Published: 28.02.08
Space biology

Root-coilers in space

The European Columbus Space Laboratory has begun its work. One of the first experiments studies the behaviour of plants in conditions of weightlessness. The experiments are controlled from Zurich by ETH Zurich space biologists.

Thomas Langholz
The different root growth patterns are clearly recognisable here. The wild type is at the top. It responds to gravity and prefers to form wavy roots. The coil-shaped roots are visible in the case of the genetically modified seeds (bottom). Photo: NASA
The different root growth patterns are clearly recognisable here. The wild type is at the top. It responds to gravity and prefers to form wavy roots. The coil-shaped roots are visible in the case of the genetically modified seeds (bottom). Photo: NASA (large view)

After the Atlantis space shuttle had returned to Earth safely, the three astronauts who had remained on the ISS International Space Station began to complete an extensive research programme. The first experiment in the Columbus Biolab module concerns itself with the behaviour of plants in zero gravity. The experiment’s name – WAICO – stands for “Waving and Coiling of Aridopsis roots at different g-levels”. Plants can detect weightlessness and adjust their growth movements accordingly. Roots grow towards the centre of the Earth and shoots grow away from the Earth’s centre. This process is called gravitropism. Plants control this growth via gravitation sensors, statoliths, in the root cap. Another phenomenon is that roots grow in coils or waves. Growth in coils is called circumnutation. The researchers hope the experiments will help provide important information about the various factors influencing plant growth.

Important knowledge about plant growth

The Arabidopsis plant, also called thale cress, will be used to study the two phenomena. The experiment will employ two different seeds; firstly the naturally-occurring wild type and secondly a genetically modified form. The genetically modified form has a very small response to gravity. Four series of experiments will be germinated in space under Earth-like conditions (1 G) for two days. Then two series will be subjected to zero gravity. Sonia Vadrucci, Head of the Biotechnology Space Support Center (Biotesc), which is conducting the experiments, says “This means we have several growing plants: in each case we have the wild type and the genetically modified type under Earth-like conditions, and the same series in zero gravity.” Up to now it has been unclear whether spiral growth (circumnutation) is affected by gravity or whether it is an internal plant mechanism that happens even without gravity. Based on the shape of the roots, the researchers will afterwards be able to determine how the mechanism operates. It could be that the coiling (circumnutation) is independent of gravity, and the roots will then grow in a spiral shape. Gravitropism will stretch the roots and form waves. With the mutant form, which does not respond so strongly to gravity, the roots will then develop a coiled shape. Under micro-gravity conditions the wild type would now also form spirals to a greater extent because gravitropism can no longer take effect. On the other hand, if coiling depends on gravity and the latter is absent, the roots will no longer have a spiral shape but will grow straight and more elongated.

One hour of live images from space

ETH Zurich space biologists will look after the Hanover University experiment. The space biologists are satisfied so far. The module was commissioned successfully and preparations for the experiment are going according to plan. With the experiment underway, the Zurich researchers can follow it live for one hour each day: a camera transmits the images from the ISS research station. Sonia Vadrucci explains that “The Columbus space laboratory enables us to intervene in the experiments directly from the ground. For example the moisture for the plants can be regulated.” After the experiments have been completed, the samples will be returned to Earth with the next shuttle mission in late March. The plants will then be studied using molecular and cell biology methods to track down the cellular mechanisms.

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