Paclobutrazol Bioassay Using the Axillary Growth of a Grape Shoot

in HortScience
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  • 1 Agriculture Canada Research Branch, Research Station, Harrow, Ont. NOR 1G0, Canada
  • | 2 Department of Horticultural Science, University of Guelph, Guelph, Ont. N1G 2W1, Canada

A system was developed to evaluate the response of grapes (Vitis spp. `Seyval') to soil-applied paclobutrazol. The youngest fully expanded leaf, and its axillary bud, on single shoots 6 to 9 nodes long developing on rooted softwood cuttings, were retained for use in a bioassay. The shoot that developed from the axillary bud exhibited a dosage-dependent growth inhibition following soil applications of paclobutrazol at 4 dosages between 1 and 1000 μg·g-1 soil. Other aerial components showed no response to paclobutrazol. This test plant system has potential for use in physiological studies with soil-applied plant growth regulators. Chemical name used: β -[(4-chlorophenyl)methyl]- α -(1,1-dimethylethyl)1H-1,2,4-triazole-1-ethanol (paclobutrazol).