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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

PROFESSIONAL PUBLICATIONS...
CO₂ EFFECTS ON VEGETATION

Item #d89aug26

"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.

Item #d89aug27

"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.

Item #d89aug28

"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.