Title: The Direct Effects of Atmospheric Change on Vegetation
1The 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
2Topics
3Topics
Rising CO2 and O3
Mechanisms of response acclimation and
expectations
Free-Air Concentration Enrichment (FACE)
Re-visiting our approach and expectations
4U.N. Intergovernmental Panel on Climate Change
The Scientific Basis 3rd Assessment Report
(2001) -
5Ozone 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)
6Surface ozone over 24h
7IPCC (2001) WG1 projection of global surface
ozone levels
Global surface ozone high (yellow - red -
brown) low (white - blue).
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9Topics
Rising CO2 and O3
Mechanisms of response acclimation and
expectations
Free-Air Concentration Enrichment (FACE)
Re-visiting our approach and expectations
10Response to ? CO2 0 1500 ppm
?CO2
11Rubisco 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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13 Increased CO2
RubP
Rubisco
14Stimulation of photosynthesis predicted from
Rubisco kinetics370 ppm -gt 550 ppm
15Response to ? CO2 0 1500 ppm
?CO2
16H2O
H2O
Less transpiration and more photosynthesis.
How?!
Ambient CO2
Elevated CO2
17Stomatal limitation (l) (A-A)/A 0.136
20
A
CO2 uptake -A (µmol m-2 s-1)
10
Current
0
370
572
Intercellular CO2 - ci (ppm)
18Stomatal conductance Decreased 35 l 0.045
l 0.136
Aº
A
Aº
20
A
Transpiration 35 ? Photosynthesis 2 ?
CO2 uptake -A (µmol m-2 s-1)
10
Elevated
Current
0
370
572
Intercellular CO2 - ci (ppm)
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2040
TNC
Increase in elevated CO2
Potential Photosynthesis
TNC
Actual Photosynthesis
Dry matter
Seed
0
21How ozone decreases photosynthesis?
From Long Naidu, 2002.
22?Photosynthesis (C3 only)
?CO2
?Stomatal aperture
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24Meta-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
25Mean crop responses to ozone estimated from
chamber
studies (Source USDA).
Lowest
Mean
Highest
100
Sorghum
C4
80
Yield no ozone
Corn
60
Wheat
C3
Soybean
40
0
40
80
120
Seasonal average of daily peak 7h ozone (ppb)
26Topics
Rising CO2 and O3
Mechanisms of response acclimation and
expectations
Free-Air Concentration Enrichment (FACE)
Re-visiting our approach and expectations
27Controlled environment hypothesis on
mechanism From genetics, biochemistry physiology
Field Laboratory Test of reality (does it happen,
does it matter? )
Predictions ecosystems, global food supply
28Too 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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31www.soyface.uiuc.edu
32Temp. (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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34Have we learnt anything new from this effort in
FACE?
35Acclimation of Photosynthesis
- Long-term elimination of stimulation due to
decreased N - OR
- Improved fitness by re-allocation of N away from
Rubisco
36Less Rubisco and more photosynthesis How?
CO2 uptake rate (A)
37If this occurs
- Vc,max/Jmax should decrease
- AND
- Rubisco decrease should account for decreased N
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40More 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
41Northern 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
42Stimulation is lost in the long-term? 10 year
pasture experiment
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44Elevated CO2 accelerates development (110 prior
studies of soybean). But does it?
451
2
3
4
5
6
7
8
Soybean Reproductive Phenology 2004
Reproductive Stage
Days After Planting
46Elevated CO2 delays crop maturation by 2-7 days,
depending on germplasm
47FACE shows differences in physiology, but does it
affect the bottom line?
48 Increase in yield of the 5 major grain crops
elevation of CO2 to 550-570 ppm
49What about ozone in FACE do findings differ?
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51Effect of ozone on efficiency of photosynthetic
electron transport.
Mean 0.363
CONTROL
Mean 0.259
OZONE
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53Topics
54Re-visiting our approach and expectations
OR About-face!
55Can Agriculture Provide Substitutes for Fossil
Fuels and Ameliorate Atmospheric Change?
56Miscanthus (Miscanthus x giganteus)
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58Winter 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.
59Harvesting Equipment
Winter cutting (followed by baling) of
demonstration plot of Miscanthus x giganteus at
the South Farms, University of Illinois, Urbana,
early 2004.
60Cellulosic 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.