Growth and photosynthetic responses of wheat plants grown in space.
Growth and photosynthesis of wheat (Triticum aestivum L. cv Super Dwarf) plants grown onboard the space shuttle Discovery for 10 d were examined. Compared to ground control plants, the shoot fresh weight of space-grown seedlings decreased by 25%. Postflight measurements of the O2 evolution/photosynthetic photon flux density response curves of leaf samples revealed that the CO2-saturated photosynthetic rate at saturating light intensities in space-grown plants declined 25% relative to the rate in ground control plants. The relative quantum yield of CO2-saturated photosynthetic O2 evolution measured at limiting light intensities was not significantly affected. In space-grown plants, the light compensation point of the leaves increased by 33%, which likely was due to an increase (27%) in leaf dark-respiration rates. Related experiments with thylakoids isolated from space-grown plants showed that the light-saturated photosynthetic electron transport rate from H2O through photosystems II and I was reduced by 28%. These results demonstrate that photosynthetic functions are affected by the microgravity environment.
Tripathy
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BC
National Aeronautics and Space Administration, and The Dynamac Corporation, Kennedy Space Center, Cape Canaveral, Florida, USA. bct@jnuniv.ernet.in
Brown
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CS
Levine
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HG
Krikorian
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AD
D002338:Carotenoids / Q000032:analysis; D002734:Chlorophyll / Q000032:analysis; D002736:Chloroplasts / Q000737:chemistry; D004579:Electron Transport; D010788:Photosynthesis / Q000502:physiology*; D018515:Plant Leaves / Q000378:metabolism*; D018520:Plant Shoots / Q000254:growth & development; D018531:Spacecraft; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D014908:Triticum / Q000254:growth & development* / Q000528:radiation effects
D002734:Chlorophyll; D002338:Carotenoids