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Growth manipulations of Leucospermum cut flowers with the application of plant growth regulators
Thesis (PhDAgric)--Stellenbosch University, 2020.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2020
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| _version_ | 1867614088203337728 |
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| access_status_str | Open Access |
| author | Louw, Eugenie-Lien (nee Bezuidenhout) |
| author2 | Hoffman, E. W.
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| author_browse | Hoffman, E. W.
Louw, Eugenie-Lien (nee Bezuidenhout) |
| author_facet | Hoffman, E. W.
Louw, Eugenie-Lien (nee Bezuidenhout) |
| author_sort | Louw, Eugenie-Lien (nee Bezuidenhout) |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhDAgric)--Stellenbosch University, 2020. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/108432 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:46:28.519Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2020 |
| publishDateRange | 2020 |
| publishDateSort | 2020 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/108432 Growth manipulations of Leucospermum cut flowers with the application of plant growth regulators Louw, Eugenie-Lien (nee Bezuidenhout) Hoffman, E. W. Jacobs, Gerard Stellenbosch University. Faculty of Agrisciences. Dept. of Horticulture. Leucospermum -- Growth Plant growth regulators Growth (Plants) -- Regulation Gibberellins -- Synthesis -- Regulation Gibberellins -- Physiological effect 6-Benzyladenine Plant growth promoting substances -- Physiological effect Plants, Flowering of -- Climatic factors UCTD Thesis (PhDAgric)--Stellenbosch University, 2020. ENGLISH ABSTRACT: Leucospermum, an indigenous South African cut flower genus, is cultivated worldwide for its striking and boldly-coloured inflorescences. However, the over-production of short (linked to disbudding or production in warm areas) and curved (associated with certain cultivars’ spreading growth habits) shoots negatively affects the Cape flora brand and profitability. This study therefore evaluated the efficacy of selected plant growth regulator (PGR) treatments to overcome the growth and developmental limitations that lead to short and curved shoots in selected Leucospermum cultivars. When Leucospermum shoot growth was monitored to determine the timing of appendage formation relative to internode extension, the full complement of true leaves was found to be differentiated early during shoot extension. This period proved to be the optimum period for PGR application to promote shoot length and straightness. Seven PGR treatments consisting of 6-benzyladenine (6-BA) and/or gibberellin (GA3, GA4 and GA7) were applied to single ‘Succession II’ and ‘Soleil’ shoots in 2013–14. In 2014– 15 the following treatments were applied to ‘Succession II’ and ‘Soleil’ at the environmentally contrasting Arnelia and Pomona farms, as well as to ‘Jelena’ at Pomona: 3×500 mg L−¹ GA3, 1×250 mg L−¹ 6-BA followed by 2×500 mg L−¹ GA3, and 3×100 mg L−¹ 6-BA and GA4+7. In 2015–16, ‘Soleil’ at Arnelia and ‘Jelena’ at Pomona received applications of 3×500 mg L−¹ GA3 or 3×100 mg L−¹ 6-BA and GA4+7. The PGR treatments elongated shoots by as much as 20 cm, producing more, but smaller, lighter leaves and higher stem dry weights cm−¹, while inflorescence quality was generally unaffected. Plants treated with PGRs displayed more upright growth, which resulted in straighter stems, thereby increasing the stem marketability by 40%. This adjusted plant morphology may be linked to higher gibberellin levels, smaller leaves, and a more even distribution of xylem in the vascular bundles. Based on trials on ‘Soleil’ plants at Arnelia in 2016–17, the lowest GA3 application to significantly affect shoot length was 100 mg L−¹. Three applications of combined 100 mg L−¹ GA3 and 100 mg L−¹ 6-BA and GA4+7 at 7–14 day intervals, when developing shoots are generally shorter than 10 cm, is therefore recommended for commercial use. Despite significant shoot variability, PGR treatment successfully improved yields of shoots in the 60–70 cm length categories. To explore the curvature-inducing effects of gravity and wind on Leucospermum shoots, ‘Succession II’ and ‘Soleil’ plants, with their contrasting growth habits, were compared for their response to gravity as well as rate of lignification. ‘Succession II’ displayed a lower modulus of elasticity and produced bends with a large radius of curvature. Results suggested that the desirable, upright growth habit of ‘Succession II’, despite exposure to constant early summer winds, may be due to its weak reaction to gravity, as was observed when stems were placed at an angle. The commercial impact of this study is significant and the PGR protocol to extend shoot length and increase shoot straightness may be expanded to other problematic cultivars. AFRIKAANSE OPSOMMING: Leucospermum, ‘n inheemse Suid-Afrikaanse snyblom genus, word wêreldwyd verbou vir sy opvallende en helder-kleurige bloeiwyses. Die oormatige produksie van kort (gekoppel aan ontknopping of produksie in warm gebiede) en krom (gepaardgaande met sekere kultivars se verspreide groeiwyse) stele benadeel egter die “Cape flora”-handelsmerk en verminder winsgewendheid. Hierdie studie het derhalwe die effektiwiteit van gekose plantgroei- reguleerderbehandelings (PGR) geëvalueer om die groei en ontwikkelingsbeperkings wat tot kort en krom stele in geselekteerde Leucospermum-kultivars lei, te oorkom. Die groei van Leucospermum-lote was bestudeer om die tydsberekening van aanhangselvorming, relatief tot die verlenging van internodes, te bepaal. Daar is bevind dat die totale aantal ware blare tydens vroeë lootgroei gedifferensieër word. Vroeë lootgroei word beskou as die optimale periode vir PGR-toediening vir langer en meer reguit lote. Sewe PGR-behandelings wat bestaan het uit 6-bensieladenien (6-BA) en/of gibberellien (GA3; GA4 en GA7), was in 2013–14 op enkel 'Succession II' en 'Soleil' lote toegedien. In 2014–15 was 3×500 mg L−¹ GA3, 1×250 mg L−¹ 6-BA gevolg deur 2×500 mg L−¹ GA3, en 3×100 mg L−¹ 6-BA en GA4+7 toegedien op 'Succession II' en 'Soleil' plante soos verbou op die twee omgewingskontrasterende persele Arnelia- en Pomona-boerderye, asook op 'Jelena' te Pomona. In 2015–16 was 3×500 mg L−¹ GA3 of 3×100 mg L−¹ 6-BA en GA4+7 toegedien op 'Soleil' by Arnelia en 'Jelena' by Pomona. Die PGR-behandelings het lote tot 20 cm langer gemaak met meer, maar kleiner, ligter blare en hoër stamdroëgewig cm⁻¹, terwyl die bloeiwyse se gehalte nie beïnvloed is nie. Plante behandel met PGRs het ‘n regop groeiwyse vertoon, wat gelei het tot meer reguit lote en sodoende die lote se verkoopbaarheid met 40% verhoog het. Hierdie aangepaste plantmorfologie kan gekoppel word aan hoër gibberellienvlakke, kleiner blare en 'n meer egalige verspreiding van xileem in die vaatbondels. Gebaseer op waarnemings op 'Soleil'- plante by Arnelia in 2016–17, was die laagste GA3-konsentrasie om lootlengte beduidend te verleng, 100 mg L−¹. Vir kommersiële gebruik word drie toedienings van 100 mg L−¹ GA3 gekombineer met 100 mg L−¹ 6-BA en GA4+7 met tussenposes van 7–14 dae, wanneer lote in die algemeen korter as 10 cm is, dus aanbeveel. Ondanks die wisselvalligheid van die lootstadium tydens aanwending, het die PGR-behandeling die frekwensie van lote in die 60– 70 cm kategorieë suksesvol verbeter. Om die effekte van swaartekrag en wind wat kromming veroorsaak op die lote van Leucospermum te ondersoek, is ‘Succession II’- en 'Soleil'-plante, met hul kontrasterende groeiwyse, met betrekking tot hul reaksie op swaartekrag sowel as die tempo van lignifikasie vergelyk. 'Succession II' vertoon 'n laer elastisiteitsmodulus en lote het 'n groot krommingsradius. Resultate dui daarop dat dié wenslike, regop groeiwyse van 'Succession II', ondanks blootstelling aan konstante somerwinde, moontlik te wyte is aan sy swak reaksie teen swaartekrag, soos waargeneem is toe lote teen 'n hoek geplaas is. Die kommersiële impak van hierdie studie is beduidend sodat dit die uitbreiding van die PGR-protokol om die lengte van die lote te verleng en die aantal reguit lote te verhoog, na ander problematiese kultivars regverdig. Doctoral 2020-02-21T20:36:18Z 2020-04-28T15:13:39Z 2020-02-21T20:36:18Z 2020-04-28T15:13:39Z 2020-04 Thesis http://hdl.handle.net/10019.1/108432 en Stellenbosch University x, 220 pages : illustrations (some color) application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Leucospermum -- Growth Plant growth regulators Growth (Plants) -- Regulation Gibberellins -- Synthesis -- Regulation Gibberellins -- Physiological effect 6-Benzyladenine Plant growth promoting substances -- Physiological effect Plants, Flowering of -- Climatic factors UCTD Louw, Eugenie-Lien (nee Bezuidenhout) Growth manipulations of Leucospermum cut flowers with the application of plant growth regulators |
| title | Growth manipulations of Leucospermum cut flowers with the application of plant growth regulators |
| title_full | Growth manipulations of Leucospermum cut flowers with the application of plant growth regulators |
| title_fullStr | Growth manipulations of Leucospermum cut flowers with the application of plant growth regulators |
| title_full_unstemmed | Growth manipulations of Leucospermum cut flowers with the application of plant growth regulators |
| title_short | Growth manipulations of Leucospermum cut flowers with the application of plant growth regulators |
| title_sort | growth manipulations of leucospermum cut flowers with the application of plant growth regulators |
| topic | Leucospermum -- Growth Plant growth regulators Growth (Plants) -- Regulation Gibberellins -- Synthesis -- Regulation Gibberellins -- Physiological effect 6-Benzyladenine Plant growth promoting substances -- Physiological effect Plants, Flowering of -- Climatic factors UCTD |
| url | http://hdl.handle.net/10019.1/108432 |
| work_keys_str_mv | AT louweugenielienneebezuidenhout growthmanipulationsofleucospermumcutflowerswiththeapplicationofplantgrowthregulators |