Maria Stolarz E-mail: maria.stolarz@poczta.umcs.lublin.pl Department of Biophysics Faculty of Biology and Biotechnology Maria Curie-Sklodowska University ul. Akademicka 19 20-033 Lublin, Poland
Circumnutation (Latin circus for circle, nutatio for sway, CN) is an endogenous movement of plant organs such as hypocotyls, coleoptiles, epicotyls, stems, shoots, tendrils, petioles, or roots, the apex of which outlines a circle, ellipsis, pendulum-like shape, or irregular zigzags within a several minute- to several hour-long period. Due to organ elongation, series of a single trajectory of CN form a more or less regular helix.
Film 1 Circumnutation of the stem of a three-week old sunflower. Time-lapse photography took three days in constant light conditions (1 frame per 5 min). The plant grew approx. 3.5 cm while doing 30 circumnutations (ca. 10 per day, one circumnutation has an average length of approx. 4 cm and takes approx. 145 minutes). On average, the apex of the stem of approx. 20 cm high sunflower covered a path of approx. 120 cm within 3 days.
Film 2 Circumnutations in the first phase of sunflower seedling growth. The straightening of the hypocotyl hook and the opening of the cotyledon are also visible. The film presents three days; plants in hydroponic cultivation.
Film 3 Circumnutation and growth of one-week-old sunflower seedlings. Three days of filming, constant lighting, plants in hydroponic cultivation.
Film 4 Circumnutation and growth one-week-old sunflower seedlings - top view. One day of filming. Clearly visible slow “torsion” movements, i.e. twisting of the hypocotyl together with the cotyledons in a counter-clockwise direction.
Examples of helical circumnutation trajectory
The technique of time-lapse photography is also useful in investigations of development of flowers and the role of biological clock in the regulation of flowering time e.g.
Stolarz M (2009) Circumnutation as a visible plant action and reaction: physiological, cellular and molecular basis for circumnutations. Plant Signaling & Behavior 4: 380-387
The most visible feature of these movements is a ultradian rhythm with a period of approx. 2,5 hours named an ultradian rhythm. The period of CN depends of the species but we have also shown that it can fluctuate in a daily manner and can be changed by environmental conditions.
A daily rhythm of changes in the length of the CN trajectory has also been shown.
CN is a common phenomenon among plants but the knowledge of CN is not widespread. In our laboratory, CN have been registered and studied since 1993 mainly in Helianthus annuus plants but also in
CN mechanism is based on cell turgor and volume changes driven by ion fluxes, similar to that in stomatal movement and pulvinus motor cells e.g. in Desmodium motorium,
