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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 7, JULY 1989

PROFESSIONAL PUBLICATIONS...
IMPACTS ON LAND AND VEGETATION

Item #d89jul40

"Sensitivity of Crop Yields and Land Resource Potential to Climatic Change in Ontario, Canada," B. Smit (Dept. Geog., Univ. Guelph, Guelph, Ontario N1G 2W1, Can.), M. Brklacich et al., Clim. Change, 14(2), 153-174, 1989.

Examines the potential implications of a climatic change corresponding to a doubling of atmospheric concentrations of CO₂ on crop production in Ontario, a major food producing region in Canada. Crop yields and the area of land capable of supporting specific crops would vary according to region, soil quality and crop type. Most notable are enhanced opportunities for grains and oilseeds in the northern regions, and diminished production of most crops in the most southerly areas.

Item #d89jul41

"Sensitivity of Evapotranspiration in a Wheat Field, a Forest, and a Grassland to Changes in Climate and Direct Effects of Carbon Dioxide," P. Martin (NCAR, POB 3000, Boulder CO 80307), N.J. Rosenberg, M.S. McKenney, ibid., 117-151.

Micrometeorological and physiological measurements were used to develop Penman-Monteith models of evapotranspiration for a wheat field in eastern Nebraska, a forest in Tennessee, and a grassland in east-central Kansas. The model fit the measurements well over the periods of observations. Simulation studies show that when all climatic and plant factors are considered, evapotranspiration estimates can differ greatly from those that consider only temperature and can differ from the control (no climate or plant change) by about -20 to +40%.

Item #d89jul42

"Effects of CO₂ Concentration on Rubisco Activity, Amount and Photosynthesis in Soybean Leaves," W.J. Campbell (Agronomy Dept., S-215 Turner Hall, 1102 S. Goodwin Ave., Univ. Illinois, Urbana IL 61801), L.H. Allen Jr., G. Bowes, Plant Physiol., 88(4), 1310-1316, Dec. 1988.

Plants, grown from seed in outdoor controlled-environment chambers under natural solar irradiance, had photosynthetic rates, measured during the seed filling stage, up to 150% greater with leaflets grown at 660 compared to 330 microliters of CO₂ per liter when measured across a range of intercellular CO₂ concentrations and irradiance. The amount of rubisco protein (the enzyme which initiates C3 photosynthesis) was constant as growth CO₂ concentration was varied, and averaged 55% of the total leaflet soluble protein. Although CO₂ is required for activation of rubisco, results indicated that within the range of CO₂ concentrations used, rubisco activity was not regulated by CO₂.

Item #d89jul43

"Correlation of Stomatal Conductance with Photosynthetic Capacity of Cotton Only in a CO₂-Enriched Atmosphere: Mediation by Abscisic Acid?" J.W. Radin (U.S. Dept. Agric., Western Cotton Res. Lab., Phoenix AZ 85040), W. Hartung et al., ibid., 1058-1062.

Describes field experiments to test for the existence of a factor or messenger, other than CO₂, that coordinates variability in photosynthesis with variability in stomatal conductance of field-grown cotton. Among individual sunlit leaves, the photosynthetic rate (A) was significantly correlated with stomatal conductance (g). Enriched CO₂ greatly increased stomatal response to the mesophyll metabolite abscisic acid (ABA) injected into intact leaves. The data show no evidence for a messenger to coordinate g with A at ambient levels of CO₂, but in a CO₂-enriched atmosphere ABA may function as a messenger because the sensitivity of the system to ABA is enhanced.