The Direct Effects of Atmospheric Change on Vegetation

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The Direct Effects of Atmospheric Change on
Vegetation From Gene Expression to Crop
Production in the Field
IBC 2005, Vienna
Stephen P. Long, Elizabeth A. Ainsworth, Carl J.
Bernacchi., Hans J. Bohnert, Charles P. Chen,
Andrew D.B. Leakey, Patrick B. Morgan, Shawna L.
Naidu, Randy L. Nelson, Donald R. Ort, and
Alistair Rogers. University of Illinois at
Urbana-Champaign
ILLINOIS
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Topics
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Topics
Rising CO2 and O3
Mechanisms of response acclimation and
expectations
Free-Air Concentration Enrichment (FACE)
Re-visiting our approach and expectations
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U.N. Intergovernmental Panel on Climate Change
The Scientific Basis 3rd Assessment Report
(2001) -
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Ozone formation in the Troposphere 2NO O2 ?
2NO2 (1)
NO2 hv (? 290-430 nm) voc? O? NO . (2)
 voc volatile organic compounds (unburnt
gasoline and isoprenes from vegetation)
O? O2 ? O3 .. (3)
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Surface ozone over 24h
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IPCC (2001) WG1 projection of global surface
ozone levels
Global surface ozone high (yellow - red -
brown) low (white - blue).
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Topics
Rising CO2 and O3
Mechanisms of response acclimation and
expectations
Free-Air Concentration Enrichment (FACE)
Re-visiting our approach and expectations
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Response to ? CO2 0 1500 ppm
?CO2
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Rubisco The primary basis of the direct
response of photosynthesis and C3 plants to
rising CO2.

• Ribulose 15 bisphosphate carboxylase/oxygenase
  (Rubisco)
• Plastid encoded
• Highly conserved
• Low catalytic rate
• 50 Leaf soluble protein
• 25 Leaf N

As a result Primary response of C3 species
highly predictable.
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Increased CO2
RubP
Rubisco
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Stimulation of photosynthesis predicted from
Rubisco kinetics370 ppm -gt 550 ppm
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Response to ? CO2 0 1500 ppm
?CO2
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H2O
H2O
Less transpiration and more photosynthesis.
How?!
Ambient CO2
Elevated CO2
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Stomatal limitation (l) (A-A)/A 0.136
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A
CO2 uptake -A (µmol m-2 s-1)
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Current
0
370
572
Intercellular CO2 - ci (ppm)
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Stomatal conductance Decreased 35 l 0.045
l 0.136
Aº
A
Aº
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A
Transpiration 35 ? Photosynthesis 2 ?
CO2 uptake -A (µmol m-2 s-1)
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Elevated
Current
0
370
572
Intercellular CO2 - ci (ppm)
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TNC
Increase in elevated CO2
Potential Photosynthesis
TNC
Actual Photosynthesis
Dry matter
Seed
0
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How ozone decreases photosynthesis?
From Long Naidu, 2002.
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?Photosynthesis (C3 only)
?CO2
?Stomatal aperture
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Meta-analysis Ozone Impact on Soybean of ca. 60
ppb O3 (53 peer-reviewed journal articles)
Variables
-40
-30
-20
-10
0
10
Percentage Change Relative to Carbon Filtered Air
Morgan et al. (2003) Plant Cell Env. 26, 1317
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Mean crop responses to ozone estimated from
chamber
studies (Source USDA).
Lowest
Mean
Highest
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Sorghum
C4
80
Yield no ozone
Corn
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Wheat
C3
Soybean
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0
40
80
120
Seasonal average of daily peak 7h ozone (ppb)
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Topics
Rising CO2 and O3
Mechanisms of response acclimation and
expectations
Free-Air Concentration Enrichment (FACE)
Re-visiting our approach and expectations
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Controlled environment hypothesis on
mechanism From genetics, biochemistry physiology
Field Laboratory Test of reality (does it happen,
does it matter? )
Predictions ecosystems, global food supply
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Too small Too different warmer, less
precipitation, more humid, edge effects, and
altered atmospheric coupling (Heagle et al. 1989
J Env Qual 18, 361.) Barrier to insect dispersal.
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www.soyface.uiuc.edu
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Temp. (C)
CO2 (µmol mol-1)
35.0
750
96 of minute averages within 10
32.5
550
Fumigation On
350
30.0
000
6.00
1200
1800
0.00
Time (h)
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Have we learnt anything new from this effort in
FACE?
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Acclimation of Photosynthesis

• Long-term elimination of stimulation due to
  decreased N
• OR
• Improved fitness by re-allocation of N away from
  Rubisco

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Less Rubisco and more photosynthesis How?
CO2 uptake rate (A)
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If this occurs

• Vc,max/Jmax should decrease
• AND
• Rubisco decrease should account for decreased N

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More growth with limiting N how?
CO2
-
Rubisco
Leaf TNC
Growth
Other Chloroplast proteins
HXK?
Glucose
Gene expression
Protein synthesis
N pool
Drake, Gonzalez-Meler Long, 1997
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Northern and Southern blots of wheat
N concn. high
low mM CO2 concn. amb elev
amb elev µmol/mol

rbcS
Chl.FbPase
northern
SbPase
rbcL
rbcL Southern
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Stimulation is lost in the long-term? 10 year
pasture experiment
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Elevated CO2 accelerates development (110 prior
studies of soybean). But does it?
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Soybean Reproductive Phenology 2004
Reproductive Stage
Days After Planting
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Elevated CO2 delays crop maturation by 2-7 days,
depending on germplasm
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FACE shows differences in physiology, but does it
affect the bottom line?
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Increase in yield of the 5 major grain crops
elevation of CO2 to 550-570 ppm
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What about ozone in FACE do findings differ?
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Effect of ozone on efficiency of photosynthetic
electron transport.
Mean 0.363
CONTROL
Mean 0.259
OZONE
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Topics
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Re-visiting our approach and expectations
OR About-face!
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Can Agriculture Provide Substitutes for Fossil
Fuels and Ameliorate Atmospheric Change?
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Miscanthus (Miscanthus x giganteus)
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Winter Stand
Demonstration plot of Miscanthus x giganteus just
before harvest, winter 2003. Winter harvest has
the advantage of a very low moisture content in
the biomass and allows provides employment for
farm equipment that would otherwise be idle at
this time of year.
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Harvesting Equipment
Winter cutting (followed by baling) of
demonstration plot of Miscanthus x giganteus at
the South Farms, University of Illinois, Urbana,
early 2004.
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Cellulosic Ethanol Potential?

• Illinois 35.6 million acres if 10 was
  Miscanthus it would provide 50Mt dry mass per
  year.
• 35Mt Cellulose (70 content)
• Assuming 50 efficiency of digestion to ethanol
  
• 9 Mt Ethanol
• 118 billion gallons.