Germination and Growth of Spinach under Hypobaric Conditions.

Abstract

In a plant production facility designed for human life support in vacuum space, lowering total air pressures within the facilities is expected to have the engineering advantage of reducing the construction cost. In this study, low total pressure treatments were applied to spinach over the entire production period from seeding to harvest. An environment control system was constructed to grow plants under low total pressure for long durations. Spinach seeds were directly sowed on a hydroponic plant bed placed in a reduced-pressure growth chamber. The total and O2 partial pressures within the growth chamber were set at 101 and 21 kPa, 25 and 21 kPa, and 25 and 10 kPa, respectively. The CO2 partial pressure was constant at 40 Pa. At 21 kPa of O2 partial pressure, there were no significant differences in fresh and dry weights, leaf area, and shoot length of spinach at harvest between 101 and 25 kPa of total air pressure. At 10 kPa of O2 partial pressure and 25 kPa of total pressure, the dry weight was not affected, but the leaf area and shoot length at harvest were smaller than those at 21 kPa of O2. According to these results, it was evident that the entire cultivation of spinach from seeding to harvest could be carried out at one-fourth atmospheric pressure when the O2 and CO2 partial pressures are at atmospheric levels.