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Title: THE EFFECTS OF FREE-AIR CO2 ENRICHMENT AND SOIL WATER AVAILABILITY ON SPATIAL AND SEASONAL PATTERNS OF WHEAT ROOT GROWTH.

Author
item WECHSUNG, G - HUMBOLDT UNIV GERMANY
item WECHSUNG, F - POTSDAM-INST GERMANY
item Wall, Gerard - Gary
item Adamsen, Floyd
item Kimball, Bruce
item Pinter Jr, Paul
item La Morte, Robert
item GARCIA, R - LI-COR INC NE
item KARTSCHALL, TH - POTSDAM-INST GERMANY

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/1998
Publication Date: N/A
Citation: Wechsung, G., Wechsung, F., Wall, G.W., Adamsen, F.J., Kimball, B.A., Pinter Jr, P.J., La Morte, R.L., Garcia, R.L., Kartschall, T. 1999. The effects of free-air co2 enrichment and soil water availability on spatial and seasonal patterns of wheat root growth. Global Change Biology 5:519-529.

Interpretive Summary: The CO2 concentration of the atmosphere is rising, which may affect future precipitation patterns and the soil water supply. Elevated carbon dioxide (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 the maturing rate during reproductive growth. This change in the growth pattern of a wheat crop's root system due to 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 root growth and senescence rates and total dry mass produced for 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 two soil moisture regimes (100 and 50% replacement of evapotranspiration) in a free-air-CO2 enrichment (FACE) experiment conducted at the University of Arizona Maricopa Agricultural Research Center. Root cores were taken both in-the-row and between-rows (86 mm ID, 1 m length) for six growth stages. A maximum of 37% increase in total root dry mass was observed in FACE compared with Control at stem- elongation. During early vegetative growth, root dry mass of the inter-row space was significantly higher for FACE compared with Control, suggesting that elevated CO2 promoted the productivity of first-order lateral roots per main axis. During reproductive growth, more branching of lateral roots occurred in FACE compared with Control because of water stress. Significantly higher root dry mass was measured in the inter-row space for FACE where soil water supply was limited. These sequential responses in root growth and morphology to elevated CO2 and reduced soil water supply support the premise that wheat plants grown in a high-CO2 environment may better compensate for soil-water stress.