ISHS Acta Horticulturae 630: XXVI International Horticultural Congress: Nursery Crops; Development, Evaluation, Production and Use
DELAYED RELEASE OF PRIMARY DORMANCY AND INDUCTION OF SECONDARY DORMANCY IN SEEDS OF WOODY TAXA CAUSED BY TEMPERATURE ALTERNATIONS |
| Authors: | S.U. Larsen, E.N. Eriksen |
| Keywords: | Germination, cold stratification, seed treatment, germination uniformity |
| Abstract:
The effect of temperature alternations on the release of primary embryo dormancy and induction of secondary dormancy is very poorly understood. The topics were studied in seeds of the woody taxa Amelanchier canadensis, Malus sargentii, Pyrus communis, and Berberis thunbergii. Fully imbibed seeds of Pyrus communis, Malus sargentii, and Amelanchier canadensis were placed at 5°C for cold stratification and germination. High temperature treatments were applied by transferring seeds to 25°C for two weeks and subsequently returning seeds to 5°C. The high temperature treatment increased the time to 50% germination (T50) from 16.0 to 23.1 weeks in Amelanchier canadensis, from 12.3 to 22.7 weeks in Malus sargentii, and from 16.4 to 21.8 weeks in Pyrus communis. The delay in germination indicates that the high temperature not only delayed the dormancy release processes but also reverted the seeds into a state of deeper dormancy than seeds of the control treatment, i.e. induction of secondary dormancy. The high temperature treatment often induced a more uniform germination compared to the control at 5°C continuously. Seeds of Berberis thunbergii were placed at 5°C, and after 14 days the treatment was interrupted by a period at 25°C lasting for 0 (control), 1, 3, 5, 10, 15, 20 and 25 days, respectively, and seeds were then returned to 5°C. Final germination percentages (ranging from 78 to 87%) did not differ among treatments. The 1, 3 and 5 days treatments did not affect T50, but after 10 to 25 days at 25°C T50 increased. The delay in germination increased linearly with time at 25°C but with a slope of 2.19, indicating that seeds gradually reverted to a state of deeper dormancy. The results suggest that in Berberis thunbergii, a period of more than 5 days at 25°C is required to induce secondary dormancy. The relationship between delay of primary dormancy and induction of secondary dormancy is discussed. | |
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