Agriculture Reference
In-Depth Information
The circadian rhythmic cell (cyanobacterial and eukaryotic) is consid-
ered to be a hydro-electrochemical oscillator (Wagner et al. 1997) synchro-
nised by the daily light-dark cycles, with temporal compartmentation of
metabolism and a network of metabolic sequences to compensate for oxida-
tive stress in adapting to the light environment, e.g. by separating nitrogen
fixation from photosynthetic oxygen production (Sherameti et al. 2002).
25.5
Circadian Rhythmic Organisation of Energy
Metabolism in
C. rubrum
and the Gating
of Photoreceptor (Phytochrome) Action
In
C. rubrum
a circadian rhythm in overall energy transduction has been
observed. The rhythm results from an oscillatory network between glycoly-
sis and oxidative phosphorylation, coupled to photophosphorylation. This
network produces a circadian rhythm in adenylate energy charge and re-
dox state (NADP/NADPH
2
). The nucleotide ratios themselves could act as
rate effectors in compartmental feedback and thus fulfil the requirements
of precise temperature-compensated time-keeping (Wagner et al. 1975,
Table 25.2.
Rhythmic organisation of metabolism in
Chenopodium rubrum
(the period
lengths of the subpeaks are in
parentheses
) (Complemented after Bünning 1977)
Phenomenon
Period length (h)
Photoperiodic light sensitivity
30
Betacyanine accumulation
24-30 (15)
Betacyanine turnover
24-30
Adenylate kinase activity
30 (15)
Energy charge (ATP + 1/2 ADP/ATP + ADP + AMP)
21-24 (11-13)
NADPH
2
/NADP ratio
21-24
Dark respiration
21-24
Chlorophyll accumulation
15
Net photosynthesis
15
Triose phosphate dehydrogenase activity (NADH
2
;NADPH
2
)
15
Malate dehydrogenase activity
12-15
Glutamate dehydrogenase activity
12-15
Glucose-6-phosphate dehydrogenase activity
12-15
Gluconate-6-phosphate dehydrogenase activity
12-15
Pyridine nucleotide, pool size [NAD(H
2
); NADP(H
2
)]
12-15 (6)
Turgor-controlled growth phenomena
Stem extension rate
23-27
Leaf movement
23-27
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