title: Gibberellin mediates the development of gelatinous fibres in the tension wood of inclined Acacia mangium seedlings.
abstract: OBJECTIVE
  Gibberellin stimulates negative gravitropism and the formation of tension wood in tilted Acacia mangium seedlings, while inhibitors of gibberellin synthesis strongly inhibit the return to vertical growth and suppress the formation of tension wood. To characterize the role of gibberellin in tension wood formation and gravitropism, this study investigated the role of gibberellin in the development of gelatinous fibres and in the changes in anatomical characteristics of woody elements in Acacia mangium seedlings exposed to a gravitational stimulus.
  
  
  METHODS
  Gibberellin, paclobutrazol and uniconazole-P were applied to the soil in which seedlings were growing, using distilled water as the control. Three days after the start of treatment, seedlings were inclined at 45 ° to the vertical and samples were harvested 2 months later. The effects of the treatments on wood fibres, vessel elements and ray parenchyma cells were analysed in tension wood in the upper part of inclined stems and in the opposite wood on the lower side of inclined stems.
  
  
  RESULTS
  Application of paclobutrazol or uniconazole-P inhibited the increase in the thickness of gelatinous layers and prevented the elongation of gelatinous fibres in the tension wood of inclined stems. By contrast, gibberellin stimulated the elongation of these fibres. Application of gibberellin and inhibitors of gibberellin biosynthesis had only minor effects on the anatomical characteristics of vessel and ray parenchyma cells.
  
  
  CONCLUSIONS
  The results suggest that gibberellin is important for the development of gelatinous fibres in the tension wood of A. mangium seedlings and therefore in gravitropism.
authors.affiliation: Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu-Tokyo 183-8509, Japan.
authors.forename: Widyanto Dwi
authors.initials: WD
authors.lastname: Nugroho
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nakaba
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yamagishi
authors.forename: Shahanara
authors.initials: S
authors.lastname: Begum
authors.forename: Sri Nugroho
authors.initials: SN
authors.lastname: Marsoem
authors.forename: Jae-Heung
authors.initials: JH
authors.lastname: Ko
authors.forename: Hyun-O
authors.initials: HO
authors.lastname: Jin
authors.forename: Ryo
authors.initials: R
authors.lastname: Funada
mesh_terms: D000045:Acacia / Q000187:drug effects / Q000502:physiology*; D005780:Gelatin / Q000187:drug effects*; D005875:Gibberellins / Q000494:pharmacology*; D018522:Gravitropism / Q000187:drug effects; D018547:Plant Stems / Q000187:drug effects / Q000502:physiology; D036226:Seedlings / Q000187:drug effects / Q000502:physiology*; D014230:Triazoles / Q000494:pharmacology; D014934:Wood / Q000187:drug effects / Q000502:physiology*
chemical_list: D005875:Gibberellins; D014230:Triazoles; C511205:uniconazole-P; C053370:paclobutrazol; D005780:Gelatin
keywords: Acacia mangium; gelatinous fibres; gibberellin; gravitropism; paclobutrazol; tension wood; uniconazole-P
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