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2.12 IN VITRO PROPAGATION OF GEOPHYTES Literature review ZIV (1997) defines geophytes as plants pereniating by underground storage organs. Geophytes are generally capable of developing tubers, corms or bulbs in vitro (STEINITZ & LILIEN-KIPNIS, 1989). Many ornamental geophytes are used for gardening, pot plant production, flowering pot plant production, cut flower production and the production of phytochemicals (ZIV, 1997). Plant biotechnology has provided geophyte production with clonal propagation, virus elimination, breeding and crop improvement through embryo rescue, in vitro fertilization, somaclonal variation, protoplast isolation and somatic hybridisation, and haploid production (ZIV, 1997). Genetic transformation is also aiding in geophyte development. Benefits include improving horticultural traits and induction of disease resistance (ZIV, 1997). Gene mapping and DNA fingerprinting are also additional developing areas (ZIV, 1997). Micropropagation has been achieved by enhanced axillary bud development, organogenesis and adventitious bud formation or by somatic embryogenesis (ZIV, 1997). Explants used for propagation of bulbous, cormous and tuberous plants include the leaf lamina, petiole, mesophyll and epidermis (ZIV, 1997). Inflorescence peduncle, pedicel, tepals, petals, sepals, ovaries, anthers, ovules and embryos have also been used (ZIV, 1997). Other explants include the basal plate, scales, twin- scales and nodal and storage tissue of bulbs, corms and tubers (ZIV, 1997). The use of the underground pereniating organ as an explant source is often associated with heavy pathogen contamination (ZIV, 1997). This is a destructive use of the pereniating organ and eliminates the possibility of further vegetative or horticultural evaluation (ZIV, 1997). Different parts of the young flower and inflorescence stem can be cultured (ZIV, 1997). This is a source of pathogen-free totipotent explants (ZIV, 1997). Totipotency depends on the developmental stage at time of excision and position from which the explant was isolated (ZIV, 1997). Explants isolated from tissue positioned immediately next to the basal plate have a 85
Literature review higher regenerative potential in some species of geophytes than explant obtained from tissue in the upper sections of the inflorescence stem (ZIV, 1997). 2.13 IN VITRO PROPAGATION OF BULBOUS PLANTS Micropropagation protocols are available for many bulbous plants. The only bulbous species for which a large scale micropropagation program is however functional is Lilium sp (DEBERGH, 1994). Producing cormlets has an advantage over producing plantlets, as it prevents the development of vitreous leaves (ZIV, 1989). 2.14 IN VITRO PROPAGATION OF IRIDACEOUS SPECIES Within one family there are often similar requirements or difficulties in micropropagation (KYTE & KLEYN, 1996). Understanding the culture requirements of species in the same family (Iridaceae) could shed some light on the culture conditions needed for the successful propagation of species in genus Romulea. An excellent review of Iridaceae micropropagation protocols has recently been published by ASCOUGH et al. (2009), this section will therefore only be considering studies involving direct shoot and corm organogenesis. These were chosen because they are the micropropagation steps used most commonly in this study and for species of Iridaceae. Direct shoot organogenesis and corm induction is summarized separately in Table 2.7 and 2.8 and is discussed separately in relation to results for some Romulea species in chapter five and six. 86
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Propagation of Romulea species Pier
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Contents 2.7 GERMINATION PHYSIOLOGY
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Contents 5.3.1 Explants from seedli
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Abstract The suitability of various
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Declarations I Pierre André Swart,
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Declarations DETAILS OF CONTRIBUTIO
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Publications from this thesis ASCOU
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List of Figures Figure 2.13: Suther
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was significantly different from th
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List of Tables Table 2.1: Names of
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List of Abbreviations 2,4-D 2,4-Dic
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Die vlakhaas spits sy oor hy het di
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As die mens dan ook so sy dankbaarh
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Introduction where a great number o
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Introduction The subgenera Romulea
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2 Literature review Leef van daad e
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Literature review Figure 2.2: Life
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Literature review Figure 2.4: Life
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Literature review The plants are sh
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Literature review flowers (DE VOS,
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Literature review often found on cl
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Literature review flowers of R. lei
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Literature review flattened upper s
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2.2.16 Romulea tabularis Literature
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Literature review extinct, R. papyr
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Literature review R. leipoldtii occ
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Literature review Figure 2.8: Calvi
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Literature review Figure 2.14: Fras
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Figure 2.20: Nieuwoudtville weather
Page 59 and 60: Literature review Figure 2.26: Grah
Page 61 and 62: Literature review Figure 2.29: Diag
Page 63 and 64: Literature review Figure 2.30: A te
Page 65 and 66: Literature review Macronutrients ca
Page 67 and 68: Literature review The soils of the
Page 69 and 70: Literature review The embryo is the
Page 71 and 72: Literature review Phase 2 is seen a
Page 73 and 74: Literature review endogenous gibber
Page 75 and 76: Literature review tolerable level (
Page 77 and 78: Literature review these channels pe
Page 79 and 80: Literature review 2.8.7 Seed dorman
Page 81 and 82: Literature review the embryo (COPEL
Page 83 and 84: Literature review germinated under
Page 85 and 86: Literature review (COPELAND, 1976).
Page 87 and 88: 2.9 BRIEF REVIEW OF IN VITRO CULTUR
Page 89 and 90: Literature review (DEBERGH, 1994).
Page 91 and 92: Literature review PIERIK (1997) sta
Page 93 and 94: Literature review The distinguishin
Page 95 and 96: Literature review The essential fun
Page 97 and 98: 2.9.3.4 Abscisic acid Literature re
Page 99 and 100: Table 2.6: Example of a matrix to e
Page 101 and 102: Literature review Young embryos req
Page 103 and 104: Literature review and the addition
Page 105 and 106: Literature review organ is then pro
Page 107 and 108: Literature review environmental str
Page 109: 2.11 IN VITRO FLOWERING Literature
Page 113 and 114: Subfamily Ixioideae (continued) Tri
Page 115 and 116: Literature review Table 2.8: Corm i
Page 117 and 118: 3 Investigation into the habitat of
Page 119 and 120: Soil sampling and analysis The firs
Page 121 and 122: Soil sampling and analysis Table 3.
Page 123 and 124: 4 Germination physiology 4.1 INTROD
Page 125 and 126: 4.2.2 Water content and imbibition
Page 127 and 128: Germination physiology (-N), phosph
Page 129 and 130: Germination physiology rosea seeds
Page 131 and 132: Germination physiology Figure 4.4:
Page 133 and 134: Germination (%) 50 40 30 20 10 0 77
Page 135 and 136: Germination (%) 100 80 60 40 20 0 c
Page 137 and 138: Germination physiology The relative
Page 139 and 140: Germination physiology seeds of R.
Page 141 and 142: 5.2 MATERIALS AND METHODS In vitro
Page 143 and 144: In vitro culture initiation and mul
Page 145 and 146: 5.2.3 Explant comparison In vitro c
Page 159 and 160: 5.4 DISCUSSION In vitro culture ini
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In vitro culture initiation and mul
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6 In vitro corm formation and flowe
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In vitro corm formation and floweri
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6.3 RESULTS 6.3.1 Corm formation In
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Commercialization potential of Romu
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Commercialization potential of Romu
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BASKIN, C. C., and BASKIN, J. M. (1
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Literature cited DOWLING, P. M., CL
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Literature cited HILTON-TAYLOR, C.
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Literature cited KUMAR, A., SOOD, A
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Literature cited PIERIK, R. L. M. (
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Literature cited STEINITZ, B., COHE
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