ISHS Acta Horticulturae 179: V International Symposium on Growth Regulators in Fruit Production
HORMONAL REGULATION OF FLOWERING AND FRUIT SET IN THE GRAPEVINE |
| Author: | M. G. Mullins |
| Abstract:
The complex morphology of the grapevine shoot system and the origin of inflorescences will be reviewed. Flowering is a 3-step process: (i) formation of Anlagen ("uncommitted primordia") by apices of specialized lateral buds (latent buds) on shoots of the current season (ii) differentiation of Anlagen either as tendril primordia or as inflorescence primordia (iii) formation of flowers from the inflorescence primordium. Control of flowering is at two levels - a coarse control which involves formation of the Anlage (inflorescence axis) and a fine control which involves switching of Anlagen into either the inflorescence or tendril pathways. Gibberellin is concerned with both Anlagen formation and Anlagen development. Exogenous GA induces precocious formation of Anlagen and production of tendril primordia. Inflorescence primordia are inhibited by GA. Anlagen formation and tendril elongation are inhibited by chlormequat. Inflorescence primordium formation results from branching of Anlagen and is promoted by cytokinin. Tendrils may be converted to inflorescences by cytokinin treatment. Flower formation from the inflorescence primordium is also a cytokinin-dependent process. The role of phytohormones in fruit set has still to be resolved. There may be specific effects on the constituent processes (resumption of cell division in the ovary wall, inhibition of abscission) but most evidence suggests that the action of hormones and growth regulators on fruit set is primarily through partitioning of organic nutrients. | |
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