Desiccation tolerance of yeheb (Cordeauxia edulis Hemsl.) seeds
In this master's thesis, the desiccation tolerance of seeds from yeheb, Cordeauxia edulis Hemsley, a multipurpose, evergreen shrub, native to the semi-desert areas in the horn of Africa, is studied. Due to overexploitation and bad regeneration, yeheb is now threatened with extinction. Seeds of...
| Autor principal: | |
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| Formato: | Otro |
| Lenguaje: | sueco Inglés |
| Publicado: |
2008
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| Materias: | |
| Acceso en línea: | https://stud.epsilon.slu.se/10894/ |
| _version_ | 1855571770523779072 |
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| author | Liew, Josefine |
| author_browse | Liew, Josefine |
| author_facet | Liew, Josefine |
| author_sort | Liew, Josefine |
| collection | Epsilon Archive for Student Projects |
| description | In this master's thesis, the desiccation tolerance of seeds from yeheb, Cordeauxia
edulis Hemsley, a multipurpose, evergreen shrub, native to the semi-desert areas in
the horn of Africa, is studied. Due to overexploitation and bad regeneration, yeheb is
now threatened with extinction.
Seeds of different species can be classified into three storage behaviour categories,
depending on their desiccation tolerance, longevity and tolerance to low temperatures
during storage. When determining the storage behaviour of seeds, the first step is to
study desiccation tolerance. Seeds that maintain their viability at <5% moisture
content (wwb=wet weight basis), are probably orthodox. If they tolerate 10-12.5%
moisture content (MC), but not lower, they may be intermediate, and if most seeds die
when desiccated to moisture contents >15-20%, then they are recalcitrant. Desiccation
tolerance of seeds is controlled by several physiological processes, and depends on
factors such as drying rate, tissue, degree of development at harvest and
environmental influence of the mother plant prior to seed maturation/harvest.
To achieve the desiccation of seeds, silica gel was used. The seeds were dried to six
different moisture contents: 9.6, 12.3, 24.4, 27.4, 33.4 and 39.3% (wwb). Moisture
content of the fresh seeds was 41.6%. Desiccation tolerance was assessed by
germination tests followed by a tetrazolium test of viability on ungerminated seeds
that were not estimated to be clearly dead at the end of the germination test.
Germination tests were done on desiccated and fresh seeds, and on seeds from 'control
of time factor during drying' -replications, in which vermiculite were used instead of
silica gel during the drying treatment. Germination percentage was dependent on seed
moisture content (p-value 0.0001), seen as a reduction of germinability when seed
moisture content dropped from >24.4 to 12.3% (p-value 0.0062). Further drying to
9.6% moisture content, reduced germination percentage even more (70-83.8% at MC
>24.4%, 57.5% at 12.3% MC and 41.3% at 9.6% MC). The reduction of germination
capacity at the latter MC was highly significant compared to the control replications
(p-value 0.0001). Yeheb seeds may therefore be classified as having seeds of
intermediate storage behaviour. However, further studies on viability in storage and
tolerance to low temperatures are necessary before any certain conclusions on the
classification of seed storage behaviour of yeheb can be drawn. |
| format | Otro |
| id | RepoSLU10894 |
| institution | Swedish University of Agricultural Sciences |
| language | Swedish Inglés |
| publishDate | 2008 |
| publishDateSort | 2008 |
| record_format | eprints |
| spelling | RepoSLU108942018-10-09T10:43:35Z https://stud.epsilon.slu.se/10894/ Desiccation tolerance of yeheb (Cordeauxia edulis Hemsl.) seeds Liew, Josefine Plant ecology In this master's thesis, the desiccation tolerance of seeds from yeheb, Cordeauxia edulis Hemsley, a multipurpose, evergreen shrub, native to the semi-desert areas in the horn of Africa, is studied. Due to overexploitation and bad regeneration, yeheb is now threatened with extinction. Seeds of different species can be classified into three storage behaviour categories, depending on their desiccation tolerance, longevity and tolerance to low temperatures during storage. When determining the storage behaviour of seeds, the first step is to study desiccation tolerance. Seeds that maintain their viability at <5% moisture content (wwb=wet weight basis), are probably orthodox. If they tolerate 10-12.5% moisture content (MC), but not lower, they may be intermediate, and if most seeds die when desiccated to moisture contents >15-20%, then they are recalcitrant. Desiccation tolerance of seeds is controlled by several physiological processes, and depends on factors such as drying rate, tissue, degree of development at harvest and environmental influence of the mother plant prior to seed maturation/harvest. To achieve the desiccation of seeds, silica gel was used. The seeds were dried to six different moisture contents: 9.6, 12.3, 24.4, 27.4, 33.4 and 39.3% (wwb). Moisture content of the fresh seeds was 41.6%. Desiccation tolerance was assessed by germination tests followed by a tetrazolium test of viability on ungerminated seeds that were not estimated to be clearly dead at the end of the germination test. Germination tests were done on desiccated and fresh seeds, and on seeds from 'control of time factor during drying' -replications, in which vermiculite were used instead of silica gel during the drying treatment. Germination percentage was dependent on seed moisture content (p-value 0.0001), seen as a reduction of germinability when seed moisture content dropped from >24.4 to 12.3% (p-value 0.0062). Further drying to 9.6% moisture content, reduced germination percentage even more (70-83.8% at MC >24.4%, 57.5% at 12.3% MC and 41.3% at 9.6% MC). The reduction of germination capacity at the latter MC was highly significant compared to the control replications (p-value 0.0001). Yeheb seeds may therefore be classified as having seeds of intermediate storage behaviour. However, further studies on viability in storage and tolerance to low temperatures are necessary before any certain conclusions on the classification of seed storage behaviour of yeheb can be drawn. I det här examensarbetet studeras torktoleransen hos frön från yeheb, Cordeauxia edulis Hemsley, en användbar, städsegrön buske, endemisk för semi-arida ökenområden på Afrikas Horn. På grund av överexploatering och bristande reproduktion hos bestånden, är yeheb utrotningshotad. Frön från olika växtarter kan delas in i tre olika lagringsbeteendekategorier, beroende på tolerans mot torkning, låga temperaturer och livslängd vid lagring. Det första steget vid klassificering av frönas lagringsbeteende, är att undersöka deras torktolerans. Frön som tål <5% vattenhalt (våtviktsbasis) med bibehållen livsduglighet är förmodligen ortodoxa. Om de tål nedtorkning till 10-12.5% vattenhalt (vh), men inte lägre, är de troligen intermediära och om de flesta frön dör vid vattenhalter över 15-20%, är de recalcitranta. Torktolerans hos frön kontrolleras av flera fysiologiska processer, och är beroende av faktorer som torkningshastighet, vävnad, utvecklingsgrad vid skörd samt moderplantans miljö innan frömognad/skörd. För att torka fröna till sex olika vattenhalter: 9.6, 12.3, 24.4, 27.4, 33.4 och 39.3% användes kiselkorn. Vattenhalten hos färska frön var 41.6%. Torktoleransen utvärderades genom groningstest följt av ett tetrazoliumtest av livsduglighet på ogrodda frön som inte klart kunde bedömas vara döda efter groningstesten. Groningstest gjordes på färska och torkbehandlade frön samt frön från 'en test av tidsfaktorn', där vermikulit ersatte kiselkorn under torkningsbehandlingen. Groningen var beroende av frönas vattenhalt (p-värde 0.0001), vilket kunde ses som minskad groning när frövattenhalten minskade från >24.3 till 12.6% (p-värde 0.0062 jämfört med kontrollerna). Groningen försämrades ytterligare när vattenhalten minskade till 9.6% (70-83.8% grodda frön vid vattenhalt >24.4%, 57.5% vid 12.3% vattenhalt och 41.3% vid 9.6%). Jämfört med kontrollerna var groningsreduktionen vid 9.6% vattenhalt starkt signifikant (p-värde 0.0001). Yeheb skulle därför kunna klassificeras som en art med intermediära frön. Dock är det nödvändigt med studier av livslängden vid lagring samt tolerans mot låga temperaturer innan det är möjligt att dra säkra slutsatser om yehebfrönas kategoritillhörighet med avseende på lagringsbeteende. 2008-01-28 Other NonPeerReviewed application/pdf sv https://stud.epsilon.slu.se/10894/1/liew_j_170921.pdf Liew, Josefine, 2003. Desiccation tolerance of yeheb (Cordeauxia edulis Hemsl.) seeds. UNSPECIFIED, Uppsala. Uppsala: (NL, NJ) > Dept. of Crop Production Ecology <https://stud.epsilon.slu.se/view/divisions/OID-500.html> urn:nbn:se:slu:epsilon-s-7063 eng |
| spellingShingle | Plant ecology Liew, Josefine Desiccation tolerance of yeheb (Cordeauxia edulis Hemsl.) seeds |
| title | Desiccation tolerance of yeheb (Cordeauxia edulis Hemsl.) seeds |
| title_full | Desiccation tolerance of yeheb (Cordeauxia edulis Hemsl.) seeds |
| title_fullStr | Desiccation tolerance of yeheb (Cordeauxia edulis Hemsl.) seeds |
| title_full_unstemmed | Desiccation tolerance of yeheb (Cordeauxia edulis Hemsl.) seeds |
| title_short | Desiccation tolerance of yeheb (Cordeauxia edulis Hemsl.) seeds |
| title_sort | desiccation tolerance of yeheb (cordeauxia edulis hemsl.) seeds |
| topic | Plant ecology |
| url | https://stud.epsilon.slu.se/10894/ https://stud.epsilon.slu.se/10894/ |