Schematic representation of a rose axillary bud: (a) axillary bud at a leaf axil and (b) cross-section of an axillary bud showing seven leaf primordia and two secondary axillary buds with two leaf primordia. The article mainly deals with recurrent-flowering roses.įig.
In this article the roles of assimilate supply, axillary bud age, topophysis, root formation, temperature, irradiance and cytokinins in axillary bud growth regulation are discussed, together with some future prospects for axillary bud growth regulation. Cultivars (scions) on low-yielding rootstocks have lower cytokinin concentrations than scions on high-yielding rootstocks. Auxin has long been known to inhibit axillary bud growth, while cytokinins promote axillary bud growth. The control mechanism of axillary bud growth is thought to be mainly mediated by plant hormones ( see GROWTH REGULATION | Hormones in Growth and Development GROWTH REGULATION | Influences of Abiotic Factors in Growth and Development). Rose cultivars may respond differently to the same growing conditions ( Table 1). In addition, gravitropism is believed to be due to a lateral redistribution of auxin with a resulting difference in rate of cell elongation on the two sides of the bud. External factors include the quality and quantity of light, photoperiod, relative humidity, growing medium and temperature. Internal factors on which axillary bud growth depends include genotype, assimilate availability, nutritional status, age (chronological and ontogenetical), competition between plant parts (stem/leaf/petiole/axillary buds), hormone concentrations and topophysis. Scientia Horticulturae 64: 103–111.Ĭontrol of axillary bud growth can be decisive in achieving the synchronous growth and development essential for automation of plant-handling processes. Interactive effect (cultivar × propagation material): P = 0.001 for both axillary bud and shoot growthīased on Bredmose N and Hansen J (1995) Regeneration, growth and flowering of cut rose cultivars as affected by propagation material and method. In some cut-rose cultivars, the borderline between them is only two to three nodes below the flower. Sylleptic axillary buds are mainly formed in the axils of leaves with one to three leaflets and proleptic axillary buds in the axils of leaves with five leaflets. they undergo a period of inhibition prior to the onset of axillary bud growth. In contrast, most medial and all basal axillary rose buds are proleptic, i.e. This is because the apical dominance ceases when the apical bud is converted into an inflorescence. their growth continues, without interruption, immediately on formation. In rose, the apically positioned axillary buds are sylleptic, i.e.
In Rosa canina, for example, low temperature stimulates the onset of growth in these axillary buds, leading to the formation of basal shoots. Abscisic acid is thought to inhibit their growth. Some basal axillary buds may remain inhibited even after the shoot has been decapitated.
At the moment of release from inhibition, or when a shoot is decapitated or an axillary bud is excised, most axillary bud meristems produce a specific number of leaves before initiating a terminal flower bud ( see GROWTH REGULATION | Floral Induction). Axillary buds elongate visibly only if apical dominance is removed, the bud has matured and the environmental conditions for growth are suitable. However, leaf initiation occurs during growth inhibition, and leaf primordia slowly accumulate in the axillary bud. The apical meristem within the axillary bud remains inhibited as long as the shoot apex is intact and active. (b) Schematical cross-section of ontogenetically mature primary axillary rose bud showing seven leaves and leaf primordia, and two secondary axillary buds with two leaf initials.Īxillary bud growth is under the influence of the shoot apex. (a) Single-node cutting with five-leaflet leaf.
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