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Leaf Temperature of Radish (Raphanus sativus) in Response to Increased Transpiration under Hypobaric Conditions.  J.D. Peterson1 and P.A. Fowler2  1Midland Lutheran College, Fremont, NE.  2Dynamac Corporation, Kennedy Space Center, Florida

    Increasing interest in the possibility of a human mission to Mars has generated a growing desire to understand plant responses to hypobaria.  This research investigated the effects of hypobaric conditions on internal and external leaf temperature.  Under typical Earth pressures, ambient air temperatures are nearly equivalent to internal leaf temperatures.  However, under hypobaric conditions, plants lose heat more rapidly as a result of increased transpiration.  This discrepancy between ambient air temperature and internal leaf temperature has significant effects on plant transpiration rate and drought-stress mechanisms.  This research examined plant heat loss over time due to transpiration under both Earth-like pressures and hypobaric conditions.  Leaf temperature decreased directly in response to increased transpiration under hypobaria.