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Title: | A study on the germination and dormancy of the African satinwood seed (zanthoxylum gilletii (de wild) waterman |
Authors: | Okeyo, Michael M. |
Keywords: | seed phenology zanthoxylum gilletii seed maturity seed germination seed dormancy |
Issue Date: | Sep-2009 |
Publisher: | Moi university |
Abstract: | African Satinwood [Zanthoxylum gilletii (De Wild.) Waterman; is valued for its structural timber, agroforestry and medicinal properties. It is useful in rehabilitation of degraded natural forests and its seedlings are in high demand. However, the species can only be raised from seed because other propagation methods are unknown. Fresh seeds have been reported to germinate poorly after several weeks of incubation and germination declines further during storage. Poor germination of Zanthoxylum species have been attributed to dormancy associated with their oiliness and optimum germination conditions have not been documented. This study investigated phenology, seed germination, short term storage and dormancy releasing pretreatments on Z. gilletii seeds. Red and green fruits were harvested from Kakamega and Koiwa forests and dried at 200e and 20% relative humidity to dehisce. Seeds dried to 11.5% Me were separated in two lots: one lot was washed with 10% sodium hydroxide, while the other remained unwashed. Seeds were sown in 1% agar and subjected to germination tests in incubators at constant temperatures: 20, 25 and 30oe; and alternating temperatures: 20/35 and 20/30oe. Other seeds were sown in sand in the glass house at 18/35±4°e. Some seeds were also subjected to pre-sowing treatments: stratification at 4°e, scarification with 98% sulphuric acid for 5, 10, 15,20,25 and 30 minutes, soaking in water, 0.5% GA3and 2 Molar (M) Potassium nitrate (KN03) for 1, 2, and 3 days. Germination experiments were laid out in completely randomized design. Total germination and mean germination time were analyzed using GenStat® computer package. Analysis of variance was done and means separated using least significant difference (LSD) at 0.05. Unwashed Z. gilletii seeds from Kakamega and Koiwa provenances sown in sand in the glass house had a germination of 2.5 and 9.8%, while those washed with 10% NaOH germinated up to 12.3 and 29% respectively after 17 weeks. Washing Z. gilletii seed with NaOH removed lipids on the seed coat and leached off chemical inhibitors and improved germination. Seeds scarified with H2S04 for 20 minutes and those soaked in 0.5% GA3for two days gave a similar ~ermination of 20%, while those scarified at 4°e had a germination of 18.5% by the 12 week. Seeds soaked in water or 2M KN03 for two days and those dried at 45°e for one week had low germination of 11.5, 4.5 and 8.8% respectively. Seeds stored at 22, 4 and -20oe for six months then soaked in 1% GA3 gave a high germination of 40.8, 57 and 30.5%, respectively. However, stored seed scarified with H2S04 for 20 minutes, soaked in water and 2M KN03 for two days and the controls failed to germinate. Seed stored at 4 and 200e and soaked in 1% GA3 gave significantly higher germination than seed not stored. Seeds subjected to pre-sowing treatments and sown on 1% agar in incubators at constant and alternating temperatures germinated poorly (3.5%); probably due to chemical inhibitors within the seed. Zanthoxylum gilletii seed should be harvested when 50% of the fruits have changed colour from green to red. Seeds should be washed with NaOH and sown in sand in germination trays which drain excess water for good germination results. The results suggest that Z. gilletii seed exhibit physiological dormancy. The dormancy condition is partly attributed to chemical inhibitors, lipids and hard seed coat. Zanthoxylum gilletii seed can be dried to low moisture content (8 - 11%) and stored at 4°e for at least six months without losing viability. |
URI: | http://10.10.20.22:8080//handle/123456789/290 |
Appears in Collections: | Thesis and Dissertation |
Files in This Item:
File | Description | Size | Format | |
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A study on the germination and dormancy of the african satinwood seed.pdf | 28.1 MB | Adobe PDF | View/Open |
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