodulated Soybean to Elevated Carbon Dioxide," J.D. Cure (Dept. Bot.,
Duke Univ., Durham NC 27706), T.W. Rufty Jr., D.W. Israel, Agron. J.,
80(6), 897-902, 1988.
Nonnodulating soybean plants were grown from germination to maturity in
controlled environment chambers at 350 and 700 micro L/L CO2 and supplied with
a complete nutrient solution containing either 0.005, 0.10, 0.25, 0.50, or 1.00
mM P. Growth and seed yield were maximized at the 0.25 and 0.50 mM P
concentrations at 350 and 700 micro L/L CO2, respectively. Growth and yield were
significantly increased by CO2 enrichment at all except the lowest P
concentration. Results indicate that CO2 enrichment can result in stimulation of
growth and yield of nonnodulated, (NO3-)-fed soybean plants, even at
concentrations of P that limit plant growth at ambient CO2 concentrations.
"Effects of Various Levels of CO2 on the Induction of Crassulacean
Acid Metabolism in Portulacaria afra (L.) Jacq.," A.J. Huerta, I.P.
Ting (Dept. Bot., Univ. Calif., Riverside CA 92521), Plant Physiol.,
88(1), 183-188, 1988.
Hypothesizes that stomatal closure due to water stress may induce changes in
internal CO2 concentration and that these changes in CO2 could be a factor in
Crassulacean Acid Metabolism (CAM) induction. Laboratory experiments showed
that, in water-stressed and in well-watered plants, CAM induction remained
unaffected by low, normal, or high CO2 treatments. In well-watered plants,
however, both low and high ambient concentrations of CO2 tended to reduce
organic acid concentrations. Concludes that exposing the plants to the CO2
concentrations mentioned had no effect on inducing or reducing the induction of
CAM. The effect of water stress on CAM induction is probably mediated by its
effects on biochemical components of leaf metabolism.
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