Microgravity effects on water supply and substrate properties in porous matrix root support systems

The control of water content acid water movement in granular substrate-base d plant root systems in microgravity is a complex problem. Improper water a nd oxygen delivery to plant roots has delayed studies of the effects of mic rogravity on plant development and the use of plants in physical and mental life support systems. Our international effort (USA, Russia and Bulgaria) has upgraded the plant growth facilities on the Mir Orbital Station (OS) and used them to study th e full life cycle of plants. The Bulgarian-Russian-developed Svet Space Gre enhouse (SG) system was upgraded on the Mir OS in 1996. The US developed Ga s Exchange Measurement System (GEMS) greatly extends the range of environme ntal parameters monitored. The Svet-GEMS complex was used to grow a fully developed wheat crop during 1996. The growth rate and development of these plants compared well with ea rth grown plants indicating that the root zone water and oxygen stresses th at have limited plant development in previous long-duration experiments hav e been overcome. However, management of the root environment during this ex periment involved several significant changes in control settings as the re lationship between the water delivery system, water status sensors, and the substrate changed during the growth cycles. (C) 2001 published by Elsevier Science Ltd. All rights reserved.