Does circumnutation follow tidal plumb line variations

The Morlet wavelet coherences and spectro-temporal coherences were applied to detect common oscillations in sunflower autonomic movements (circumnutations) and variations of the direction of the gravity vector. The mean coherence between time series of sunflower coordinates and the theoretical plumb line model was of the order of 0.6–0.8 for oscillations with periods greater than two days. We also detected weak common oscillations with periods of 0.5 and 1.0 days, which may correspond to semidiurnal and diurnal tides, respectively. Computing the common signal in the time series of sunflowers used in the experiment revealed a low, but statistically significant coherence for semidiurnal and diurnal oscillations. Although we cannot determine if plumb line variations indeed influence circumnutation in sunflower, we prove that there is a significant correlation between these two phenomena.