How do you stop gravity

WAICO: How do plants orient themselves without gravity?

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The WAICO plant growth experiment is intended to answer this question. It was determined by the ESA as the first of four experiments for the Biolab laboratory. Seeds of a selected plant species are germinated. Based on the growth of these plant seedlings, conclusions can be drawn about the influence of gravity on their orientation performance. It is a so far unsolved mystery: How do the plants know in which direction they and their roots should grow? What is certain is that in addition to light and the supply of water and nutrients, gravity must also play a role in the complex growth process.

It is known that plants perceive gravity and process it by growing their organs in very specific directions: the roots are moved towards the center of the earth, the shoots away from the center of the earth. The roots are equipped with cells that contain gravitational receptors called statholites. How do these statholites behave when the influence of gravity diminishes, even ceases entirely? A question that can only be investigated in the space laboratory.

If gravity is completely or partially eliminated over longer periods of time, the influence of other growth factors can also be examined more closely. The results of this research are used to breed new plant varieties with optimized growth, but could also lead to the development of new fertilizers. In addition, the growth experiments in Earth orbit provide new insights into the cultivation of agricultural crops in space, for example during long-term trips to other planets.

First experiment in the biological research laboratory Biolab

Questions about the gravitational biology of plants are examined in the Biolab, the biological research laboratory on the ISS. The Biolab, which is housed in an equipment cabinet, contains facilities for largely automated biological research with microorganisms, tissue cells, small plants or small invertebrates. This also includes two centrifuges with which samples can be exposed to various influences of gravity. They range from microgravity to double gravity.

The WAICO experiment from Germany marks the start of biological research experiments in the Biolab. Scientists from the Ornamental Plant and Wood Science Institute at Leibniz University Hannover want to use WAICO - Waving and Coiling Response of Arabidopsis Roots at Different g-levels - to investigate the growth behavior of the roots of a particular plant.
The small flowering plant Arabidopsis (thale cress) was selected as the test object. Because of its advantages - easy cultivation in a limited space and a short, approximately 6-week life cycle from sowing to seed maturity - Arabidopsis has become a model organism for basic researchers.

A mini greenhouse in space

WAICO works like a small greenhouse. It is monitored around the clock by cameras that transmit their images in real time to the Columbus control center in Oberpfaffenhofen, from where they are distributed to the individual test managers. The researchers on earth can intervene in the course of the experiments in the Biolab by remote control.

The Bremen-based space company OHB-System AG has taken on the development, construction and testing of the hardware for the WAICO experiment, including the life support system. In some cases extreme challenges had to be overcome: "We had to use valves and pumps from microsystem technology in order to be able to precisely dose the smallest amounts of liquid for the test container." reports Dr. Klaus Slenzka, head of the WAICO project at OHB.

“Ride a carousel” in space with WAICO

On February 29, WAICO was put into operation by the French ESA astronaut Léopold Eyharts. The astronaut's task was essentially to equip the 16 experiment containers filled with nutrient medium with seeds of the thale cress plant and to place them on centrifuges in the Biolab incubator. This provides the atmospheric living conditions for the organisms by means of a life support system. The air humidity and the content of gases such as oxygen, carbon dioxide or nitrogen in the test atmosphere are regulated. At the same time, the ethylene that the plants form during their growth is sucked off.

The filled containers can be placed on the centrifuges. During the course of the experiment, you will “drive carousel” over and over again for two weeks. The centrifuges simulate the different levels of gravity - from weightlessness to double the gravity of the earth. The focus of the investigations is the root growth. After two weeks, the experimenters artificially stop plant growth and preserve the samples on the ground for evaluation. The samples will be returned with the STS 123 space shuttle mission.

Comparative tests on earth

In parallel to the experiments in space, thale cress plants are growing in Cologne under terrestrial conditions for comparison purposes in absolutely identical experiment containers. The work is carried out at the Facility Responsible Center (FRC) for Biolab, which in turn is housed in the Microgravity User Support Center (MUSC) Cologne.

MUSC is the user support center of the German Aerospace Center (DLR) in Cologne-Porz, which supports research institutions and companies in the preparation and implementation of their work on board the ISS on behalf of ESA. It is integrated into the network of European “User Support and Payload Operations Centers” for the ISS.
The FRC in Cologne has overall responsibility for all Biolab systems on behalf of ESA. The biological research laboratory is designed for a period of at least ten years.

Contact Person
Prof. Dr. Günther Scherer
Gottfried Wilhelm Leibniz University of Hanover
Institute for Ornamental Plant and Wood Science
Department of Molecular Yield Physiology
Email: scherer @ zier.uni-hannover.de
Tel: +49 (0) 511/762 - 3153

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