Lunar gravity affects leaf movement of Arabidopsis thaliana in the International Space Station
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Cyclic leaf ascent and descent occur in synchrony and phase congruence with the lunisolar tidal force under a broad range of conditions.
Digitized records of the vertical leaf movements of Arabidopsis thaliana were collected under space flight conditions in the International Space Station (ISS). Oscillations of leaf movements with periods of 45 and 90 min were found under light-adapted conditions, whereas in darkness, the periods were 45, 90, and 135 min. To demonstrate the close relationship between these oscillations and cyclical variations of the lunisolar gravitational force, we estimated the oscillations of the in-orbit lunisolar tide as they apply to the ISS, with the aid of the Etide software application. In general, in-orbit lunisolar gravitational profiles exhibited a periodicity of 45 min. Alignment of these in-orbit oscillations with the oscillations of Arabidopsis leaf movement revealed high degrees of synchrony and a congruence of phase. These data corroborate previous results which suggested a correlative relationship and a possible causal link between leaf movement rhythms obtained on ground and the rhythmic variation of the lunisolar tidal force.
KeywordsCircadian clock Etide Lunisolar Zeitgeber
International Space Station
European Modular Cultivation System
We are grateful to Prof. Dr. Anders Johnsson (Department of Physics, Norwegian University of Science and Technology, N-7491 Trondheim, Norway), Dr. Bjarte Solheim (Department of Physics, Norwegian University of Science and Technology, N-7491 Trondheim, Norway), and Prof. Dr. Tor-Henning Iversen (Department of Biology, The Plant BioCentre, Norwegian University of Science and Technology, N-7491 Trondheim, Norway) for providing additional results and details of the conditions in the ISS during the in-orbit experiments, for reading the manuscript and providing valuable comments. We would like to thank Prof. Dr. Nima Yazdanbakhsh for critical discussion of the described experiments. Special thanks to Prof. Dr. em. Enno Brinckmann for providing valuable further details on the construction of the EMCS.
Conflict of interest
We declare no conflict of interests.
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