The Fascinating Journey of Earth’s Smallest Plant in Hypergravity

The smallest flowering plant on Earth, watermeal, is being studied for its potential use as a food source for astronauts and as a source of oxygen. Researchers from Mahidol University in Thailand conducted experiments on watermeal aboard ESA’s Large Diameter Centrifuge (LDC), subjecting the plants to 20 times normal Earth gravity. The LDC is an 8-meter diameter four-arm centrifuge located at ESA’s ESTEC technical center in the Netherlands, which provides access to hypergravity for extended periods of time.

Watermeal, which is smaller than duckweed, floats on water bodies in Thailand and Asia. The Mahidol University team became interested in studying watermeal because it lacks roots, stems, or leaves, making it a ideal model for understanding how plants respond to changes in gravity. Additionally, watermeal produces a significant amount of oxygen through photosynthesis and is a good source of protein. In Thailand, watermeal has been consumed for a long time and is used in various dishes such as soups and salads.

Previously, the team studied watermeal using clinostats to simulate microgravity conditions by continuously shifting the orientation of the gravity vector. However, little difference was observed between plant growth at 1g and simulated microgravity. The team aims to study the plants’ growth and adaptation across a range of gravity environments using the LDC. Watermeal has a short life cycle of five to 10 days, allowing for comprehensive observations within a short period.

During the experiments, watermeal samples were placed in boxes equipped with LED lights that mimic natural sunlight. These boxes were then placed in a centrifuge gondola and spun at 20 times Earth’s gravity. The team plans to examine the plants directly and render extracts into solid pellet form for further analysis. Chemical analysis of the samples will provide insights into watermeal’s response to hypergravity.

In addition to the LDC, the team utilized ESA’s Life Support & Physical Sciences Instrumentation Laboratory facilities and the adjacent Materials and Electrical Components Laboratory to prepare their experiments and finalize samples. Following the watermeal experiments, an all-female team from Universidad Católica Boliviana ‘San Pablo’ in Bolivia will conduct experiments on how hypergravity affects the breakup of human red blood cells using the LDC.

Visitors to ESA’s Open Days at ESTEC will have the opportunity to see the LDC in operation and learn more about the ongoing research on watermeal and its potential applications in space exploration.