Green onion plants grown using aeroponics (IMAGE) NASA/Johnson Space Center Caption Green onion plants grown using aeroponics are held to display their roots. The XROOTS study tests hydroponic (water-based) and aeroponic (air-based) techniques to grow plants in space. Credit Sierra Space Usage Restrictions No restrictions. License Public Domain Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.