Doctoral Dissertations

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Plant, Soil and Environmental Sciences

Major Professor

B. S. Pickett

Committee Members

Hendrik van de Werken, David Coffey, Larry S. Jeffery, Homer D. Swingle


The effect of various growth regulators on the development and longevity of potted chrysanthemum flowers (Chrysanthemum morifolium Ramat.) was studied. Plants were grown on greenhouse benches under conditions favorable for flowering. Five growth regulators at 2 concentrations were applied to plants at 2 stages of flower development: just prior to disbudding when terminal flower buds were 6.0 to 8.3 mm in diameter (stage 1) and when the outer row of flower petals were recurved (stage 5), Applica-tions were made at stage 1 only, at stage 5 only and at both stages 1 and 5. The growth regulators 5-chloro,2-thenyl,tri-n-butyl-phosphonium-chloride (CTBP) and ancymidol were the most effective in delaying flower development. Some objectional damage to flowers and foliage resulted from the use of these chemicals. This effect may be partly the result of high concentrations used in this study. Succinic acid 2,2-dimethyl-hydrazide (SADH) and indoleacetic acid (lAA) were next in delaying flower development through 4 stages, while ethyl hydrogen 1-propylphosphonate (HHP) caused no delay, Ancymidol, CTBP and SADH were effective in increasing flower longevity with the effect of SADH being most pronounced. The chemicals lAA and EHP were not appreciably effective in increasing flower longevity. High and low concentrations of most growth regulators did not differ in effect on flower development. High concentrations of CTBP and SADH were more effective in increasing flower longevity than low concentrations, Generally, applications of growth regulators at stage 1 of flower development and both stages 1 and 5 were more effective in delaying full bloom than applications at stage 5. Growth-regulator applications at both stages 1 and 5 increased flower longevity to a greater extent than applications at either stage 1 or 5. In general, ancymidol and CTBP retarded the growth of flowers and plants, while SADH retarded growth to a lesser extent, The growth regu-lators EHP and lAA affected growth least.

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