Looking for the smallest level of gravity a plant can still sense

Cultivating plants for food was a significant step in the history of mankind. Growing plants for food in space and on other planets will be necessary for exploration of our Universe. Stems and leaves grow towards the light and against gravity, while roots follow gravity. What role does gravity play in this process and what can we learn from growing plants in weightlessness? Which unknown aspects of plants will be discovered by this kind of research? Research in space focuses on the Arabidopsis thaliana plant, a model plant used as a reference for biologists. It has already been shown that plants 'feel' gravity at a cellular level, mainly in cells located at the tip of the root. Experiments on the International Space Station are investigating how this process works, from the primary step of sensing gravity to investigating how the whole plant responds. One of the experiments flown on the Space Station, GRAVI-1, looked at the smallest level of gravity a plant can sense. The results imply that plant's sense of gravity is amplified, because they react to very-low gravity levels.