title: Arabidopsis thaliana root growth kinetics and lunisolar tidal acceleration.
abstract: • All living organisms on Earth are continually exposed to diurnal variations in the gravitational tidal force due to the Sun and Moon. • Elongation of primary roots of Arabidopsis thaliana seedlings maintained at a constant temperature was monitored for periods of up to 14 d using high temporal- and spatial-resolution video imaging. The time-course of the half-hourly elongation rates exhibited an oscillation which was maintained when the roots were placed in the free-running condition of continuous illumination. • Correlation between the root growth kinetics collected from seedlings initially raised under several light protocols but whose roots were subsequently in the free-running condition and the lunisolar tidal profiles enabled us to identify that the latter is the probable exogenous determinant of the rhythmic variation in root elongation rate. Similar observations and correlations using roots of Arabidopsis starch mutants suggest a central function of starch metabolism in the response to the lunisolar tide. The periodicity of the lunisolar tidal signal and the concomitant adjustments in root growth rate indicate that an exogenous timer exists for the modulation of root growth and development. • We propose that, in addition to the sensitivity to Earthly 1G gravity, which is inherent to all animals and plants, there is another type of responsiveness which is attuned to the natural diurnal variations of the lunisolar tidal force.
authors.affiliation: Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Fisahn
authors.affiliation: Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam, Germany.
authors.forename: Nima
authors.initials: N
authors.lastname: Yazdanbakhsh
authors.affiliation: Institute of Geodesy and Photogrammetry, ETH-Hönggerberg, CH-8093 Zürich, Switzerland.
authors.forename: Emile
authors.initials: E
authors.lastname: Klingele
authors.affiliation: School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Barlow
mesh_terms: D017360:Arabidopsis / Q000254:growth & development* / Q000528:radiation effects*; D002940:Circadian Rhythm / Q000528:radiation effects; D006112:Gravitation; D007700:Kinetics; D008027:Light; D016081:Moon; D017440:Photoperiod; D018517:Plant Roots / Q000254:growth & development* / Q000528:radiation effects*; D036226:Seedlings / Q000254:growth & development / Q000528:radiation effects; D016082:Solar System