title: A spaceflight experiment for the study of gravimorphogenesis and hydrotropism in cucumber seedlings.
abstract: Seedlings of Cucurbitaceae plants form a protuberance, termed peg, on the transition zone between hypocotyl and root. Our spaceflight experiment verified that the lateral positioning of a peg in cucumber seedlings is modified by gravity. It has been suggested that auxin plays an important role in the gravity controlled positioning of a peg on the ground. Furthermore, cucumber seedlings grown in microgravity developed a number of the lateral roots that grew towards the water containing substrate in the culture vessel, whereas on the ground they oriented perpendicular to the primary root growing down. The response of the lateral roots in microgravity was successfully mimicked by clinorotation of cucumber seedlings on the three dimensional clinostat. However, this bending response of the lateral roots was observed only in an aeroponic culture of the seedlings but not in solid medium. We considered the response of the lateral roots in microgravity and on clinostat as positive hydrotropism that could easily be interfered by gravitropism on the ground. This system with cucumber seedlings is thus a useful model of spaceflight experiment for the study of the gravimorphogenesis, root hydrotropism and their interaction.
authors.affiliation: Institute of Genetic Ecology, Tohoku University, Sendai, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Takahashi
authors.forename: H
authors.initials: H
authors.lastname: Mizuno
authors.forename: M
authors.initials: M
authors.lastname: Kamada
authors.forename: N
authors.initials: N
authors.lastname: Fujii
authors.forename: A
authors.initials: A
authors.lastname: Higashitani
authors.forename: S
authors.initials: S
authors.lastname: Kamigaichi
authors.forename: S
authors.initials: S
authors.lastname: Aizawa
authors.forename: C
authors.initials: C
authors.lastname: Mukai
authors.forename: T
authors.initials: T
authors.lastname: Shimazu
authors.forename: K
authors.initials: K
authors.lastname: Fukui
authors.forename: M
authors.initials: M
authors.lastname: Yamashita
mesh_terms: D018553:Cucumis sativus / Q000235:genetics / Q000254:growth & development*; D003470:Culture Media; D017343:Genes, Plant; D006112:Gravitation; D018527:Hydroponics; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development; D007210:Indoleacetic Acids / Q000235:genetics / Q000502:physiology; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development; D012399:Rotation; D013026:Space Flight; D018523:Tropism; D014867:Water; D014893:Weightlessness; D018474:Weightlessness Simulation
chemical_list: D003470:Culture Media; D007210:Indoleacetic Acids; D014867:Water