title: The effect of gravity on surface temperature and net photosynthetic rate of plant leaves.
abstract: To clarify the effects of gravity on heat/gas exchange between plant leaves and the ambient air, the leaf temperatures and net photosynthetic rates of plant leaves were evaluated at 0.01, 1.0, 1.5 and 2.0 G of 20 seconds each during a parabolic airplane flight. Thermal images of leaves were captured using infrared thermography at an air temperature of 26 degrees C, a relative humidity of 15% and an irradiance of 260 W m-2. The net photosynthetic rates were determined by using a chamber method with an infrared gas analyzer at an air temperature of 20 degrees C, a relative humidity of 50% and a photosynthetic photon flux of 0.5 mmol m-2 s-1. The mean leaf temperature increased by 1 degree C and the net photosynthetic rate decreased by 13% with decreasing gravity levels from 1.0 to 0.01 G. The leaf temperature decreased by 0.5 degree C and the net photosynthetic rate increased by 7% with increasing gravity levels from 1.0 to 2.0 G. Heat/gas exchanges between leaves and the ambient air were more retarded at lower gravity levels. A restricted free air convection under microgravity conditions in space would limit plant growth by retarding heat and gas exchanges between leaves and the ambient air.
authors.affiliation: Graduate School of Agriculture and Biological Sciences, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kitaya
authors.forename: M
authors.initials: M
authors.lastname: Kawai
authors.forename: J
authors.initials: J
authors.lastname: Tsuruyama
authors.forename: H
authors.initials: H
authors.lastname: Takahashi
authors.forename: A
authors.initials: A
authors.lastname: Tani
authors.forename: E
authors.initials: E
authors.lastname: Goto
authors.forename: T
authors.initials: T
authors.lastname: Saito
authors.forename: M
authors.initials: M
authors.lastname: Kiyota
mesh_terms: D006112:Gravitation; D001467:Hordeum / Q000378:metabolism / Q000502:physiology; D006358:Hot Temperature; D018471:Hypergravity; D027723:Ipomoea batatas / Q000378:metabolism / Q000502:physiology; D010788:Photosynthesis / Q000502:physiology*; D018515:Plant Leaves / Q000378:metabolism* / Q000502:physiology; D013026:Space Flight; D013696:Temperature; D013997:Time Factors; D014893:Weightlessness