The amounts of mRNA of subunit-c (proteolipid) of the V-ATPase of mature leaves of Mesembryanthemum crystallinum L. in the state of C3-photosynthesis were analyzed for a time-series of 96 h under constant conditions in continuous light. Fourier-transform analysis of the data showed endogenous oscillations of the mRNA with period lenghts of 48, 24 and 12 h, ie harmonic frequency resonances.