Space Agriculture: Evolution of Plant Growth Technologies.

Several decades of spaceflight plant experiments were dedicated to determining how plant life cycle functions (germination, embryo formation, pollination, seed formation) perform in microgravity. Chamber technologies for environmental control (air temperature, humidity, degree of air ventilation, light intensity, CO₂ concentration, and root zone moisture) used for these early experiments were improved incrementally. Examples of these chamber systems will be discussed. These studies determined that plant growth in microgravity was being affected by indirect effects of spaceflight (e.g. lack of boundary layer convection and the dominance of capillary forces in the absence of gravity) that were not being mitigated by chamber environmental controls. Recent experiments in the last decade have focused primarily on food production aboard spacecraft for enhancing crew diets with fresh salads. These efforts included crop selection, rooting media selection, increasing the chamber growing area, as well as, developing procedures for disinfecting salad crops for human consumption.