title: Ethylene is not involved in adaptive responses to flooding in the Amazonian wild rice species Oryza grandiglumis.
abstract: The Amazonian wild rice Oryza grandiglumis has two contrasting adaptation mechanisms to flooding submergence: a quiescence response to complete submergence at the seedling stage and an escape response based on internodal elongation to partial submergence at the mature stage. We investigated possible factors that trigger these responses. In stem segments excised from mature O. grandiglumis plants, complete submergence only slightly promoted internodal elongation with increased ethylene levels in the internodes, while partial submergence substantially promoted internodal elongation without increased ethylene levels in the internodes. Incubation of non-submerged stem segments under a continuous flow of humidified ethylene-free air promoted internodal elongation to the same extent as that observed for partially submerged segments. Applied ethylene had little effect on the internodal elongation of non-submerged segments irrespective of humidity conditions. These results indicate that the enhanced internodal elongation of submerged O. grandiglumis plants is not triggered by ethylene accumulated during submergence but by the moist surroundings provided by submergence. The growth of shoots in O. grandiglumis seedlings was not promoted by ethylene or complete submergence, as is the case in O. sativa cultivars possessing the submergence-tolerant gene SUB1A. However, because the genome of O. grandiglumis lacks the SUB1A gene, the quiescence response of O. grandiglumis seedlings to complete submergence may be regulated by a mechanism distinct from that involved in the response of submergence-tolerant O. sativa cultivars.
authors.affiliation: Graduate School of Agricultural Science, Kobe University, Nada-ku, Kobe 657-8501, Japan.
authors.forename: Takuma
authors.initials: T
authors.lastname: Okishio
authors.affiliation: Graduate School of Agricultural Science, Kobe University, Nada-ku, Kobe 657-8501, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sasayama
authors.affiliation: Graduate School of Agricultural Science, Meijo University, Tenpaku-ku, Nagoya 468-8502, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Hirano
authors.affiliation: School of Agriculture, Obihiro University of Agriculture and Veterinary Medicine, Inada, Obihiro 080-8555, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Akimoto
authors.affiliation: Graduate School of Agricultural Science, Kobe University, Nada-ku, Kobe 657-8501, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Itoh
authors.affiliation: Graduate School of Agricultural Science, Kobe University, Nada-ku, Kobe 657-8501, Japan. Electronic address: azuma@kobe-u.ac.jp.
authors.forename: Tetsushi
authors.initials: T
authors.lastname: Azuma
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects* / Q000235:genetics; D001938:Brazil; D005030:Ethylenes / Q000494:pharmacology*; D055868:Floods; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D005875:Gibberellins / Q000494:pharmacology; D012275:Oryza / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development; D018547:Plant Stems / Q000187:drug effects / Q000254:growth & development
chemical_list: D005030:Ethylenes; D005875:Gibberellins; C036216:ethylene
keywords: Deepwater rice; Ethylene; Floating rice; Flood resistance; Hypoxia