David Rosenthal - Crop Fertilization in a CO2 enriched world: is it good to be C3? (presentation from Adaptation session at CCAFS Science Workshop, December 2010)

1. Crop Fertilization in a CO2
enriched world: is it good
to be C3
David M. Rosenthal
CCAFS Science Workshop, Cancun, Dec 1 and 2, 2010

2. Outline
• Plant responses to elevated CO2 and
other agents of climate change at
SoyFACE
• Why is photosynthesis of crop plants in
the field stimulated less by CO2 than
predicted by theory?
• Some approaches to optimize (adapt)
photosynthesis to global change

3. Recent evidence indicates atmospheric [CO2] is
increasing more rapidly than the most aggressive
IPCC AR4 projection .

4. How does elevated CO2 stimulate photosynthesis that
is the basis for the projected increases in yield?

5. Rubisco is not the most efficient enzyme

6. Energy conversion in C3 and C4 plants
Zhu et al 2008

7. SoyFACE Experiment
Maize Soybean

8. 20 meters

12. [CO2] (µmol mol-1)
750
96% of minute
averages within ±10%
550
Fumigation
350 On
0:00 6.00 12:00 18:00 0.00
Time (h)

13. Increased photosynthesis in C3 crops grown at
elevated CO2 increases yield
Long, Ainsworth, Leakey, Nosberger, Ort (2006) Science 312, 1918-21

14. Meta analysis of C3 crops grown at elevated CO2 in
FACE experiments
Crop Yield
Biomass
SLA
LAI
Plant Height
Leaf #
Starch
Sugar
Narea
Rubisco
Jmax
Vcmax
ci/ca
gs
A'
Asat
-40 -20 0 20 40 60 80 100 120
Percent Change in Elevated [CO2]
Ainsworth and Long (2005) New Phyt. 165:351=-372

15. No CO2 stimulation in Cassava
Greehouse Experiment
Gleadow et al. (2009) Plant Biol 11:79-82

16. Cassava an increasingly important crop

17. CassavaFACE
cv 60444
April 5, 2010
June 7, 2010
August 9, 2010 April 15, 2010
July 2, 2010
July 19, 2010

18. Growth at elevated [CO2] at SoyFACE stimulates cassava
photosynthesis
Rosenthal et al. unpublished

19. Cassava canopies are larger at elevated CO2
plant
Ambient CO2 Elevated CO2 Rosenthal et al. unpublished

20. Rosenthal et al. unpublished

21. Cassava harvested
after only 3.5
months !
Elevated Ambient

22. Ambient CO2 Elevated CO2 Rosenthal et al. unpublished

23. Rubisco is down regulated at elevated CO2 in cassava

24. Cassava leaf Carbon/Nitrogen ratio declines at
elevated CO2
Rosenthal et al. unpublished

25. Growth at elevated [CO2] does not increase leaf or
tuber cyanide content at SoyFACE
Miller, Gleadow unpublished

26. “[CO2] Fertilization” of C3 crop
photosynthesis falls short of theory
Long, Ainsworth, Leakey, Nosberger, Ort (2006) Science 312, 1918-21

27. Why is photosynthesis of crop plants in
the field stimulated less by CO2 than
predicted by theory?

28. 400
Current value
320
240
160
Years below 280 ppm, 395 000 (96%)
80
Years below 240 ppm, 280 000 (67%)
Years below 200 ppm, 83 500 (20%)
0
400 320 240 160 80 0
Time before present, 103 years
Various sources ; Luthi et al (2008) NATURE 453: 379-382

30. Zhu et al. (2007) Plant Physiol 145: 513-526

31. Tobacco over-expressing SBPase grown at
elevated [CO2]
WT SBP 30 SBP 11

32. Over expression of SBPase enhances photosynthesis at
elevated [CO2]
Rosenthal et al. unpublished

33. Over expression of SBPase enhances biomass formation at
elevated [CO2]
Rosenthal et al. unpublished

34. PGA PGA
CH2OPO32- CH2OPO32-
HO C H CH2OPO32- HO C H
O2 CO2
COO- C O COO-
H C OH
COO- H C OH COO-
CH2OPO32- CH2OPO32- HO C H
Ribulose-1,5- CH2OPO32-
2-phospho- bisphosphate
glycolate PGA

35. Non-green
algae
C4
Terrestrial
C3
Mutants Prokaryotes

36. There is a trade off between ability of Rubisco to
discriminate between CO2 and O2 Rubisco catalytic rate
Increase ?
Decrease ?
Current C3
crop Rubisco

37. Lowering increases light saturated leaf photosynthesis but
lowers light limited photosynthesis
= -10%

38. C3
Average

39. Adding „foreign‟ Rubisco
Species Ac' = CANOPY εc Asat
PHOTOSYNTH. (% inc.) ( mol m-2 s-1)
(mmol m-2 day-1)
Current average C3 crop
(kcc = 2.5, = 92.5) 1040 0% 14.9
Amaranthus edulis (C4)
(kcc = 7.3, = 82) 1250 17% 28.3
Amaranthus edulis/current
(kcc = 7.3/2.5, = 82/92.5) 1360 31% 28.3
(2004) Plant Cell and Environment, 27, 155-165

40. Rising tropospheric ozone
0.5 – 2.5 % per year
Ozone – Parts Per Billion of Air
80
60
40
2000 2020 2040 2060 2080 2100
(UN-IPCC 2001)

41. Relationship between Soybean Yield & Ozone
Fishman et al.2010 Atmospheric Environment

42. Summary
• Growth at elevated [CO2] stimulated cassava
photosynthesis.
• Rubisco was down regulated in cassava at elevated [CO2],
consistent lower leaf N (no change in cyanide content).
• Fresh and dry tuber biomass significantly increased with
[CO2], as did harvest index.
• Cassava responded similarly to other C3 plants treated with
elevated [CO2].
• CO2 stimulation of photosynthesis is less than predicted by
theory.
- lack of adaptation to rapid increase in [CO2]
- inhibition due to increasing levels of tropospheric O3
- increased rates of respiration in CO2-grown plants
- temperatures above optimum for photosynthesis.

43. CassavaFACE collaborators:
Becky Slattery (UIUC)
Kat Grennan (UIUC)
Bec Miller (Monash U)
Ros Gleadow (Monash U)
Claude Fauquet (ILTAB)
SBPase overexpression collaborators
Christine Raines (U Exeter)
Anna Locke (UIUC)
Stephen Long (UIUC)
SoyFACE 2010