Download Atmospheric CO 2 concentration

The Optimal Atmospheric CO2
Concentration For the Growth of Winter
Wheat (Triticum aestivum)
Ming Xu
Rutgers University
Chinese Academy of Sciences
Email: [email protected]
Agri-2015, July 13-15, Beijing
The Greenhouse Effect
Greenhouse Gasses (Big 3!)
Climate Change Impacts
The HUGE climate challenge !!!
CO2 Emissions from Fossil Burning
Projections of Sea Level Rising
Atmospheric CO2 concentration: Past, present and
future (Data from CMIP5-RCP8.5) of IPCC-AR5)
2000
Atmospheric CO2 concentration (ppm)
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800
600
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0
1750
1800
1850
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Year
2100
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2300
CO2 fertilization Effect: Food for Plants
Photosynthesis
CO2 + H2O
• Raw material for
photosynthesis
• Higher CO2
concentration higher
reaction rate
• Confirmed by
experiments and
models
Respiration
(CH2O)n + O2
Net Impacts
Climate
change impacts
CO2
fertilization
effects
CO2 Fertilization Effect
?
?
?
CO2 Concentration (ppm)
CO2 fertilization saturation Effect
CO2
Fertilization
Effect
Up to 2300 ppm
Amthor 2001
890ppm
Environmental Growth Chamber
Plants after germination (1
week)
PVC pipe wrapped with duct
tape on dish
Plants After Germination (2 weeks)
8 pots in each chamber
CO2 Controlling System
Five growth chambers with CO2 concentration
regulated to 400, 600, 800, 1000, and 1200 ppm
with CO2 tanks (high purity 99.99%)
Growth chamber control loop
Other Environmental Factors
•
•
•
•
•
Temperature: 21oC
Humidity: 60-70%
Light intensity: 1000 μmol m-2 s-1 PAR, 6am-8pm
Soil type: fritted clay
Water amount: 200 ml/pot, watered every other
day
• Water type: plain tap water
• Fertilization: half-strength Hoagland’s solution
once weekly
Plants After Germination (2 Weeks)
Nail varnish mold peeled off with tweezers
Nail varnish mold is mounted onto clear
microslide
Slide under Nikon Eclipse 80i
Microscope
Picture in Autodesk Inventor
where stomata lengths are traced
with Line Tool and dimensioned
A
B
Figure 4. Measurements of leaf gas exchange (A) and leaf stomatal size and density (B, C)
C
Thelco Laboratory
Oven used to dry plant
leaves
Laboratory oven
settings and
values
Effects of CO2 enrichment on biomass
growth of winter wheat
16
894.2ppm
14
Biomass (grams/pot)
12
y = -2.93E-05x2 + 5.24E-02x - 1.00E+01
R² = 0.95
10
889.6ppm
8
y = -1.54E-05x2 + 2.74E-02x - 4.03E+00
R² = 0.97
Xu 2015, J. Plant
Physiology
6
909.4ppm
y = -1.38E-05x2 + 2.51E-02x - 6.02E+00
R² = 0.87
4
2
Aboveground
Root
700
900
Total
0
300
400
500
600
800
CO2 Concentration (ppm)
1000
1100
1200
1300
Diminishing of CO2 fertilization effect with the
increase of CO2 concentration
0.03
CO2 fertilization effect (g biomass/ppm CO2)
0.025
0.02
0.015
0.01
0.005
0
400
-0.005
500
600
700
800
900
1000
1100
CO2 concentration (ppm)
-0.01
-0.015
-0.02
Root
Aboveground
Total biomass
1200
CO2effects on plant height and leaf
characteristics of winter wheat
60
10
Leaf Length
Leaf width
a
50
9
a
a
b
a
40
a
a
b
a
a
c
b
7
a
a
8
a
30
6
5
4
20
3
2
10
1
0
0
400
600
800
CO2 concentration (ppm)
1000
1200
Leaf width (mm)
Plant height and leaf length (cm)
Plant height
CO2 effects on leaf stomatal density
Stomata density (stomata/mm2)
60
Abaxial
Adaxial
55
y = -0.00001x2 + 0.00506x + 56.032
R² = 0.89
50
y = -0.00001x2 + 0.002x + 54.794
R² = 0.88
45
40
35
300
400
500
600
700
800
900
CO2 concentration (ppm)
1000
1100
1200
1300
CO2 effects on adaxial and abaxial stomata length
44
y = -0.00005728x2 + 0.09896x + 6.9319
R² = 0.95
Stomata length (µm)
42
Abaxial
Adaxial
40
Abaxial
Adaxial
38
y = -0.00005342x2 + 0.0925x + 8.8104
R² = 0.98
36
Optimal CO2 : 772 ppm Optimal CO2 : 776ppm
34
32
30
300
400
500
600
700
800
900
1000
CO2 Concentration (ppm)
1100
1200
1300
CO2 Effects on the Spatial Pattern of Stomatal
Distribution on Leaf Surfaces
8
6
4
Lhat (d)
2
0
0
-2
50
100
150
200
250
300
350
400
Scale (μm)
-4
-6
-8
Upper 95%
Lower 95%
400 ppm
600 ppm
800 ppm
1000 ppm
1200 ppm
-10
450
500
CO2 effects on net leaf photosynthetic
rate under growth CO2 concentrations
Net leaf photosynthetic rate
(μmolCO2 m-2 s-1)
20
y = -0.0000287292x2 + 0.0556x - 10.7240
R² = 0.95
18
16
14
12
967.8 ppm
10
8
6
4
300
400
500
600
700
800
900
1000
1100
CO2 concentration (ppm)
1200
1300
Stomatal conductance (µmol CO2 m-2s-1Pa-1)
CO2 effects on stomatal conductance
measured under growth CO2 concentrations
1.5
y = -9E-07x2 + 0.0008x + 1.1926
R² = 0.98
1.4
1.3
1.2
444 ppm
1.1
1
0.9
0.8
300
400
500
600
700
800
900
1000
CO2 concentration (ppm)
1100
1200
1300
CO2 effects on the maximum carboxylation
rate (Vcmax)
65
y = -6.89E-05x2 + 0.1235x + 2.7572
R² = 0.96
60
Vcmax (µmol CO2 m-2s-1)
55
50
895.5 ppm
45
40
35
30
300
400
500
600
700
800
900
1000
CO2 concentration (ppm)
1100
1200
1300
CO2 effects on the maximum electron
transport rate (Jmax)
110
Jmax (µmol CO2 m-2s-1)
105
Min: 524 ppm
100
95
90
Max: 1041 ppm
85
80
y = -3.0447E-07x3 + 7.1467E-04x2 - 4.9825E-01x + 1.9158E+02
R² = 8.8485E-01
75
300
400
500
600
700
800
900
1000
CO2 Concentration (ppm)
1100
1200
1300
CO2 effects on the ratio of Vcmax to
Jmax (Vcmax/Jmax)
Conclusions
1. Initial increase in atmospheric CO2 concentration
dramatically enhanced winter wheat growth
through the CO2 fertilization effect before reaching
an optimum of about 900 ppm;
2. Further increase in CO2 concentration beyond this
concentration substantially decreased the plant
growth;
3. Elevating CO2 concentration not only reduced
stomatal density, length and conductance, but also
changed the spatial distribution pattern of stomata
on leaves, leading to more regular patterns.
Acknowledgements
Drs. Bingru Huang and Yali Song
Drs. Patrick Burgess and Yunpu Zheng
USDA-INFA ISE