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Title: ACCLIMATION RESPONSE OF SPRING WHEAT IN A FREE-AIR CO2 ENRICHMENT (FACE) ATMOSPHERE WITH VARIABLE SOIL NITROGEN REGIMES. 3. CANOPY ARCHITECTURE AND GAS EXCHANGE

Author
item BROOKS, TALBOT - ARIZONA STATE UNIV
item Wall, Gerard - Gary
item Pinter Jr, Paul
item Kimball, Bruce
item La Morte, Robert
item LEAVITT, S - UNIV OF ARIZONA
item MATHIAS, A - UNIV OF ARIZONA
item Adamsen, Floyd
item Hunsaker, Douglas - Doug
item WEBBER, A - ARIZONA STATE UNIV

Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2000
Publication Date: 7/15/2000
Citation: Brooks, T.J., Wall, G.W., Pinter Jr, P.J., Kimball, B.A., La Morte, R.L., Leavitt, S.W., Mathias, A.D., Adamsen, F.J., Hunsaker, D.J., Webber, A.N. 2000. Acclimation response of spring wheat in a free-air co2 enrichment (face) atmosphere with variable soil nitrogen regimes. 3. canopy architecture and gas exchange. Plant Cell and Environment. 66:97-108

Interpretive Summary: Using light energy, all plant life incorporates atmospheric carbon dioxide (CO2) into simple sugars through the process of photosynthesis. Global atmospheric CO2 concentration is projected to double by the end of the century. Using an innovative field technique [Free-air CO2 enrichment (FACE)], this investigation determined how increased atmospheric CO2 and nitrogen stress affected whole-plant photosynthesis rate. Results indicated that increased atmospheric CO2 will increase photosynthesis by as much as 600% during the early stages of growth, whereas nitrogen stress limited it by 300%. However, these percentages were reduced to a 12% increase due to CO2 enrichment and a 23% reduction due to nitrogen stress by the time final harvest occurred. These findings not only advance scientific research at cooperating government agencies and universities, but serve as important data for validation of computer models currently used by climate change scientists.

Technical Abstract: The response of whole-canopy CO2 exchange rate (CER) and canopy architecture to CO2 enrichment and N stress during 1996 and 1997 for field-grown wheat ecosystem (Triticum aestivum L. cv. Yecora Rojo) are described. Using the Free-Air CO2 Enrichment (FACE) method, the treatments were: ambient-CO2 (~370 umol mol-1), high-N, (CH); ambient- CO2, N-limited (CL); CO2-enriched (ambient +185 umol mol-1), high-N (FH); and CO2-enriched, N-limited (FL). N-limited treatments constituted initial soil content amended with supplemental nitrogen applied at a rate of 70 kg N ha-1 (1996) and 15 kg N ha-1 (1997), whereas high-N treatments were supplemented with 350 kg N ha-1 (1996 and 1997). Integrated seasonal daytime CER for FACE wheat was enhanced by 14% when compared with control. N-stress reduced CER by 17% when CL was compared with CH and 28% when FL was compared with FH. Green plant area index 76 days after planting green plant area index (GPAI) was 6.50 and 7.75 for FH, 5.75 and 6.25 for CH, 4.00 and 3.75 for FL, and 3.75 and 4.00 for CL treatments during 1996 and 1997, respectively. Leaf tip angle distribution (LTA) indicated that low-N canopies were more erectophile than those of high-N canopies: 48 degrees for FH, 52 degrees for CH, and 58 degrees for both FL and CL treatments. Temporal trends in canopy greenness indicated a decrease in leaf chlorophyll content from the flag to flag-2 leaves of 25% for FH, 28% for CH, 17% for CL, and 33% for FL during 1997. These results indicate that significant modification of canopy architecture occurs in response to both CO2 and N-stress. Optimization of canopy architecture may serve as a mechanism to diminish CO2 and N-stress, effects on CER.