Plant Respiratory Efficiency

1
Plant Respiratory Efficiency
Oscar Nagel and Richard Bligny Centre dEtudes
Nucléaires de Grenoble Laboratoire Physiologie
Cellulaire Végétale Grenoble France
2
Respiration Mechanisms
36ADP 36Pi Glucose 36H 6O2 ? 36ATP
6CO2 42H2O

• Respiratory efficiency
• Animals 36 ATP per glucose, 3 ATP per O-atom
  (P/O 3)
• Plants 12-36 ATP / glucose, 1 P/O 3
• Plants have two parallel pathways with different
  efficiency
• Cytochrome (P/O 3) and Alternative (P/O 1)

3
Respiration

• Respiratory efficiency
• Animals 36 ATP per glucose
• 3 ATP per O-atom (P/O 3)
• Plants 12-36 ATP per glucose
• 1 P/O 3
• Plants have two parallel pathways with different
  efficiency
• Cytochrome (P/O 3) and Alternative (P/O 1)

4
Respiration Pathways
Growth Maintenance Transport
ATP
Pi ADP
Pi ADP
ATP
NADH
Glucose
O2
Cyt
I
e-
e-
KCN
H2O
NAD
CO2
e-
O2
Alt
SHAM
H2O
5
What Determines Contribution?

• Determine effect inhibitors on O2-consumption
• Problem
• Activities of both pathways interdepend
• ? O2 uptake rates do not give enough information

6
NMR spectroscopy

• Measure P/O-ratios as a measure of efficiency
• ATP-synthesis rate
• saturation transfer Pi to g-ATP
• O2-consumption rate
• oxygen electrode

7
NMR Experiment
Pump
Analysis cuvette
Reference cuvette
Arabidopsis cell suspension
O2 monitor
Perfusion medium
NMR tube
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NMR Spectrum
9
Results

• P-status strongly influences quality NMR spectra
  and respiration rates
• KCN reduces ATP, thus blocks Cytochrome
• SHAM does not affect ATP
• Both inhibitors reduce flow through respective
  pathway, but enhance total O2-consumption rate
• Activities of both pathways are far below
  capacities