Relationship between gibberellin and cytokinin activity and flowering in Rosa damascena Mill.

Abstract

Kinetin at 1Omg 1-l increased the number of flowers produced on Rosa damascena plants while GA, inhibited flowering. In the leaves of non-flowering plants GA-like activity was high while specific cytokinin activity (fraction-II) was significantly higher in flowering plants. A novel compound IO-methyldihydrozeatin riboside and isopentenyl-adenine were identified from TLC fraction-II while TLC fraction-I yielded zeatin and 2-hydroxy-6-methylaminopurine.Abbreviations: TLC = thin layer chromatography; BA = N6-benzyladenine; GA, = gibberellic acid.

The Effect of Gibberellins on Flowering in Roses

“…However, low concentrations of GAs permit floral induction in 'Little White Pet' throughout the growing season. The higher gibberellin-like activity in leaves of nonflowering compared with flowering plants of R. damascena (Abad Farooqi et al 1994) also provides evidence of inhibition of floral initiation by high concentrations of GAs.…”

“…Applications of GA 3 also resulted in suppression of flowering in the short-season roses, R. wichuraiana (this investigation) and R. damascena (Abad Farooqi et al 1994) but not in the recurrent-flowering rose 'Eyepaint' (this investigation). One interpretation of this is that the combined concentrations of exogenous and endogenous gibberellins were sufficiently high to suppress flowering in the shortseason roses but not in the recurrent-flowering roses.…”

“…Previously, GA-like activity was studied in leaves of the rose 'Baccara' by paper chromatography and bioassay (Zieslin and Halevy 1976a), GA-like substances were studied in vegetative tissues of R. damascena by TLC and bioassay (Abad Farooqi et al, 1994), and 13-hydroxy GAs were studied in reproductive organs of R. hybrida by HPLC and immunoassay (Bianco et al 1991). However, this work reports the first identification of GAs in vegetative tissues of roses.…”

“…The hypothesis that floral development is permitted only when concentrations of GAs are low is suggested as a subject worthy of further investigation. Abad Farooqi et al (1994) showed that applications of cytokinins could increase the number of flowers produced on R. damascena (short season) and that there may be interactive effects of gibberellins and cytokinins.…”

“…Abad Farooqi et al (1994) showed that leaves of nonflowering shoots of R. damascena (shortseason) contained higher concentrations of GA-like substances than flowering shoots. Furthermore, applications of GA 3 reduced the number of flowers per plant and the proportion of flowering plants.…”