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Relevant Factors Influencing Seed Set in Commercial Sunflower (Helianthus Annuus) In South Africa
Thesis (DPhil (Botany)--University of Pretoria, 1999.
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| Format: | Thesis |
| Language: | English |
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University of Pretoria
2022
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| _version_ | 1867613491500679168 |
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| access_status_str | Open Access |
| author2 | Coetzer, Louw A. |
| author_browse | Coetzer, Louw A. |
| author_facet | Coetzer, Louw A. |
| collection | Thesis |
| dc_rights_str_mv | © 2020 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Thesis (DPhil (Botany)--University of Pretoria, 1999. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/85523 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:36:59.722Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/85523 Relevant Factors Influencing Seed Set in Commercial Sunflower (Helianthus Annuus) In South Africa Coetzer, Louw A. Du Toit, Adriaan Pieter UCTD Seed Commercial Sunflower Helianthus Annuus South Africa Thesis (DPhil (Botany)--University of Pretoria, 1999. Low seed set and hollow seededness are amongst the main problems of the sunflower oilseed production industry in South Africa. This study of eighteen sunflower cultivars on seventeen different localities was conducted to address these and other problems. It was undertaken in collaboration with the national sunflower trials. The study has revealed that a lack of pollinators had the least significant influence on seed set. Neither could the percentage hollow seeds at each locality be attributed to a low number of insect pollinators. Commercial sunflowers in cages with honeybees gave a seed yield of I,859 kg ha-I (72% seed set) compared to I,22I kg ha-I (45% seed set) in cages with no insect pollinators. The percentage unfilled seeds differed significantly between localities and cultivars. However, the incidence of both hollow seeds and unfilled seeds differed highly significantly with the increase in plant density from I 5,000 plants per ha to 90,000 plants per ha. Yields also decreased as plant density increased. Although the boron levels differed between soil, leaf and floret samples for the variables of locality, cultivar and plant density, no relationship was found between the boron levels and differences observed in the percentage hollow seeds and unfilled seeds between the eighteen sunflower cultivars. Slow pollen movement was identified as the main cause responsible for hollow seededness. A lack of nutrients resulted in the high levels of unfilled seeds found. Recommendations are given regarding these problems. Viability and vitality of the sunflower pollen was good. It was, however, not possible to germinate the trinucleate sunflower pollen in vitro using conventional palynological methods and techniques. It is hypothesized that an unidentified "pollen growth factor", occurring on the stigmas, regulates germination of sunflower pollen. Plant Science DPhil (Botany) Unrestricted 2022-05-17T11:22:14Z 2022-05-17T11:22:14Z 27/7/2021 1999 Thesis * https://repository.up.ac.za/handle/2263/85523 en © 2020 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | UCTD Seed Commercial Sunflower Helianthus Annuus South Africa Relevant Factors Influencing Seed Set in Commercial Sunflower (Helianthus Annuus) In South Africa |
| title | Relevant Factors Influencing Seed Set in Commercial Sunflower (Helianthus Annuus) In South Africa |
| title_full | Relevant Factors Influencing Seed Set in Commercial Sunflower (Helianthus Annuus) In South Africa |
| title_fullStr | Relevant Factors Influencing Seed Set in Commercial Sunflower (Helianthus Annuus) In South Africa |
| title_full_unstemmed | Relevant Factors Influencing Seed Set in Commercial Sunflower (Helianthus Annuus) In South Africa |
| title_short | Relevant Factors Influencing Seed Set in Commercial Sunflower (Helianthus Annuus) In South Africa |
| title_sort | relevant factors influencing seed set in commercial sunflower helianthus annuus in south africa |
| topic | UCTD Seed Commercial Sunflower Helianthus Annuus South Africa |
| url | https://repository.up.ac.za/handle/2263/85523 |