Effects of the Growth Retardant CCC on Floral Initiation and Growth in Pharbitis nil

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Abstract
The plant growth retardant (2-chloroethyl)-trimethylammonium chloride (CCC or Cycocel) inhibits flower formation in the short-day plant Pharbitis nil, strain "Violet," if applied to seedlings via the roots before the inductive night, but not if applied after the long night. Stem growth is reduced at all times by CCC treatment. Application of gibberellin A3 (GA3) completely overcomes inhibition of flower formation by CCC. But 50-100 times more GA3 is required for overcoming CCC-induced growth suppression of the 1st internode. CCC does not act as a competitive inhibitor of GA3 Pharbitis plants grown continuously in long days show a dwarfed habit of growth for several weeks after CCC applications and produce flower buds on lower nodes than control plants. Differences in lengths of 1st internodes of control plants and those treated with CCC are due to differences in cell number. The growth retardant CCC, therefore, inhibits cell division in the plumule of Pharbitis and thus prevents expression of the floral stimulus in flower primordia.