S11 - Session P1 - The effect of different atmospheric pressure conditions at low and high partial pressures of carbon dioxide on the growth of lettuce

Authors: Akinori Shimada *, Hiroyuki Watanabe

Agriculture on Moon and Mars is important aspect for long-term residence in space. On the space agriculture, the hypobaric cultivation method is thought to be a good way of growing plants in space because hypobaric conditions can reduce the differences between external and internal environments of plant cultivation facilities. The objective of this study is to investigate the effect of different atmospheric pressure conditions on gas exchange of carbon dioxide and growth in lettuce under low ( p CO 2 30 Pa, p O 2 21 kPa) or high ( p CO 2 100 Pa, p O 2 21 kPa) partial pressures. We carried out the experiments using a reduced pressure plant cultivation system to culture lettuce under hypobaric condition. The total pressure, carbon dioxide and oxygen partial pressure, temperature and relative humidity in the hypobaric plant growth chambers were controlled throughout the experiments. Fresh weight of lettuce grown under hypobaric condition at low partial pressure of carbon dioxide was higher than that at normal atmospheric condition. Gas exchange rate of carbon dioxide in lettuce under hypobaric condition was higher than that under normal atmospheric condition. In addition, the increasing ratio of gas exchange rate at low partial pressure of carbon dioxide was higher than that at high partial pressure of carbon dioxide. We showed that molecular diffusion rate under hypobaric condition may increase strongly at low partial pressure of carbon dioxide rather than high partial pressure of carbon dioxide.