POSSIBLE ROLE OF GROWTH SUBSTANCES IN MULTIPLE CONTROL OF FLOWERING

Growth substances may act in organogenesis such as flowering at different levels: a) as organ determinants, instructing tissues not yet determined, b) as inducers or inhibitors of tissues already determined, c) as factors of organ correlations which either control the response to inductive stimuli or the expression of induced state.
It is assumed that organ correlations represent the most promising field of application of morphoregulators when affecting flowering of ornamental plants.
Some data gained in studying the effects of growth substances in flowering of model plants Chenopodium rubrum (short day plant) and Brassica campestris (long day plant) are summarized in order to illustrate this idea.
Cytokinins and auxins inhibit the expression of floral state in Chenopodium as well as in Brassica, the former by inducing the initiation and growth of leaves, the latter by suppressing the formation and growth of axillary buds.
Gibberellins and abscisic acid are beneficial to flowering by increasing the rate of initiation and growth of axillary buds.
Such effects do not necessarily reflect organ specificity of action of growth substances but rather the changes in responsiveness of shoot apical meristem.

Symposium on Growth Regulators in Floriculture

J. Krekule

https://doi.org/10.17660/ActaHortic.1979.91.4