The scientific term for this type of reactions is microgravitropism.

For this purpose, I fixed the plants onto a wheel of a clinostat (a device allowing to simulate a certain gravity through the centrifugal force of a rotating bicycle wheel).

The study was divided into two parts. The first part focused on the germination of sunflower seedlings at a low gravity. The second part focused on the seedlings' reactions to a low gravity, and on the minimal force required by the plants in order to grow normally.

The first study showed that after two weeks, the plants had been unable to germinate at a gravity equivalent to 0,4 G (1 G: gravity on Earth (9,81 N)). Plants having previously germinated in "normal conditions ", however, where able to grow on the clinostat, although not as fast ad the plants exposed to the normal gravitation.

The second study showed that the minimal gravity needed by sunflower seedlings to grow normally is about 0,2 G. This value is higher than the one for beans, but lower than the one for Soya e.g. . At a lower gravity, the seedlings become brownish and smooth, and they grow into any direction.

As a conclusion, one can say that a low gravity strongly disturbs the plants' germination and growth.

Unfortunately, little work has been done in that scientific area until now, but the results of research projects about microgravitropism are gaining in importance with the progress of space exploration. It is, for example, interesting to see that sunflower seedlings would have more difficulties to grow under the gravitational conditions of Mars (0,4 G) than beans.

The microgravitational effects can be studied on the morphological level, but also on the biochemical level, and I actually plan to investigate the role of auxines in microgravitropism in my next research project.

Florence FOLMER,

participant at the London International Youth Science Forum (LIYSF) 1996

the project has been presented at:

- the national contest for Young Scientists in Luxembourg in 1997

- the EXPO SCIENCE INTERNATIONALE 97' in PRETORIA, South Africa.

- the International Science Festival 98' in Moscow, Russia.

- the EXPO SCIENCE INTERNATIONALE 99' in PUEBLA, Mexico.

1.1. The idea of the project

1.2. Preliminary study

1.3. Structure of the study

2.1. The material

2.1.1. The clinostat

2.1.2. The plants

2.2. The Manipulations

2.2.1. First study

2.2.2. Second study

3.1. Observations

3.1.1. First study

3.1.2. Second study

3.2. Interpretation

I. Information about the article " Growing seedlings at less than 1 G " (CARLSON. S. 1996. Growing Seedlings at Less Than 1 G. Scientific American. February 1996. pp. 110-111.)

II. Brief history of research on gravitropism