Factors Affecting Floral Stalk Elongation of Flowering Tulips1

Factors affecting floral stalk elongation of tulips during the period from floral bud coloring (budded flower) to the senescence of the perianth were studied. All internodes elongated, however, the greatest elongation occurred in the internode directly beneath the flower and most of the elongation occurred in the upper two-thirds of the internode. Cut tulips elongated less than plants left in the forcing flats. Removal of the budded flower inhibited elongation of the last internode while removal of the leaves was stimulatory with some cultivars. With cut tulips, the perianth appeared to be the primary organ controlling floral stalk elongation followed by the gynoecium and androecium. When the flowers were left intact on the plant the gynoecium exerted the greatest control followed by the perianth and androecium. When the complete flower was removed and IAA or NAA was applied as a lanolin paste to replace the flower, the last internode elongated in a manner similar to the intact flower. Similar applications of kinetin and GA 3 were ineffective.