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.
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.
Allum
J F
JF
School of Health and Bioscience, University of East London, Romford Road, London E15 4LZ, UK.
Bringloe
D H
DH
Roberts
A V
AV
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*
D004136:Dinitrobenzenes; D006540:Herbicides; D013424:Sulfanilamides; C012465:oryzalin