Changes in dormancy levels ofFraxinus excelsior L. embryos at different stages of morphological and physiological maturity |
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Authors: | Johanna Wagner |
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Institution: | 1. Institut für Botanik, Universit?t Innsbruck, Sternwartestrasse 15, A-6020, Innsbruck, Austria
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Abstract: | The dormancy status ofFraxinus excelsior embryos at different developmental stages under environmental conditions was examined over a period of 2 years. For each
sampling date the length of the fruit, of the seed, and of the embryo were measured, and the embryological stage determined.
The depth of dormancy was assayed by the germination behaviour of isolated embryos under aseptic conditions on an agar medium
without nutrients. As an approach towards a quantitative estimate of the dormancy status, the degree of inhibiton of germinative
growth in the embryonic organs was evaluated on the basis of four categories from none to full germinative growth. From these
ratings a dormancy index was calculated, expressing the mean dormancy status of the embryos at a given date. Embryo dormancy
already became apparent during embryogenesis and reached its highest level during the later phase of reserve deposition in
the seed. A marked loss of embryo dormancy occurred during the phase of maturation drying in autumn, followed by a moderate
increase in winter. In hydrated seeds in spring the embryo was gradually released from dormancy and enlarged further. In maintaining
the embryo ofF. excelsior in a developmental but not germinative mode, dormancy mechanisms within the embryo and the endosperm, combined with environmental
factors, may be involved. |
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Keywords: | Embryo dormancy Fraxinus excelsior In vitro germination Seed development |
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