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ISHS Acta Horticulturae 618: XXVI International Horticultural Congress: Environmental Stress and Horticulture Crops

MOLECULAR AND PHYSIOLOGICAL MECHANISMS OF BUD DORMANCY REGULATION

Author:   J.E. Olsen
Keywords:   abscisic acid, auxin, cell cycle regulation, cytokinin, gibberellin, phytochrome, plant hormone
Abstract:
Dormancy can be defined as a developmental process involving a temporary suspension of visible growth of any plant structure containing a meristem. Dormancy is a survival mechanism assuring a seasonal synchronization of growth, but is also contributing to the control of plant architecture. Dormancy of seeds, bulbs and buds may certainly involve common metabolic processes, but there might also be fundamental differences due to the different roles of these organs. Knowledge of the molecular basis of dormancy is still scarce, but since it is associated with reduced rates of cell division, control of dormancy must at some level interact with the mechanisms of cell cycle regulation, which also involve hormonal signals. Several dormancy-associated genes have been identified, and some of them are involved in the regulation of cell division, some are hormone related, and others are involved in phytochrome responsiveness. In particular, the roles of hormones in different aspects of dormancy have been widely studied. Auxin and cytokinin are well known to be involved in the regulation of dormancy of axillary and adventitious buds that is due to an inhibitory control by the shoot apex, but also other signals and factors apparently have important roles. In the seasonal cycles of growth and winter dormancy in perennial woody plants the light climate, particularly the daylength, is a primary determinant acting through the phytochrome system. This is in turn interacting with gibberellin metabolism, but also abscisic acid is considered an important factor. Under conditions inducing winter dormancy communication between cells of the apical meristem ceases as a consequence of a breakdown of symplastic fields, and is re-established upon breakage of dormancy. The nature of the signals involved is unknown, but a role of hormones can be hypothesized. An overview of possible physiological and molecular mechanisms of dormancy regulation will be presented, emphasizing bud dormancy.
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