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EFFECT OF THE HIGH CONCENTRATION OF ATMOSPHERIC CO2 ON GROWTH AND
DEVELOPMENT OF SUGAR CANE (SACCHARUM OFFICINARUM)
M. Gaspar, A.P. Souza, M. Marabesi, J.R.L. Godoy, M.P.M. Aidar, M.S.Buckeridge
CO2 INCREASE: WHY STUDYING C4 PLANTS?
• Research on the effect of CO2 enrichment on C4 plants is limited compared to C3 plants.
• Although C4 plants represent a small percentage (about 3%) of the total Angiosperm species, they make a substantial contribution to productivity on a global scale.
• Many agronomically important crops are C4 plants (maize, sorghum and sugar cane...).
C4 PLANTS AND CO2
• C4 plants have a photosynthetic metabolism that concentrates CO2 3 to 8 times the atmospheric CO2 concentrations.
What is C4 metabolism?
C4 PLANTS AND CO2
• This led to the suggestion that the rise in CO2 may have little or no effect on C4 photosynthesis and growth...
WHY STUDYING SUGARCANE?
• One ton has an energy potential that is equivalent to 1.2 oil barrels.
• Besides sugar and alcohol, sugarcane generates several products: biodegradable plastic, paper, pharmaceutical products, fertilizers, herbicides and insecticides, etc.
• SUCEST: database containing 238.000 EST from several organs and tissues sampled at different developmental stages.
Lima et al. 2001 Genetics and Molecular Biology 459 cell wall related genes in Sugar
Cane, 9 of them belong to the family CesA
SUGARCANE IN BRAZIL
• Brazil is the highest world producer, followed by India and Australia.
• 55% of Brazilian sugarcane is turned into alcohol and 45% into sugar.
• Sugar cane plants grown in open top chambers in the atmosphere of 360ppm (control) and 720ppm.
• Short-term experiments: 50 days
CO2 TREATMENT
SUGARCANE RESPONSE TO CO2 ENRICHMENT
Plant height
0
10
20
30
40
50
60
70
80
90
10 20 30 40 50
day after planting (DAP)
he
igh
t (c
m)
360 ppm
720 ppm
AaAb
Ac
Ad
Ae
Af
BaBa
Bb
Bc
Bd
Be
Increase of 16% in plant height
SUGARCANE RESPONSE TO CO2 ENRICHMENT
Leaf area
0
20
40
60
80
100
120
140
160
360ppm 720ppm
treatments
leaf
are
a (c
m2 )
0
1
2
3
4
5
6
36 42 49
DAP
nu
mb
er o
f le
aves
360ppm
720ppm
Number of leaves
• Slight increase in the rate of leaf production
• Trend to increasing in leaf area
SUGARCANE RESPONSE TO CO2 ENRICHMENT
Net CO2 Assimilation
0
5
10
15
20
25
30
35
25 30 35 40
DAP
A (
um
oL
CO
2 m
-2 s
-1)
360 ppm
720 ppm
Aa
AbAc
Aa
AbAc
Increase of about 25% in CO2 assimilation
SUGARCANE RESPONSE TO CO2 ENRICHMENT
0,0
0,1
0,2
0,3
0,40,5
0,6
0,7
0,8
0,9
Root Stem Leaf Roll Leaves
tissues
mas
s (g
)
360ppm
720ppm
Biomass
59%38%
SUGARCANE RESPONSE TO CO2 ENRICHMENT
4.29 3.67 b
4.31 2.16 b
stem
13.78 5.88 a
9.02 2.41 a
leaves
720ppm360ppm
ReducingSugars
(ug/mgDW)
4.29 3.67 b
4.31 2.16 b
stem
13.78 5.88 a
9.02 2.41 a
leaves
720ppm360ppm
ReducingSugars
(ug/mgDW)
31.21 14.66 b
32.91 8.52 b
stem
50.74 5.2 a
55.28 3.41 a
leaves
720ppm360ppm
Total sugars
(ug/mgDW)
31.21 14.66 b
32.91 8.52 b
stem
50.74 5.2 a
55.28 3.41 a
leaves
720ppm360ppm
Total sugars
(ug/mgDW)
15,93 1,01 a
15,40 0,71 a
colmo
20,20 1,74 a
19,09 0,53 a
folhas
720ppm360ppmCellulose (%)
15,93 1,01 a
15,40 0,71 a
colmo
20,20 1,74 a
19,09 0,53 a
folhas
720ppm360ppmCellulose (%)
• No significant differences in the levels of soluble sugars and cellulose
• Higher assimilation of carbon by sugar cane plants is stored as biomass rather than sugar
PERSPECTIVES
• Long-term experiments ( 1.5 years)
• Expression analysis from different genes expressed in leaves and stem (photosynthesis, sugar metabolism, cell wall and others) using SUCEST database
• HPLC analysis from cell wall components