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Title: BIOMASS AND GROWTH RATE OF A SPRING WHEAT ROOT SYSTEM GROWN IN FREE-AIR CO2ENRICHMENT (FACE) AND AMPLE SOIL MOISTURE.

Author
item WECHSUNG, G - HUMBOLDT UNIV GERMANY
item WECHSUNG, F - POTSDAM INST GERMANY
item Wall, Gerard - Gary
item Adamsen, Floyd
item Kimball, Bruce
item GARCIA, R - U.S. WATER CONS LAB AZ
item Pinter Jr, Paul
item KARTSCHALL, T - POTSDAM INST GERMANY

Submitted to: Journal of Biogeography
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/1994
Publication Date: N/A
Citation: Wechsung, G., Wechsung, F., Wall, G.W., Adamsen, F.J., Kimball, B.A., Garcia, R.L., Pinter Jr, P.J., Kartschall, T. 1995. Biomass and growth rate of a spring wheat root system grown in free-air co2enrichment (face) and ample soil moisture. Journal of Biogeography 22:623-634.

Interpretive Summary: The CO2 concentration of the atmosphere is rising, which may affect future precipitation patterns and the soil water supply. Elevated CO2 has been known to increase the rate that plants use CO2 and to decrease the rate that they use water. A greater supply of the building blocks for growth will increase potential growth of both above- and below- ground organs. Elevated CO2 increased the rate of root growth during vegetative growth, but had only a slight effect on reducing maturity rate during reproductive growth. This change in the growth pattern of a wheat crop's root system because of elevated CO2 increased the total amount of carbon transported from above- to below- ground. Because root growth was more prolific, elevated CO2 increased grain production per acre. Assuming that CO2 does not adversely affect climate, this increase in yield should benefit both producers and end-users.

Technical Abstract: The CO2 concentration of the atmosphere is rising, which may affect potential growth of spring wheat (Triticum aestivum L) roots. This study determined both root growth and senescence rates, and total dry mass produced of a wheat crop during the 1992-93 and 1993-94 growing seasons. 'Yecora Rojo' was grown under two levels of atmospheric CO2 concentration, 550 (elevated) or 370 (ambient) umol mol-1, and with ample water supply, in a free-air-CO2 enrichment (FACE) experiment conducted at the University of Arizona, Maricopa Agricultural Research Center. Both in-the-row and between-rows (86 mm ID, 1 m length) root cores were samples throughout the growing season. Total root mass was higher in FACE compared with control by 34% at 3-leaf, 21% at tillering, 23% at stem-elongation, 28% at dough development and 19% at harvest. A more prolific root system in FACE compared with control was due to a significantly greater growth rate during gvegetative growth. Although senescence rates were similar between FACE and control, the absolute difference in root mass was greater due to elevated CO2. These positive responses in root growth and morphology to elevated CO2 enabled greater exploration of the soil profile for moisture and nutrients.