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