title: Composition and physical properties of starch in microgravity-grown plants.
abstract: The effect of spaceflight on starch development in soybean (Glycine max L., BRIC-03) and potato (Solanum tuberosum, Astroculture-05) was compared with ground controls by biophysical and biochemical measurements. Starch grains from plants from both flights were on average 20-50% smaller in diameter than ground controls. The ratio delta X/delta rho (delta X --difference of magnetic susceptibilities, delta rho--difference of densities between starch and water) of starch grains was ca. 15% and 4% higher for space-grown soybean cotyledons and potato tubers, respectively, than in corresponding ground controls. Since the densities of particles were similar for all samples (1.36 to 1.38 g/cm3), the observed difference in delta X/delta rho was due to different magnetic susceptibilities and indicates modified composition of starch grains. In starch preparations from soybean cotyledons (BRIC-03) subjected to controlled enzymatic degradation with alpha-amylase for 24 hours, 77 +/- 6% of the starch from the flight cotyledons was degraded compared to 58 +/- 12% in ground controls. The amylose content in starch was also higher in space-grown tissues. The good correlation between the amylose content and delta X/delta rho suggests, that the magnetic susceptibility of starch grains is related to their amylose content. Since the seedlings from the BRIC-03 experiment showed elevated post-flight ethylene levels, material from another flight experiment (GENEX) which had normal levels of ethylene was examined and showed no difference to ground controls in size distribution, density, delta X/delta rho and amylose content. Therefore the role of ethylene appears to be more important for changes in starch metabolism than microgravity.
authors.affiliation: Biology Dept., University of Louisiana at Lafayette, LA 70504-2451, USA.
authors.forename: O A
authors.initials: OA
authors.lastname: Kuznetsov
authors.forename: C S
authors.initials: CS
authors.lastname: Brown
authors.forename: H G
authors.initials: HG
authors.lastname: Levine
authors.forename: W C
authors.initials: WC
authors.lastname: Piastuch
authors.forename: M M
authors.initials: MM
authors.lastname: Sanwo-Lewandowski
authors.forename: K H
authors.initials: KH
authors.lastname: Hasenstein
mesh_terms: D000687:Amylopectin / Q000378:metabolism; D000688:Amylose / Q000378:metabolism; D018548:Cotyledon / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D018546:Hypocotyl / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D008280:Magnetics; D018521:Plant Physiological Phenomena; D018087:Plastids; D011198:Solanum tuberosum / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D013025:Glycine max / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D013026:Space Flight; D013213:Starch / Q000378:metabolism* / Q000502:physiology; D014893:Weightlessness; D000516:alpha-Amylases / Q000378:metabolism
chemical_list: D013213:Starch; D000688:Amylose; D000687:Amylopectin; D000516:alpha-Amylases