Flower Bud Atrophy in Baccara Roses

Abstract

The activity of various growth substances in the upper leaves of Baccara roses was compared between flowering and non-flowering shoots. Flowering shoots had a higher level of gibberellins, auxins and cytokinins. The changes in level of these growth substances during different stages of shoot development were more marked in flowering than in non-flowering shoots. The level of inhibitors was higher in leaves of "blind" shoots. At least two inhibitors are present; one of them was identified as abscisic acid, while the other appears in the neutral fraction.

The Effect of Gibberellins on Flowering in 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.…”

“…Furthermore, applications of GA 3 reduced the number of flowers per plant and the proportion of flowering plants. However, in a study of flower-bud atrophy in R. hydrida 'Baccara, ' Zieslin, and Halevy (1976a) reported that concentrations of endogenous growth substances, including those with GA-like activity, were lower in leaves of nonflowering shoots than flowering shoots. Also, shoot blindness could be alleviated by spray applications of 100 mg L −1 GA 3 but, when the concentration was increased to 1000 mg L −1 , flowering was inhibited (Zieslin and Halevy 1976b).…”

Flower Bud Atrophy in Baccara Roses. V. The Effect of Different Growth Substances on Flowering

“…The growth substances were given to plants grown under conditions of full light in a greenhouse with a maximum solar light energy fiux of 340 W/m\ and to plants raised under partial shade. The shade treatment was used in order to create conditions which would bring about partial atrophy of the fiower buds (Zieslin and Halevy 1975) and to examine the effect of materials which might reduce atrophy under such conditions. On the other hand, materials liable to cause fiower atrophy were given under full light conditions.…”

“…The differences in content of various growth substances between fiowering and non-fiowering shoots was discussed in a previous paper (Zieslin and Halevy 1976b). It was shown that leaves of fiowering shoots contained a higher level of auxins, gibberellins and cytokinins, and a lower level of inhibitors than did leaves of a non-fiowering shoot, A lower level of various growth substances in shoots with aborted fiowers may be the result of atrophy of fiower parts, which normally serve as a source of auxins (Kaldewey 1957, Jeffcoat andCockshull 1972), cytokinins (Mayak and Halevy 1970) and gibberellins (Sircar et al 1970, Jeffcoat andCockshull 1972).…”

“…It was shown that leaves of fiowering shoots contained a higher level of auxins, gibberellins and cytokinins, and a lower level of inhibitors than did leaves of a non-fiowering shoot, A lower level of various growth substances in shoots with aborted fiowers may be the result of atrophy of fiower parts, which normally serve as a source of auxins (Kaldewey 1957, Jeffcoat andCockshull 1972), cytokinins (Mayak and Halevy 1970) and gibberellins (Sircar et al 1970, Jeffcoat andCockshull 1972). On the other hand, changes in the content of growth substances as a result of changes in environmental conditions or injury to the plants (Zieslin andHalevy 1975, 1976a) may be a reason for this abortion. If this latter alternative is the correct one, then the addition of exogenous growth substances should prevent or reduce the incidence of fiower atrophy.…”