title: Chromosome doubling in a Rosa rugosa Thunb. hybrid by exposure of in vitro nodes to oryzalin: the effects of node length, oryzalin concentration and exposure time.
abstract: Chromosome doubling was induced in vitro in a diploid hybrid of Rosa rugosa Thunb. using oryzalin as the spindle inhibitor. Nodal sections, 2 mm long, were exposed to 2.5 or 5 microM oryzalin and 10 mm nodal sections were exposed to 5 microM oryzalin for 0 (controls), 6, 12, 24 and 48 h. The ploidy of the emergent shoots was determined by flow cytometry. The frequency of tetraploid and mixoploid leaves that developed from 2 mm nodal sections exposed to 5 microM oryzalin peaked at 12 h exposure, when 35% of the leaves were tetraploid, but fell after longer exposures. Fewer tetraploid and mixoploid leaves were found when 2 mm nodes were exposed to 2.5 microM oryzalin for 6 and 12 h, indicating that it took longer for a spindle inhibiting concentration of oryzalin to build up in the meristem. However, the frequencies of tetraploid and mixoploid leaves continued to rise after 12 h and were highest at 48 h, when 44% were tetraploid. In treatments with 5 microM oryzalin, the frequencies of tetraploid and mixoploid leaves were lower, at equivalent exposure times, in 10 mm nodes than 2 mm nodes. This suggests that oryzalin diffused to the meristem mainly via the cut surfaces and that access via the epidermis and cuticle was impeded.
authors.affiliation: School of Health and Bioscience, University of East London, Romford Road, London E15 4LZ, UK.
authors.forename: J F
authors.initials: JF
authors.lastname: Allum
authors.forename: D H
authors.initials: DH
authors.lastname: Bringloe
authors.forename: A V
authors.initials: AV
authors.lastname: Roberts
mesh_terms: D032461:Chromosomes, Plant / Q000187:drug effects / Q000235:genetics*; D003433:Crosses, Genetic; D004136:Dinitrobenzenes / Q000494:pharmacology*; D006540:Herbicides / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects / Q000502:physiology; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000502:physiology*; D011123:Polyploidy; D027826:Rosa / Q000235:genetics / Q000502:physiology*; D013424:Sulfanilamides / Q000494:pharmacology*
chemical_list: D004136:Dinitrobenzenes; D006540:Herbicides; D013424:Sulfanilamides; C012465:oryzalin