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Title: Some aspects of seed biology of rowan (Sorbus aucuparia L.)
Author: Basharuddin, Jamaluddin B.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1991
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This study is in two parts. The first part is concerned with the study of dormancy, after-ripening and germination in Sorbus acuparia L.(rowan) seeds. The second part deals with the development of a suitable micropropagation system from juvenile parts of the same species. Seeds of rowan possess both testa-imposed and embryo dormancy at maturity. They have a wide range of in the depth of dormancy and germinated in the cold (4oC) after different periods of after-ripening. After-ripening of intact seeds at 1oC was found to be superior to that at 4oC by having an earlier Intensive Germination Period (IGP) and of shorter IGP duration. However, Total Germination % (TG%) was not significantly different. Freshly collected seeds were found to be the best in their TG% (90%), with shortest duration and time arriving at IGP. Alternating warm (20oC) period (2 weeks) with a cold (4oC) period (26 weeks) improved its TG% and IGP duration greatly but lengthened the time to IGP. TG and IGP duration of stored seeds could be improved alternating warm and cold stratification. The stratification medium can modify dormancy breaking during the cold stratification of seeds. The highest percentage of germination after 10 weeks of stratification (4oC) was obtained in the order of sand> vermiculite> peat> polythene bag. A mixture of sand and peat was the best medium for stratification and post dormancy development of seedlings. Cytokinins in the testa, mesocarp and embryos were extracted at various stratification periods using TLC techniques. At least four cytokinins were identified and are the first reported in this species. Both in vitro and in vivo application of 0.1 and 2 mg/1 of BAP respectively, were able to release embryo dormancy more rapidly. For these treated embryos the rate of cotyledon greening, growth of hypocotyl, roots, shoots and its germination percentage were determined after incubation at 20oC in continuous light for one month. A micropropagation system for rowan was successfully developed. This study demonstrated that BAP alone or in combination with IBA were successful in inducing shoot proliferation from nodal segments and shoot tips of 2 and 8-month old aseptically produced seedlings. The shoots produced could be further recycled, proliferating more shoots. The best levels of BAP that stimulated multiple shoots production were BAP 0.2 mg/1 in combination with either 0.01, or 0.02 mg/1 of IBA. Good rooting of these shoots were obtained by cutting individual explants measuring &60 1 cm and transferring them to a rooting medium supplemented with either 0.01, 0.05 or 0.10 mg/1 of IBA or IAA. However, in vitro produced shoots of rowan were found to be easier to root in vivo and produced a higher rooting percentage by using a commercial rooting powder; Seradix 3. It has several advantages as aseptic techniques are not required and more shoots could be rooted in the covered propagator trays in the green house making sure the atmosphere inside the propagators were humid enough to avoid dessication. Two weeks were needed for hardening.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available