Endogenous oscillations in pathways of energy transduction as related to circadian rhythmicity and photoperiodic control

Evidence is presented for endogenous rhythmicity in energy transducing sequences of cellular metabolism which result in a circadian rhythm in adenylate “energy charge” and redox state (NADPH/NADP). From phase dependent photocontrol of enzymatic activity and pyridine nucleotide pool-size levels it is concluded that light — via photoreceptor(s) of photoperiodic control — modulates energy flow under conditions where overall energy transduction displays a circadian rhythm. The results are discussed in relation to temporal organization of development in general.