Title page for ETD etd-07092008-090525


Document Type Doctoral Thesis
Author Wu, How-Chiun
Email hcwu@tuks.co.za
URN etd-07092008-090525
Document Title Improving in vitro propagation of Protea cynaroides L. (King Protea) and the roles of starch and phenolic compounds in the rooting of cuttings
Degree PhD (Horticulture)
Department Plant Production and Soil Science
Supervisor
Advisor Name Title
Prof C F Reinhardt Co-Supervisor
Prof E S du Toit Supervisor
Keywords
  • phenolic compounds
  • somatic embryogenesis
  • micrografting
  • in vitro germination
  • Protea cynaroides
  • starch
Date 2007-04-17
Availability unrestricted
Abstract
Protea cynaroides L. (King Protea) is a well known cutflower. Seeds and stem cuttings are commonly used to propagate P. cynaroides. However, the success rate and rooting rate of seeds and cuttings, are inconsistent and slow. The potential of in vitro propagation as an alternative method to produce P. cynaroides plantlets was investigated. In vitro studies consisted of in vitro germination of mature zygotic embryos, micrografting and direct somatic embryogenesis of zygotic embryos and excised cotyledons. In the germination study, temperature was the most important factor in obtaining a high germination percentage. Alternating temperatures of 21±2șC/12±2șC (light/dark) was suitable for germination and over 90% of embryos germinated, while the germination percentage of embryos at 25±2șC was poor. Plantlets were successfully established in ex vitro conditions when planted in a peat/coir/sand mixture. Micrografting of P. cynaroides was done by grafting microshoots (microscion), which was taken from in-vitro-established nodal explants, onto roots of decapitated in-vitro-germinated seedlings. After the graft union formed, buds on the microscion sprouted. A protocol to induce direct somatic embryogenesis was developed. Direct somatic embryogenesis was achieved on both P. cynaroides mature zygotic embryos and excised cotyledons. The addition of auxins such as NAA and 2,4-D singly or in combination with TDZ, BAP or kinetin suppressed the formation of somatic embryos. Formation of somatic embryos was observed in medium lacking growth regulators. Germination of somatic embryos was highest in medium containing GA3. The roles of starch and phenolic compounds in the rooting of P. cynaroides cuttings were also studied. Starch and total soluble phenol analyses results revealed a positive correlation between high root formation and increased starch and phenolic content. NMR and MS analyses identified high amounts of 3,4-dihydroxybenzoic acid in stems of P. cynaroides. In vitro bioassay showed that 3,4-dihydroxybenzoic acid stimulated and inhibited root growth of P. cynaroides explants, depending on the concentration. A link was made between the endogenous concentration levels of 3,4-dihydroxybenzoic acid and rooting of P. cynaroides stem cuttings. Findings of this study contribute towards a better understanding of the roles starch and phenolic compounds play in the rooting of P. cynaroides.

© 2006 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.

Please cite as follows:

Wu, HC 2006, Improving in vitro propagation of Protea cynaroides L. (King Protea) and the roles of starch and phenolic compounds in the rooting of cuttings, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-07092008-090525/ >

D260/ag

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