Effects of Gravity on Stem Sap Flow and Water and Heat Exchange in the Leaves of Sweetpotato

Abstract

Plants play an important role in bio-regenerative life support systems (BLSSs) for long-term manned space missions. During parabolic airplane flights, we investigated stem sap flow without forced air movement and water vapor conductance with forced air movement using sweetpotato plants. Stem sap flow was promoted under microgravity, but only when forced air movement was applied to the plants. The water vapor conductance of the plant leaves increased under microgravity at an air velocity of 0.25 m･s(exp -1). Leaf temperatures also increased under microgravity at an air velocity of 0.02 m･s(exp -1). This suggests that forced air movement is important in maintaining long-term, healthy plant growth in BLSSs.