title: Variation in stem morphology and movement of amyloplasts in white spruce grown in the weightless environment of the International Space Station.
abstract: One-year-old white spruce (Picea glauca) seedlings were studied in microgravity conditions in the International Space Station (ISS) and compared with seedlings grown on Earth. Leaf growth was clearly stimulated in space whereas data suggest a similar trend for the shoots. Needles on the current shoots of ground-based seedlings were more inclined towards the stem base than those of seedlings grown in the ISS. Amyloplasts sedimented in specialized cells of shoots and roots in seedlings grown on Earth while they were distributed at random in similar cells of seedlings tested in the ISS. In shoots, such amyloplasts were found in starch sheath cells located between leaf traces and cortical cells whereas in roots they were constituents of columella cells of the cap. Nuclei were regularly observed just above the sedimented amyloplasts in both organs. It was also frequent to detect vacuoles with phenolic compounds and endoplasmic reticulum (ER) close to the sedimented amyloplasts. The ER was mainly observed just under these amyloplasts. Thus, when amyloplasts sediment, the pressure exerted on the ER, the organelle that can for instance secrete proteins destined for the plasma membrane, might influence their functioning and play a role in signaling pathways involved in gravity-sensing white spruce cells.
authors.affiliation: Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., P.O. Box 10380, Stn. Sainte-Foy, Quebec, QC, G1V 4C7, Canada. Electronic address: danny.rioux@rncan-nrcan.gc.ca.
authors.forename: Danny
authors.initials: D
authors.lastname: Rioux
authors.affiliation: Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., P.O. Box 10380, Stn. Sainte-Foy, Quebec, QC, G1V 4C7, Canada.
authors.forename: Marie
authors.initials: M
authors.lastname: Lagacé
authors.affiliation: Canadian Space Agency, 6767, route de l'Aéroport, St-Hubert, QC, J3Y 8Y9, Canada.
authors.forename: Luchino Y
authors.initials: LY
authors.lastname: Cohen
authors.affiliation: Natural Resources Canada, Canadian Forest Service, Canadian Wood Fibre Centre, 1055 du P.E.P.S., P.O. Box 10380, Stn. Sainte-Foy, Quebec, QC, G1V 4C7, Canada.
authors.forename: Jean
authors.initials: J
authors.lastname: Beaulieu
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005118:Extraterrestrial Environment; D018522:Gravitropism / Q000502:physiology*; D018466:Gravity Sensing / Q000502:physiology*; D028222:Picea / Q000254:growth & development*; D018515:Plant Leaves / Q000254:growth & development*; D018520:Plant Shoots / Q000254:growth & development*; D018547:Plant Stems / Q000254:growth & development* / Q000378:metabolism; D018087:Plastids / Q000378:metabolism* / Q000648:ultrastructure; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism; D013026:Space Flight; D013213:Starch / Q000378:metabolism; D014893:Weightlessness
chemical_list: D013213:Starch
keywords: Amyloplast; Anatomy; Columella; Endoplasmic reticulum; Growth; Leaves; Microgravity; Microscopy; Nucleus; Picea glauca; Roots; Sedimentation; Sheath; Starch