PREPARATORY EXPERIMENTS FOR LONG TERM OBSERVATION OF ARABIDOPSIS CIRCUMNUTATIONS IN MICROGRAVITY

摘要

The MULTIGEN-1 ISS experiment has two objectives: a complete life cycle seed-to-seed growth experiment (about 70 days) and simultaneous observations of circumnutations, i.e. plant growth movements often describing circular or elliptical paths. MULTIGEN-1 is carried out in the European Modular Cultivation System (EMCS) hardware. The subject for this study is the shoot system of the plant Arabidopsis thaliana. The experiment provides the first long term observations of circumnutations in microgravity. Preparatory experiments in the Experiment Reference Model and under controlled laboratory conditions are performed. These evaluate 1-g growth behaviour under similar growth conditions as in the EMCS on the ISS. The rapid movements observed on Earth for hypocotyls, leaves and flower stalks require frequent image capture over several weeks. The circumnutations are 3D movements, but with only one video camera available per growth chamber, only two dimensions can easily be extracted. Triangulation of different plant parts using one video source is discussed. Limited bandwidth for downlink of images and limited onboard local storage combined with the image frequency required for recording fast moving circumnutations is also a strain on the system. Examples illustrating the different techniques and growth patterns are presented, as well as available solutions and various compromises.