Preparatory experiments for long term observation of Arabidopsis circumnutations in microgravity
- Paper number
IAC-05-A1.6.06
- Author
Mr. Bjarte Gees Bokn Solheim, Norwegian University of Science and Technology, Norway
- Coauthor
Ms. Ann-Iren Kittang, Norwegian University of Science and Technology, Norway
- Coauthor
Prof., dr.philos Tor-Henning Iversen, Norwegian University of Science and Technology, Norway
- Coauthor
Prof., fil.dr. Anders Johnsson, Norwegian University of Science and Technology, Norway
- Year
2005
- Abstract
Plants often show rotational movements during growth, e.g. rotational movements around the plumb line - so-called circumnutations. The studies of these movements have received considerable interest already since Darwin published a book on plant movements. The movements seem to be driven by inherent oscillatory processes but are also modified by the acceleration force (gravity or centripetal forces). Circumnutations have been observed in Helianthus annuus, cv. “Teddy Bear”, in a short-term microgravity experiment (HEFLEX, Spacelab-1). Here, circumnutation frequency and amplitude were changed, indicating that gravity is not a prerequisite for circumnutations, but probably a modifying factor. Understanding the mechanisms behind this nearly universal growth behaviour is complicated by the fact that no single factor seems to produce the observed growth behaviour (Johnsson, A., 1997).
The MULTIGEN-1 ISS experiment scheduled for 2006 has two main objectives: a complete life cycle seed-to-seed growth experiment (60-90 days) and simultaneous observations of circumnutations. This experiment is carried out in the European Modular Cultivation System (EMCS). A 1-g centrifuge in the EMCS will provide a space based 1-g control in addition to ground based controls. The subject for this study is the shoot system of the well known model plant Arabidopsis thaliana. The experiment provides the first long term observations of circumnutations in microgravity.
Preparatory experiments both in the Experiment Reference Model (ERM) and under controlled laboratory conditions are performed. These evaluate 1-g growth behaviour under similar growth conditions as in the EMCS on the ISS (e.g. soil composition, RH, atmospheric flow, light conditions, water supply). The rapid movements observed on Earth for hypocotyls, leaves and flower stalks (circumnutation periods about 30-140 minutes) and long term behaviour changes require frequent image capture over prolonged periods of time. This taxes the EMCS control and observation systems in new ways. Preparatory experiments therefore include finding techniques to maximise scientific data output within tight system constraints.
Circumnutations involve movement in three dimensions, but with only one video camera available per growth chamber, only two dimensions can easily be extracted. Different techniques to obtain three dimensional positioning of different plant parts using only one video source are developed and discussed. These techniques include a novel method of panning the video camera around its central axis. By this method slightly different vantage points enable 3d positioning. The use of mirrors and physical reference points inside the growth chambers is an alternative approach and will also be considered. Given the available bandwidth for downlink of images and onboard local storage, the image frequency required for recording fast moving circumnutations is yet another strain on the system. Examples illustrating the different techniques and growth patterns will be presented, as well as available solutions and various compromises.
References: Johnsson, A. 1997. Circumnutations: results from recent experiments on Earth and in space. Planta. 203: S147-S158.
- Abstract document
- Manuscript document
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